Harris Fred S, Martin Craig E
Department of Botany, University of Kansas, 66045-2106, Lawrence, KS, USA.
Oecologia. 1991 May;86(4):575-584. doi: 10.1007/BF00318325.
The degree of CAM-cycling was examined in plants from 23 populations representing five morphologically similar species of Talinum to determine how CAM-cycling correlates with site aridity and drought stress. In the field, CAM-cycling, as indicated by the amount of malic acid accumulated in plant tissues overnight, and stable carbon isotope ratio (δC) were positively correlated with an index of site aridity. The relative levels of CAM-cycling and δC values among populations in the field reversed when plants were grown under less arid conditions in a growth chamber such that populations with the highest average CAM-cycling and δC in the field had the lowest averages in the growth chamber. In both cases, plants from all populations showed significantly higher levels of CAM-cycling under drought-stressed conditions relative to conditions known or predicted to be less arid. CAM-cycling was also positively correlated with tissue water content in both well-watered and drought-stressed plants, possibly reflecting greater water conservation associated with reductions in stomatal conductance. Biomass accumulation in plants exhibiting the greatest degree of CAM-cycling in the growth chamber was suppressed by drought stress to a similar degree as in the other plants, yet reproductive biomass of these plants was inhibited to a smaller degree. Thus, the importance of CAM-cycling increases in these species of Talinum during drought stress, due to increased malic acid accumulation overnight, potentially enhancing their water status, survival, and reproduction.
研究了代表土人参属五个形态相似物种的23个种群的植物中的景天酸代谢（CAM）循环程度，以确定CAM循环与生境干旱度和干旱胁迫之间的关系。在野外，植物组织中一夜之间积累的苹果酸量所表明的CAM循环和稳定碳同位素比率（δC）与生境干旱度指数呈正相关。当植物在生长室中较不干旱的条件下生长时，野外种群中CAM循环和δC值的相对水平发生了逆转，以至于在野外平均CAM循环和δC最高的种群在生长室中的平均值最低。在这两种情况下，相对于已知或预计较不干旱的条件，所有种群的植物在干旱胁迫条件下均表现出显著更高的CAM循环水平。在水分充足和干旱胁迫的植物中，CAM循环也与组织含水量呈正相关，这可能反映出与气孔导度降低相关的更强的水分保持能力。在生长室中表现出最大程度CAM循环的植物的生物量积累受到干旱胁迫的抑制程度与其他植物相似，但其生殖生物量受到的抑制程度较小。因此，在干旱胁迫期间，由于一夜之间苹果酸积累增加，这些土人参属物种中CAM循环的重要性增加，这可能会提高它们的水分状况、存活率和繁殖能力。
