In Vitro Germination of Several South African Summer Rainfall Disa (Orchidaceae) Species: Is Seed Testa Structure a Function of Habitat and a Determinant of Germinability?

Thompsona, Dave I.; Edwardsb, Trevor J.; Stadena, Johannes van

doi:10.2307/3668704

Cited by 14 publications

(16 citation statements)

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“…The low efficacy of disinfection reported in this study was attributed to (i) the reticulate-foveate arrangement of the testa cells of these smallseeded Disa species (Thompson et al 2001) and (ii) the difficulty experienced in wetting the Plant growth regulators b 2,4-D (auxin) at 0, 0.2, 0.5, 1 and 2 mg l -1 Arditti and Ernst (1984), Van Waes (1987), Yam et al (1990), Rasmussen (1995) and Wodrich (1997) BA (cytokinin) at 0, 0.2, 0.5, 1 and 2 mg l -1 GA 3 (Gibberelic acid) at 0, 0.2, 0.5, 1 and 2 mg l -1 2,4-D:BA factorial grid at 0, 0.5 and 1 mg l -1 Undefined media additives c Liquid endosperm (coconut milk) at 100 ml l -1 Yam et al (1990), Chu and Mudge (1994), Michel (2002) and H. Crous (pers. comm.)…”

Section: Decontaminationmentioning

confidence: 52%

“…After Hendrickson (1951), Raghavan and Torrey (1964), Arditti (1967Arditti ( , 1982, Borris (1969), Harvais (1972Harvais ( , 1973, Pierik and Steegmans (1972), Smith (1973), Mead andBulard (1975, 1979), Strauss andReisinger (1976), Lucke (1977), Arditti and Ernst (1984), Van Waes and Debergh (1986b), Van Waes (1987), Yam and Weatherhead (1988), Butcher and Marlow (1989), Yam et al (1990), George (1993), Miyoshi and Mii (1995), Rasmussen (1995) and Michel (2002) a Carbon sources suitable for germinating orchid seed were reported by Arditti (1967Arditti ( , 1979Arditti ( , 1982, Ernst (1967), Ernst et al (1971), Butcher and Marlow (1989) and reviewed by Arditti and Ernst (1984) and Rasmussen (1995) (February-April;-2001. A minimum of 15 capsules were removed from at least 10 plants for each species.…”

Section: Introductionmentioning

confidence: 88%

“…Sectional classification (Linder and Kurzweil 1999), seed type (s, small; l, large) and rainfall-mediated endemism (Thompson et al 2001) are included; w, winter-rainfall species, ws, widespread species. Threatened Disa species are highlighted in grey (Hilton-Taylor 1996a, b, 1997Victor 2002) whilst an asterisk denotes those currently registered with the Royal Horticultural Society (RHS; Michel 2002)…”

Section: Introductionmentioning

confidence: 99%

“…Germinated Disa species are winter-rainfall or widespread species in that they experience only (i) winter and non-seasonal or (ii) winter and summer rainfall maxima across their respective distributions (Thompson et al 2001). Only 11 species (7% of the genus) are germinated consistently in vitro and are registered with the Royal Horticultural Society (Table 2).…”

Section: Introductionmentioning

confidence: 99%

“…Summer-rainfall Disa species, which experience summer-rainfall maxima (Thompson et al 2001), have never been germinated in vitro. Although this may be attributed in part to neglect, lack of visual appeal or provenance, cultures for these species that have been attempted have been unsuccessful.…”

Section: Introductionmentioning

confidence: 99%

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Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

2006

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Many Disa species (80%) have not been germinated in vitro, fuelling conservation fears. Winter-rainfall species are typically germinable, whilst summer-rainfall species are exclusively intractable in vitro. We aimed to establish the in vitro germination requirements for previously ungerminated Disa species. Conventional asymbiotic seed culture protocols were reviewed and their efficacy in summer-rainfall Disa established. Mature seed was subjected to manipulations of media composition and viscosity, incubation temperature and illumination. Immature cultures were also established across four seed maturity classes. Four first-time germinations (D. cooperi, D. nervosa, D. pulchra and D. woodii) resulted from media with increased water availability. Germination rate (>12 weeks), percentage (< 30%) and synchrony were not in accordance with values reported for winter-rainfall species (>80% germination in 8 weeks). Germination of immature seed under control conditions was similar to mature seed germination under modified conditions, but neither percentage approached the calculated germination potential (~viability). Germination control in Disa is proposed as a trade-off between water availability and the presence of phyto-inhibitors in the environment of the embryo-two features typical of seeds exhibiting water-impermeable dormancy.

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Section: Decontaminationmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

2006

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Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

Zhang

Zhou

et al. 2006

Plant Growth Regul

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The effects of 5-aminolevulinic acid (ALA), a key precursor in the biosynthesis of porphyrins such as chlorophyll and heme, on development and salt tolerance of microtubers of two potato (Solanum tuberosum L.) cultivars Jingshi-2 and Zihuabai were examined under in vitro conditions. ALA at 0.3-3 mg/l promoted microtuber formation by increasing the average number, diameter, and fresh weight of microtubers especially under 0.5% NaCl stress conditions, but further increase in ALA concentration resulted in a reduction of microtuber yield irrespective of NaCl stress. Under 1.0% NaCl stress conditions, microtuberization was seriously repressed and could not be restored by the addition of ALA. The accumulation of malondialdehyde in the microtubers treated with 30 mg/l ALA increased by 22% compared to the controls (no salinity), while only a 7% increase was observed when the microtubers were exposed to 0.5% NaCl, indicating that ALA functions as a protectant against oxidative damages of membranes. Under 0.5% NaCl stress conditions, the highest activities of peroxidase and polyphenoloxidase were detected in microtubers treated with ALA at 0.3 and 3 mg/l, being by 73% and by 28% greater than those in the untreated controls, respectively. These results demonstrate that ALA at lower concentrations of 0.3-3 mg/l promotes development and growth of potato microtubers in vitro and enhances protective functions against oxidative stresses, but ALA at 30 mg/l and higher concentrations seems to induce oxidative damage probably through formation and accumulation of photooxidative porphyrins.

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A novel dual-phase culture medium promotes germination and seedling establishment from immature embryos in South African Disa (Orchidaceae) species

2007

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In vitro germination as a conservation aid demands propagation systems that yield increasingly larger numbers of plants as rapidly as possible. However, summer-rainfall Disa species are germinated infrequently under asymbiotic conditions. Attempts to bypass impermeable testae in these species resulted in the formulation of a dual-phase protocol-with the specific aim of increasing water availability to the embryo. Dual-phase cultures were initiated using seed from green capsules and comprised a solid, charcoal-rich medium overlaid with a reduced strength, liquid medium fraction of the same type. The former served to negate the influence of leached phenols and allowed protocorms to establish polarity, whilst the latter increased water availability. The dual-phase protocol germinated nine Disa species (including D. cooperi, D. nervosa, D. pulchra and D. woodi); representing five first time reports (D. brevicornis, D. crassicornis, D. patula, D. stachyoides and D. versicolor). Furthermore, germination was comparatively rapid and percentages for most species approached their estimated germination potential (*viability). Congruency here suggests that dualphase conditions are amenable to germinating a number of seeds that reflects the maximum number of viable embryos-critical for conservation efforts.

show abstract

In Vitro Germination of Several South African Summer Rainfall Disa (Orchidaceae) Species: Is Seed Testa Structure a Function of Habitat and a Determinant of Germinability?

Cited by 14 publications

References 10 publications

Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

Evaluating asymbiotic seed culture methods and establishing Disa (Orchidaceae) germinability in vitro: relationships, requirements and first-time reports

A novel dual-phase culture medium promotes germination and seedling establishment from immature embryos in South African Disa (Orchidaceae) species

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