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- Author or Editor: Jingtair Siriphanich x
- Journal of the American Society for Horticultural Science x
Abstract
‘Climax’ lettuce (Lactuca sativa L.) exhibited more severe CO2 injury symptoms than ‘Salinas’ and ‘Winterhaven’ lettuce when exposed at 20°C to air for 1 day following treatment for 6 days at 0° with 15% CO2 in air. All 3 cultivars, however, had similar decreases as revealed by NMR analysis, of about 0.4 and 0.1 pH units in the cytoplasm and vacuole, respectively. This result indicates that variation in the buffering capacity was not related to differences in susceptibility to CO2 injury among these cultivars. Although CO2 reduced pH, it also reduced titratable acidity of lettuce tissue. This change resulted in a higher pH when the lettuce was moved to air. Exposure of lettuce at 0° to light reduced CO2 injury by about 50% relative to tissue kept in the dark. Lettuce tissue kept in air had a higher glucose-6-phosphate content than the CO2-treated lettuce. A hypothesis regarding alternate energy supply mechanisms for resistance of lettuce tissue to elevated CO2 injury is discussed.
Abstract
An atmosphere of air + 15% CO2 caused CO2 injury in lettuce (Lactuca sativa L.) in about 10 days at 0°C. However, subsequent removal of CO2 was necessary for the brown stain symptoms to develop. Under CO2 treatment, phenylalanine ammonia lyase (PAL) was induced and its activity correlated well with the development of the injury. Nevertheless, PAL activity did not seem responsible for the differences in susceptibility to CO2 injury among the 3 lettuce cultivars included in this study. Prevention of the development of brown stain symptoms by CO2 probably was due to its inhibition of phenolics production and the inhibition of polyphenol oxidase activity.
Abstract
An atmosphere of air + 15% CO2 prevented the development of cinnamic acid-4-hydroxylase in both lettuce (Lactuca sativa L.) and potato (Solanum tuberosum L.) tissues. Subsequent removal of CO2 did not allow the enzyme development to proceed, whereas total phenolic content increased and browning became visible. In addition, CO2 did not have an inhibitory effect on the enzyme, prepared from potato tissue, per se. Thus, the effects of CO2 on inhibition of lettuce tissue browning does not appear to involve this enzyme. No tyrosine ammonia lyase activity was found in lettuce tissue.