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  • Author or Editor: W. F. Campbell x
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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.

Open Access
Authors: and

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.

Free access

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.

Open Access

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.

Open Access

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.

Open Access

Abstract

The effect of imbibition and drying rates on colyledon cracking in snap beans, Phaseolus vulgaris L., was studied. Six snap bean cultivars, representing various degrees of susceptibility to cotyledon cracking, were compared. Data indicated that differences in the rate of imbibition and drying were not responsible for differences in susceptibility to cotyledon cracking. The crack-resistant ‘Improved Higrade’ and moderately-resistant ‘Earliwax’ imbibed water faster than the crack-susceptible cultivars. Anatomical studies indicated that cracking was more frequent across the cell walls of the cotyledon cells than along the middle lamellae in all cultivars.

Open Access

Abstract

The firmness, pericarp color, total pectins, total sugars, free reducing sugars, pH, titratable acidity, organic acids, amino acids, and tannins were analyzed in apricots, Prunus armeniaca L. cvs. Moorpark and Large Early Montgamet and in peaches, Prunus persica L. cv. Elberta. Fruit was stored under varying CO2 concentrations and 5.0% 02. Results of these treatments were compared to those obtained with conventional refrigerated storage fruit.

The data indicated that firmness, total pectins, titratable acidity, total sugars, and tannins decreased with duration of storage time. However, they usually decreased at a slower rate in CA-stored fruit than in refrigerator-stored fruit. Color, pH, and free reducing sugars increased with storage time, but the organic and amino acids content varied erratically with the treatment and length of storage time. The organic acids were generally depleted as storage was extended. Succinic acid occurred only under elevated CO2 concns. increasing the CO2 accelerated accumulation of succinic acid and the depletion of malic acid. Increased CO2 caused alanine to accumulate and aspartic acid to decrease.

Apricot fruit appeared to benefit most when stored in 2.5% CO2. Under this CO2 cone, fruit did not develop detrimental effects as rapidly as at other concns. of CO2 tested. Peach fruit did not appear to be satisfactorily stored under the conditions of this experiment.

Open Access

Abstract

Effects of boric, indole-3-acetic, gibberellic, succinic and fumaric acids, and water extract from onion bulbs on onion pollen germination and tube growth were studied. Boric acid stimulated pollen germination and tube growth at 100 mg/liter but was toxic at 200 mg/liter. Indole-3-acetic acid slightly increased pollen germination and tube elongation at 0.05 mg/liter, but inhibited pollen tube growth at 200 mg/liter. Gibberellic acid not only enhanced germination percentage, but the higher concentrations also increased the pollen tube lengths. Succinic and fumaric acids stimulated germination, but pollen tubes burst at the higher concentrations. At 200 mg/liter of fumaric acid no germination of pollen grains was observed, but with 25 ml of bulb extract in the culture medium, germination and tube growth were stimulated. Pollen tubes developed abnormally at higher concentrations.

Open Access

Abstract

Freshly dehisced pollen of Allium cepa L. was stored under various conditions of temperature and relative humidity for up to 198 days. One series of treatments was freeze dried before storage. The degree of viability was determined by germination percentages at periodic intervals. Germination of approximately 60% of the initial germination was maintained in pollen samples freeze dried and stored at −18° and 5% relative humidity. Without freeze drying, approximately 38% of initial germination was maintained in samples of onion pollen stored 198 days at −18° and 10% relative humidity. Pollen stored at −18° and 80% relative humidity germinated 34% of initial germination after 56 days of storage and gradually declined to 4% by 170 days.

Open Access

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.

Open Access