|Shahak, Yosepha - INST HORTICULTURE ISRAEL|
Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 5, 1999
Publication Date: N/A
Technical Abstract: Demand for mango (Mangifera indica L.) has increased dramatically in the USA, western Europe and Japan during the last decade, encouraging production in temperate areas. Moderate temperatures (e.g. <15 degree C) are known to limit photosynthetic productivity of mango, and mechanistic basis for this is unknown. In mango, inhibition of photosynthesis appears correlated with cool nights instead of combined high light and low temperature. Chilling potted mango plants overnight at 10 degree C had no effect on the new CO2 assimilation rate(A) measured during the first 2 hours following photoperiod at 30 degree C and 700.umol m**-2s**-1 PPFD. After 3 hours there was significant inhibition of A which was maintained through the rest of photoperiod. This reduction in photosynthesis was not a product of photoinhibition of PSII, as the quantum efficiencies of PSII photochemistry measured concurrently with A (phiPSII) or after 20 minutes dark-adaptation (Fv/Fm) were not significantly inhibited. The cause of reduction in photosynthesis was not due to stomatal closure reducing leaf intercellular CO2 concentration (c,), and stomatal limitation of A was not increased following the dark chill. Examination of the relationship between A and ci revealed a dark chill-induced decline in maximum velocity of carboxylation of ribulose 1,5bisphosphate (RuBP) by Rubisco (Vc,max), and maximum rate of electron transport contributing to RuBP regeneration by Calvin cycle (Jmax). In addition, end-product feedback inhibition of photosynthesis, by reduced utilization of triose phosphates limiting inorganic phosphate (Pi) return to chloroplast, may be involved in observed inhibition of photosynthesis by chilling mango in the dark.