Search Results
You are looking at 31 - 40 of 52 items for
- Author or Editor: Mikal E. Saltveit Jr. x
Abstract
A method is described for studying the 3-dimensional distribution of roots grown in a medium consisting of small pieces of glass. After growing to a desired size, the plant is sacrificed by evaporating all water from the media with flowing air. To visualize the undisturbed root system, an immersion oil with the same refractive index as the glass is added to the glass container in which the plant was grown.
Abstract
Investigations employing gases other than air, e.g. mixtures of O2, CO2, N2, C2H4, etc., in dynamic systems usually employ gas mixtures prepared in high pressure cylinders or by elaborate metering devices and mixing chambers using component gases from high pressure sources (1, 2, 3). Both systems require analysis of the resultant mixture to confirm that the composition is within the desired range. Physiological investigations often require thousands of liters of unique and portable gas mixtures. Commercially prepared mixtures in high pressure cylinders are expensive and metering systems are cumbersome. We have devised a simple method for rapidly preparing (ca. 10 min) dilute (μl/liter) gas mixtures in portable laboratory-owned cylinders at pressures of ca. 140 kg/cm2 (2000 psi). This method can also be used to prepare gas mixtures in percentage composition at lower pressures, ca. 70 kg/cm2 (1000 psi). This method uses a pressure differential between 2 cylinders of compressed gas to inject a known quantity of another gas from a connecting manifold into the lower pressure cylinder.
Sugar peas (Pisum sativum var. saccharatum cv. Manoa Sugar) were stored for 14 or 21 days under controlled atmospheres (CA) of 21% or 2.4% O2, plus 0%, 2.6%, or 4.7% CO2 at 10 or 1C. Changes in appearance, weight, and in the concentrations of chlorophyll, total soluble sugars, insoluble solids, and soluble protein were evaluated before and after storage. After 14 days of storage at 10C there were minor changes in all indicators of quality under the various storage conditions, but the appearance of sugar peas was better under CA than under 21% O2. When quality was evaluated after 21 days, however, storage under CA at 10C was not as beneficial as storage in 21% O2, at 1C. Holding peas in 2.4% O2, for up to 3 weeks at l0C, a higher than recommended storage temperature, maintained better quality than 21% O2. Increasing the CO, concentration from 0% to 2.6% or 4.7% had no adverse effects on quality and had a beneficial effect in some treatments. Compared with storage in 21% O2, the appearance of the peas was better, the concentrations of chlorophyll and soluble sugar were maintained at higher levels, and the insoluble solids were decreased in all atmospheres with 2.4% O2. Appearance and concentrations of chlorophyll, soluble sugars, and proteins were maintained at 1C regardless of treatments.
Abstract
The ethanol content of ‘Harrison’ and ‘Jersey’ highbush (Vaccinium corymbosum L.) and ‘Premier’ rabbiteye blueberries (V. ashei Reade) increased linearly with time (1 to 4 hours) and exponentially with temperature (0° to 30°C) during exposure to an atmosphere of pure N2 or CO2. CO2 production was depressed about 20% under N2 gas. Berries which were placed in air after 4 hours in CO2 lost half the CO2 they contained every 30 minutes. After 3 hours, CO2 evolution from treated and control fruit was the same. Fruit quality was unaffected by exposure at 0° to 30° to pure N2 or CO2 gas for up to 4 hours. However, 22 hours in a CO2 atmosphere at either 0° or 30° reduced fruit quality. An equation was derived to calculate ethanol accumulation under different cooling rates.
Abstract
The ethanol concentration of ‘Carlos’ grapes (Vitis rotundifolia Michx.) increased linearly with time (1 to 4 hours) and exponentially with temperature (0° to 30°C) during exposure to an anaerobic N2 or CO2 atmosphere. Ethanol loss from grapes placed in air after 4 hours in CO2 was dependent on the concentration of ethanol accumulated during anaerobiosis. Fruit quality was unaffected by 0° exposure to an anaerobic CO2 atmosphere for up to 72 hours after 6 hours in CO2 at 30°. However, 30 hours in a CO2 atmosphere at 30° reduced fruit quality. An equation was derived to calculate ethanol accumulation during cooling of warm fruit under anaerobic atmospheres.
The physiological responses associated with chilling of horticulturally mature cucumber (Cucumis sativus L.) fruit were examined using 13 lines that differ in chilling sensitivity. The low correlation coefficient between pitting and decay suggested that these two early manifestations of chilling injury are not significantly related. Likewise, fruit pitting and decay were not highly correlated with the tolerance of seedlings to chilling, suggesting that fruit and seedlings of the same line may have dissimilar sensitivity to chilling temperatures. Exudates from fruit cut in half transversely were collected on filter paper. The amount of exudate showed a significant correlation with pitting, decay, and percent ion leakage after 10 days of chilling. The fresh and dry weight of the exudates from fruit kept for 8 days at 12.5C ranged from 141- to 346-mg fresh weight and from 15 to 47-mg dry weight, respectively. Cucumber lines that were more sensitive to chilling had watery exudate, as indicated by their lower dry weight and percent solids. The conductivity of exudates from sensitive lines was higher (60 μsiemen/cm) than from chilling resistant lines (30 μsiemen/cm). Chilling-induced ethylene production was higher in sensitive than in resistant lines, and chilling caused a greater loss of ethylene forming enzyme activity in resistant lines than from chilling sensitive lines.
Abstract
Application of 0.3-0.5 M Ca or 0.1−1.0 mM 2,4-D strongly inhibited russet spotting (RS) in iceberg lettuce (Lactuca sativa L.) leaf tissues and significantly reduced extractable phenylalanine ammonia-lyase (PAL) activity. Since neither Ca nor 2,4-D reduced PAL activity in vitro, they may inhibit RS development by inhibiting in vivo PAL biosynthesis. Chemical names used: (2,4-dichlorophenoxy)acetic acid (2,4-D); and 1H-indol-3-acetic acid (IAA).
Abstract
Free galactose was detected in outer pericarp tissue from fruit of ‘Heinz 1350’ and nor tomato (Lycopersicon esculentum Mill.). The amount of free galactose increased almost 8-fold in ‘Heinz 1350’ fruit during ripening. In contrast, it did not change significantly in 32- to 52-day-old (post-pollination) nor fruit. A 25 μl drop of water ± 100 μg galactose was applied to the locular surface of 1.5 cm diameter pericarp disks. While disks from 40- and 60-day-old nor tomatoes, and from mature green and pink ‘Heinz 1350’ tomatoes, were able to reduce the level of free galactose to levels found in control tissue within 48 hr, disks of red ripe tissue were only able to metabolize 45% of the added galactose within this time. Pink ‘Heinz 1350’ tomatoe disks lost galactose more slowly than disks of mature green tomatoes. The results suggest that the increased amount of free galactose in pericarp tissue of ripening tomatoes may be the result of their progressive inability to metabolize galactose as they ripen.
Abstract
Wounding freshly harvested or cured sweet potato [Ipomoea batatas (L.) Lam.] roots by either breaking, or cutting them in half stimulated C2H4 production in all 13 cultivars and selections examined. Ethylene production was stimulated within 1 day of wounding and generally continued to increase for 7 days before decreasing. At the peak of production, wounded freshly harvested roots produced about 22 times more C2H4 than controls, while C2H4 production from wounded cured roots of the same cultivar or selection increased about 86 times. Wounding stimulated CO2 production by about 72% over the controls. There were marked cultivar differences in the maximum rate of wound-induced C2H4 production.
Abstract
Periodic shaking increased the resistance of potted poinsettia (Euphorbia pulcherrima Klotzsch ex. Willd., cv. Annette Hegg Diva) plants to mechanically induced leaf epinasty, but this resistance was lost within 24 hours of discontinuing the shaking. Bending petioles, not their reorientation in the gravitational field, caused increased ethylene production by excised petioles. Foliar sprays containing 40 μm cycloheximide, which were applied 24 hours before the plants were sleeved for 24 hours, completely prevented mechanically induced leaf epinasty, but were phytotoxic to the bracts.