Zea mays

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the phloem and some represent companion cells_ The minor veins are enclosed within compact bundle sheaths (2.9, 3.3, 5.18) so that the vascular tissue is not normally directly exposed to the intercellular space system of the mesophyll. The sheath is often composed of parenchyma but sometimes a several-layered sheath is formed from parenchyma and sc1crenchyma. The minor veins usually contain protoxylem tracheids (5.17,5.18) but not vessels, while sieve elements are often lacking in the finest veins. Anatomy of the petiole in many leaves the vascular supply from the stem passes to the leaf blade via rhe petiole (1.17, 1.19, 5.3,5.10). The simplest vascular arrangement is a single, large crescent-shaped vein with adaxial xylem but several veins are often present (5.44). The peripheral ground tissue commonly contains collenchyma and sclerenchyma (3.23, 5.44). The leaves of many plants lie extended in day-light (5.45) but undergo a slow drooping at night 5.1 Large floating [eaves of the water [i1ies Nymphoeo gigonua (foreground) and Vietona amazonico (rear) which are t"onnecred by long petioles to the roorstock growing in the mud on [he bonom of the pond. The leaf storrnua arc confined to the adaxial surface which is exposed 10 the atmosphere and the spongy mesophyll on the abaxial leaf surface has very extensive air spaces to assist ....o1lh aer:rtion, whits[ large branched sclereids strengthen this lISsm::. In Victoria largc spines occur on Ihe ribs of the abaxial epidermis and the leaves are capable of bearing the weighl of a moderate-sized adult human. 100 (5.46) in response to various external or internal stimuli. This movement results from loss of turgor in the extensive zone of peripheral parenchyma located in a joint-like thickening (pulvinus) present at the base of the petiole, or at the bases of petiolules in compound leaves. The more rapid response of the leaf of the sensitive Mimosa (M. pt/dica) to [Ouch is also due to the activity of the numerous pulvini. In both deciduous and evergreen species an abscission :lOne occurs at the base of the petiole (5.47). Here the xylem is often restricted to tracheids or narrow, often d.iscontinuous, vessels (5.48). Such tracheary elements reduce the risk of embolism when the blade is wind damaged or eaten and also when the senescent leaf abscises. At the basal face of the abscission zone a subcrised protective layer of cork develops which covets the scar (5.49) formed when the petiole becomes detached. In some perennial monocotyledons several abscission zones occur and in palms [he leaf base may persist after the petiole and lamina are detached (5.50). 5.2 5.2 Clusrcrs of sword-shaped Ica"es borne on the evergrcen monocotyledon Pandanus. Due to a diffusc second'lry growth this specics can grow into large trees (d., 1.26).
5.3 ,--------------, 5.3 Large fan-shaped of the monocotyledon Licuala grandis. This palm is indigenous to S. E. Asia and Australia and bears simple leaves on long petioles. 5.4 Part of the compound leaf of the fcrn Angiopteris. "'lore the longitudinal midribs in each pinna from which lateral, dichotomously-branched veins supply the lamina. 5.5 5.6 ).) Hanging mass of the tropical ep,phytic flowering plam Tillandsia usm:oides (Spanish moss). This is rootless but the numerous fine, cylindrical leaves absorb water from the moist atmosphere. 5.6 Variegated plant uf Chlorophytul1l comosum (spider plam). The elongated, sword-shaped leaves arc typical of a monocotyledon. Note the leafy plantlct (1) which has developed adventitiously on the infiorts
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A Colour Atlas of PLA T STRUCTURE B
Page 4:
5 The green leaf 97 Introduction 97
Page 7 and 8:
• CHAPTER 1 Introduction The asso
Page 11:
1.6 1.6 L}'copusicon e$culentum (to
Page 15 and 16:
1.17 1.19 ,--------------::c-=-----
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1.22 1.22 Group of rail Cordy/hIe a
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1.32 B 24 1 6 \ -H-r 14 13 c 11 """
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times becomes highly lobed (2.15, 2
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stack (2.14, 2.52) of smooth cister
Page 34:
2.14 2.14 Diagram of the fine-struc
Page 43:
2.39 Longitudinally-sl:crionl:d l:h
Page 55: CHAPTER 3 Plant histology Disttibut
Page 60: 3.1 3.2 3.1 TS of the: petrified st
Page 66: 3.21 ,-------------, 3.23 3.2J Non-
Page 69: 3.31 TS of n cortienl mucil:lge duc
Page 72: 3.41 -+-2 3.39 L$ of the phloem of
Page 78: 3.58 80 3.56 3.56 TS of tbe seconda
Page 83 and 84: absent or may develop some distance
Page 85: 4.2 4.3 r-----;; 4.2 RLS of the ext
Page 91: 4.24 4.24 TS of a vascular bundle f
Page 97: secretion may temporarily accumulat
Page 112 and 113: 5.45 5.44 IS of the petiole of the
Page 114 and 115: 5.50 116 5.50 Base of the mature tr
Page 116 and 117: fibres often develop in the outer p
Page 120: 6.7 6.7 5hool of the monocotyledon
Page 129 and 130: 6.33 6.32 TS showing distribution o
Page 134: 7.4 I'neumatophores of Alliceimia n
Page 137: 7.14 l.S of a later:J.1 root primor
Page 142 and 143: 7.26 7.26 Fine rOOfS from a large t
Page 144 and 145: pappus (calyx, 8.9) of each floret
Page 146: tube frequently corers the embryo s
Page 155 and 156:
S.19 TS of imm,lIure pollen sacs in
Page 157:
8.25 8.25 Mature pollen grain of th
Page 169:
8.64 hnmarure fruir of rhe dleot)·
Page 180 and 181:
a tetraploid h3.S a double: set. Po
Page 183 and 184:
Vacuole An organelle bounded by rhe
Page 185 and 186:
Cell (continued) meiosis 158, 161,
Page 188:
Sanicula europea (sanicle) 68 Sanse
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Zea mays

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