,3-dichloropropene plus chloropicrin (Pic), when combined with a highly retentive mulch ( Chase et al., 2006 ; Santos et al., 2006 ; Wang et al., 2001 ). Previous studies showed that fumigant retention in the soil could be improved with virtually impermeable films
Bielinski M. Santos, James P. Gilreath, and Myriam N. Siham
Sanjeev K. Bangarwa, Jason K. Norsworthy, Ronald L. Rainey, and Edward E. Gbur
impermeable film mulch has reduced the losses of methyl and phenyl ITCs compared with conventionally used low-density polyethylene mulch ( Austerweil et al., 2006 ; Bangarwa et al., 2010 ). In addition to weed control efficacy, the success of any methyl
Xiuli Shen and Myeong-Je Cho
, and embryo were assessed by immersing intact seeds, hulled seeds, and naked embryos in methylene blue for up to 7 d. Staining was examined daily in longitudinally cut seeds. Seeds of sugar pine were found to have a water-impermeable seedcoat because no
Haley Rylander, Anusuya Rangarajan, Ryan M. Maher, Mark G. Hutton, Nicholas W. Rowley, Margaret T. McGrath, and Zachary F. Sexton
northeastern United States to reduce tillage by decreasing weed pressure and maintaining prepared beds before planting. Tarps are reusable sheets of 0.15-mm (5–6 mil) opaque polyethylene impermeable to water and sized to cover multiple crop rows at one time
Monica Ozores-Hampton, Eric Simonne, Fritz Roka, Kelly Morgan, Steven Sargent, Crystal Snodgrass, and Eugene McAvoy
perched water table above an impermeable soil layer (hard pan) located at the 90 to 150 cm depth. Ground water is pumped into canals or ditches, then moves horizontally between two adjacent ditches (spaced 25 to 35 m). When the water fronts from two
Ed Etxeberria, Pedro Gonzalez, and Javier Pozueta
To determine whether the mechanisms of sucrose accumulation into the low acid `Sweet Lime' (Citrus limmetioides Blanco) juice cells are consistent with those previously reported for the more acidic cultivars, we followed similar developmental changes in determinants of sink strength. In addition, we followed the incorporation and distribution of quantum dots and fluorescent endocytic probes into the cell with time of incubation. As in other citrus fruits, sucrose levels, sucrose synthase, sucrose phosphate synthase, and sucrose phosphate phosphatase increased throughout fruit development. The pH however, was much higher than in the more acidic cultivars. Sucrose uptake into energized plasmalemma vesicles was inhibited by gramicidin, in accordance with the presence of an active symport mechanism of sucrose from the apoplast into the cytosol. On the contrary, tonoplast vesicles were shown to lack active transport mechanism of sucrose into the vacuole. In conformity with recent findings showing the occurrence of an endocytic mechanism in `Murcott' mandarin, `Sweet Lime' juice cells were shown to incorporate membrane-impermeable dyes into their vacuoles in the presence of sucrose. High-definition confocal microscopy revealed the co-localization of membrane-impermeable markers in cytoplasmic vesicles, in membrane-bound intermediate structures such as the endosome and multi-vesicular body, and the eventual distribution of such fluorescent particles. The data provide strong evidence for an endocytic system of transport that allows direct incorporation of sucrose from the apoplast to the vacuole and for the visualization of intermediate distribution and cargo centers in the cell.
C.C. Pasian and M.A. Bennett
Some transplanted crops, like tomato and marigolds, tend to stretch very early after germination, especially if grown in low light environments. By the time growers apply growth regulators (PGRs), the stretching of the hypocotyl has already occurred and sprays are ineffective. Seeds of marigold `Bonanza Gold' and tomato `Sun 6108' were soaked for 6, 16, and 24 h in paclobutrazol solutions of 0, 500, and 1000 ppm. After imbibition, seeds were dried for 24 h before sowing in plugs. Sixteen, 26, and 36 days after sowing, seedling height and percent emergence were measured. Increasing concentrations of PGR and time of imbibition produced shorter seedlings. Tomato seedling heights measured 36 days after sowing were 1.9, 1.5, and 1.7 cm when imbibed in water for 6, 16, and 24 h, respectively. When PGR was used at 500 ppm, seedling heights were: 1.4, 1.2, and 1.2 cm, respectively. Similar reductions were observed for marigolds. It was hypothesized that some seeds have coats that are impermeable to PGRs. These impermeable coats might serve as PGR carriers, delivering the chemical into the growing medium of the plug cell. When the root emerges from the seed, it absorbs the growth regulator. These preliminary results indicate that this method of PGR application may be feasible and could benefit plug growers of marigold and other ornamental plant species prone to early stretching (e.g., cosmos).
Ed Etxeberria, Pedro Gonzalez, and Javier Pozueta-Romero
To investigate the mechanisms of sucrose transport and its accumulation into `Murcott' mandarin (Citrus reticulata Blanco) fruit, developmental changes in determinants of sink strength such as sucrose metabolizing enzymes, and sucrose transport across both plasmalemma and tonoplast were analyzed. Concurrently with sucrose levels, sucrose synthase, sucrose phosphate synthase and sucrose phosphate phosphatase increased throughout fruit development. Plasmalemma and tonoplast vesicles isolated from fruit collected at different developmental stages were analyzed for their transport capabilities. Sucrose uptake into energized plasmalemma vesicles was abolished by gramicidin, which is in accordance with the presence of an active symport mechanism of sucrose transport from the apoplast into the cytosol. Unexpectedly, tonoplast vesicles were shown to lack active transport mechanism of sucrose into the vacuole. More importantly, however, and in conformity with recent findings showing the occurrence of an endocytic mechanism of ion uptake in maize (Zea mays L.) root cells, citrus (Citrus L.) juice cells were shown to incorporate membrane impermeable dyes into their vacuoles in the presence of sucrose. High definition confocal microscopy revealed the co-localization of membrane impermeable markers in cytoplasmic vesicles and the formation of vesicles at the plasmalemma. The data provide evidence for an endocytic system of transport that allows direct incorporation of sucrose from the apoplast to the vacuole bypassing both the plasmalemma and tonoplast.
R. Holubowicz, A.G. Taylor, M.C. Goffinet, and M.H. Dickson
During imbibition, water always follows the same pattern when entering the seed testa in semihard seeds (SHS) of snap bean (Phaseolus vulgaris L.). Water first enters the raphe and the chalazal region of the testa (R-CT), then migrates circumferentially along the midline of the seed, leaving the lateral faces the last to be fully imbibed. The R-CT region is the main site of primary uptake of both water vapor and liquid water by SHS. The hilum, micropyle, and strophiole play only a minor role in water uptake in SHS. In comparison to the readily permeable seeds of ‘Bush Blue Lake 47’, SHS have more total phenols in the osteosclereid cells and more pectic substances in the palisade cells of the CT. The presence of these compounds may account for the impermeable nature of SHS. Measurements made of palisade cell length and width in the R-CT region revealed that cell length increased and width decreased in the chalazal testa region (CT) as seed moisture content increased from 6% to 12%. It is proposed that semihardening of bean seeds is mainly a result of the reversible physical changes in the length and width of the palisade cells in the R-CT region. Seeds imbibe at high moisture content (12%) because the palisade cells have stretched, which allows water uptake. Seeds are impermeable at low moisture content (6%) because the palisade cells change in size and form a physical barrier to water movement.
Marilyn H.Y. Hovius, John T.A. Proctor, and Richard Reeleder
American ginseng seed is important as the primary source of propagation. Little is known about ginseng seed stratification and germination. The green seeds are harvested in August/September and stratified in boxes outdoors for 12 to 14 months. Then the after-ripened seeds are field-seeded; they germinate in the spring. Ginseng seeds undergo long dormancy periods caused by embryo dormancy and impermeable seedcoats. The objectives of this research are to shorten the dormancy period, increase the percent germination, and study the changes that occur during stratification using growth regulator and temperature treatments. Seeds stored at 15C from harvest to January and treated with 1000 ppm gibberellic acid (GA3) resulted in the most embryo growth, highest percent germination, and best growth after one growing season compared to 20C and no GA3. Tissue culturing immature zygotic embryos showed a requirement for GA3 (3–5 μM). Radicle growth may need an attached suspensor for development.