Search Results
Abstract
Carrot roots (Daucus carota L.) and onion bulbs (Allium cepa L.) were planted in Kidman silt loam immediately after DCPA (dimethyl tetrachloroterephthalate), ethofumesate (2-ethoxy-2,3-dmydro-3,3-dimethyl-5-benzofuranol methanesulfonate), linuron (3-(3,4-dichlo-rophyenyl)-l-methoxy-l-methylurea), napropamide (2-(a-naphthoxy)N,N-diethylpropiona-mide), or trifluralin (a,a,a-trifluoro-2,6 dinitro-N,N-dipropyl-p-toluidine) had been soil incorporated. In a second experiment, carrot roots and onion bulbs were planted in a conventionally-prepared seed bed or among vigorously growing wheat plants (7 to 10 cm tall). DCPA, linuron, and oryzalin (3,5-dinitro-N 4,N 4-dipropylsulfanilamide) plus glyphosate (N-(phos-phonomethyl)glycine) were surface applied to these seedbeds after planting but prior to crop emergence. Methazole (2-(3,4-dichlorophenyl)-4-methyl-l,2,4-oxadiazolidine-3,5-dione) and nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) were applied postemergence. Chemical treatments significantly altered the seed yields within the no-tillage method. Carrots grown in the tilled plots exhibited no effect of chemical treatments on seed yield. Comparison of tillage methods indicated a highly significant reduction in carrot seed yield relative to the no-tillage plots. Those on the non-weeded control and no-tillage plots showed a highly significant reduction in seed yield. Many of the onion bulbs from male-fertile lines failed to develop seedstalks in the plots sprayed with linuron and napropamide and those that did were delayed in development. Linuron and ethofumesate reduced the numbers of onion flowers per umbel. Onions grown in the tilled plots exhibited no effect of chemical treatments on seed yield. Those on the non-weeded control and no-tillage plots showed a highly significant reduction in onion seed yield. Comparison of tillage methods indicated a highly significant reduction in onion seed yield relative to the no-tillage plots.
Evolution of hydrogen gas (H2) during N2 reduction in root nodules results in inefficient use of energy needed for N2 fixation. Cultivars of chickpea (Cicer arietinum L.) were inoculated with Rhizobium strains with and without genes for uptake hydrogenase (Hup) activity. H2 evolution, acetylene reduction activity, and uptake hydrogenase (Hup) activity were assayed on the resulting nodules. The Hup– strains produced higher plant yields than the Hup+ strains. The +N controls produced significantly higher yields than the –N controls and plants inoculated with Rhizobium strains. Hydrogen uptake activity by Rhizobium strains was influenced by the cultivar characteristics. Expression of the plasmid-borne hup genes (pHU52) of Bradyrhizobium japonicum was modified by the host cultivar. The average nodule fresh weight and shoot and root dry weights of the cultivars significantly increased following inoculation with the transconjugant Hup+ Rhizobium strain. Thus, biological N2 fixation may be enhanced by selecting Rhizobium strains that are appropriately matched to the particular cultivar. Incorporation of transconjugant Hup+ genes can increase rhizobial activity.
Abstract
Inbred onions, Allium cepa L., were grown with different levels of fertilizer and soil moisture to determine treatment influence on seed yield. Nitrogen (253 kg/ha) alone or in combination with P (162 kg/ha) reduced plant survival, umbels per plant, pollination index, and seed yield where soil moisture was low but the reduction was nil or not as severe where soil moisture was high.
Abstract
We investigated the areas of water penetration and the anatomical structures of hilar regions of permeable and impermeable seed coats of lima beans (Phaseolus lunatus L.). Results indicate that water can enter permeable seeds through the hilum, raphe, and micropyle. In impermeable seeds water cannot pass through any of these areas. Anatomical data confirm that there were no structural differences in the testae of permeable and impermeable seeds, but a noticeable difference was apparent in the hilar region. In permeable seeds the palisade layer did not connect evenly in the hilar canal. By contrast, the hilar canals of impermeable seeds had connected palisade layers that were uniformly coated with a cuticular layer. Micropylar openings were clearly visible in permeable seeds, but these openings were occluded and well covered with cuticle in impermeable seeds. Visible differences were evident in the raphe.
Abstract
A path-coefficient analysis was used to furnish information on the inter-relationships of pollinating insect activity and components of seed yield in inbreds of Allium cepa L. The inbreds differed very significantly in their attractiveness to pollinating insects. Only one inbred exhibited a significant correlation (P <0.05 positive) between numbers of honey bees and seed yields. Separating the correlation coefficients into components of direct and indirect effects indicated that pollination attractiveness was not the limiting factor in seed set for inbreds in the experiment. Moreover, most of the variation in seed yield could be attributed to indirect effects on the components of yield, umbels per plant, flowers per umbel, percent per fertilized flower, and seeds per fertilized flower.
Calcium chloride (CaCl2) enhances turgidity and quality of postharvest sour cherry, Prunus cerasus L., fruit. Mechanisms by which plasma membrane (PM) ATPase maintains the electrochemical gradient in cell turgor were studied in isolated PM vesicles isolated from tapwater-, CaCl2- and chelated amino acid-calcium-treated Montmorency sour cherry fruit. Electron microscopy and periodic-chromicphosphotungstic acid staining indicated 85-90% closed PM vesicles. Protein activity associated with the PM was four times higher in both Ca treatments than in untreated cherries. ATPase activity was insensitive to NO3 and NaN3, but inhibited by vanadate, indicating absence or low levels of tonoplast and mitochondrial ATPases. PM vesicles exhibited a pH jump in the presence of acridine orange (A493-530nm). Cherry fruit appeared to have a PM ATPase similar to that of other plant species. Generation of a positive membrane potential across the PM was dependent upon ATP.
Abstract
Abscisic acid (ABA) concentrations were significantly higher in young leaves of N-deficient (stressed) plants of tomato (Lycopersicon esculentum Mill.) both at day 2 and day 7 after transfer to a N-free Hoagland's solution. In old leaves, N-deficiency significantly increased ABA concentrations after 2 days but not after 7 days.
Abstract
The discovery of cytoplasmic male sterility in onions, and its application to commercial seed production, was a major breakthrough in vegetable breeding. Initial use of this new technique was moderately successful and seedsmen assumed that experience would lead to higher seed yields. Instead, yields have been disappointing; many fields have not even been harvested. The resulting economic problem has become serious for both seedsmen and onion producers. Many suggestions have been made as to the cause of low yields but there is no agreement on the biological nature of the problem. Therefore, during the 1966 growing season we began to analyze the problem by following the development of the seed crops in commercial fields in southwestern Idaho. We believe our methods and preliminary data may be useful in stimulating other workers to also examine this problem.
Abstract
Measurable differences in length, width, and depth of seeds of bean (Phaseolus vulgaris L.), from normal and flat-podded “rogues” were observed. Selective milling removed more than half of the seeds that would have given rise to flat pods, resulting in faster and easier field roguing in subsequent crops. The method is suitable only for stock seed purification because of the high loss (60 to 90%) of normal seeds.
Abstract
Abscisic acid (ABA) metabolism of 6-week-old seedlings of cool- and warm-season crops was determined after a 24-hr exposure to supra- and sub-optimal temperatures. Plants were grown at 25°C and then exposed to 10, 25, or 40°C. After a 24-hr exposure, free (FABA) and hydrolyzable (HABA) abscisic acid and dihydrophaseic acid (DPA) were measured in the plant tops by gas chromatography. Warm-season crops, exposed to 10°C exhibited elevated levels of FABA, HABA and DP A compared to those plants exposed to 25 or 40°C. Among cool-season crops, only peas had higher FABA and HABA levels at 40°C than at 10 or 25°C, while beets had lower levels of HABA at 25°C than at 10 or 40°C. DPA existed at much higher concentrations than FABA and HABA in all plants. The increases in ABA and DPA in warm-season crops exposed to 10°C are attributed to low temperature stress.