Chapter 5.pdf - DSpace@UM

CHAPTER 5LOWER LEAF SURFACE MICROMORPHOLOGYEven after the observation by Stace (1965) that angiosperm leaf surfacemorphology or leaf epidermal (or cuticular) studies have generally received littleattention, such studies have been scanty for the Rubiaceae. However, someinvestigations have focused on the anatomical aspects of leaves in certain groups of theGardenieae, e.g., Burchellia R. Br., Coddia Verdc., Euclinia Salisb., and MitriostigmaHochst. (Robbrecht & Puff, 1986).Thus far, no studies on leaf surfacemicromorphology have been reported for Rothmannia and related taxa, such asKochummenia, except for general documentation of domatia types in some Africanspecies of Rothmannia (Bridson & Verdcourt, 1988; Palgrave, 1988; Retief & Herman,1997).It is useful to consider the various leaf surface features that have been of someinterest in the past. The term domatium, introduced by Lundstroem (1887), is of Greekderivation, meaning “a little house”, or translated as “formations or transformations onplants adapted to the habitation of guests whether animal or vegetable which are ofservice to the host”. According to Metcalfe & Chalk (1979), domatia today usuallyrefer to depressions, pockets, sacs or tufts of hairs in the principal vein axils where theyoccur exclusively on the lower leaf surfaces of leaves. Domatia have been found tooccur most frequently on woody plants of humid tropical or subtropical regions, veryrarely from permanently dry regions. Little is known about their formation andfunction, although mites and other similarly minute arthropods use them as shelter129

(Stace, 1965). Among woody dicotyledons, the Rubiaceae have been documented tohave a significant number of species with domatia (Jacobs, 1966). They are normallyfound in the axils of secondary veins but may also occur in the axils of tertiary veins,e.g., Oligocodon Keay and Pleiocoryne Rauschert (Gardenieae) (Robbrecht, 1988).The taxonomic significance of domatia in the Rubiaceae appears to be mostly confinedto the specific level (Penzig & Chiabrera, 1903; Robbrecht, 1988). However, they aresometimes of value in higher taxa, e.g., subgenera or genera, which are characterizedby a peculiar type of domatia (Robbrecht, 1988).The stomatal complex, sometimes called stomatal apparatus, comprises thestoma, a pair of guard cells with the stomatal aperture or pore between them, and alsothe subsidiary cells or modified cells surrounding the guard cells (Stace, 1965) thatparticipate in the mechanism of closing and opening of the pore (Van Cotthem, 1970).In most Rubiaceae, the stomatal type simply referred to as the “rubiaceous” type byVesque (1889), later came to be termed paracytic by Metcalfe & Chalk (1950).Trichomes have been defined generally as hairs or bristles (Lawrence, 1951), and morespecifically, as epidermal outgrowths of diverse form, structure and function (Esau,1965). The trichome type has been found to be of considerable value for taxonomicpurposes (Theobald et. al., 1979), especially at the specific level (Theobald, 1967),compared to trichome length, size and density, as these are variable and may beinfluenced by environmental conditions (Metcalfe & Chalk, 1950). Verdcourt (1958)surveyed the “external indumentum” on the leaves and flowers of several tribes in theRubiaceae and classified them based on three main types, i.e., septate, uniseriate,composed of separate cells; incompletely septate (i.e., hairs with rather thick walls andweak or strong transverse ingrowths that do not completely partition the lumen); andsimple, non-septate hairs. He found that hair structure can be useful as a supportivecharacter.130

This chapter summarises the characters of the lower leaf surfacemicromorphology that have been investigated. These have been studied for theirpossible systematic value at the specific, and generic levels in the Rothmannia complex(e.g., Kochummenia and other elements thought aberrant in Rothmannia).5.1 DomatiaMost of the domatia in Rothmannia occur in the axils of the secondary veinswith the midrib but can sometimes be found in other vein junctions (e.g., at junctions ofthe secondary and tertiary veins) on the lower leaf surfaces in R. anisophylloides, R.attopevensis, R. eucodon, R. kampucheana, R. leytensis, R. macromera, R. merrillii, R.nigrescens, R. papuana, R. pseudoternifolia var. pseudoternifolia, R. sootepensis, R.uvarioides, R. venalis, R. vietnamensis and R. wittii (Asian) and R. munsae ssp.megalostigma (African, Somers & Robbrecht (1991)) (see Table 2 for more details).The classification of leaf domatia adopted here is based on Wilkinson (1979) [that wasin turn based on Lundstroem (1887), Hamilton (1896), Penzig & Chiabrera (1903),Briquet (1920), Chevalier & Chesnais (1941), Stace (1965), Jacobs (1966)] andRobbrecht (1988).Among the taxa surveyed (as shown in Table 2), the following types of domatiawere found:(i) Pit-domatiaThese are defined as shallow depressions in the leaf surfaces, with openings orpores in various shapes, ranging from rounded, ovoid to slit-like at the top. This typeof domatia varies from being glabrous to minute-hairy or long-hairy. Generally, theglabrous to minute-hairy pit-domatia is the only type in some Asian and SW Pacificspecies, such as R. eucodon, R. lagunensis (Fig. 32A), R. merrillii (Fig. 32B), R.nigrescens, R. papuana, R. pulcherrima, R. ridsdalei (Fig. 32C), R. sootepensis, R.131

Table 2. (this page and the following) Location and type of domatia on the lower leaf surface of varioustaxa in the Rothmannia complex.Species Domatia location Domatia typeIn axils ofsecondaryveinsIn axils oftertiaryveinsMALESIARothmannia anisophylloides + + long-hairy pit-domatiaRothmannia forsteniana + - long-hairy pit-domatia tooccassionally hairy pocket-domatiaRothmannia graciliflora - - long-hairy pit-domatiaRothmannia grandis + - long-hairy pit-domatiaRothmannia kassamensis + - long-hairy pit-domatiaRothmannia lagunensis + - minute-hairy pit-domatiaRothmannia leytensis + + long-hairy pit-domatiaRothmannia macromera + + long-hairy pit-domatiaRothmannia merrillii + + glabrous to minute-hairy pitdomatiaRothmannia negrosensis + - long-hairy pit-domatiaRothmannia nigrescens + + minute-hairy pit-domatiaRothmannia papuana + + glabrous pit-domatiaRothmannia pseudoternifolia + + long-hairy pit-domatia, rarelyvar. pseudoternifoliaglabrous pit-domatiaRothmannia pseudoternifolia + - long-hairy pit-domatiavar. hispidaRothmannia ridsdalei + - glabrous to occasionally minutehairypit-domatiaRothmannia schoemannii + - long-hairy pit-domatiaRothmannia sundaensis + - glabrous to minute-hairy pitdomatiaRothmannia uvarioides + + long-hairy pit-domatiaRothmannia sp. indet 1 + - long-hairy pit-domatiaRothmannia sp. indet 2 + - glabrous to minute-hairy pitdomatiaOUTSIDE MALESIAAfrica (corolla lobes contortedto the right)Rothmannia annae + - long-hairy pit-domatiaRothmannia capensis + - long-hairy pit-domatiaRothmannia fischeri ssp. + - glabrous to long-hairy pitfischeridomatiaRothmannia fischeri ssp. + - glabrous to long-hairy pitmorambollaedomatiaRothmannia fischeri ssp + - Glabrous to long-hairy pitverdcourtiidomatiaRothmannia hispida - - glabrous to long-hairy pitdomatia134

Table 2, continued.Species Domatia location Domatia typeIn axils ofsecondaryveinsIn axils oftertiaryveinsRothmannia ravae + - glabrous to longhairypit-domatiaRothmannia urcelliformislong-hairy pit-domatia,occasionally hairypocket- domatiaAfrica (corolla lobescontorted to the left)Rothmannia engleriana + - tuft-domatiaRothmannia longiflora + - tuft-domatia orglabrous to minutepit- domatiaRothmannia lujae + - glabrous pit-domatiaRothmannia manganjae + - long-hairy pit- domatiaRothmannia whitfieldii - - AbsentAsiaRothmannia attopevensis + + long-hairy pit- domatiaRothmannia eucodon + + glabrous to minutehairyRothmannia kampucheana + + tuft-domatiaRothmannia pulcherrima + - glabrous to minutehairypit-domatiaRothmannia sootepensis + + glabrous to minutehairypit-domatiaRothmannia venalis + + long-hairy pit-domatiaRothmannia vidalii ? ? ?Rothmannia vietnamensis + + glabrous to minutehairypit-domatiaRothmannia wittii + + long-hairy pitdomatiaABERRANT ANDRELATED TAXARothmannia macrophylla + - glabrous to minute-hairy pit-domatiaRothmannia globosa + - hairy pocket-domatiaKochummenia parviflora - - AbsentKochummenia stenopetala + - glabrous pit-domatiaNotes: + = present; - = absent; ? = data unavailable.135

136

137

specially distinguished in their domatial characteristics. R. macrophylla has glabrous tominute-hairy pit-domatia that are also found in some species of Rothmannia whereas R.globosa has the hairy pocket-domatia (Fig. 32H), also found in a couple of Rothmanniaspecies.5.2 Cuticular ornamentationSolereder (1908) emphasized that the kinds of markings on the cuticular surfaceis of value in specific diagnoses. However, there has been practically no investigationof this for the Rubiaceae in general.The lower leaf cuticular surface in the taxa surveyed can be distinguished asfollows:(i) SmoothThis type has generally no cuticular markings, except at the base of the trichome(for species with trichomes) where short, minor, “buttress-like” strands can be seen.Smooth laminar surfaces are the only type found in the Asian species, R. eucodon andR. pulcherrima and the African species in R. annae, R. capensis (Fig. 33I), R. fischerissp. fischeri, R. longiflora, R. lujae (Fig. 33J), R. manganjae and R. urcelliformis.(ii) StriateThis type has striations over the entire lamina surface, with striae generallysurrounding the stoma in an irregular meshwork, as well as radiating striations at thetrichome base and occassionally at certain stomata. Some variation in the striationssurrounding the stoma can be observed in R. grandis (Fig. 33A), R. merrillii (Fig. 33B),R. sootepensis (Fig. 33C), R. whitfieldii (Fig. 33D), R. fischeri ssp. moramballae (Fig.33E), R. engleriana (Fig. 33F), R. ridsdalei (Fig. 33G), and R. schoemannii (Fig. 33H).138

Table 3. (this page and the following) Cuticular ornamentation on lower leaf lamina surface ofvarious taxa in the Rothmannia complex.SpeciesCuticular ornamentationMALESIARothmannia anisophylloidesstriateRothmannia forstenianastriateRothmannia graciliflorastriateRothmannia grandisstriate to smoothRothmannia kassamensisstriateRothmannia lagunensisstriateRothmannia leytensisstriateRothmannia macromerastriateRothmannia merrilliistriateRothmannia negrosensis* striateRothmannia nigrescensstriateRothmannia papuana ?Rothmannia pseudoternifolia var. pseudoternifoliastriate to smoothRothmannia pseudoternifolia var. hispidastriate to smoothRothmannia ridsdaleistriateRothmannia schoemanniistriateRothmannia sundaensisstriateRothmannia uvarioides ?Rothmannia sp. indet 1 ?Rothmannia sp. indet 2striateOUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaesmoothRothmannia capensissmoothRothmannia fischeri ssp. fischerismoothRothmannia fischeri ssp. moramballaestriateRothmannia fischeri ssp. verdcourtiistriateRothmannia hispida ?Rothmannia ravaestriateRothmannia urcelliformissmoothAfrica (corolla lobes contorted to the left)Rothmannia englerianaRothmannia longifloraRothmannia lujaeRothmannia manganjaeRothmannia whitfieldiiAsiaRothmannia attopevensisRothmannia eucodonRothmannia kampucheanaRothmannia pulcherrimaRothmannia sootepensisRothmannia venalisstriatesmoothsmoothsmoothstriatestriatesmoothstriatesmoothstriatestriate139

Table 3, continued.SpeciesCuticular ornamentationRothmannia vidalii ?Rothmannia vietnamensisstriateRothmannia wittiistriateABERRANT AND RELATED TAXARothmannia macrophyllastriateRothmannia globosagranularKochummenia parviflora ?Kochummenia stenopetalasmoothNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina.Nonetheless, there are some species which have both striate and smoothcuticular surfaces over the subsidiary or epidermal cells occurring in differentindividuals of the same species. Examples include R. grandis and R.pseudoternifolia (both varieties).(iii) GranularThis type is defined as having epidermal cells with a highly undulatingsurface caused by the presence of many minute protrusions. This is unique to R.globosa (Fig. 33L).Table 3 shows the distribution of cuticular ornamentation types on the lowerleaf lamina among the taxa of the Rothmannia complex studied. Briefly, two typesof lamina cuticular ornamentation occur in Rothmannia. Our survey shows that K.stenopetala (Fig. 33K) also has a smooth lamina surface found also in some speciesof Rothmannia. R. macrophylla also has a similar cuticular surface as some otherRothmannia species, i.e., striated. However, R. globosa, seems to be distinguishedfrom the rest of the taxa in having a granular lamina surface.140

141

142

Thus, cuticular ornamentation on the lamina surface may have some taxonomicutility at the specific level.5.3 Epidermal Cells5.3.1 ShapeThe majority of the Rothmannia species have irregularly shaped epidermalcells, such as in the Asian species R. grandis (Fig. 34F), R. eucodon (Fig. 34L), R.schoemannii (Fig. 34G), R. sundaensis (Fig. 34H) and R. vietnamensis (Fig. 34M);and the African species, R. capensis (Fig. 34I), R. fischeri ssp. moramballae (Fig.34J), R. longiflora (Fig. 34E) and R. lujae (Fig. 34K).However, there are some species which have epidermal cells varying frompolygonal to irregular, such as in a few African species, R. engleriana (Fig. 34A), R.fischeri ssp. verdcourtii, R. hispida, R. manganjae (Fig. 34B) and R. whitfieldii andthe Asian R. papuana (Fig. 34C & D).Irregular epidermal cell shapes are also noted in Kochummenia stenopetala(Fig. 34N) and the otherwise aberrant taxon, R. macrophylla (Fig. 34O). The otheraberrant taxon, R. globosa seems to have exclusively polygonal epidermal cells (Fig.34P). Table 4 shows the epidermal cell shapes on the lower leaf surfaces of theRothmannia complex.It can be concluded that epidermal cell shape does not appear to be distinctamong the individual genera or main groups. Both epidermal cell shapes occur inRothmannia, whereas limited survey shows Kochummenia (represented by K.stenopetala, Fig. 34N) and the otherwise aberrant taxon, R. macrophylla (Fig. 34O)to have the irregular epidermal cell shape found also in the majority of theRothmannia species. The other aberrant taxon, R. globosa, has polygonal epidermalcell shapes which is in common with a number of Rothmannia species.143

Table 4. (this page and the following) Epidermal cell shape on lower leaf surfaces of various taxa inthe Rothmannia complex.SpeciesEpidermal cell shapeMALESIARothmannia anisophylloidesirregularRothmannia forstenianairregularRothmannia graciliflorairregularRothmannia grandisirregularRothmannia kassamensisirregularRothmannia lagunensisirregularRothmannia leytensisirregularRothmannia macromerairregularRothmannia merrilliiirregularRothmannia negrosensis*irregularRothmannia nigrescensirregularRothmannia papuanapolygonal to irregularRothmannia pseudoternifolia var. pseudoternifoliairregularRothmannia pseudoternifolia var. hispidairregularRothmannia ridsdaleiirregularRothmannia schoemanniiirregularRothmannia sundaensisirregularRothmannia sp. indet 1 ?Rothmannia sp. indet 2 ?OUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaeRothmannia capensisRothmannia fischeri ssp. fischeriRothmannia fischeri ssp. moramballaeRothmannia fischeri ssp. verdcourtiiRothmannia hispidaRothmannia ravaeRothmannia urcelliformisAfrica (corolla lobes contorted to the left)Rothmannia englerianaRothmannia longifloraRothmannia lujaeRothmannia manganjaeRothmannia whitfieldiiirregularirregularirregularirregularpolygonal to irregularpolygonal to irregularirregularirregularpolygonal to irregularirregularirregularpolygonal to irregularpolygonal to irregularAsiaRothmannia attopevensisirregularRothmannia eucodonirregularRothmannia kampucheanairregularRothmannia pulcherrimairregularRothmannia sootepensisirregularRothmannia venalisirregularRothmannia vidalii ?144

Table 4, continued.SpeciesEpidermal cell shapeRothmannia vietnamensisRothmannia wittiiirregularirregularABERRANT AND RELATED TAXARothmannia macrophyllairregularRothmannia globosapolygonalKochummenia parviflora ?Kochummenia stenopetalairregularNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion.Thus, epidermal cell shape does not seem to be especially distinctive at boththe species and generic levels.5.3.2 Anticlinal wall outlinesThe classification of anticlinal wall outlines of the epidermal cells observedamong taxa in the Rothmannia complex was modified from Stace (1965) andWilkinson (1979) (see Appendix 9).In some cases, anticlinal wall outlines may be somewhat obscured by stronglydemarcated striations on the lamina, such as in R. anisophylloides, R. engleriana(Fig. 34A), R. forsteniana, R. kampucheana, R. kassamensis, R. macromera, R.uvarioides and R. whitfieldii. In such cases, the wall outlines could only bedetermined from examining many slide preparations.Anticlinal wall outlines of epidermal cells can be categorized into threegeneral types (see Appendix 9). Type A has straight to gently curved sections of thecell outline, with basically low-frequency, low-amplitude sinuations corresponding toTypes 1 and 2 of the system of Stace (1965) and Wilkinson (1979). Type B haspronounced sinuations of higher frequency and low to medium amplitudes, includingTypes 3, 4 and 5 of Stace and Wilkinson. Type C (Stace’s and Wilkinson’s Type 6)145

has pronounced sinuations of high frequency and large amplitudes (i.e., deepsinuations) in addition to these features.Type A outlines (straight to gently curved) are found in the African speciesonly, viz., R. engleriana (Fig. 34A), R. manganjae (Fig. 34B) and R. whitfieldii andthe aberrant taxon, R. globosa (Fig. 34P). Type B outlines (with pronounced wavesof low to medium amplitudes) are by far the most common condition. This type isfound in both the Asian, such as, R. anisophylloides, R. grandis (34F), R. papuana(Fig. 34C), R. schoemannii (Fig. 34G), R. sundaensis (Fig. 34H), R. eucodon (Fig.34L), and R. vietnamensis (Fig. 34M) and African species, e.g., R. longiflora (Fig.34E), R. capensis (Fig. 34I), R. fischeri ssp. morambollae (Fig. 34J), and R. lujae(Fig. 34K). Type C outlines (deep sinuations, i.e. waves with very large amplitudes)are found only in Kochummenia stenopetala (Fig. 34N). Table 5 shows the types ofanticlinal wall outlines of epidermal cells in the Rothmannia complex.In terms of anticlinal wall outline, both R. macrophylla (Fig. 34O) and R.globosa (Fig. 34P) are not specially distinguished from most of the Rothmanniaspecies. However, the anticlinal wall outline in Kochummenia stenopetala appears tobe unique among members of the complex.5.4 The stomatal complex5.4.1 Stomatal typesStomatal types in the investigated Rothmannia taxa are very variable: they may beexclusively paracytic (i.e., the guard cells are flanked on either side by one or morespecialized cells or subsidiary cells parallel to the long axis of the pore and guardcells); or the paracytic type may occur together with anisoparacytic stomata (whereone of the pair of the subsidiary cells is smaller than the other), or with anomocyticstomata (epidermal cells around the guard cells are not distinguishable146

Table 5. (this page and the following) Anticlinal wall outlines on lower leaf surfaces of various taxain the Rothmannia complex.SpeciesType ofanticlinal wall outlineMALESIARothmannia anisophylloidesBRothmannia forstenianaBRothmannia gracilifloraBRothmannia grandisBRothmannia kassamensisBRothmannia merrilliiBRothmannia negrosensis *BRothmannia nigrescensBRothmannia papuanaBRothmannia pseudoternifolia var. pseudoternifoliaBRothmannia pseudoternifolia var. hispidaBRothmannia ridsdaleiBRothmannia schoemanniiBRothmannia sundaensisBRothmannia uvarioides ?Rothmannia sp. indet 1 ?Rothmannia sp. indet 2 ?OUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaeRothmannia capensisRothmannia fischeri ssp. fischeriRothmannia fischeri ssp. moramballaeRothmannia fischeri ssp. verdcourtiiRothmannia hispidaRothmannia ravaeRothmannia urcelliformisAfrica (corolla lobes contorted to the left)Rothmannia englerianaRothmannia longifloraRothmannia lujaeRothmannia manganjaeRothmannia whitfieldiiBBBBBBBBABBAAAsiaRothmannia attopevensisBRothmannia eucodonBRothmannia kampucheanaBRothmannia pulcherrimaBRothmannia sootepensisBRothmannia venalisBRothmannia vidalii ?Rothmannia vietnamensisB147

Table 5, continued.SpeciesType ofanticlinal wall outlineRothmannia wittiiBABERRANT AND RELATED TAXARothmannia macrophyllaBRothmannia globosaAKochummenia parviflora ?Kochummenia stenopetalaCNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina.from other epidermal cells), or with anisocytic stomata (in which the stoma issurrounded by three cells, one of which is usually smaller than the other twoepidermal cells). Baranova (1972) has advocated that the paracytic type as primitivewithin the angiosperms.The stomata in Kochummenia stenopetala were observed in the present workto be exclusively anisoparactyic, but a mixed condition occurs in the two taxa thathave aberrant morphological characters (see preceding chapter), i.e., R. macrophyllaand R. globosa, which cannot be distinguished from the other Rothmmania speciesinvestigated (see Table 6 for details).Thus, stomatal type does not appear to be taxonomically useful at bothspecific and generic levels.5.4.2 Guard cell dimensions and stomatal outlineThe guard cell or stomatal dimensions of the investigated Rothmannia speciesare very variable.The length varies from 11.3 µm to 33.2 µm, while the widthvaries from 5.0 µm to 22.0 µm. Based on Wilkinson (1979), the stomatal length inRothmannia can be considered within the small-to-medium size range (i.e., from148

Table 6. (this page and the following) Stomatal types on lower leaf surfaces of various taxa in theRothmannia complex.SpeciesStomata typeMALESIARothmannia anisophylloidesparacytic, anisoparacytic, rarely anisocyticRothmannia forstenianaparacytic, sometimes anisoparacyticRothmannia gracilifloraparacytic, anisoparacyticRothmannia grandisanisoparacytic, paracyticRothmannia kassamensisparacyticRothmannia lagunensisparacytic, anisoparacyticRothmannia leytensisparacyticRothmannia macromeraparacyticRothmannia merrilliiparacytic, anisoparacyticRothmannia negrosensis*paracyticRothmannia nigrescensparacyticRothmannia papuanaparacyticRothmannia pseudoternifolia var. pseudoternifoliaparacyticRothmannia pseudoternifolia var. hispidaparacyticRothmannia ridsdaleiparacytic, anisoparacyticRothmannia schoemanniiparacyticRothmannia sundaensisparacyticRothmannia uvarioidesparacyticRothmannia sp. indet 1 ?Rothmannia sp. indet 2paracyticOUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaeRothmannia capensisRothmannia fischeri ssp. fischeriRothmannia fischeri ssp. moramballaeRothmannia fischeri ssp. verdcourtiiRothmannia hispidaRothmannia ravaeRothmannia urcelliformisparacyticparacyticparacytic, anomocyticparacytic, anomocytic to anisocyticparacyticparacytic, anisoparacytic, anomocyticto anisocyticparacytic, sometimes anomocyticanomocytic to paracytic, sometimesanisocyticAfrica (corolla lobes contorted to the left)Rothmannia englerianaRothmannia longifloraRothmannia lujaeRothmannia manganjaeRothmannia whitfieldiiAsiaRothmannia attopevensisRothmannia eucodonRothmannia kampucheanaRothmannia pulcherrimaRothmannia sootepensisparacyticparacytic, anisocytic, sometimes anomocyticparacytic, anisoparacyticparacyticparacyticparacytic, anomocyticparacytic, anisoparacyticparacyticparacyticparacytic149

Table 6, continued.SpeciesStomata typeRothmannia venalisparacytic, anisoparacyticRothmannia vidalii ?Rothmannia vietnamensisparacyticRothmannia wittiiparacyticABERRANT AND RELATED TAXARothmannia macrophyllaRothmannia globosaKochummenia parviflora ?Kochummenia stenopetalaanisoparacyticparacytic, anisoparacyticparacytic, anisoparacytic, sometimesanomocyticNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina.< 15 µm long, considered small, up to about 38 µm, beyond which is consideredlarge).Although the length and width may be considered variable amongst theMalesian species, they can be used to differentiate among certain African species.Guard cell width can also distinguish among certain mainland Asian species.Stomatal outline in Rothmannia species is generally variable, particularly inthe Asian species, in which they vary from elliptic, broadly elliptic to rounded, and(rarely to) oblong or narrowly elliptic. However, it is observed that among theAfrican species, a number have an exclusively broadly elliptic stomatal outline, e.g.,R. longiflora (Fig. 34E) whereas others may have stomatal outlines varying from(elliptic) broadly elliptic to rounded, e.g. R. capensis (Fig. 34I), R. engleriana (Fig.34A), R. fischeri ssp. moramballae (Fig. 34J), and R. manganjae (Fig. 34B). Only acouple of species have exclusively elliptic stomatal outlines, e.g., R. annae and R.lujae (Fig. 34K). In contrast, many species from Asia and SW Pacific have generallyelliptic stomatal outlines, e.g., R. eucodon (Fig. 34L), R. papuana (Figs. 34C & D)and R. schoemannii (Fig. 34G). This may vary into broadly elliptic outlines (e.g., R.150

151

.152

153

grandis, Fig. 34F, and R. vietnamensis, Fig. 34M). Only a few Asian taxa havebroadly elliptic to rounded stomatal outlines, e.g., R. kampucheana, R.sootepensis, R. sundaensis (Fig. 34H) and R. sp. indet 2. Exclusively narrowlyelliptic stomatal outlines can be found in R. uvarioides and exclusively oblongoutlines in R. vidalii (see Table 7 for details).The stomatal length, width and length/width ratios for K. stenopetala, R.macrophylla and R. globosa are not individually distinguished. The stomatal outlinefor K. stenopetala varies from elliptic to narrowly elliptic (Fig. 34N), whereas in R.macrophylla (Fig. 34O) and R. globosa (Fig. 34P), it is exclusively elliptic, and socannot be distinguished from that in the other Rothmannia species.Thus, guard cell length, width, length-width ratio and stomatal outline may beused to a very limited extent in differentiating species within Rothmannia and appearnot useful at all at the generic level.5.4.3 Level of stomata in relation to epidermal cellsThe majority of the investigated Rothmannia species have stomata that are atthe same level as the epidermal cells, including the Asian R. merrillii (Fig. 35F), R.negrosensis (Fig. 35I), and R. sootepensis (Fig. 35G); and the African R. whitfieldii(Fig. 35A), R. annae (Fig. 35B), R. lujae (Fig. 35C), R. fischeri ssp. verdcourtii (Fig.35E) and R. manganjae (Fig. 35H). However, the stomata may also vary from beingat the same level to being sunken (depressed) in relation to the epidermal cells, in R.pseudoternifolia var. pseudoternifolia and R. schoemannii (Fig. 35K) (Asian) and R.longiflora (African). Exclusively sunken stomata appear to occur in e.g., R. eucodon(Fig. 35J), R. ridsdalei (Fig. 35M) (both Asian) and R. fischeri ssp. fischeri (African,Fig. 35L) (see Table 8 for details).154

Table 7. (this page and the following) Guard cell length (GCL), width (GCW), length-width ratios(GCL:GCW) and stomatal outline (SO) on lower leaf surfaces of various taxa in the Rothmanniacomplex.Species Guard cell Guard cell GCL:GCW StomatalLength Width (GCW) Ratio Outline (SO)(GCL)MALESIARothmannia anisophylloides 17.3–(21.9)–25.2 10.8–(12.2)–13.4 1.42–(1.80)–2.16 elliptic to broadlyellipticRothmannia forsteniana 21.3–(24.6)–31.1 11.8–(13.8)–16.5 1.46–(1.78)–2.29 ellipticRothmannia graciliflora 15.6–(19.8)–23.9 10.4–(11.7)–14.4 1.28–(1.70)–2.11 oblong to ellipticRothmannia grandis 14.0–(20.2)–26.8 9.7–(13.4)–18.5 1.05–(1.51)–2.15 broadly elliptic toellipticRothmannia kassamensis 21.3–(25.0)–28.5 12.0–(15.2)–19.1 1.38–(1.66)–2.00 elliptic to broadlyellipticRothmannia lagunensis 18.8–(22.7)–28.2 11.0–(14.5)–18.9 1.33–(1.58)–2.12 ellipticRothmannia leytensis 16.9–(22.5)–27.3 11.1–(15.1)–18.5 0.91–(1.51)–1.88 ellipticRothmannia macromera 19.4–(23.6)–26.9 12.2–(14.1)–18.2 1.32–(1.68)–1.90 elliptic to oblongRothmannia merrillii 21.1–(23.4)–27.7 12.0–(15.1)–17.6 1.24–(1.56)–1.92 broadly ellipticRothmannia negrosensis *20.1–(23.0)–27.8 *10.9–(13.3)–14.8 *1.40-(1.56)–1.92 *ellipticRothmannia nigrescens 20.6–(24.9)–29.9 11.4–(14.9)–17.1 1.24-(1.68)–2.08 ellipticRothmannia papuana 18.1–(21.2)–24.4 9.5–(11.2)–12.8 1.52-(1.92)–2.34 ellipticRothmannia pseudoternifolia 13.8–(22.1)–30.4 9.5–(14.2)–21.9 1.09–(1.57)–2.46 broadly elliptic,var. pseudoternifoliaoblong to ellipticRothmannia pseudoternifolia 12.3–(17.9)–27.6 5.0–(10.5)–20.1 1.02–(1.84)–2.87 elliptic to broadlyvar. hispidaellipticRothmannia ridsdalei 12.5–(19.0)–26.9 5.7–(9.9)–15.0 1.58–(1.97)–2.70 ellipticRothmannia schoemannii 16.0–(22.3)–30.8 7.1–(11.6)–15.7 1.27–(1.98)–3.02 ellipticRothmannia sundaensis 17.1–(19.9)–23.6 11.5–(13.3)–16.1 1.21–(1.51)–1.87 broadlly elliptic toroundedRothmannia uvarioides 21.1–(23.0)–25.4 13.8–(15.6)–18.4 1.24–(1.48)–1.72 narrowly ellipticRothmannia sp. indet 1 ? ? ? ?Rothmannia sp. indet 2 19.9–(24.6)–29.3 15.4–(17.4)–19.8 1.12–(1.42)–1.65 broadly elliptic toroundedOUTSIDE MALESIAAfrica (corolla lobescontorted to the right)Rothmannia annae 19.9–(22.9)–26.2 12.2–(14.4)–16.5 1.33–(1.59)–1.97 ellipticRothmannia capensis 17.7–(21.2)–24.5 11.1–(13.9)–16.4 1.25–(1.54)–1.89 elliptic to roundedRothmannia fischeri ssp. 25.0–(26.9)–30.0 13.5–(16.9)–19.6 1.29–(1.61)–1.96 broadly ellipticfischeriRothmannia fischeri ssp. 20.9–(23.0)–24.9 15.9–(17.3)–19.5 1.13–(1.33)–1.47 broadly elliptic tomoramballaeroundedRothmannia fischeri ssp. 24.4–(27.3)–30.7 15.0–(18.2)–20.9 1.30–(1.51)–1.69 broadly ellipticverdcourtiiRothmannia hispida 14.3–(16.6)–20.5 8.5–(11.0)–13.0 1.31–(1.52)–2.06 broadly ellipticRothmannia ravae 17.9–(23.8)–26.9 14.9–(17.7)–20.3 1.04–(1.35)–1.63 rounded tobroadly ellipticRothmannia urcelliformis 18.7–(21.1)–23.9 12.0–(13.8)–15.5 1.40–(1.53)–1.75 broadly elliptic155

Table 7, continued.Species Guard cell Guard cell GCL:GCW StomatalLength (GCL) Width (GCW) Ratio Outline (SO)Africa (corolla lobes contortedto the left)Rothmannia engleriana ? ? ? broadly ellipticto roundedRothmannia longiflora 22.4–(24.9)– 27.6 15.8–(18.2)–20.4 1.21–(1.37)–1.63 broadly ellipticRothmannia lujae 15.8–(18.2)–23.2 11.1–(13.3)–15.9 1.12–(1.37)–1.60 ellipticRothmannia manganjae 25.3–(28.4)–33.2 16.7–(19.6)–22.0 1.19–(1.45)–1.64 broadly ellipticto roundedRothmannia whitfieldii 21.2–(24.5)–28.2 15.9–(18.0)–20.5 1.19–(1.37)–1.58 broadly ellipticto roundedAsiaRothmannia attopevensis 21.4–(25.2)–29.5 11.8–(15.0)–18.1 1.38–(1.70)–2.14 ellipticRothmannia eucodon 18.2–(21.4)–25.2 10.5–(13.1)–15.7 1.24–(1.64)–2.11 ellipticRothmannia kampucheana 17.0–(23.2)–26.6 13.8–(16.4)–18.8 0.98–(1.43)–1.93 broadly ellipticto roundedRothmannia pulcherrima 11.3–(17.9)–22.3 10.9–(12.0)–13.5 0.94–(1.49)–1.69 elliptic tobroadly ellipticRothmannia sootepensis 13.9–(17.9)–24.4 8.4–(13.0)–18.9 1.00–(1.40)–2.05 broadly ellipticto roundedRothmannia venalis 19.3–(22.7)–26.1 15.1–(16.3)–18.0 1.09–(1.39)–1.65 broadly ellipticto ellipticRothmannia vidalii ? ? ? oblongRothmannia vietnamensis 14.5–(18.4)–21.8 11.0–(13.0)–16.6 1.07–(1.42)–1.72 elliptic tobroadly ellipticRothmannia wittii 19.2–(20.7)–22.6 11.1–(12.5)–14.0 1.41–(1.66)–2.01 ellipticABERRANT ANDRELATED TAXARothmannia macrophylla 21.0–(22.8)–25.6 13.2–(15.0)–17.5 1.31–(1.52)–1.72 ellipticRothmannia globosa 19.4–(23.0)–25.9 12.1–(15.2)–17.4 1.30–(1.52)–1.94 ellipticKochummenia parviflora ? ? ? ?Kochummenia stenopetala 12.6–(19.7)–26.6 5.7–(10.7)–19.5 1.28–(1.97)–3.00 elliptic tonarrowlyellipticNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina; values in parentheses are average values.156

157

158

Table 8. (this page and the following) Level of stomata in relation to epidermal cells on lower leafsurfaces (LSE) of various taxa in the Rothmannia complex.SpeciesLSEMALESIARothmannia anisophylloidessunkenRothmannia forstenianasame levelRothmannia graciliflorasame levelRothmannia grandissame levelRothmannia kassamensissunkenRothmannia lagunensissame levelRothmannia leytensissame levelRothmannia macromerasunkenRothmannia merrilliisame levelRothmannia negrosensis*same levelRothmannia nigrescenssunkenRothmannia papuanasunkenRothmannia pseudoternifolia var. pseudoternifoliasunken to same levelRothmannia pseudoternifolia var. hispidasunkenRothmannia ridsdaleisunkenRothmannia schoemanniisunken to same levelRothmannia sundaensissame levelRothmannia uvarioidessame levelRothmannia sp. indet 1 ?Rothmannia sp. indet 2same levelOUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaesame levelRothmannia capensissame levelRothmannia fischeri ssp. fischerisunkenRothmannia fischeri ssp. moramballaesame levelRothmannia fischeri ssp. verdcourtiisame levelRothmannia hispida ?Rothmannia ravaesame levelRothmannia urcelliformissame levelAfrica (corolla lobes contorted to the left)Rothmannia englerianaRothmannia longifloraRothmannia lujaeRothmannia manganjaeRothmannia whitfieldiisame levelsame level to sunkensame levelsame levelsame level159

Table 8, continued.SpeciesLSEAsiaRothmannia attopevensisRothmannia eucodonRothmannia kampucheanaRothmannia pulcherrimaRothmannia sootepensisRothmannia venalisRothmannia vidaliiRothmannia vietnamensisRothmannia wittiisunkensunkensame levelsame levelsame levelsame levelsame levelsame levelsame levelABERRANT AND RELATED TAXARothmannia macrophylla ?Rothmannia globosasunkenKochummenia parviflora ?Kochummenia stenopetalasame levelNotes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk(*) indicating measurements from apical portion from the leaf lamina.The level of the stomata in relation to epidermal cells does not appear to beuseful at the generic level. A limited sampling of Kochumennia (represented by K.stenopetala) indicates that the stomata are at the same level as the epidermal cells(Fig. 35D). In the morphologically aberrant taxon, R. globosa, the stomata aresunken in relation to the epidermal cells (Fig. 35N). These conditions are also foundgenerally among the other Rothmannia species. This feature was not investigated forR. macrophylla.Thus, the elevation of stomata in relation to epidermal cells may not be a veryclear-cut character and may be useful for taxonomic utility at the specific level only.5.4.4 Outer stomatal ledge: aperture length, width and L/W ratioThe outer stomatal ledge aperture length and width of the investigatedRothmannia species are very variable. The length varies from 2.7 µm to 18.4 µm160

long with average length ranges from 4.3 µm to 13.4 µm. The width varies from 0.7µm to 10.5 µm wide, with average width ranges from 1.2 µm to 7.2 µm.Although, the length values may be considered variable amongst theMalesian species, they can be used to differentiate among certain African andmainland Asian species of Rothmannia. Furthermore, the width values of the outerstomatal ledge aperture can apparently be used to distinguish between certain speciesin Rothmannia.Similarly, although, the length-width ratios (L/W) of the outer stomatal ledgeaperture are variable, they can be used to distinguish between certain species inRothmannia. The L/W ratio ranges from 0.82–15.25 whereas the average valueranges from 1.69–7.63 (see Table 9 for details).It can be deduced that the outer stomatal ledge aperture length and lengthwidthratios are not distinguishable between genera in the Rothmannia s.l. complex.However, the outer stomatal ledge aperture width is considered relatively wider inthe aberrant taxon, R. macrophylla, i.e., 4.1–6.9 µm compared to Kochummeniastenopetala (1.3–3.8 µm) but overlaps with R. globosa (1.8–4.8 µm) and otherRothmannia species.Thus, the outer stomatal ledge aperture length, width and L/W ratios can beused only to a small extent in distinguishing certain species within Rothmannia.5.4.5 Outer stomatal ledge: level in relation to guard cells andcoverageIn the majority of the Asian Rothmannia species, the outer stomatal ledgeappears to be raised in relation to the guard cells, such as R. merrillii (Fig. 35F), R.negrosensis (Fig. 35I), R. schoemannii (Fig. 35K), R. ridsdalei (Fig. 35M), R.sootepensis (Fig. 35G), R. eucodon (Fig. 35J). The ledge is at the same level as the161

Table 9. (this page and the following) Outer stomatal ledge aperture length (OSLL), width (OSLW)and length-width ratio (OSLL:OSLW) on lower leaf surfaces of various taxa in the Rothmanniacomplex.Species OSLL OSLW OSLL:OSLWMALESIARothmannia anisophylloides 7.0–(10.7)–14.9 1.2–(2.0)–2.9 3.26–(5.66)–10.28Rothmannia forsteniana 6.6–(10.5)–14.8 1.1–(1.9)–3.2 3.13–(6.05)–11.60Rothmannia graciliflora 5.1–(7.1)–10.1 1.1–(1.6)–2.4 3.11–(4.57)–6.25Rothmannia grandis 3.4–(7.2)–11.6 1.3–(2.1)–2.4 1.41–(3.57)–7.76Rothmannia kassamensis 10.2–(12.8)–16.1 1.2–(2.1)–3.0 3.77–(6.26)–10.44Rothmannia lagunensis 6.2–(8.4)–12.3 1.4–(2.0)–3.1 2.90–(4.29)–6.52Rothmannia leytensis 4.4–(8.0)–11.8 1.3–(1.9)–2.7 2.28–(4.36)–6.67Rothmannia macromera 8.8–(11.3)–16.9 1.0–(1.8)–3.0 3.45–(7.06)–15.25Rothmannia merrillii 8.1–(11.5)–15.5 2.0–(2.9)–4.5 2.23–(4.11)–5.69Rothmannia negrosensis *7.7–(11.4)–15.4 *2.0–(2.9)–4.0 *1.92–(4.22)–7.89Rothmannia nigrescens 6.2–(9.2)–12.2 1.2–(1.8)–2.7 2.38–(5.45)–7.60Rothmannia papuana 8.3–(10.0)–11.3 1.0–(1.4)–2.6 3.54–(7.63)–11.88Rothmannia pseudoternifolia 4.0–(10.6)–18.4 1.0–(2.3)–5.8 1.56–(5.20)–13.34var. pseudoternifoliaRothmannia pseudoternifolia 3.8–(8.7)–13.6 1.2–(1.9)–3.0 2.12–(4.75)–8.02var. hispidaRothmannia ridsdalei 5.3–(8.4)–12.2 1.3–(2.0)–3.2 2.43–(4.38)–8.14Rothmannia schoemannii 4.4–(8.5)–11.2 0.7–(1.7)–2.6 3.29–(5.38)–10.25Rothmannia sundaensis 5.9–(9.1)–13.8 1.0–(1.8)–2.9 2.15–(5.55)–10.25Rothmannia uvarioides 7.4–(9.0)–12.6 2.7–(3.4)–4.5 1.63–(2.70)–4.01Rothmannia sp. indet 1 ? ? ?Rothmannia sp. indet 2 7.7–(10.9)–13.5 3.3–(4.7)–6.5 1.43–(2.35)–3.41OUTSIDE MALESIAAfrica (corolla lobes contorted to theright)Rothmannia annae 6.1–(8.6)–12.1 1.7–(3.6)–5.1 1.63–(2.61)–5.39Rothmannia capensis 5.4–(7.40)–9.8 1.4–(3.6)–6.0 1.05–(2.24)–4.85Rothmannia fischeri ssp. fischeri 9.1–(10.6)–13.5 4.0–(6.3)–8.2 1.27–(1.72)–2.42Rothmannia fischeri ssp. moramballae 7.5–(10.3)–12.8 2.7–(4.4)–6.8 1.58–(2.42)–3.19Rothmannia fischeri ssp. verdcourtii 10.6–(12.4)–14.1 4.8–(6.4)–7.8 1.50–(1.97)–2.41Rothmannia hispida 2.7–(4.3)–5.9 1.0–(1.5)–2.6 1.54–(3.11)–4.68Rothmannia ravae 7.7–(9.9)–12.5 4.6–(5.9)–7.1 1.34–(1.69)–2.10Rothmannia urcelliformis 5.0–(6.6)–9.7 1.8–(2.6)–3.6 1.73–(2.62)–5.04Africa (corolla lobes contorted to theleft)Rothmannia engleriana ? ? ?Rothmannia longiflora 10.0–(12.5)–14.3 4.1–(6.4)–10.5 1.26–(1.99)–2.52Rothmannia lujae 4.5–(7.1)–9.2 1.7–(2.7)–4.2 1.06–(2.77)–4.47Rothmannia manganjae 10.6–(12.4)–14.9 5.4–(6.6)–7.6 1.45–(1.89)–2.28Rothmannia whitfieldii 10.7–(13.4)–15.6 5.9–(7.2)–8.4 1.34–(1.88–2.34162

Table 9, continued.Species OSLL OSLW OSLL:OSLWAsiaRothmannia attopevensis 11.1–(13.2)–16.8 1.5–(2.6)–3.4 3.40–(5.44)–8.60Rothmannia eucodon 6.2–(8.7)–13.7 1.0–(1.5)–2.4 3.76–(6.63)–13.62Rothmannia kampucheana 6.8–(8.2)–10.8 2.0–(3.9)–5.4 1.50–(2.18)–3.84Rothmannia pulcherrima 5.1–(7.3)–9.9 0.7–(1.2)–1.7 3.26–(6.40)–12.00Rothmannia sootepensis 3.6–(8.2)–12.7 1.3–(2.8)–4.5 1.36–(3.30)–8.50Rothmannia venalis 7.6–(9.9)–12.5 3.6–(4.5)–5.5 1.38–(2.21)–3.19Rothmannia vidalii ? ? ?Rothmannia vietnamensis 4.0–(6.7)–9.6 1.4–(2.2)–3.5 1.89–(3.20)–5.23Rothmannia wittii 6.4–(7.8)–9.2 2.0–(3.2)–7.8 0.82–(2.69)–3.65ABERRANT AND RELATED TAXARothmannia macrophylla 10.5–(12.1)–13.7 4.1–(5.5)–6.9 1.71–(2.26)–3.05Rothmannia globosa 4.7–(8.8)–12.9 1.8–(3.2)–4.8 1.75–(2.91)–4.57Kochummenia parviflora ? ? ?Kochummenia stenopetala 6.7–(9.6)–12.2 1.3–(2.3)–3.8 2.50–(4.40)–7.00Notes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina; values in parentheses are average values.guard cells only in three species, i.e., R. graciliflora, R. lagunensis and R. sp. indet 2.Most African species have their outer stomatal ledge at the same level as the guardcells, e.g., R. whitfieldii (Fig. 35A), R. annae (Fig. 35B) and R. lujae (Fig. 35C), andonly rarely is the ledge raised, i.e., in R. fischeri ssp. verdcourtii (Fig. 35E) and R.fischeri ssp. fischeri (Fig. 35L), R. engleriana and R. manganjae (Fig. 35H). InKochummenia stenopetala (Fig. 35D) and R. globosa (Fig. 35N), the outer stomatalledge is at the same level as the guard cells (see Table 10 for details).The outer stomatal ledge coverage can be very variable in the Malesianspecies of Rothmannia, i.e., varying from intermediate (coverage ¼–½ of the outerstomatal ledge aperture) to wide (coverage > ½ of the outer stomatal ledge aperture)in e.g., R. grandis and R. merrillii (Fig. 35F); but consistently wide in others, e.g., R.graciliflora, R. lagunensis, R. negrosensis (Fig. 35I) and R. ridsdalei (Fig. 35M).Intermediate ledge coverage is found in e.g., R. schoemannii (Fig. 35K) and R.sundaensis. In the mainland Asian species, e.g., R. kampucheana, R. pulcherrima163

and R. sootepensis (Fig. 35G), and the African species, e.g., R. annae (Fig. 35B), R.fischeri ssp. fischeri (Fig. 35L), R. fischeri ssp. verdcourtii (Fig. 35E), R. lujae (Fig.35C), R. manganjae (Fig. 35H) and R. whitfieldii (Fig. 35A), the outer stomatal ledgecoverage is predominantly wide. Consistently intermediate outer stomatal ledgecoverage is found in R. attopevensis, R. eucodon (Fig. 35J) and R. wittii (mainlandAsian). In R. urcelliformis (African), the outer stomatal ledge coverage varies fromintermediate to wide (see Table 10 for details). None of the taxa surveyed hadnarrow outer stomatal ledge coverage, i.e., < ¼ of the outer stomatal ledge aperture.In conclusion, the level of the outer stomatal ledge in relation to guard cellsand also the outer stomatal ledge coverage, do not appear to distinguish individualgroups or genera very well. Both Kochummenia stenopetala (Fig. 35D) and theaberrant taxon, R. globosa (Fig. 35N) have outer stomatal ledges that are at the samelevel as the guard cells, a feature also seen in other Rothmannia species.Unfortunately, this feature was also not studied for the other aberrant taxon, i.e., R.macrophylla. Similarly, the outer stomatal ledge coverage for both Kochummeniastenopetala (Fig. 35D) and the aberrant taxon, R. globosa (Fig. 35N) are wide,whereas in R. macrophylla, it is intermediate, as also found in some Rothmanniaspecies.Thus, the level of the outer stomatal ledge in relation to guard cells and alsothe outer stomatal ledge coverage may be only occasionally useful taxonomically atthe specific level.164

Table 10. (this page and the following) Level of outer stomatal ledge in relation to guard cells (OSLR(E)) and coverage (OSLR (C)) on lower leaf surfaces of various taxa in the Rothmannia complex.Species OSLR (E) OSLR (C)MALESIARothmannia anisophylloides raised IRothmannia forsteniana raised IRothmannia graciliflora same level WRothmannia grandis raised I, WRothmannia kassamensis raised WRothmannia lagunensis same level WRothmannia leytensis raised WRothmannia macromera raised IRothmannia merrillii raised I, WRothmannia negrosensis *raised *WRothmannia nigrescens raised I, WRothmannia papuana raised I, WRothmannia pseudoternifolia var. pseudoternifolia raised I, WRothmannia pseudoternifolia var. hispida raised I, WRothmannia ridsdalei raised WRothmannia schoemannii raised IRothmannia sundaensis raised IRothmannia uvarioides raised IRothmannia sp. indet 1 ? ?Rothmannia sp. indet 2 same level WOUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annae same level WRothmannia capensis same level WRothmannia fischeri ssp. fischeri raised WRothmannia fischeri ssp. moramballae same level WRothmannia fischeri ssp. verdcourtii raised WRothmannia hispida ? ?Rothmannia ravae same level WRothmannia urcelliformis same level I, WAfrica (corolla lobes contorted to the left)Rothmannia engleriana raised WRothmannia longiflora same level WRothmannia lujae same level WRothmannia manganjae raised WRothmannia whitfieldii same level W165

Table 10, continued.Species OSLR (E) OSLR (C)AsiaRothmannia attopevensis raised IRothmannia eucodon raised IRothmannia kampucheana raised WRothmannia pulcherrima raised WRothmannia sootepensis raised WRothmannia venalis raised WRothmannia vidalii ? ?Rothmannia vietnamensis raised WRothmannia wittii raised IABERRANT AND RELATED TAXARothmannia macrophylla ? IRothmannia globosa same level WKochummenia parviflora ? ?Kochummenia stenopetala same level WNotes: ?= unavailable data; I = intermediate; W=wide; italicized data indicating measurements from basal portion of the leaflamina; data with asterisk (*) indicating measurements from apical portion of the leaf lamina.5.4.6 Stomatal DensityWilkinson (1979) remarked that the mid-lamina region of the lower surface isconsidered the least variable in terms of stomatal density. In spite of this, the lowerleaf surface stomatal density in the investigated Rothmannia species is quite variablewithin a species and even a variety. It ranges from 24.0 mm - ² to 160.0 mm - ² with anaverage range from 29.5 to 89.6 mm - ² (see Table 11 for details).Although the stomatal density in the aberrant taxon, R. globosa is higher(58.0–75.0 mm - ²) compared to Kochummenia stenopetala (20.0–37.0 mm - ²) and R.macrophylla (30.0–40.0 mm - ²), it overlaps with species of Rothmannia.There appears to be little taxonomic utility for stomatal density in this group.166

Table 11. (this page and the following) Stomatal density on lower leaf surfaces of various taxa in theRothmannia complex.SpeciesStomatal density(mm - ²)MALESIARothmannia anisophylloides 37.0–(55.7)–73.0Rothmannia forsteniana 39.0–(44.5)–51.0Rothmannia graciliflora 48.0–(64.8)–81.0Rothmannia grandis 35.0–(63.9)–101.0Rothmannia kassamensis 29.0–(35.7)–42.0Rothmannia lagunensis 36.0–(41.8)–48.0Rothmannia leytensis 53.0–(60.4)–70.0Rothmannia macromera 28.0–(34.2)–42.0Rothmannia merrillii 25.0–(29.5)–37.0Rothmannia negrosensis *27.0–(32.5)–38.0Rothmannia nigrescens 36.0–(43.7)–53.0Rothmannia papuana 42.0–(45.5)–49.0Rothmannia pseudoternifolia var. pseudoternifolia 40.0–(65.7)–160.0Rothmannia pseudoternifolia var. hispida 37.0–(49.0)–72.0Rothmannia ridsdalei 40.0–(49.0)–56.0Rothmannia schoemannii 24.0–(45.9)–69.0Rothmannia sundaensis 48.0–(63.1)–70.0Rothmannia uvarioides 29.0–(36.8)–43.0Rothmannia sp. indet 1 ?Rothmannia sp. indet 2 36.0–(42.1)–46.0Africa (corolla lobes contorted to the right)Rothmannia annae 42.0–(45.9)–51.0Rothmannia capensis 44.0–(54.7)–63.0Rothmannia fischeri ssp. fischeri 42.0–(47.5)–56.0Rothmannia fischeri ssp. moramballae 40.0–(47.9)–58.0Rothmannia fischeri ssp. verdcourtii 29.0–(33.1)–37.0Rothmannia hispida 63.0–(79.7)–95.0Rothmannia ravae 44.0–(50.7)–58.0Rothmannia urcelliformis 59.0–(71.3)–84.0Africa (corolla lobes contorted to the left)Rothmannia engleriana 58.0–(72.4)–84.0Rothmannia longiflora 57.0–(64.0)–70.0Rothmannia lujae 56.0–(64.7)–78.0Rothnannia manganjae 36.0–(42.3)–48.0Rothmannia whitfieldii 82.0–(85.6)–88.0167

Table 11, continuedSpeciesStomatal density(mm - ²)AsiaRothmannia attopevensis 46.0–(60.7)–71.0Rothmannia eucodon 52.0–(56.8)–61.0Rothmannia kampucheana 73.0–(80.8)–93.0Rothmannia pulcherrima 80.0–(89.6)–97.0Rothmannia sootepensis 46.0–(72.3)–107.0Rothmannia venalis 49.0–(54.1)–59.0Rothmannia vidalii ?Rothmannia vietnamensis 66.0–(85.4)–97.0Rothmannia wittii 55.0–(67.1)–89.0RELATED AND ABERRANT TAXARothmannia macrophylla 30.0–(36.1)–40.0Rothmannia globosa 58.0–(67.3)–75.0Kochummenia parviflora ?Kochummenia stenopetala 20.0–(26.5)–37.0Notes: ? = data unavailable; italicized data indicating measurements from basal portion of the leaf lamina; data with asterisk (*)indicating measurements from apical portion of the leaf lamina; values in parentheses are average values.5.5 Leaf hairiness and trichome cuticular ornamentationThe lower leaf lamina for many of the investigated species of Rothmanniafrom Asia was found to be hairy but in several African species, it is completelyglabrous. Likewise, in the majority of the Malesian species, the leaves are in generalhairy, with various degrees and types of hairiness and very few are completelyglabrous, only in R. papuana and R. sundaensis.In the case of Kochummenia, the species are also generally found to be hairy,to the same degree and of the same type as in a number of Rothmannia species.Likewise, in the aberrant taxa, R. macrophylla and R. globosa, the indumentum onthe lower leaf surfaces is also not distinguishable from that of some Rothmanniaspecies.Trichomes comprise the main internal and external indumentum feature andare found on both the vegetative and floral parts of many taxa in the Rothmannia168

complex. In this study, only the hairs that occur on the lower leaf surfaces werestudied.The trichomes on the lower leaf surfaces of some investigated Rothmanniaspecies can be identified with the third type or “non-septate hairs” in Verdcourt’s(1958) system. Under LM examination, the trichomes in all the investigatedRothmannia species are observed to be simple, unbranched, unicellular and nonglandular(sensu Theobald et al., 1979) and of the cylindrical type (sensu Robbrecht,1988), i.e., outer hair walls thickened; individual cells not distinguished on thestraight outline of the cylindrical hair; septa (if present) much thinner than the outerwalls (see Figs. 36A–D).The outer surface or cuticular ornamentation of the trichomes is quite diverse,it can be exclusively smooth or warty, or varying from smooth to warty, sometimesstriated or minutely dippled in the taxa surveyed. Trichome surface ornamentationcan be recognized as the following types:(i) SmoothThis type does not have any markings on the trichome surface. These arefound consistently in the Asian and SW Pacific species, R. eucodon, R.kassamensis, R. lagunensis, R. uvarioides, R. venalis, R. vidalii and R. sp.indet 2.(ii) WartyThis type is characterized by short protuberances occurring sparsely over thetrichome surface. This is the most common type, found in R. anisophylloides,R. forsteniana, R. graciliflora, R. grandis, R. kampucheana, R. leytensis (Fig.37C), R. negrosensis, R. nigrescens (Fig. 37D) (Asian and SW Pacific); andR. engleriana (Fig. 37E), R. hispida and R. urcelliformis (Fig. 37B) (African).169

(iii) StriateIn this type, coarse striae form a meshwork over the trichome surface. This isonly found exclusively in R. macromera (Fig. 37H) and R. vietnamensis (Fig.37I).(iv) Minutely dippledThis type has minute depressions occurring all over the trichome surface.This can be found in R. wittii (Fig. 37J, Asian).In some taxa surveyed, the smooth and warty trichome surfaces can be foundin different individuals within the same species, e.g., R. attopevensis, R.pseudoternifolia var. hispida, R. pseudoternifolia var. pseudoternifolia (Fig. 37A),and R. schoemannii in Asia (see Table 12 for details).It can therefore be deduced that trichome ornamentation may not be useful indistinguishing genera very well. In Rothmannia, a diverse range of trichomeornamentation exists. In Kochummenia stenopetala (Fig 37F) and K. parviflora (Fig.37G), as well as R. macrophylla, the trichome ornamentation is warty, a conditionalso found in the majority of the Rothmannia species. In R. globosa, trichomes areabsent. Thus, trichome ornamentation is found to be of potential taxonomic utilityonly at the specific level.170

Table 12. (this page and the following) Trichome cuticular ornamentation (TCO) on lower leafsurfaces of various taxa in the Rothmannia complex.SpeciesTrichome cuticularOrnamentation (TCO)MALESIARothmannia anisophylloideswartyRothmannia forstenianawartyRothmannia graciliflorawartyRothmannia grandiswartyRothmannia kassamensissmoothRothmannia lagunensissmoothRothmannia leytensiswartyRothmannia macromerastriateRothmannia merrillii ?Rothmannia negrosensis*wartyRothmannia nigrescenswartyRothmannia papuanan.a.Rothmannia pseudoternifolia var.pseudoternifoliasmooth to wartyRothmannia pseudoternifolia var. hispidasmooth to wartyRothmannia ridsdalein.a.Rothmannia schoemanniismooth to wartyRothmannia sundaensisn.aRothmannia uvarioidessmoothRothmannia sp. indet 1 ?Rothmannia sp. indet 2smoothOUTSIDE MALESIAAfrica (corolla lobes contorted to the right)Rothmannia annaeRothmannia capensisRothmannia fischeri ssp. fischeriRothmannia fischeri ssp. moramballaeRothmannia fischeri ssp. verdcourtiiRothmannia hispidaRothmannia ravaeRothmannia urcelliformisn.a.n.a.n.a.n.a.n.a.wartyn.a.wartyAfrica (corolla lobes contorted to the left)Rothmannia englerianawartyRothmannia longifloran.a.Rothmannia lujaen.a.Rothmannia manganjaen.a.Rothmannia whitfieldii ?AsiaRothmannia attopevensisRothmannia eucodonRothmannia kampucheanasmooth to wartysmoothwarty171

Table 12, continued.SpeciesTrichome cuticularOrnamentation (TCO)Rothmannia pulcherriman.a.Rothmannia sootepensis ?Rothmannia venalissmoothRothmannia vidaliismoothRothmannia vietnamensisstriateRothmannia wittiiminutely dippledRELATED AND ABERRANT TAXARothmannia macrophyllaRothmannia globosaKochummenia parvifloraKochummenia stenopetalawartyn.a.wartywartyNotes: ? = data unavailable; n.a. = non-applicable; italicized data indicating measurements from basal portion of leaf lamina;data with asterisk (*) indicating measurements from apical portion of leaf lamina.ABCDFig. 36. LM images of the lower leaf surfaces of Rothmannia showing “non-septate”,simple, unbranched and unicellular or of cylindrical type trichomes. —A, R. pseudoternifoliavar. pseudoternifolia, B, R. attopevensis, C, R. wittii, D, R. macromera.172

173

174

5.6 Taxonomic value of lower leafsurface micromorphology within the Rothmannia complexPrior to this study, no documentation has been made of microcharacters of thelower leaf surfaces in members of the Rothmannia complex. Hence, this studyserves as a first attempt to assess the taxonomic value of various features of the lowerleaf surface micromorphology in this group.The findings of this study showed that certain characteristics in the domatia,leaf cuticle, stomata and trichomes of the lower leaf surfaces in Rothmannia areprobably and primarily only useful in distinguishing some species from others.Within the Malesian Rothmannia species, characters such as domatia location andtype, cuticular ornamentation on the lamina surface, the level of the outer stomatalledge in relation to guard cells, stomatal outline, leaf hairiness and trichome surfaceornamentation may be useful in differentiating certain species. To a lesser potential,the level of stomata in relation to epidermal cells, outer stomatal ledge coverage, andouter stomatal ledge width are only diagnostic in a few species. Nonetheless, as inthe Malesian R. pseudoternifolia (both varieties) and R. schoemannii, some of thesecharacters (level of stomata in relation to epidermal cells, outer stomatal ledgeaperture length and L/W ratio, outer stomatal ledge coverage, stomatal density, andtrichome outer surface ornamentation) may be very variable within the species itself.Some of these features may have a directly ecological basis, rather than beingof phylogenetic significance. In general, it is observed that the majority of theinvestigated Rothmannia species from Africa (and to some extent, some species frommainland Asia) have leaf characteristics that are generally adapted to drier orseasonal climate and also more open vegetation, by having e.g., more broadly ellipticto rounded stomatal outlines and more conspicuous (or wider-coveraging) outerstomatal ledges which are perhaps adaptations against water loss. In contrast, the175

Malesian species in general (especially those occurring within the wetter core areas)have more elliptic to broadly elliptic, sometimes to oblong (generally moreelongated) stomatal outlines, and outer stomatal ledges that are not very conspicuous(most of the species have intermediate coverage).It is noteworthy that a very limited number of specimens was used forstudying these characters in most of the species. Hence, the results obtained may nothave captured the whole variation that exists within the species. Only in the case ofR. pseudoternifolia (in var. pseudoternifolia), a sufficiently high number of sampleswere used. Hence, the large variation seen within this variety for most of theparameters (e.g., guard cell length and width; stomatal density; outer stomatal ledgelength and width; stomatal outline; and cuticular ornamentation of trichome) is notsurprising. According to Baas (1975), the variation below the species level(infraspecific variability) may be due to genetic variability or ecological factors. Forthis variety, it is likely that ecological factors could be significant because it is foundwithin a whole range of habitats (lowland to hill forests to c. 1640 m, includingkerangas forests, limestone and seasonal flood-plain areas).In some Malesian species, sections from the basal e.g., R. anisophylloides, R.kassamensis, R. macromera and R. uvarioides (New Guinea species) and the apicalportions, e.g., R. negrosensis (Philippines species) were used because ofunavailability of the mid-section portion. The apex section is considered the mostmature part of the leaf, while the basal portion the least mature (refer Stace, 1965).This may also contribute to the variation in character-states that were examined.According to Stace (1965), variation in cuticular characters may be due to threemajor causes, viz., age of the leaf or maturity; the environment in which the plant isfound and leaf position on the plant. Hence, it may not be surprising that characterssuch as stomatal density and size, and outer stomatal ledge aperture size, are to some176

extent very variable in Rothmannia. Wilkinson (1979) has also warned that stomatalfrequency or density could be much variable due to environmental conditions.Some of the lower leaf surface characteristics may have limited utility at ahigher taxonomic level. Kochummenia can be readily distinguished from Rothmanniaand the morphologically aberrant R. macrophylla, based on the unique pattern ofanticlinal wall outlines of epidermal cells. In R. globosa, the leaf surfacecharacteristics show some significant difference compared to most or all the othertaxa in Rothmannia, Kochummenia and R. macrophylla. These include a uniquegranular cuticular surface ornamentation; and the combination of guard cells sunkenin relation to epidermal cells and an outer stomatal ledge at the same level as theguard cells. As noted in Chapter 4, this taxon has a different branch system from therest of the other members of the Rothmannia complex.Hence, we can deduce here that most micro-characters of the lower leafsurface, are of restricted taxonomic utility. Perhaps, only the type of anticlinal walloutline of epidermal cells could be said to have some diagnostic value at the genericlevel.177