Browsing by Author "Jett, Lewis W."

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    The effects of priming on vigor and viability of broccoli (Brassica oleracea var. italica Plenck) seeds
    Jett, Lewis W. (Virginia Tech, 1994-12-15)
    Seed priming is a controlled hydration process, followed by dehydration, that allows pregerminative metabolic activity to proceed without germination. The objective of this research was to investigate the effects of priming on intrinsic characteristics of seed germination including temperature, water, and development, in order to understand how priming affects the germination of broccoli (Brassica oleracea var. italica Plenck) seeds. Priming of broccoli seeds consistently improved germination and emergence rate in the laboratory and field and was related to the accumulation of a specific level of hydropriming units expressed in MPa*h. Priming reduced the sensitivity of seed germination to temperature and increased the temperature range of germination but did not lower the minimum temperature for germination. Primed seeds leaked less electrolytes at supraoptimal temperatures (≥ 35°C) compared to nonprimed seeds. In the field, primed seeds produced a greater plant stand and yield under stressful emergence conditions. Under optimal conditions in the field for stand establishment, the advancement in emergence of primed seeds did not carry over to earlier, greater yields. Matric priming, using calcium silicate as the carrier in the ratio 1.0:0.8:1.8 (seed:carrier:water; by weight) for 7 d at 20°C, was superior to osmotic priming using polyethylene glycol (pEG 8000) at -1.2 :MPa in nearly all variables examined. This may be attributed to reduced respiration during priming of seeds in PEG or nutrient uptake by seeds in calcium silicate. The testa was observed to be a barrier to broccoli seed germination. Priming-induced changes to the physical characteristics of broccoli seeds included increased volume (32%) and an irreversibly expanded, and weakened testa with some minute cracking near the area where the radicle emerges. Primed seeds germinated faster, in part by maintaining a lower hydrotime constant, and thus exhibited a greater progression towards germination per unit water potential at a constant temperature compared with nonprimed seeds. It was hypothesized that, since the testa threshold was reduced after priming by expansion and formation of free spaces, the reversibly expanded embryo of primed seeds does not become immediately appressed to the testa upon rehydration. Thus the yield threshold component controlling the rate of germination of primed seeds is lower by the amount of the testa threshold. The priming effect is more than just reducing the yield threshold as indicated by a significant invigoration of seeds with split testae. Despite the increased volume as a result of the formation of free spaces, primed broccoli seeds did not imbibe more water or have a greater turgor at full hydration. Priming did not lower the minimum water potential allowing germination, and primed seeds did not plateau in water uptake but, instead, moved immediately from imbibition to expansive growth. Priming improved the germination rate of broccoli seeds at all stages of maturity with the most significant effects at stages before attainment of maximum dry weight. Dry storage of broccoli seeds at harvest able maturity (≥ 56 days after pollination) did not improve germination, indicating a lack of post harvest dormancy.
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    The Mid-Atlantic Berry Guide for Commercial Growers, 2013-2014
    Demchak, Kathleen; Elkner, Timothy E.; Esslinger, C. John; Frazier, Maryann; Guiser, Scott D.; Halbrendt, John M.; Harper, Jayson K.; Krawczyk, Grzegorz; Richards, Kerry M.; Heckman, Joseph R.; Majek, Bradley W.; Nitzsche, Peter; Oudemans, Peter V.; Pavlis, Gary; Polk, Dean; Rodriguez-Saona, Cesar; Sciarappa, William J.; Ward, Daniel L.; Johnson, Gordon C.; Butler, Bryan R.; Fiola, Joseph A.; Lantz, Wwillie; Ehlenfeldt, Mark; Derr, Jeffrey F.; Johnson, Charles S.; Pfeiffer, Douglas G.; Straw, R. Allen; Yoder, Keith S.; Biggs, Alan R.; Jett, John W.; Jett, Lewis W.; Mashburn, Eed; Swarz, Harry (Penn State University, 2013)
    The Mid-Atlantic Berry Guide is intended to provide information for commercial berry growers within the region. Homeowners may use this publication for background information; however, many of the recommendations contained in this guide assume that the production is on a large scale and that producers have a commercial pesticide applicator’s license. Uses of pesticides listed in this publication were current as of July 1, 2012. However, changes in registration status may occur at any time, so please consult the label before use—the label is the law. If there are differences in use patterns between the pesticide label in your possession and those listed in this guide, follow the instructions on the label. If in doubt, consult your cooperative extension educator.
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    Production and postharvest quality maintenance of single unit and bunching broccoli in Virginia
    Jett, Lewis W. (Virginia Tech, 1990-11-05)
    Broccoli (Brassica oleracea L. var. italica) has become an increasingly popular vegetable with American consumers. Much of the attractiveness of fresh broccoli is derived from this vegetable's high nutrition and excellent organoleptic properties. In a consumer response survey, Virginia Master Gardeners indicated a preference for broccoli that has less stalk and more florets by weight. The objectives of this research were to produce single unit broccoli, and to examine vacuum and shrink-film wrapping of single unit and bunching broccoli as alternatives to the standard post harvest practice of top icing in order to preserve post harvest quality attributes: vitamin C, color, odor, and turgidity. Broccoli cv. 'Symphony' was direct seeded and transplanted at two sites in Virginia (within row spacing 20 cm , .9 m centered, 3 row bed). Single unit broccoli was classified as broccoli with head diameters greater than or equal to 20 cm (i.e., equivalent to one bunch of broccoli). Single unit and bunching broccoli for post harvest experimentation was vacuum or shrink-film wrapped with plastic film wraps of varying gauges. The broccoli was held in cold storage from 12 to 22 days with no supplemental ice. Single unit broccoli was produced successfully at one site only. The yields, however, were a fraction of total bunching broccoli yields. There was no significant difference in marketable yields with either planting method (direct seeded vs transplanting) at site 2. Transplants, however, out yielded the direct seeded broccoli at site 1. Vacuum and shrink-film wrapping proved to be very effective in preserving organoleptic attributes of single unit and bunching broccoli even when never receiving ice. Vitamin C and chlorophyll retention were not influenced by wrapping.