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- Author or Editor: Tim D. Davis x
Plugs of Zinnia elegans Jacq. `California Giant' and Tagetes erecta L. `Golden Climax' and `Grange Lady' were treated with foliar sprays of uniconazole solutions at 0, 5, 25, or 50 mg·liter-1 (spray volume = 120 ml·m-2). Ten days later individual plants were transplanted to OS-liter pots for evaluation of subsequent growth and flowering. All uniconazole treatments reduced height 10 days after application; the extent of reduction depended on uniconazole spray concentration. With zinnia, only the 50-mg·liter-1 foliar spray caused undesirable stunting for at least 1 month after transplanting. None of the uniconazole treatments affected time to anthesis for zinnia. With both marigold cultivars, all uniconazole treatments reduced growth the 2 weeks following transplanting. The highest concentration reduced marigold shoot growth during this period to 25% to 30% of untreated controls. Between 2 and 4 weeks after transplanting growth of all uniconazole-treated marigolds recovered to levels similar to the control. Time to anthesis was increased by the 50 mg·liter-1 treatment for both marigold cultivars. These results suggest that foliar sprays of uniconazole at 5 to 25 mg·liter-1 can control plug height during production without adversely affecting subsequent growth and flowering. with both zinnia and marigold, a single GA3 foliar spray of 100 mg·liter-1 at transplanting partially reversed the adverse post-production effects of the 50 mg·liter-1 uniconazole foliar spray.
Indonesia is one of the most populated countries in the world and is rich in plant biodiversity. The country’s hot humid climate is conducive to the production of many tropical horticultural crops. There are many plant species indigenous to Indonesia that have potential as horticultural crops but which have not been fully evaluated and therefore remain underused. Many of these plants have market potential and may have value for human health and nutrition. Furthermore, horticulture has been identified as one of the priority areas for collaboration between U.S. and Indonesian universities and for Indonesian agricultural development. Accordingly, we are presently working with three Indonesian universities to facilitate agricultural development related to horticulture by: 1) strengthening their curriculum related to plant biodiversity; 2) conducting research aimed at identifying bioactive compounds in underused plants that may have benefit to human health; 3) establishing university-led outreach education programs that lead to a better understanding of plant biodiversity and use; and 4) fostering enterprise based on underused Indonesian plant species. Other untapped agricultural research and development opportunities exist in the postharvest handling of tropical fruits and vegetables. Overall, the climate for collaboration between U.S. and Indonesian academic institutions is quite favorable from both a political and a scientific perspective.
Seeds of moth bean (Vigna aconitifolia Jacqu. Marechal cv. Jaadia) were germinated in the presence of 0, 0.1, 1, or 2 μm 24-epibrassinolide (EBL). After 72 h, cotyledons were excised and the seedlings exposed to 22 or 48 °C for 90 min. At 48 °C EBL increased total electrolyte, K+, and sugar leakage relative to the untreated control. Following exposure to 48 °C, EBL-treated seedlings had higher malondialdehyde concentrations than controls indicating that EBL enhanced high temperature-induced lipid peroxidation. At 48 °C, EBL increased ascorbic acid oxidase activity and decreased superoxide dismutase activity relative to the control. Taken together, these data do not support the hypothesis that brassinosteroids confer thermotolerance to plants. On the contrary, EBL increased high temperature-induced damage and reduced the activity of some antioxidant systems that may protect against stress-induced cellular damage.
Seeds of four lupine species (L. microcarpus var. aureus, L. havardii, L. succulentis, and L. texensis) were subjected to 0, –2, –4, –6, or –8 bars osmotic potential using PEG 8000 solutions. Seeds of all species were acid scarified prior to placement in petri dishes containing the osmotic solutions. Petri dishes were placed in a seed germination chamber at 25°C with germination data collected daily for 15 days. Seeds of L. havardii, a desert species native to west Texas exhibited the greatest germination as osmotic potential declined while L. succulentis, a species adapted to moist sites, exhibited the greatest decline in germination as osmotic potential decreased. The other species exhibited intermediate germinability under the lower osmotic potentials.
Moth bean (Vigna aconitifolia Jacqu. Marecbal cv. Jaadia) seeds were germinated in 0, 0.1, 1, or 2 μm EBL. After 72 hours, seedlings were exposed to 22 or 48C for 90 minutes. At 48C, EBL increased total electrolyte, K+, and sugar leakage from the seedlings relative to the control. Following exposure to 48C, EBGtreated seedlings bad higher malondialdebyde concentrations than controls, indicating that EBL enhanced high-temperature-induced lipid peroxidation. At 48C, EBL increased ascorbic acid oxidase activity but decreased superoxide dismutase activity relative to the control. Taken collectively, these data do not support a hypothesis that brassinosteroids confer beat shock tolerance to moth bean. Chemical name used: 24-epibrassinolide (EBL).
This study was initiated to test the embryogenic potential of immature cotyledons (3-5 mm long) of Texas bluebonnet (Lupinus texensis). The embryo initiation medium consisted of B5 salts and vitamins with 3% sucrose and 22.6 μM 2,4-D alone or in combination with 1-15 μM of various cytokinins. Within 15-20 days, globular embryos were formed on the distal end of the cotyledons. Eventually the entire cotyledon surface was covered by embryo-like structures. Addition of cytokinins to the medium did not increase the percentage of cultures which formed embryos. In fact, addition of thidiazuron severely inhibited embryogenesis. Following transfer to an embryo maturation medium (MS medium with 0.38 μM abscisic acid alone or in combination with benzyladenine or zeatin) for 10-14 days, the embryos were placed in MS medium supplemented with GA (2.9 μM) or glutamine (200 mg/liter) with or without activated charcoal (0.5%) for embryo germination and plantlet development. Most of the embryos exhibited precocious germination and well-developed roots but failed to produce normal shoots. Therefore, additional work is needed to improve embryo conversion frequency.
Carnation cultivars `German Red' and `Chabaud' were planted in the field in Dallas, Texas, on 26 May 1994. During the subsequent 3 months, the average daily high temperature was 33C, and the average daily low temperature was 22C. `German Red' plants increased in height and diameter several-fold during this period. In contrast, `Chabaud' did not increase in height or diameter. `German Red' plants began flowering in early August, and by 2 Sept., all of the plants were blooming. None of the `Chabaud' plants produced flowers, and only 50% of the original plants were still alive on 2 Sept. Mean shoot dry weight per plant on 2 Sept. was 71.6 g for `German Red' and only 2.4 g for `Chabaud'. These results document the extraordinary heat tolerance of `German Red' carnation. This plant not only survived the summer, but also grew and began blooming during the hottest time of the year.
`German Red' is a thermotolerant cultivar of carnation (Dianthus caryophyllus) that blooms almost year-round in Texas. This study was initiated to evaluate the feasibility of inducing somatic embryos for use in gene transfer Studies and rapid mass propagation. Internodal explants, obtained from microshoots of plantlets cultured on MS medium containing 5 μM benzyladenine (BA) and 0.5 μM naphthaleneacetic acid (NAA), were used to initiate callus. Callus formation was induced on MS medium containing 3% sucrose, 0.1% casein hydrolysate and 2,4-D (1-5 μM) alone or in combination with BA (2 or 4 μM) or kinetin (2 or 4 μM). After about 5 weeks, the callus was transferred to either semisolid or liquid MS basal medium with or without kinetin and BA. Within 20-30 days, pro-embryogenic callus masses were observed. The embryos developed from white embryonic tissue and exhibited typical stages of embryogenesis. After 5 weeks, up to 70% of the cultures grown in the liquid medium with or without BA exhibited a profusion of embryo-like structures. Because only a small percentage of these developed into plantlets, more work is needed to enhance conversion frequency.
The Big Bend bluebonnet, Lupinus havardii Wats., is a showy winter annual native to a narrow geographical range in southwestern Texas with blue, fragrant 0.5–1.0-m-long racemes. The L. havardii raceme has considerable potential in the floral industry, because there is a need for high-quality, durable, raceme-type cut flowers. We began a research and breeding project in 1991 aimed at evaluating the potential for this species as a specialty cut flower. Breeding strategies included the development of selfed populations as well as random pollinations among selected individuals with the aim of improving flower color, uniformity, yield, and postharvest performance. Recurrent phenotypic selection has resulted in the development of blue, pink, and white color lines. Concurrently with the breeding efforts, research on seed germination, greenhouse culture for year-round production, postharvest handling, and shipping requirements have been conducted. Trials have indicated that L. havardii is adaptable to greenhouse culture and that individual plants can produce 15–25 marketable racemes within 4–5 months from sowing. Two years of commercial greenhouse trials have been completed. Blue and white cultivars will be released by Texas A&M Univ. within the next year.