Nilsen Erik T, Meinzer F C, Rundel P W
Department of Biology, Virginia Polytechnic Institute and State University, 24061, Blacksburg, VA, USA.
Hawaiian Sugar Planters' Association, P.O. Box 1057, 96701, Aiea, Hawaii, USA.
Oecologia. 1989 May;79(2):193-197. doi: 10.1007/BF00388478.
Stem photosynthetic responses to environmental parameters were investigated with Psorothamnus spinosus in the Sonoran Desert of California. Light saturation of stem photosynthesis was equal to maximum midday summer irradance (1600-2000 μmol·m·s). The optimum temperature for stem photosynthesis was 39°C, and lower stem temperatures (27-35°C) caused significant decreases (up to 50%) in stem photosynthesis. Positive stem photosynthesis was maintained up to 51°C. Stem photosynthesis was relatively insensitive to increasing vpd up to 5 kPa; However, stem conductance decreased by 25% at a vpd of 5 kPa. At vpd greater than 5 kPa stem photosynthesis decreased relatively more than that of stem conductance causing a decrease in water use efficiency and an increase an intercellular carbon dioxide concentration. Maximum stem photosynthetic rates were low (6.2-10.6 μmol·m·s) on a stem surface area, but, stem photosynthetic rates of young shoots were substantially higher (19.5-33.3 μmol· m·s) on a projected area basis.
在加利福尼亚州索诺兰沙漠，对多刺补骨脂的茎光合对环境参数的响应进行了研究。茎光合作用的光饱和等于夏季中午的最大辐照度（1600 - 2000 μmol·m·s）。茎光合作用的最适温度为39°C，较低的茎温度（27 - 35°C）会导致茎光合作用显著下降（高达50%）。在高达51°C时仍保持正向的茎光合作用。茎光合作用对vpd增加至5 kPa相对不敏感；然而，在vpd为5 kPa时，茎导度下降了25%。当vpd大于5 kPa时，茎光合作用的下降相对大于茎导度的下降，导致水分利用效率降低和细胞间二氧化碳浓度增加。基于茎表面积的最大茎光合速率较低（6.2 - 10.6 μmol·m·s），但基于投影面积，幼嫩枝条的茎光合速率显著更高（19.5 - 33.3 μmol·m·s）。
