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  • Author or Editor: Mary Ann Lila x
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Osmotic adjustment in response to decreasing media water availability was observed for in vitro Chrysanthemum morifolium Ramat. cultivars Bright Golden Anne, Deep Luv, and Lucido. Water stress was induced by increasing sorbitol (0, 0.1, 0.2, 0.3, 0.4 M), mannitol (0, 0.1, 0.2, 0.3, 0.4 M), and sucrose (30, 45, 60, 75, 90 g·l-1) concentrations in modified MS media (2 mg·l-1 BA and 0.1 mg·l-1 NAA). Osmotic adjustment was evidenced by a significant reduction in measured cell sap osmotic potential (R2 = 0.78, 0.96, 0.91 for sucrose, sorbitol, and mannitol respectively) in all cultivars. Shoot length, weighted density (apparent mass), and proliferation were significantly reduced by sorbitol and mannitol treatments. Sucrose reduced shoot proliferation, increased length, and had an inconsistent effect on weighted density. Cultures grown on media without hormones showed tremendous increase in root number up to 60 g·l-1 sucrose. Sorbitol had a negligible effect on rooting at 0.1 M but no roots developed at higher sorbitol concentrations or in any mannitol treatments. Plants transferred to a non-water-stress media after they had experienced in vitro water stress exhibited no change in osmotic properties from the stress treatments.

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Horticulture Research Methodology courses are an important if not essential introduction to research for beginning graduate students. Such courses are often characterized by presentation of a series of experimental techniques, lacking continuity and out of context with real-world research situations. In the described course, students gained expertise with a range of environmental and plant measurement techniques within the framework of a semester-long experiment. The experimental techniques were introduced and incorporated into the experiment at appropriate stages. Each student engaged in hands-on participation in development of a proposal; experimental set up, implementation, and daily maintenance; and data accumulation, analysis, and reporting (in HortScience manuscript format). In addition to direct experience with all subject techniques, each student had individual responsibility for characterization of a. selected plant (or environmental) parameter. This format successfully accomplished the provision of direct and coherent experience with a wide variety of important horticultural research techniques within a real-world setting.

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Anatomical and physiological comparisons were made between tissues of Betula platyphylla var. szechuanica (Schneid.) Rehd. (Asian white birch) obtained directly from microcultured shoots, from seedlings grown in a micro-culture-like environment, or from micropropagated plants grown in a greenhouse. The diminished stature of microcultured shoots resulted primarily from reduced cell division, although their leaves had reduced cell size as compared to shoots from greenhouse-grown plants. The area occupied by vascular tissue in midrib veins and petioles was significantly reduced in microcultured shoots as was the extent of the palisade layer, indicating that cell differentiation had also been altered. The photosynthetic capacity of leaves from microcultured shoots was less than half that of leaves from greenhouse-grown plants. However, this capacity was restored after non-in vitro rooting of the microcultured shoots. Unlike greenhouse-grown plants, photosynthetic rates of leaves from microcultured shoots were not influenced by decreasing light intensities from 1200 to 200 μmol·s−1·m−2 nor was the respiration rate strongly inhibited by cyanide. Seedlings from a high-humidity, microculture-like environment generally had characteristics intermediate between those of microcultured and greenhouse-grown tissues, indicating that the environment and not the juvenile state of the tissue was probably of overriding importance in influencing these trends.

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Spinach (Spinacea oleracea L.) is a valuable agricultural crop that accumulates phytoecdysteroids, polyhydroxylated triterpenoids, which may play a role in plant defense and have purported health benefits for human consumers. In this study, phytoecdysteroid accumulation was measured in seeds and shoots of 15 spinach accessions to determine whether phytoecdysteroid levels vary between spinach varieties and whether seed content could reliably predict relative levels in the edible foliage. Additionally, phytosterols, precursors to phytoecdysteroids, were examined to determine potential points of regulation of spinach phytoecdysteroid biosynthesis. Significant variations in phytoecdysteroid levels between accessions were observed (P < 0.05), suggesting the potential for genetic manipulation through traditional breeding or genetic engineering to increase phytoecdysteroid levels in spinach. However, results suggest that estimation of phytoecdysteroid levels in shoots may not be achieved by measuring levels in the seeds. Levels of phytoecdysteroids in spinach ranged from 19.9 to 44.1 μg per shoot, 0.7 to 1.2 μg·mg−1 dry mass shoot, 3.2 to 9.6 μg per seed, and 0.5 to 1.1 μg·mg−1 seed. Several phytosterols connected to the phytoecdysteroid biosynthetic pathway were identified by gas chromatography–mass spectroscopy, predominantly spinasterol, 5-dihydroergosterol, and 22-dihydrospinasterol, which comprised 79.8%, 6.3%, and 4.6% of the total phytosterol content, respectively. Detection of the phytosterols cycloartenol and lanosterol in spinach suggests that spinach may also have dual biosynthetic pathways to phytosterols that contribute to the production of phytoecdysteroids.

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