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- Author or Editor: Mikal E. Saltveit Jr. x
Abstract
Foliar sprays of either 10 mM aminoethoxyvinylglycine or 3 mM silver ions applied 24 hours before potted poinsettia plants (Euphorbia pulcherrima Klotzsch ex. Willd., cv. Annette Hegg Diva) were sleeved for 24 hours, significantly reduced the development of leaf epinasty after removal of the sleeves.
Abstract
Compressed air was injected into fruit of pickling cucumber (Cucumis sativus L.) to simulate the build-up of gas during brining. Four size grades were tested from 4 cultivars over 2 harvests and 2 seasons. Carpel adhesion, as measured by the air pressure required to separate the carpels, was negatively correlated with fruit size. Higher air pressure was required to separate the carpels of cultivars resistant to balloon bloating. The formation of balloon bloaters in cucumbers brined in commercial tanks was correlated with results from the compressed air test of carpel adhesion, especially with fruit 45 to 51 mm in diameter.
Abstract
Basipetal auxin transport occurred in intact and excised Dracaena marginata stem sections at an apparent velocity of about 5 mm/hr. Application of 20 µl of 0.1 mm 2,3,5-triiodobenzoic acid (TIBA) to the basal cut end of a 3-cm stem segment excised 20 cm from the apex of 1-m-tall plants reduced basipetal auxin transport by 60%. Similar application to the apical end had no effect on acropetal auxin movement. Lateral auxin movement was observed 24 hours after application of radioactive auxin to decapitated stems which had grown horizontally for at least 30 days.
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.
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
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°.
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
Inhibitors of ethylene biosynthesis—aminoethoxyvinylglycine, aminooxyacetic acid, and α-aminoisobutyric acid—inhibited ethylene and lycopene biosynthesis in 1.5-cm disks of excised pericarp tissue of tomato (Lycopersicon esculentum Mill. cv. Michigan-Ohio Hybrid). Application of 10 μl/liter ethylene promoted normal lycopene synthesis, but did not stimulate ethylene synthesis.
Abstract
Mechanically bent petioles of potted poinsettia plants (Euphorbia pulcherrima Klotzsch ex. Willd., cvs. V-14, Eckespoint C-1 Red, Annette Hegg Diva, Annette Hegg White, and Annette Hegg Hot Pink) produced 3 to 70 times as much ethylene as petioles from unstressed plants. The Annette Hegg cultivars which were most susceptible to leaf epinasty after being sleeved for 24 hours showed the greatest enhancement of ethylene evolution after being mechanically stressed for 24 hours. Exposure to 10 ppm ethylene in air produced the same cultivar dependent pattern of epinasty in 4 hours as was produced by 24 hours of mechanical stress. Spraying with 250 ppm AgNO3, an antagonist of ethylene synthesis and action, reduced the severity of epinasty in ‘Annette Hegg Diva’ plants sleeved for 24 hours. The less susceptible ‘Eckespoint C-1 Red’ and ‘V-14’, produced less stress ethylene and were less susceptible to ethylene-induced epinasty.
Abstract
Ag(I), applied in aqueous solution as AgNO3, inhibited ethylene synthesis and ripening of mature green banana fruit slices and pericarp discs of mature green tomato fruit. It also inhibited ethylene production by cortical tissue from post-climacteric apples. Concentrations of Ag(I) which reduced ethylene synthesis had an inconsistent effect on CO2 production: no effect on banana slices (1.0 mm Ag+), stimulation in apple tissue (0.1 mm Ag+), and inhibition in tomato tissue (0.3 mm Ag+). This was accompanied by a slight amount of tissue necrosis at these concentrations. Of the 7 metallic salts tested, only Ag(I) inhibited ripening and ethylene synthesis at observed non-phytotoxic levels. Inhibition of ripening and ethylene synthesis by Ag(I) was evident in tissue treated with sufficient exogenous ethylene to elicit both responses in control tissue. The inability of applied ethylene to overcome the inhibitory effect of Ag(I) suggests that the silver ion may interfere with the primary action of ethylene in the tissue.