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Abstract
Tomato plants (Lycopersicon esculentum Mill. cv. Bonny Best) grown in sand culture and provided with a complete nutrient solution or solutions containing sub- or supraoptimal Mg concentrations were fumigated with hydrogen fluoride (HF) at 5.0 or 9.7 μg F/m3 for 7 days. The severity of HF-induced chlorosis on apical and medial leaves was enhanced in Mg-deficient plants and suppressed in plants grown at the highest level of Mg. Foliar accumulation of fluoride (F) from exposure to the highest HF concentration was inhibited in plants provided the lowest and highest Mg levels. The presence of necrotic tissue probably suppressed the accumulation of F in Mg-deficient plants; however, it was not a factor in plants given supraoptimal Mg. The interactive effects of HF and Mg on foliar injury and F accumulation revealed that Mg-deficient plants were more susceptible and plants given excess Mg were more tolerant to HF than plants cultured on complete nutrient medium.
Abstract
Field plots of bean (Phaseolus vulgaris L. cv. Tendergreen) and tomato (Lycopersicon esculentum Mill. cv. Fireball 861 VR) were exposed for 43 and 99 days, respectively, to filtered ambient air or air containing hydrogen fluoride (HF) at a mean concentration of 0.6 µgF m-3. Comparisons between these treatments revealed that chronic exposure of bean to HF did not affect growth or induce foliar injury, whereas the fresh mass of marketable pods was reduced by almost 25%. There was no effect of HF exposure on growth or fruiting in tomato.
Abstract
The production of CO2 by apple and pear fruit was measured during and after alternating 12-hr exposures to air and N2 atmospheres. Typical stimulation of CO2 evolution in the absence of O2 was observed. Five or more anaerobic cycles imparted a permanent reduction on the subsequent aerobic respiration rate. The differences between control respiration and aerobic CO2 evolution by fruit exposed to cyclic anaerobiosis indicated that the capacity for aerobic respiration was reduced by the early anaerobic cycles. Suppression of the anaerobic stimulation of CO2 production was observed after several cycles suggesting that the capacity for fermentation was accumulatively impaired. Subsequent measurements of physical characteristics showed that flesh softening and chlorophyll degradation, processes which generally coincide during ripening, were differentially affected by cyclic anaerobiosis. Apple scald was induced by anaerobiosis. Pear fruits subjected to anaerobic cycles or continuous anaerobiosis did not ripen during the 14-day poststorage period at 21°C.