Vol. 72 No: 4

Title:
Photosynthetic Oxygen Evolution by Four Coffea Arabica Genotypes Subjected to a Dehydration/Rehydration Cycle

Authors:
A.-A.F. DE ALMEIDA and M. MAESTRI

pp: 593-600

Abstract:
Photosynthetic oxygen evolution by eight month old plants of the Coffea arabica hybrids H-421 (cv. Yellow Catuaí × cv. Timor Hybrid) and H-430 (cv. Red Catuaí × cv. Timor Hybrid), a Catimor progeny, and one line of cv. Red Catuaí was followed polarographically during a dehydration/rehydration cycle. Fully hydrated plants showed a maximum photosynthetic rate (A_max) in the range of 20.6 to 34.6 µmol m^-2s^-1 and an apparent quantum yield of 0.074 to 0.086. During dehydration A_max steadily decreased as the water potential declined. Changes were not found among the slope and the intercept values, with the exception of the slope value of hybrid H-421. The recovery was regained 96.0, 96.5, 85.0 and 78.0 h after rehydration for the genotypes Catimor, H-430, Catuaí and H-421, respectively. In response to stress, the mesophyll resistance restricts carbon dioxide fixation, with after-effects of variable duration.

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