Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2000
Publication Date: N/A
Citation: N/A Interpretive Summary: Demand for subtropical fruits such as mango (Mangifera indica L.) has increased dramatically in the USA, Western Europe and Japan during the last decade. USA mango consumption increased from 70 to 370 million pounds between 1988 and 1996, and less than 2 percent of this is from domestic production (USDA, 1997). This rapidly emerging demand is encouraging production in cooler areas such as Israel and parts of the Americas even though moderately cool temperatures are known to limit the photosynthetic productivity of subtropical fruit trees. This research is intended to determine the mechanistic basis for the chill-induced limitation of photosynthesis in these tropical woody species as the essential first step in improving chill tolerance in mango and in developing management practices for growing mango in cool climates. The research reported here indicates that the deployment of shading netting in mango orchards during the coolest parts of the season holds significant promise as a chill damage avoidance strategy. Thus, this research will be of interest to agricultural scientist and fruit tree breeders concerned with developing improved stock for cultivation in temperature climates. In addition, the experimentation with shade netting to protect against chill-induced photodamage could have near term impact as a management strategy for existing mango orchards.
Technical Abstract: The effect of a cold night on photosynthesis in herbaceous chilling-sensitive crops, like tomato, has been extensively studied and is well characterized. This study examined how the behaviors of the subtropical fruit tree, mango, compared to these well-studied systems. Unlike tomato, chilling between 5 and 10C overnight produced no significant inhibition of light-saturated CO2 assimilation (A) during the first hours following rewarming measured either under controlled environment conditions, or in the field. By midday, however, there was a substantial decline in A, which could not be attributed to photoinhibition of PSII, but rather was associated with an increase in stomatal limitation of A and lower Rubisco activity. Over night chilling of tomato can cause severe disruption in the circadian regulation of key photosynthetic enzymes and is considered to be a major factor underlying the dysfunction of photosynthesis in chilling-sensitive herbaceous plants. In contrast, examination of the gas-exchange of mango leaves maintained under constant conditions for two days, demonstrated that large depressions in A during subjective night were primarily the result of stomatal closure. Chilling did not disrupt the ability of mango leaves to produce circadian rhythm in stomatal conductance. Rather, the midday increase in stomatal limitation of A appears to be the result of altered guard cell sensitivity to CO2.