Photosynthesis and water relations of drought-stressed pineapple plants
1996
Marler, T. E. | Lawton, P. D.
Water was withheld from container-grown 'Smooth Cayenne' pineapple (Ananas comosus [L.] Merrill) plants to determine the photosynthetic and water relations responses to water deficit in the climate of Guam (Iat. 13 ON). Well-watered plants exhibited a net CO2 efflux during the photoperiod, which lessened during mid-afternoon and became a net CO2 influx by about 2-h before sunset. Net CO2 influx reached maximum shortly after sunset, and remained stable throughout the nocturnal period. Maximum mean net CO2 assimilation was 2.5 to 3.0 Ilmol·m·2·s·'. About 90% of the total daily atmospheric CO2 influx occurred during the nocturnal period. Pineapple plants responded to water deficit initially with a reduction in the net CO2 influx during the nocturnal period. The daily pattern of gas exchange and the relative proportion of day/night atmospheric CO2 influx were not affected by water deficit at this stage. As drought stress continued to develop, total daily atmospheric CO2 influx of pineapple plants was reduced to about 10% of that for well-watered plants, and 100% of this influx occurred during the night. Relative leaf water content of drought-stressed plants decreased in comparison to that of well-watered plants beginning week 4. Water deficit did not influence osmotic potential of leaf tissue which was collected pre-dawn then rehydrated, but reduced osmotic potential of rehydrated root tissue about 20% below that of well-watered plants. These results indicate that in addition to the high water use efficiency which results from the presence of Crassulacean acid metabolism, osmotic adjustment of roots and stability of photochemical efficiency during the photoperiod may be other physiological features of drought adaptation for pineapple.
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