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Abstract
In vitro germination of freshly collected pollen from pecan [Carya illinoensis (Wangenh.) C. Koch) was examined following exposure to relative humidities (RH) of ≈5%, 50%, and 97% and temperatures of 25, 35, and 45C in a factorial experiment. Maximum germination percentage occurred as RH increased and temperature decreased. Pecan pollen stored for nearly 2 years at −80C and −196C, but not −10C, retained germination capacity equal to freshly collected pollen if stored pollen was given a period of controlled rehydration before in vitro assay for pollen tube formation. Differences in germination of pollen stored at −10C and −196C were substantiated with the fluorochromatic test procedure as well as light microscopy. Pollen removed from storage at −196C and left at ambient laboratory conditions for 59 days retained the capacity for in vitro germination.
Abstract
Pistachio (Pistacia vera L.) pollen was examined for capacity to germinate in vitro 2 days after anthesis and at intervals of time after storage at ambient laboratory conditions or at − 20°C. In 1986, fresh pollen of each of four clones examined had high germination percentages on a range of sucrose and agar concentrations. After 1 week at room temperature, germination percentages were < 6%. However, when the same week-old pollen was treated to effect gradual hydration at high humidity prior to being placed on the germination medium, germination increased to > 80% for ‘Peters’ pollen and 10.4% to 63.8% for the three other clones. In 1987, similar results were obtained for ‘Peters’ pollen, where pollen hydrated at high humidity had germination rates at least 50% that of fresh pollen when stored up to 18 days at ambient laboratory temperature and humidity. Pollen stored at −20° showed more exacting in vitro germination requirements than fresh pollen, particularly as time in storage increased. ‘Peters’ pollen retained germination levels comparable to fresh pollen after 4 months at −20°, but, by 12 months, germination percentages had fallen sharply.
Abstract
Conditions for in vitro germination of jojoba [Simmondsia chinensis (Link) Schneider] pollen were optimized in order to study the influence of storage temperature on viability. A medium consisting of 300 mg·liter−1 CaCl2·2H2O, 100 mg·liter−1 KNO3, 10 mg·liter−1 H3BO3, 20% sucrose, and 4% to 5% Difco Bacto-agar was optimal for germinating both fresh and stored pollen. Pollen germinated readily in media with a pH range of 4 to 8. The optimum incubation temperature range for pollen germination was 25° to 30°C. When stored at room temperature (22° to 25°), the initial pollen viability was decreased to 50% in 3 weeks and to 0% after 10 weeks, as determined by in vitro germination. Pollen stored at 4° maintained its initial viability for 10 weeks, followed by a gradual decrease in germination to 70% in 17 weeks and 0% after 22 weeks. Pollen stored at −196° in liquid nitrogen for 2 years retained a germination percentage as high as that of fresh pollen. The eryogenieally stored pollen, when used in controlled pollinations, produced normal fruit set comparable to that with fresh pollen.
Abstract
The morphology of pecan [Carya illinoensis (Wangenh C. Koch)] pollen from 4 cultivars was examined using light and scanning electron microscopy. Pollen was triporate, paraisopolar and suboblate, with a tectate and microechinate surface. The exine was thickened around pores. Pollen from the 4 cultivars was indistinguishable. Pollen germinated in vitro after 1 hr. Pollen tubes grew from 1 or 2 pores, with one germ tube becoming dominant. Pollen germination decreased dramatically after anther dehiscence. Less than 1% of the pollen germinated 5 days after collection.
This investigation documents the key anatomical features in embryo development of Cypripedium formosanum Hayata, in association with the ability of embryos to germinate in vitro, and examines the effects of culture media and seed pretreatments on seed germination. A better understanding of zygotic embryogenesis for the Cypripedium L. species would provide insights into subsequent germination events and aid in the in vitro propagation of these endangered species. In seeds collected at 60 days after pollination (DAP), soon after fertilization, no germination was recorded. The best overall germination was found at 90 DAP (≈70%), at which time early globular to globular embryos with a single-celled suspensors can be observed. After 135 DAP, the seeds germinated poorly. At this time the inner integument shrinks and forms a tight layer, which encloses the embryo, the so-called “carapace.” Using Nile red stain, a cuticular substance was detected in the carapace, which may play a role in the impermeability of the mature seed and may help the seeds survive in the stringent environment. At maturity (after 210 DAP), the embryo proper has an average size of eight cells along its length and six cells across the width. Lipids and proteins are the main storage products within the embryo. To improve seed germination, experiments were conducted to test the suitability of various media and pretreatments of seeds. When different media were used, except for the Harvais medium at 120 DAP, there was no significant difference in seed germination at three different developmental stages tested. Soaking mature seeds in 1% NaOCl or treating them with ultrasound may slightly increase the germination percentage. For seed germination, our results indicate that the timing of seed collection outweighs the composition of medium and the seed pretreatments.
1 To whom reprint requests should be addressed. Journal Article no. 249-90. Salaries and research support provided in part by state and federal funds appropriated to the Ohio Agricultural Research and Development Center and a Seed Grant to A.R. M
Abstract
Seeds of 29 terrestrial orchid species representing 15 genera were surface sterilized by immersion in 0.5% sodium hypochlorite containing a wetting agent, washed, sown on a completely defined, semisolid embryo culture medium containing macro- and microelements, sucrose, amino acids, and vitamins, and incubated in the dark at 25°C. Six months after sowing, 16 species from 9 genera germinated and continued development while 13 species from 10 genera failed to germinate. Species of Cypripedium, Goodyera, Platanthera and Spiranthes differed in response in that one or more of each germinated and one or more did not. Seedling development was similar for most germinating species and progressed to the formation of a shoot or shoot initial in all but one. Apparently the mycorrhizal association thought to be required for terrestrial orchid seed germination and early seedling development can be replaced with aseptic culture on a completely defined medium for many terrestrial orchids.
is likely due to low hydraulic conductivity and wetted seed contact area in the soil ( Hadas and Russo, 1974 ). The potential for in vitro screening methods to improve germination under water stress has been demonstrated. Two cycles of phenotypic
) with gold. Samples were examined using a SEM (JSM 5800; JEOL, Tokyo, Japan) at 15 kV. In vitro pollen germination. In vitro germination assays were conducted according to Yi et al. (2003) . Freshly collected pollen was inoculated into 96-well plates
-benzylaminopurine (BAP), glutamine, and a high concentration of sucrose, indicating that tissue culture may be a platform for recovering hybrid lilacs. Even if in vitro germination fails, callus developed from the hybrid tissue may provide another source for