The effect of continued light period and temperature changes on the diurnal changes in CO2 exchange rate and stomatal conductance in pineapple
2001
Kawamitsu, Y. (Ryukyu Univ., Nishihara, Okinawa (Japan). Coll. of Agriculture) | Oshiro, T. | Murayama, S.
In CAM plants, CO2 balance is dependent on malic acid content accumulated in the dark period, consequently the light use efficiency is low. In this paper, in order to increase the light use efficiency in pineapple plants, the diurnal changes in gas exchange parameters were examined under such conditions without dark period and of controlling temperature change. Outlines of the result are as follows ; Under the control conditions, the diurnal courses in gas exchange rate showed CAM type with four phases regardless of the change of temperature. Under the continued light period, gas exchange rate and stomatal conductance showed daily variation when temperature change was given in the transient from light to dark period. In addition, the malic acid content was decreased when the temperature changed. Light and dark period temperature gradient under the normal conditions with the dark period affected the diurnal changes in gas exchange rate and CO2 balance. Moreover, it was recognized that the temperature shift affected storage and decarboxylation process of the malic acid content. The slope of the regression line between stomatal conductance and gas exchange rate at Phase-1 and Phase-4 was significantly different, suggesting the difference in the CO2 fixing enzymes. Base on the hypothesis, the enzyme under the continued light period could be speculated. From the present study, stomata is affected by the existence of dark period and temperature change, and it seems to be controlled by the increase and decrease of malic acid content.
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