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2.8.11 Germination, dormancy and germination ecology in Iridaceae Literature review Geophytes are a very important component of Eurasian semi-deserts with cold winters. Geophytes belonging to Iridaceae in this biome exhibits morphophysiological dormancy (BASKIN & BASKIN, 1998). Such seeds are known to have underdeveloped embryos (BASKIN & BASKIN, 1998). Halophytes and emergent aquatics in the family of Iridaceae also exhibits morphophysiological dormancy (BASKIN & BASKIN, 1998). Iris angustifolia, Iris pseudacorus, Iris versicolor and Iris virginica are examples of such species (BASKIN & BASKIN, 1998). Two genera of the Iridaceae have been found in persistent seed banks (BASKIN & BASKIN, 1998). Accordingly, a species of Iridaceae could have morphological and/or morphophysiological dormancy. In a study by DIXON et al. (1995) it was found that a species in Iridaceae, Patersonia occidental, only germinated when treated with smoke. 2.8.12 Embryo and seedling morphology of Iridaceae Embryo’s of the Iridaceae are straight and poorly differentiated (TILLICH, 2003). Only at the seedling stage can three different groups, defined by their cotyledon morphology, be clearly distinguished (TILLICH, 2003). The three groups are the compact cotyledon group, the tubular cotyledon group and the assimilating cotyledon group (TILLICH, 2003). At the event of germination the cotyledonary sheath, hypocotyl and radicle are pushed through the micropyle region of the testa (TILLICH, 2003). The cotyledon then immediately bends at 90° in most cases (TILLICH, 2003). In Crocoideae the typical cotyledon is characterised by a remarkable elongation of the cotyledonary sheath and / or the development of a long coleoptile (TILLICH, 2003). The seedling morphology of Crocus and Romulea is quite rare (TILLICH, 2003). Here an elongated tubular structure is combined with a tubular cataphyll (TILLICH, 2003). Possible explanations for this is the pronounced hypogeous germination which is promoted by a strong contractile primary root (TILLICH, 2003). The cotyledons of these genera have also lost most of their ability to produce chlorophyll and appear white even in high light intensities (TILLICH, 2003). 61
2.9 BRIEF REVIEW OF IN VITRO CULTURE Literature review The term ”tissue culture” is actually a misnomer inherited from the field of animal tissue culture. Plant micropropagation involves the culture of a whole individual from isolated tissues, while animal tissue culture involves the culture of isolated tissues (KYTE & KLEYN, 1996). According to AHLOOWALIA et al. (2002), the process of micropropagation can be divided into five stages: the pre-propagation step (stage 0); the initiation of explants (stage I); the subculture of explants for multiplication or proliferation (stage II); shooting and rooting of the explants (stage III); and hardening off the cultured individuals (stage IV). The pre-propagation stage involves preparing the explant for aseptic culture. The explant and its response in vitro is significantly influenced by the phytosanitary and physiological conditions of the donor plant (KANE, 2004). Plant material used in clonal propagation should be taken from mother plants that have undergone the appropriate pre-treatment with fungicides and pesticides to minimize contamination in the in vitro cultures (AHLOOWALIA & PRAKASH, 2002). Such a piece of plant material is called an explant (SMITH, 2000b). A single explant can theoretically produce an infinite number of plants (KYTE & KLEYN, 1996). Explants can be obtained from meristems, shoot tips, macerated stem pieces, nodes, buds, flowers, peduncle pieces, anthers, petals, pieces of leaf or petiole, seeds, nucellus tissue, embryos, seedlings, hypocotyls, bulblets, bulb scales, cormels, radicles, stolons, rhizome tips, root pieces or protoplasts (KYTE & KLEYN, 1996). The explants should be surface decontaminated with antibiotic sprays before they are introduced into culture (AHLOOWALIA et al., 2002; KANE, 2004). In stage I an aseptic culture is initiated by inoculating the explant onto a sterile medium (AHLOOWALIA et al., 2002). Once such an explant is established it can be multiplied a number of times (AHLOOWALIA et al., 2002). The explants are then transferred to a contaminant free in vitro environment (AHLOOWALIA et al., 2002). 62
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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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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: Literature review (COPELAND, 1976).
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
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Germination physiology The relative
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Germination physiology seeds of R.
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5.2 MATERIALS AND METHODS In vitro
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In vitro culture initiation and mul
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5.2.3 Explant comparison In vitro c
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5.4 DISCUSSION In vitro culture ini
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6 In vitro corm formation and flowe
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In vitro corm formation and floweri
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6.3 RESULTS 6.3.1 Corm formation In
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Commercialization potential of Romu
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Commercialization potential of Romu
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BASKIN, C. C., and BASKIN, J. M. (1
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Literature cited DOWLING, P. M., CL
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Literature cited HILTON-TAYLOR, C.
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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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