Schulze E-D, Lange O L, Ziegler H, Gebauer G
Lchrstuhl Pflanzenökologie, Universität Bayreuth, Box 101251, W-8580, Bayreuth, Germany.
Lehrstuhl Botanik II, Universität Würzburg, Mittlerer Dallenbergweg 64, W-8700, Würzburg, Federal Republic of Germany.
Oecologia. 1991 Dec;88(4):457-462. doi: 10.1007/BF00317706.
Xylem-tapping mistletoe species growing on Mimosaccae, non-Mimosaceae and hosts performing Crassulacean acid metabolism (CAM) were studied along an aridity gradient in the Namib desert. °C-values of mistletoes became more negative with decreasing nitrogen (N)-concentration in their leaves, while the host plants showed no such relationship. This might suggest that mistletoes regulate their water use efficiency according to the nitrogen supply from the host. However, further inspection of the data indicates that the relations of δC-values with leaf nitrogen in mistletoes may result from carbon input from the host. This is especially true for mistletoes growing on CAM plants which exhibit a very high δC-value, but show no evidence of CAM. It is calculated that about 60% of the carbon in mistletoes growing on C3 and on CAM hosts originated from the host. The hypothesis of Marshall and Ehleringer (1990) that xylem tapping mistletoes are also carbon parasites could explain the change in δC-values with N-supply and the difference in δC-values between mistletoes growing on C3 and CAM hosts.
在纳米布沙漠中，沿着干旱梯度对生长在含羞草科、非含羞草科植物以及进行景天酸代谢（CAM）的寄主上的吸汁槲寄生物种进行了研究。随着槲寄生叶片中氮（N）浓度的降低，其δC值变得更负，而寄主植物则没有这种关系。这可能表明槲寄生根据寄主提供的氮来调节其水分利用效率。然而，对数据的进一步检查表明，槲寄生中δC值与叶片氮的关系可能源于寄主的碳输入。对于生长在具有非常高δC值但无CAM证据的CAM植物上的槲寄生来说尤其如此。据计算，生长在C3寄主和CAM寄主上的槲寄生中约60%的碳来自寄主。马歇尔和埃勒林格（1990）提出的吸汁槲寄生也是碳寄生植物的假说，可以解释δC值随氮供应的变化以及生长在C3寄主和CAM寄主上的槲寄生之间δC值的差异。
