THE LOSS OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE CAUSED BY24-HOUR RAIN TREATMENT FULLY EXPLAINS THE DECREASE IN THE PHOTOSYNTHETIC RATE IN BEAN-LEAVES/
M. Ishibashi et al., THE LOSS OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE CAUSED BY24-HOUR RAIN TREATMENT FULLY EXPLAINS THE DECREASE IN THE PHOTOSYNTHETIC RATE IN BEAN-LEAVES/, Plant physiology, 111(2), 1996, pp. 635-640
Recently, we have found that simulated rainfall causes a chronic inhib
ition of leaf photosynthesis in Phaseolus vulgaris (M. Ishibashi and I
. Terashima [1995] Plant Cell Environ 18: 431-438). Mechanisms of this
inhibition were examined in the present study. After the plants were
treated with continuous mist for 24 h and then dried to unwet conditio
ns, light-saturated photosynthetic rates of the leaves measured at 35
Pa ambient CO2 decreased to one-half of the control level. The extract
able activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubi
sco) also decreased to the same extent. Unexpectedly, this decline was
due not to the lowered activation state but to the decrease in the am
ount of Rubisco. Before or after the ''rain'' treatment, the relations
hip between the net photosynthetic rate and the amount of Rubisco was
expressed as a unique linear function with a small intercept (r(2) = 0
.84). From these it was inferred that the main cause of the rain-induc
ed decline in photosynthetic rate was the loss in amount of Rubisco.