Barnes Laboratory, The University of Chicago, Chicago, Illinois 60637.
Plant Physiol. 1986 Jun;81(2):678-80. doi: 10.1104/pp.81.2.678.
Plants of Sedum rubrotinctum R. T. Clausen were studied in a green-house over a 2-year period without watering. Only the apical leaves survived and were turgid at the end of the experiment. The midday leaf water potential of these apical leaves was -1.20 megapascals, while the leaf water potential of comparable leaves on well-watered control plants was -0.20 megapascals. The unwatered plants appear to have maintained turgor by means of an osmotic adjustment. After 2 years without water the plants no longer exhibited a nocturnal accumulation of titratable acidity. However, the daytime levels of titratable acidity of the unwatered plants were more than 2-fold greater than the levels in well-watered control plants. Well-watered plants of S. rubrotinctum exhibited seasonal shifts in biomass stble carbon isotope ratios, indicating a greater proportion of day versus night CO(2) uptake in the winter than in the summer. The imposition of water stress prevented the expression of this seasonal rhythm and restricted the plants to dark CO(2) uptake.
在两年的时间里，我们在温室中对Sedum rubrotinctum R. T. Clausen 进行了研究，期间没有浇水。只有顶叶存活下来，实验结束时仍保持饱满状态。这些顶叶的中午叶片水势为-1.20 兆帕斯卡，而浇水充足的对照植物的可比叶片的水势为-0.20 兆帕斯卡。未浇水的植物似乎通过渗透调节保持了膨压。在没有水的情况下 2 年后，植物不再表现出可滴定酸度的夜间积累。然而，未浇水植物的白天可滴定酸度水平是浇水充足的对照植物的两倍以上。浇水充足的 S. rubrotinctum 植物表现出生物量稳定碳同位素比值的季节性变化，表明冬季白天与夜间 CO2 吸收的比例大于夏季。施加水分胁迫会阻止这种季节性节律的表达，并限制植物在黑暗中吸收 CO2。
