Loreto F, Sharkey T D
Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, WI 53706, USA.
Tree Physiol. 1990 Dec;6(4):409-15. doi: 10.1093/treephys/6.4.409.
We examined the photosynthetic responses of olive (Olea europea L.) leaves exposed to either (a) two hours of high leaf-to-air vapor pressure difference (vpd) or (b) four 30-min cycles of high vpd separated by 15-min periods of recovery at low vpd. Neither treatment affected photosynthesis when vpd was less than 3.0 kPa. Photosynthesis by mature leaves was also insensitive to higher vpd, but photosynthesis of young leaves was reduced by both treatments at a vpd higher than 3.2 kPa. This effect of vpd was much smaller under high intercellular CO(2) pressure. Autoradiograms showed that under a vpd of 3.2 kPa, mature leaves photosynthesized uniformly, but patches of reduced CO(2) fixation occurred in the distal part of young leaves. We conclude that heterogeneities in photosynthesis along the length of the leaf caused the apparent reduction of photosynthesis in our experiments. This pattern of patchy photosynthesis was different from that observed in mesophytic herbs, but the effect on gas exchange analysis was the same. In this case, apparent biochemical effects of low humidity on photosynthesis of young olive leaves are likely an artifact.
我们研究了暴露于以下两种情况的油橄榄（Olea europea L.）叶片的光合响应：（a）两小时的高叶-气蒸汽压差（vpd）；（b）四个30分钟的高vpd循环，每次循环之间间隔15分钟的低vpd恢复期。当vpd小于3.0 kPa时，两种处理均未影响光合作用。成熟叶片的光合作用对较高的vpd也不敏感，但在vpd高于3.2 kPa时，两种处理均使幼叶的光合作用降低。在高细胞间CO₂压力下，vpd的这种影响要小得多。放射自显影片显示，在3.2 kPa的vpd下，成熟叶片均匀地进行光合作用，但幼叶远端出现了CO₂固定减少的斑块。我们得出结论，在我们的实验中，叶片长度方向上光合作用的异质性导致了光合作用的明显降低。这种斑驳的光合作用模式与中生草本植物中观察到的不同，但对气体交换分析的影响是相同的。在这种情况下，低湿度对幼嫩油橄榄叶片光合作用的明显生化影响可能是一种假象。
