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Abstract
Parthenocarpic cucumber fruit (Cucumis sativus L. cv. Deliva) were harvested from 3 to 30 days after an thesis. Fresh weight increase followed a single sigmoid curve. Commercial maturity was attained 10 to 11 days after anthesis, and these mature fruit had a 20- to 30-day shelf life and good color retention at 20°C. Chlorophyll content at harvest decreased with fruit age. Fruit harvested before commercial maturity showed declining rates of CO2 and C2H4 production at 20°, while commercially mature fruit maintained relatively constant rates throughout their holding period. Fruit harvested after commercial maturity showed increased respiration during holding; this increase was greatest for 30-day-old fruit. Fruit harvested 20, 25, and 30 days after anthesis showed peaks of C2H4 production during holding; this production was most pronounced for mature fruit.
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.
Abstract
Tomato fruit firmness is closely associated with its ripeness stage; as the fruit ripens it softens. Correct usage of the UC Fruit Firmness Tester requires that such variables as location of measurement on the fruit, removal of skin, and plunger (tip) diameter be specified. A negative and highly significant correlation (r = −0.75) exists between firmness measurements with the UC Firmness Tester (a destructive method) and the compression testing device (a nondestructive method). Values obtained by both methods were also highly correlated (r = 0.79, UC Firmness Tester; r = −0.81, compression testing device) with subjective evaluation scores based on finger feel. Two possible minimum firmness limits are suggested for tomato fruits at shipping point and at retail.
The udiA gene encoding the enzyme β -glucuronidase (GUS) appears promising as a genetic marker for early confirmation of successful plant cell transformation. Two strains of Agrobacterium rhizogenes and eight strains of A. tumefaciens were selected as hosts to carry a binary plasmid (pBI121) containing the marker gene encoding the GUS marker that is controlled by the CaMV35S promoter. Presence of plasmid pBI121 in the bacteria was confirmed by resistance to kanamycin, plasmid re-isolation, and restriction enzyme analysis. When the GUS enzyme was expressed in transformed plant cells, reaction with the histochemical substrate 5-bromo-4-chloro-3-indolylglucuronide (X-gluc) lead to blue pigment development. Expression of GUS in viable bacteria that had not been eliminated from transformed tissue caused problems with the early transformation detection in radish, peach, and apple stem sections by also producing a positive X-gluc color reaction. Putative transformation of apple xylem parenchyma callus was accomplished, as judged by resistance to kanamycin, opine analysis, GUS marker gene expression, and presence of the APH(3')11 enzyme. In this system, elimination of bacterial contamination was accomplished during multiple culture transfers on selective media. To be more useful as a marker, the GUS gene should be coupled with a promoter that will not be expressed by Agrobacterium. Parenchyma callus may serve as a primary screen to provide an efficient way of determining the ideal strain for transformation of deciduous tree fruit genera. In our studies, strain A281 consistently proved to be a vector superior to others tested.
Abstract
CO (5 and 10%) + 4% O2 atmospheres retarded growth of Botrytis cinerea Pers. ex Fr. (in vitro) and reduced decay incidence and severity on inoculated tomatoes (Lycopersicon escuientum Mill.) harvested at the mature-green (MG) or pink (P) stage and held at 12.5°C for up to 14 days (MG) or 10 days (P). This reduction was still evident after holding for an additional 2 to 3 days (P) or 7 days (MG) at 20° in air. CO + 4% O2 atmosphere was more effective than CO + air atmosphere in all experiments. CO + air treatments increased CO2 and C2H4 production rates and hastened ripening of MG fruits, while CO + 4% O2 atmosphere had no or very small effect on these physiological responses relative to 4% O2 atmosphere at 12.5°. After transfer to air at 20°, fruits previously exposed to CO exhibited slightly higher CO2 and C2H2 production and faster ripening than control fruits. CO added to air or 4% O2 did not affect ripening rate of fruits picked at the breaker, turning, or pink stages. CO + air or 4% O2 atmosphere slowed down softening of pink fruits during a 7- or 14-day storage period at 12.5°. Fruits subjected to CO + 4% O2 for 7 days maintained their sugar and acid content better than control fruits.
We compared transpiration estimates of three common desert landscape tree species using stem-flow gauges and lysimetry. Argentine mesquite (Prosopis alba Grisebach), desert willow [Chilopsis linearis (cav.) Sweet var. linearis], and southern live oak (Quercus virginiana Mill., seedling selection) were subjected to three irrigation regimes. Leaching fractions of +0.25, 0.00, and -0.25 were imposed for 2 years. During the summer of the second year, we conducted a comparative transpiration study. Trees growing in 190-liter plastic containers had a highly linear correlation (r = 0.98, P = 0.001) between transpiration estimated by stem-flow gauges and lysimetry. An average 18% error was measured between paired data (total runs of 14 to 72.5 hours) of stem-flow gauge and lysimetry transpiration estimates. However, a lower error was correlated significantly with longer run times (r = -0.37, P = 0.05). Based on field measurements taken in this experiment, run times would have to be >68 hours to maintain an associated error below 10%. Higher cumulative transpiration also was associated with longer run times (r = 0.80, P = 0.001). These results suggest that the stem-flow gauge can be used to estimate transpiration accurately to schedule irrigation for woody ornamental trees in an arid environment, provided that irrigation predictions are not based on short-term stem-flow gauge estimates (<68 hours).
Irrigators in arid and semiarid regions that use reuse water must maintain positive leaching fractions (LFs) to minimize salt buildup in root zones. However, with the continuous feed of NO3-N in reuse water, imposing LFs can also lead to greater downward movement of NO3-N. It is therefore essential that deep movement of NO3-N be assessed relative to nitrogen loading under such conditions. We conducted a long-term monitoring program on nine golf course fairways in southern Nevada over a 1600-d period. The fairways were predominantly bermudagrass [Cynodon Dactylon (L.) Pers.; 35 of 36 site × years] overseeded with perennial ryegrass (Lolium perenne L.; 8 of 9 courses). Courses were irrigated with fresh water, reuse water (tertiary treated municipal sewage effluent), or transitioned to reuse water during the study. Solution extraction cups were inserted at depths of 15, 45, 75, and 105 cm on fairways and sampled and analyzed for NO3-N on a monthly basis. Distribution patterns of NO3-N varied from site to site. Concentrations exceeding 100 mg·L−1 were observed at the 105-cm depth on all three long-term reuse courses. On the transitional courses, 72% of the variation in the yearly average NO3-N concentrations at the105-cm depth could be accounted for based on knowing the amount of fertilizer nitrogen (N) applied, the amount of reuse N applied, and the LF (Y = –42.5 + 0.18 fertilizer N + 0.26 reuse N –62.0 LF). Highest N fertilizer applications occurred on transition courses with little or no reduction in N applications after courses had transitioned to reuse water (pretransition courses 394 + 247 kg·ha−1 N/year versus posttransition courses 398 + 226 kg·ha−1 N/year). The results of this study indicate a need for a more scientific approach to N management on reuse irrigated courses.
Abstract
Horseradish peroxidase (PO) and mushroom polyphenol oxidase (PPO) were added to strawberry purees from ‘Cardinal’ and Arkansas breeding-line 5344 to determine their influence on color during 48 hours at 30°C. Neither enzyme affected strawberry puree color or phenolic content. PO activity was reduced to near zero 24 hours after addition and PPO activity was undetectable 1 hour after addition to puree. Aeration did not affect anthocyanin and flavonoid concentrations, but increased discoloration and nonflavonoid concentration. Strawberry purees containing 50% immature plus 50% ripe fruits were poorer in color and had higher levels of flavonoids. As holding time at 30°C increased, puree color decreased.
Abstract
A study was designed to examine the effects of production systems (i.e., standard bed, wide bed, and black plastic bed), a high and low plant population, and 3 harvest dates on the machine-harvested yield and quality of 2 strawberry (Fragaria × ananassa Duch.) clones. ‘Cardinal’ produced higher yields than A-5344, but had poorer quality. The wide-bed production system produced higher yields than the other production systems and had no adverse effects on quality. ‘Cardinal’ had optimum yield when produced under a low plant population, while A-5344 had optimum yield under a high plant population. Fruit quality was maintained throughout the 5- to 7-day harvest season each year.
Abstract
Parthenocarpic cucumber fruit (Cucumis sativus L. cv. Deliva) of marketable maturity (10 to 14 days after anthesis) were held at 12.5° or 20°C in reduced O2 levels for 5 or 18 days before transfer to air. Carbon dioxide production at reduced O2 levels was generally less than in air; however, at O2 levels < 0.5%, anaerobic respiration resulted in increased rates of CO2 production. Upon transfer to air after 18 days, all samples from reduced O2 showed increased CO2 production rates that equalled or exceeded that of the air controls. Except at 0.0% and 0.25% O2 levels, ethylene production was increased in reduced O2. After transfer to air, ethylene production increased and the increase was inversely related to the previous O2 level. Ethanol and acetaldehyde production were measureable for fruit held in 1% O2 after 18 days at 12.5° and showed dramatic increases at lower O2 levels. Low-O2 injury (pitting) developed on most fruit held at 0.0% O2 and on many fruit held at 0.25% O2. Only minima! commercial benefits are likely to be realized from storage of 1 to 3 weeks in 0.5% to 2.0% O2 at 12.5°.