Photosynthesis, leaf morphology, and shoot growth as affected by temperatures in cherimoya (Annona cherimola Mill.) trees

Shoot growth, leaf morphology, leaf chlorophyll content, and leaf gas excha nge were investigated for cherimoya trees grown in a sunlit glass-house whe re day/night temperatures were kept at 30/25 degrees C (warm) and 20/15 deg rees C (cool). The shoot growth at warm temperatures was greater than that at cool temperatures until 2 months after sprouting. After that, it became less at cooler temperatures. Both leaf number and area decreased at warm te mperatures within 3 months of sprouting. The leaf palisade and spongy layer s were thinner at warm temperatures. Specific leaf area at warm temperature s was significantly larger. The chlorophyll content of leaves at warm tempe ratures also decreased 6 weeks after the full expansion. Warm temperatures reduced leaf CO2 assimilation rate (A(c)) because of both stomatal and non- stomatal limitations. A(c) and stomatal conductance were suppressed during the midday hours at warm temperatures, suggesting that stomatal closure red uced A(c). The ratio of 1 - C-i (intercellular CO2 partial pressure)/C-a (a mbient CO2 partial pressure) at warm to that at cool temperatures indicated that CO2 fixation ability of leaves grown at warm temperatures was 59% of that at cool temperatures, irrespective of stomatal effect. The initial slo pe of the A(c)/C-i curve, which indicates ribulose bisphosphate carboxylase -oxygenase (Rubisco) activity of leaves developed at warm temperatures was 67% of those at cool temperatures. (C) 1999 Elsevier Science B.V. All right s reserved.