Poster: Water Relations

Abs # 225: Energy dissipation and photosynthetic enzyme activities in pineapple, a CAM plant, under water deficit

Presenter:	Kawamitsu, Yoshinobu , kawamitu@agr.u-ryukyu.ac.jp
Authors	Kawamitsu, Yoshinobu  (A)   Egami, Tomohito  (A)   Fukuzawa, Yasunori  (A)
Affiliations:	(A): University of the Ryukyus, Fuc. of Agriculture

Pineapple belongs to CAM type so it is considered to be the crop for drought resistance. It has been reported that gas exchange ability was recovered quickly in pineapple when rewatering after drought treatment. Therefore, it is conceivable that the pineapple leaves possessing the system that could relax out the influence of water stress. In this report, we studied on changes in photosynthetic enzymes and chlorophyll fluorescence in leaves of pineapple under water stress and rewatering conditions in order to examine physiological adaptation to water deficit. Under water deficit, the stomata was closed and the CO₂ exchange stopped before midnight. Then malate contents decreased prominently because of restricted supplying of CO₂. In this case, it was indicated that CA enzyme and PEP-C enzyme maintained their high activities to fix CO₂ in decreased CO₂. For estimating chlorophyll fluorescence, it was found that Fv/Fm values decreased in water stress conditions after that it recovered at night. As the PS II was damaged at day time, which appeared remarkably in Phase IV. So the Yield in this phase was recorded as a half of that in Phase III. The value of qP was higher in Phase III whereas qN value was higher in Phase IV, suggesting that qP worked mainly in Phase III in return qN worked mainly in Phase IV. The experiment result indicated that the O₂ evolution decreased whereas the O₂ fixation increased in the pineapple leaves under water stress conditions. After 21st days of water deficit treatment, the physiological activity of pineapple leaves was recovered as soon as rewatering. From this, it could be concluded that pineapple is adapted to water stress systematically.