Abstract

SummaryPhotosynthetic oxygen evolution by eight month old plants of the Coffea arabica hybrids H-421 (cv. Yellow Catuai × cv. Timor Hybrid) and H-430 (cv. Red Catuai × cv. Timor Hybrid), a Catimor progeny, and one line of cv. Red Catuai was followed polarographically during a dehydration/rehydration cycle. Fully hydrated plants showed a maximum photosynthetic rate (Amax) in the range of 20.6 to 34.6 µmol m−2 s−1 and an apparent quantum yield of 0.074 to 0.086. During dehydration Amax 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, Catuai 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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