Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
Tree Physiol. 2010 Jan;30(1):23-31. doi: 10.1093/treephys/tpp100. Epub 2009 Dec 3.
Nighttime transpirational water loss from C(3) trees occurs without carbon gain and is both common and substantial. However, the magnitude of this water loss varies and a better understanding of the environmental factors driving this variation is needed. We investigated the response of nighttime conductance (g(night)) and transpiration (E(night)) to soil nitrogen limitation. We used instantaneous gas exchange measurements in greenhouse studies of Populus angustifolia James (narrowleaf cottonwood) and Populus balsamifera L. spp. trichocarpa (Torr. & A. Gray ex Hook.) Brayshaw (black cottonwood). g(night) for sufficiently watered plants ranged from 0.045 to 0.308 mol m(-2) s(-1) for P. balsamifera and 0.037 to 0.188 mol m(-2) s(-1) for P. angustifolia, which was much larger than minimum leaf conductance (g(min); up to 0.005 mol m(-2) s(-1) in the dark). Long-term nitrogen limitation sufficient to substantially reduce biomass did not affect g(night) or E(night) when potentially confounding water stress effects were eliminated. We conclude that nighttime water loss from two Populus species is large and although it is under stomatal control is not regulated at night in response to soil nitrogen availability.
夜间 C(3) 植物的蒸腾性水分损失不伴随碳增益，这种现象普遍且显著。然而，这种水分损失的幅度存在差异，因此需要更好地理解驱动这种变化的环境因素。我们研究了夜间导度（g(night)）和蒸腾（E(night)）对土壤氮限制的响应。我们利用温室研究中对美洲黑杨（窄叶杨）和银白杨（黑杨）的瞬时气体交换测量来进行研究。对于充分浇水的植物，g(night)的范围为 0.045 至 0.308 mol m(-2) s(-1)，对于 P. balsamifera，而对于 P. angustifolia，g(night)的范围为 0.037 至 0.188 mol m(-2) s(-1)，这远大于最小叶片导度（g(min)；在黑暗中最高可达 0.005 mol m(-2) s(-1)）。长期氮限制足以大幅减少生物量，但在消除潜在的水分胁迫影响后，g(night)或 E(night)不受影响。我们的结论是，两种杨属植物的夜间水分损失很大，尽管它受到气孔控制，但不会根据土壤氮供应情况在夜间进行调节。
