View/Open - ResearchSpace - University of KwaZulu-Natal

More documents

Recommendations

Info

4.4 DISCUSSION Germination physiology A short rainy season plays an important role for the wild flowers of Namaqualand. Plants must complete their life-cycle during this period, ensuring successful germination and subsequent establishment due to sufficient moisture. Even under moist environmental conditions there may be constrains on germination to the seeds that are on the soil surface compared to those seeds that are buried and which form part of the soil seed bank (MEEKLAH, 1958; EVANS et al., 1967). This can be attributed to high fluctuations in moisture and humidity which results in unfavourable conditions for germination (MILLER & PERRY, 1968; DOWLING et al., 1971). Seed surface characteristics in modifying the seed/soil interface has been emphasized by SEDGLEY (1963) and HARPER AND BENTON (1966). These workers showed that germination was promoted when a greater area was in contact with the substrate. Hence size, surface and micropylar region are important factors of the seed to be considered for the process of water-uptake. Many Romulea species have a narrow and limited distribution and germination plays a significant role in their survival. It is therefore necessary to understand the seed structure of different Romulea species and their ecological relevance. In comparison to other species, high initial water content and fast imbibition of R. leipoldtii seeds can be attributed to its small seed size. Large surface area to volume ratio requires the seed to have more water reserves (as it is more prone to desiccation) and would allow the seed to absorb more water in a shorter time (when available). The small seed size of R. flava also requires it to have more water reserves to avoid dehydration. These species showed the roughest seed surface after R. rosea, R. leipoldtii and R. diversiformis, which further increase surface area and the risk of dehydration (but also allows it to imbibe more water in a shorter time). R. leipoldtii and R. flava are all found in areas with highly variable rainfall (Figure 2.21). The seeds of R. camerooniana are smooth and their seeds are larger than those of R. leipoldtii and R. flava, resulting in a small surface area to volume ratio. These seeds are however, small enough to have a relatively high imbibition rate because of the resulting larger surface area to volume ratio. This species also occur in areas with higher and more consistent rainfall than other species of this genus (Figure 2.7). The seeds of R. camerooniana therefore do not require a high initial water content. 111
Germination physiology The relatively low initial water content and slow water imbibition of R. monadelpha seeds can be attributed to their large size and smooth surface compared to the seeds of other Romulea species, while the relatively low water content of R. sabulosa seeds can be attributed to their relatively smooth seed surface and compact micropylar region. It is interesting to note that the eight species used in water content and imbibition experiments can be divided perfectly into their subgenera by looking at variability of their initial water content, as species in the subgenus Romulea (R. camerooniana, R. flava, R. leipoldtii and R. minutiflora) all had variable initial water content when compared to all studied species in the subgenus Spatalanthus (R. diversiformis, R. monadelpha, R. rosea and R. sabulosa). It was also noted that seed sizes of species in the subgenus Romulea had more variability compared to species in the subgenus Spatalanthus, which is a possible explanation for the variability in water content. The rough seed surface and membranous micropylar regions of R. rosea, enables them to absorb a relatively large amount of water; they also initiated an increase in imbibition rate 3 h before seeds of other species. R. minutiflora has a smooth seed surface, compact micropylar region and small seed size to facilitate its low water absorption capacity. The larger the seed, the higher the relative water capacity and imbibition, these are possible explanations why R. rosea is a more successful invasive plant than R. minutiflora and other species. The seeds of R. diversiformis and R. rosea showed high germination both under alternating and constant dark conditions at 10°C. These findings suggest that these seeds are not specifically light or dark requiring. Percentage germination of R. monadelpha seed was significantly higher under constant dark conditions at 15°C than any other treatment examined, which indicates a possible negatively photoblastic nature. However, this species had very low germination and therefore more investigation on seed physiology is required which may help improving germination of this species. On the other hand, R. flava seeds did not respond effectively when subjected to different temperatures under both light and dark conditions. Interestingly, this species exhibited increasing percentage germination as the cold stratification period was prolonged. It was observed that these seeds germinated during the stratification period. This suggests that R. flava seeds require a wet cold winter season for germination. R. sabulosa seeds did not respond to ex vitro germination but little germination was recorded in in vitro experiments. The 112
Page 1 and 2:
Propagation of Romulea species Pier
Page 3 and 4:
Contents 2.7 GERMINATION PHYSIOLOGY
Page 5 and 6:
Contents 5.3.1 Explants from seedli
Page 7 and 8:
Abstract The suitability of various
Page 9 and 10:
Declarations I Pierre André Swart,
Page 11 and 12:
Declarations DETAILS OF CONTRIBUTIO
Page 13 and 14:
Publications from this thesis ASCOU
Page 15 and 16:
List of Figures Figure 2.13: Suther
Page 17 and 18:
was significantly different from th
Page 19 and 20:
List of Tables Table 2.1: Names of
Page 21 and 22:
List of Abbreviations 2,4-D 2,4-Dic
Page 23 and 24:
Die vlakhaas spits sy oor hy het di
Page 25 and 26:
As die mens dan ook so sy dankbaarh
Page 27 and 28:
Introduction where a great number o
Page 29 and 30:
Introduction The subgenera Romulea
Page 31 and 32:
2 Literature review Leef van daad e
Page 33 and 34:
Literature review Figure 2.2: Life
Page 35 and 36:
Literature review Figure 2.4: Life
Page 37 and 38:
Literature review The plants are sh
Page 39 and 40:
Literature review flowers (DE VOS,
Page 41 and 42:
Literature review often found on cl
Page 43 and 44:
Literature review flowers of R. lei
Page 45 and 46:
Literature review flattened upper s
Page 47 and 48:
2.2.16 Romulea tabularis Literature
Page 49 and 50:
Literature review extinct, R. papyr
Page 51 and 52:
Literature review R. leipoldtii occ
Page 53 and 54:
Literature review Figure 2.8: Calvi
Page 55 and 56:
Literature review Figure 2.14: Fras
Page 57 and 58:
Figure 2.20: Nieuwoudtville weather
Page 59 and 60:
Literature review Figure 2.26: Grah
Page 61 and 62:
Literature review Figure 2.29: Diag
Page 63 and 64:
Literature review Figure 2.30: A te
Page 65 and 66:
Literature review Macronutrients ca
Page 67 and 68:
Literature review The soils of the
Page 69 and 70:
Literature review The embryo is the
Page 71 and 72:
Literature review Phase 2 is seen a
Page 73 and 74:
Literature review endogenous gibber
Page 75 and 76:
Literature review tolerable level (
Page 77 and 78:
Literature review these channels pe
Page 79 and 80:
Literature review 2.8.7 Seed dorman
Page 81 and 82:
Literature review the embryo (COPEL
Page 83 and 84:
Literature review germinated under
Page 85 and 86: Literature review (COPELAND, 1976).
Page 87 and 88: 2.9 BRIEF REVIEW OF IN VITRO CULTUR
Page 89 and 90: Literature review (DEBERGH, 1994).
Page 91 and 92: Literature review PIERIK (1997) sta
Page 93 and 94: Literature review The distinguishin
Page 95 and 96: Literature review The essential fun
Page 97 and 98: 2.9.3.4 Abscisic acid Literature re
Page 99 and 100: Table 2.6: Example of a matrix to e
Page 101 and 102: Literature review Young embryos req
Page 103 and 104: Literature review and the addition
Page 105 and 106: Literature review organ is then pro
Page 107 and 108: Literature review environmental str
Page 109 and 110: 2.11 IN VITRO FLOWERING Literature
Page 111 and 112: Literature review higher regenerati
Page 113 and 114: Subfamily Ixioideae (continued) Tri
Page 115 and 116: Literature review Table 2.8: Corm i
Page 117 and 118: 3 Investigation into the habitat of
Page 119 and 120: Soil sampling and analysis The firs
Page 121 and 122: Soil sampling and analysis Table 3.
Page 123 and 124: 4 Germination physiology 4.1 INTROD
Page 125 and 126: 4.2.2 Water content and imbibition
Page 127 and 128: Germination physiology (-N), phosph
Page 129 and 130: Germination physiology rosea seeds
Page 131 and 132: Germination physiology Figure 4.4:
Page 133 and 134: Germination (%) 50 40 30 20 10 0 77
Page 135: Germination (%) 100 80 60 40 20 0 c
Page 139 and 140: Germination physiology seeds of R.
Page 141 and 142: 5.2 MATERIALS AND METHODS In vitro
Page 143 and 144: In vitro culture initiation and mul
Page 145 and 146: 5.2.3 Explant comparison In vitro c
Page 159 and 160: 5.4 DISCUSSION In vitro culture ini
Page 163 and 164: 6 In vitro corm formation and flowe
Page 165 and 166: In vitro corm formation and floweri
Page 167 and 168: 6.3 RESULTS 6.3.1 Corm formation In
Page 177 and 178: Commercialization potential of Romu
Page 179 and 180: Commercialization potential of Romu
Page 181 and 182: BASKIN, C. C., and BASKIN, J. M. (1
Page 183 and 184: Literature cited DOWLING, P. M., CL
Page 185 and 186: Literature cited HILTON-TAYLOR, C.
Page 187 and 188:
Literature cited KUMAR, A., SOOD, A
Page 189 and 190:
Literature cited PIERIK, R. L. M. (
Page 191 and 192:
Literature cited STEINITZ, B., COHE
show all

View/Open - ResearchSpace - University of KwaZulu-Natal

Create successful ePaper yourself

Delete template?

Save as template?