The Effect of Night Temperature on Co2 Assimilation, Transpiration, and Water Use Efficiency in Agave Americana L

Abstract

The CO2 and water vapour fluxes arising from the tops of a plant of A. americana, growing in nutrient solution, were continuously measured at night temperatures of 15, 25, and 36°C, the day temperature being held constant at 25°C.Night temperatures of 36°C inhibited both the large nocturnal uptake of CO2 and the accumulation of titratable acidity. The highest rate of CO2 assimilation by day was about half that of the maximum rate observed by night. From the observed rhythms in transpiration rate, it was inferred that high night temperatures also reversed the usual "inverted" stomatal rhythm found in A. americana and other crassulacean plants. Relative to measurements made at a low night temperature (15°C), high night temperatures induced greater stomatal closure at night and opening during the day. The changes in the gas-exchange pattern induced by high night temperature caused the water use efficiency of this plant to fall to values normally associated with noncrassulacean plants. It is concluded that the normal high water use efficiency of A. americana, and its consequent adaptation to arid climates, is causally associated with a requirement for low night temperatures.

Resistance Analysis of Nocturnal Carbon Dioxide Uptake by a Crassulacean Acid Metabolism Succulent, Agave deserti

“…4). A similar stomatal temperature sensitivity has been observed for this species in field studies (15) and also for Agave americana (12) and F. acanthodes (16), e.g. increasing the temperature from 25 to 35 C caused at least a doubling in rwv for all three of these succulents.…”

“…A similarly small effect of 02 on dark CO2 uptake near 15 C has been observed for Kalanchoe daigremontiana (19), while a substantial drop in CO2 uptake of B. daigremontianum as the temperature was raised above 15 C was evidently caused by increased respiration (7). The low temperature optimum for nocturnal CO2 uptake (often near 15 C) is a commonly observed characteristic of CAM plants (7,12,16).…”

C3 Photosynthesis and Crassulacean Acid Metabolism in a Kansas Rock Outcrop Succulent, Talinum calycinum Engelm. (Portulacaceae)

“…The mid-day depression in CO2 uptake observed under well-watered conditions and after 3 d of drought in T. calycinum was also seen in the facultative CAM succulents Sedum acre (18) and Sempervivum montanum (27). Water use efficiencies (calculated as g CO2 uptake [g H20 loss]-') under these two hydration regimes ranged from 0.005 to 0.008 (Table II), slightly lower than those of other succulents ( 12,14,24) and other xerophytic C3 plants (21 (Figs. 2 and 3) and no water loss could be detected with the IR gas analysis system in this experiment.…”

Carbon isotope composition and water-use efficiency in plants with crassulacean acid metabolism

“…The minimisation of water expenditure results from the ability of CAM plants to fix atmospheric CO 2 at night when the driving forces for transpirational water loss are low, and to close stomata during the middle of the day when the driving forces for transpirational water loss are high. Quantification of nocturnal and diurnal net CO 2 exchange and transpiration of leaves or photosynthesising stems enclosed in gas-exchange cuvettes has provided ample evidence for a high instantaneous water-use efficiency (WUE) of CAM plants compared with C 3 plants (Neales 1973;Osmond et al 1979;Nobel 1988;Woerner and Martin 1999), although there may be exceptions (Griffiths et al 1986;Eller and Ferrari 1997). Despite the widely accepted reputation of the CAM pathway as a water-conserving Abbreviations used: CAM, crassulacean acid metabolism; TR, transpiration ratio; WUE, water-use efficiency.…”