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Germination physiology intact seed of these species may need a longer period of cold stratification, or culture conditions at 5°C. There is a period of about two months with average daily minimum temperatures of 5°C in Nieuwoudtville where R. sabulosa is found (Figure 2.20). Although R. diversiformis, R. flava, R. leipoldtii and R. minutiflora all had in vitro germination percentages higher than 57% at 15°C, seeds of other species showed very low germination. R. camerooniana was the only species of which neither the seeds germinated nor the embryos responded. Low viability of R. camerooniana seeds was indicated by TTC. However, all species endemic to South Africa showed positive responses to either seed or embryo germination treatments. The results of the temperature experiment for R. rosea confirms that of EDDY & SMITH (1975) who found that R. rosea seeds has a clear germination optimum in the temperature range of 9.5 to 13°C. These results suggest that invasive individuals of R. rosea could be eradicated (by mechanical or chemical control) when temperatures are low. EDDY & SMITH (1975) reported that pre-chilling of seeds or KNO3 treatment does not increase germination of this species. However, in the present study KNO3 significantly increased germination over the control. This result was confirmed where seed germination was low in Hoagland’s nutrient solution without K in comparison to the control (HS 50%). These findings suggest that the use of fertilizers containing high potassium should be avoided to reduce R. rosea invasion which will be higher in agricultural areas. It appears that seeds of R. diversiformis, R. flava, R. leipoldtii, R. minutiflora, R. monadelpha, and R. sabulosa all exhibit non-deep endogenous morphophysiological dormancy, as excised embryos showed a growth response and the causes could include a physiological germination inhibiting mechanism or an underdeveloped embryo (BASKIN & BASKIN, 1998). The percentage germination of R. rosea seeds on filter paper moistened with KNO3 was significantly higher than the control, this response to potassium nitrate is a characteristic of non-deep morphophysiological dormancy (COPELAND, 1976). The causes of non-deep physiological dormancy include the physical barrier created by covering structures, the resulting low oxygen supply to the embryo, inhibitors within the covering structures and/or physical/chemical changes in the covering structures (BASKIN & BASKIN, 1998). COPELAND (1976) states that the dormancy of such seeds can often be broken by a cold stratification treatment. This happened in the case of R. flava. However, this was not tested for R. leipoldtii and R. minutiflora due to limitations in seed availability. The 113
Germination physiology seeds of R. camerooniana appears to have deep endogenous morphophysiological dormancy, as excised embryos showed no growth response and the apparent causes may include a physiological germination inhibiting mechanism or rudimentary embryos (BASKIN & BASKIN, 1998). 4.5 SUMMARY • Germination experiments revealed that R. diversiformis and R. rosea seeds germinate best at 10°C. R. flava seeds germinate best when cold stratified for 21 days and R. monadelpha seeds showed some response at 15°C in the dark indicating photoblastically negative behaviour. • An initial in vitro germination experiment showed germination above 57% for R. diversiformis, R. leipoldtii, R. minutiflora and R. flava seeds placed at 15°C; while seeds of other species placed at 15°C had less than 30% germination. • Seeds of R. diversiformis, R. flava, R. leipoldtii, R. minutiflora, R. monadelpha and R. sabulosa may have non-deep endogenous morphophysiological dormancy, whereas seeds of R. camerooniana appear to have deep endogenous morphophysiological dormancy. 114
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Propagation of Romulea species Pier
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Contents 2.7 GERMINATION PHYSIOLOGY
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Contents 5.3.1 Explants from seedli
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Abstract The suitability of various
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Declarations I Pierre André Swart,
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Declarations DETAILS OF CONTRIBUTIO
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Publications from this thesis ASCOU
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List of Figures Figure 2.13: Suther
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was significantly different from th
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List of Tables Table 2.1: Names of
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List of Abbreviations 2,4-D 2,4-Dic
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Die vlakhaas spits sy oor hy het di
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As die mens dan ook so sy dankbaarh
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Introduction where a great number o
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Introduction The subgenera Romulea
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2 Literature review Leef van daad e
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Literature review Figure 2.2: Life
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Literature review Figure 2.4: Life
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Literature review The plants are sh
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Literature review flowers (DE VOS,
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Literature review often found on cl
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Literature review flowers of R. lei
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Literature review flattened upper s
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2.2.16 Romulea tabularis Literature
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Literature review extinct, R. papyr
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Literature review R. leipoldtii occ
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Literature review Figure 2.8: Calvi
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Literature review Figure 2.14: Fras
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Figure 2.20: Nieuwoudtville weather
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Literature review Figure 2.26: Grah
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Literature review Figure 2.29: Diag
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Literature review Figure 2.30: A te
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Literature review Macronutrients ca
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Literature review The soils of the
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Literature review The embryo is the
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Literature review Phase 2 is seen a
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Literature review endogenous gibber
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Literature review tolerable level (
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Literature review these channels pe
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Literature review 2.8.7 Seed dorman
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Literature review the embryo (COPEL
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Literature review germinated under
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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 and 136: Germination (%) 100 80 60 40 20 0 c
Page 137: Germination physiology The relative
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
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Literature cited PIERIK, R. L. M. (
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Literature cited STEINITZ, B., COHE
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