Centro Internacional de Agricultura Tropical, A.A. 6713, Calif, SA, Colombia.
Photosynth Res. 1986 Jan;9(3):333-43. doi: 10.1007/BF00029798.
Measurements of CO2 and H2O exchange rate and the calculated leaf conductance of attached leaves were conducted over a range of leaf-to-air vapour pressure difference (VPD) (1.5 to 5.5 kPa) to compare the response of the parasitic mistletoe, Phthirusa pyrifolia, with that of its host, the mandarin orange, Citrus reticulata. Seedlings of the host infected with the parasite were grown in well-watered and adequately fertilized large pots outdoors at the CIAT headquarters, Palmira, Colombia, South America. Observations of leaf anatomy of the parasite and nutrient analysis of young tissues of both the parasite and host were made. The photosynthetic rate of the host decreased linearly with increased VPD, whereas the parasite showed a constant rate. This trend coincided with similar responses in leaf conductance. Due to the insensitivity of the parasite stomata, the transpiration rate increased linearly with VPD as compared with an initial increase and then a decrease in the host transpiration rate. The higher photosynthetic rate and the closure of stomata of the host resulted in high water use efficiency as compared with that of the parasite. The parasite accumulated in its leaves more N, P, K and less Ca and Mg than the host. The significance of the host-parasite differential response to air humidity is discussed in relation to mechanism underlying stomatal sensitivity and in the context of host-parasite association.
在叶片-空气蒸气压差（VPD）范围为 1.5 至 5.5kPa 下，对附生叶片的 CO2 和 H2O 交换速率以及计算得出的叶片导度进行了测量，以比较寄生槲寄生（Phthirusa pyrifolia）和其宿主甜橙（Citrus reticulata）的响应。在南美洲哥伦比亚帕尔米拉的 CIAT 总部，将感染寄生植物的宿主幼苗在水分充足和施肥充分的大花盆中种植在户外。观察了寄生植物的叶片解剖结构，并对寄生植物和宿主的幼组织进行了营养分析。随着 VPD 的增加，宿主的光合速率呈线性下降，而寄生植物则保持恒定速率。这种趋势与叶片导度的相似反应一致。由于寄生植物的气孔不敏感，蒸腾速率随 VPD 线性增加，而宿主的蒸腾速率则先增加后减少。与寄生植物相比，宿主较高的光合速率和气孔关闭导致其具有较高的水分利用效率。寄生植物在叶片中积累的 N、P、K 比宿主多，而 Ca 和 Mg 则比宿主少。宿主-寄生植物对空气湿度的差异响应的意义，在气孔敏感性的机制以及宿主-寄生植物关系的背景下进行了讨论。
