ISHS Acta Horticulturae 334: I International Pineapple Symposium
PHOTOSYNTHETIC CRASSULACEAN ACID METABOLISM IN PINEAPPLE: DIEL RHYTHM OF CO2 FIXATION, WATER USE, AND EFFECT OF WATER STRESS |
| Authors: | F.X. Cote, M. Folliot, M. Andre |
| Keywords: | Ananas comosus, photosynthesis, transpiration, water deficit |
| Abstract:
Some characteristics of photosynthetic crassulacean acid metabolism (CAM) and the physiological mechanisms for the high water use efficiency in pineapple (Ananas comosus (L.) Merr) are described. When pineapples were grown under controlled conditions more than 70% of the daily CO2 fixation occurred during the dark period. The rates of fixation were comparable to those reported for other CAM plants. Compared to wheat, pineapple fixed only 25% of the CO2 per unit of occupied soil per day and transpired only 6% of the water used by wheat. In young plants raised in vitro and placed in non-limiting growth conditions, the proportion of CO2 fixed during the night (CAM) shifted from almost 0 to 70% as the plants grew over a few months from 1 to 300 g fresh weight. The low transpiration rate of pineapple was the consequence of the temporal separation of the nocturnal fixation of CO2 and its assimilation the following day when atmospheric gas exchange is reduced. A limitation of CO2 assimilation to about 66% of the potential, caused by resistance to diffusion, was demonstrated during the second part of the day. This limitation also contributed to the reduction in transpiration. In response to water deficit under controlled conditions, the rate of day CO2 fixation dropped dramatically, and the nocturnal fixation was temporarily stimulated before dropping slowly. After watering, the plant rapidly recovered its capacities of day and night fixation. | |
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