PHOTOSYNTHETIC GAS-EXCHANGE AND THE STABLE-ISOTOPE COMPOSITION OF LEAF WATER - COMPARISON OF A XYLEM-TAPPING MISTLETOE AND ITS HOST
PHOTOSYNTHETIC GAS-EXCHANGE AND THE STABLE-ISOTOPE COMPOSITION OF LEAF WATER - COMPARISON OF A XYLEM-TAPPING MISTLETOE AND ITS HOST
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DOI：
10.1111/j.1365-3040.1993.tb00480.x
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发表时间：
1993-08-01
影响因子：
7.3
通讯作者：
EHLERINGER, JR
中科院分区：
文献类型：
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作者：
FLANAGAN, LB;MARSHALL, JD;EHLERINGER, JR
对生长在犹他州南部的槲寄生（Phoradendron juniperinum）及其寄主树杜松（Juniperusosteosperma）的木质部进行了光合气体交换和叶面水的稳定同位素组成的测量。将观察到的从叶子中提取的水的同位素组成与叶子内蒸发位点同位素富集的克雷格-戈登模型的预测进行比较。与槲寄生相比，杜松的同化率较高，气孔导度较低。这导致杜松树的细胞间/环境二氧化碳值低于其槲寄生寄生虫。对于槲寄生，观察到的叶水中氢和氧同位素富集度低于模型预测的值。在杜松中，叶面水氢同位素富集度也低于蒸发富集模型预测的值。相比之下，杜松叶水中的氧同位素富集略高于叶子内蒸发部位的预测值。槲寄生叶子中的氢同位素富集显示出随茎段的系统变化，在最年轻的茎的尖端附近最高，并向槲寄生的基部降低，其中同位素组成与寄主树中茎水的组成接近。在相关模式中，随着年龄的增长，槲寄生叶子的中午气孔导度突然下降。
Photosynthetic gas exchange and the stable isotopic composition of foliage water were measured for a xylem tapping mistletoe, Phoradendron juniperinum, and its host tree, Juniperus osteosperma, growing in southern Utah. The observed isotopic composition of water extracted from foliage was compared to predictions of the Craig-Gordon model of isotopic enrichment at evaporative sites within leaves. Assimilation rates of juniper were higher and stomatal conductance was lower than the values observed for the mistletoe. This resulted in lower intercellular/ambient CO2 values in the juniper tree relative to its mistletoe parasite. For mistletoe, the observed foliage water hydrogen and oxygen isotopic enrichment was less than that predicted by the model. In juniper, foliage water hydrogen isotopic enrichment was also lower than that predicted by the evaporative enrichment model. In contrast, the oxygen isotopic enrichment in juniper foliage water was slightly greater than that predicted for the evaporative sites within leaves. Hydrogen isotopic enrichment in mistletoe foliage shows systematic variation with stem segment, being highest near the tips of the youngest stems and decreasing toward the base of the mistletoe, where isotopic composition is close to that of stem water in the host tree. In a correlated pattern, mid-day stomatal conductance declined abruptly in mistletoe foliage of increasing age.