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  • Author or Editor: Tim D. Davis x
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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).

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`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.

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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.

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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.

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A group of 53 institutions of higher education in the United States and Canada offering degrees in horticulture, or closely related plant science degrees, was surveyed to determine various characteristics associated with the degree programs offered, demographics of students and faculty, and selected procedures and practices associated with administration of these graduate programs. Total response rate was 94%, yielding 85% usable completed surveys. Very few programs (0-3 per degree type) were offered via distance education and on average only 4.1% to 4.5% of resident instruction program students participated in distance education courses. Domestic students averaged 64% to 75% of enrollment. Students were 69% to 73% white. Asian students were the predominant minority group at 12% to 16% of enrollment, followed by African Americans (3% to 8%) and Hispanics (1% to 4%). Most institutions provided out-of-state tuition waivers (75%), and often in-state-tuition waivers (61%), to those students on assistantships or fellowships. Typical commitments to students were 3 years for a PhD and 2 years for a master's degree program. Research assistantships were the dominant form of assistance at all institutions (38% to 53% of students), while teaching assistantships contributed significant secondary funding (7% to 13%). With the exception of mean maximum fellowships, mean maximum assistantships ($11,499-$13,999) at non-1862 Morrill Act universities (NMAU) averaged near the mean minimums ($13,042-$14,566) for the corresponding assistantship types at 1862 Morrill Act universities (MAU). Requirements for teaching experience ranged from 41% of PhD programs to 18% of non-thesis master's degree programs. Typical departments contained 29 faculty members, of which 44% were full professors, 27% associate professors, 19% assistant professors, 6% junior or senior lecturers, and 3% were in other classifications. Traditional 12-month appointments (65.9% of faculty) were predominant at MAU. With the exception of junior lecturer positions, mean salaries at MAU averaged $9125, $6869, $8325, and $28,505 more for professor, associate professor, assistant professor, and senior lecturer, respectively, than at NMAU. This study provides useful information for departments undergoing external review or revision of graduate programs.

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Big Bend bluebonnet (Lupinus havardii Wats.) is native to a narrow geographic range in southwestern Texas and produces attractive blue inflorescences (racemes) that may be used as cut flowers. Several crops were produced in the greenhouse to determine postharvest-characteristics of the cut inflorescences. Without any postharvest conditioning treatments, the inflorescences held in water had an average vase life of about 7 days. During this period, an average of 13 flowers abscised per inflorescence. When preconditioned for 4 hours in 40 to 160 mg·liter−1 silver thiosulfate (STS), vase life increased to 10 to 12 days and fewer than three flowers abscised per inflorescence. A commercial floral preservative (Oasis) had no effect on flower abscission or vase life of STS-treated inflorescences. Flower abscission and vase life were the same whether STS-treated inflorescences were placed in floral foam moistened with water or in water alone. Storing STS-preconditioned inflorescences in water at 5C for 72 hours did not affect flower abscission or vase life compared to the unstored control. Dry postharvest storage at 5C for 72 hours caused noticeable wilting, but, on dehydration, these inflorescences still had a vase life of about 8 days. Postharvest characteristics of pink-and white-flowered breeding lines were the same as for the blue-flowered line. These results indicate that cut inflorescences of L. havardii have desirable postharvest qualities and can be stored for up to 72 hours without seriously limiting vase life.

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Abstract

The promotion of adventitious root formation by paclobutrazol was tested by placing cuttings in solutions of the chemical for 24–40 hr, and then observing the rooting response. Paclobutrazol at relatively low concentrations (3 to 6 mg·liter-1) increased the number of roots formed on cuttings of Creeping Charlie (Plectranthus australis R. Br.) and common bean (Phaseolus vulgaris L.) by about 100% and 85%, respectively. Paclobutrazol did not affect root length greatly but reduced shoot length by about 20% compared to controls.

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Seeds of Lycopersicon esculentum Mill. cv. UC 82L were treated with hypertonic priming solutions containing KNO3 and K3PO4(10 g·liter-1 each), and various concentrations of uniconazole before sowing. Treatment of the seed with priming solution only hastened emergence by ≈ 2 days compared to untreated seed sown directly from the packet, but did not affect total emergence after 12 days. Addition of uniconazole to the priming solution had no significant effect on speed of emergence or total emergence after 12 days compared to the primed control. Seed priming plus uniconazole at 1 or 10 mg·liter-1 reduced seedling height after 2 weeks by ≈ 20% compared to the primed control. Uniconazole had no effect on the mortality of either hardened or nonhardened seedlings exposed to below-freezing temperatures for 3 hr. These data suggest that treatment of tomato seed with hypertonic solutions containing uniconazole would be of little practical value in protecting seedlings from freeze damage. Chemical names used: (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-yl)penten-3-ol (uniconazole).

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A variety of Hamelia patens (firebush) explants (nodal and internodal segments, leaf blade pieces, floral buds, shoot tips) were cultured on Murashige and Skoog's revised medium containing various concentrations of 2,4-D and kinetin. Embryogenic callus was produced only from shoot-tip explants placed on media containing 2,4-D or 2,4-D plus kinetin. None of the other explants produced embryogenic callus. Somatic embryogenesis from callus was greatest on media containing both 2, 4-D and kinetin. Direct somatic embryogenesis was observed on the roots of callus-derived primary embryos maintained on media containing 2,4-D or 2,4-D plus kinetin. Conversion of somatic embryos into plantlets only occurred on media containing 2,4-D, kinetin and activated charcoal.

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Both kinetin and BA promoted in vitro shoot formation from hypocotyl explants of Lupinus texensis Hook. placed on Murashige and Skoog (MS) medium. With either cytokinin, shoot formation was best at ≈4.5 μm. Adventitious root formation was observed only on tissue culture-derived shoots placed in MS media containing 5.4 to 54 μM NAA. IAA and IBA, at concentrations ranging from 5 to 55 μm, failed to stimulate rooting. Even at the optimal concentration of NAA, only 14% of the shoots produced roots. Thus, although hypocotyl explants readily produced shoots, adventitious root formation on these shoots occurred with relatively low frequency. Chemical names used: 6-benzylaminopnrine (BA); indole-3-acetic acid (IAA); indole-3-butyric acid (IBA); 6-furfurylaminopurine (kinetin); 1-naphthaleneacetic acid (NAA).

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