Adaptive physiology of riparian cottonwoods and hybrid poplars

美洲黑杨是适应于整个北方半球河岸（河漫滩）地带的杨树属树种。种间杂交在物种重叠的地区自然发生，也被人工生产以创造杂交杨树，这是加拿大生长最快的树木。 由于河流筑坝和改道以及其他人类活动的影响，北美西部的棉白杨种群数量急剧下降。 我建议进一步研究河岸三角杨的生理生态及其保护。 调查将涉及三个重叠的领域，水力学，激素和杂交。 水力学研究将调查连接溪流、河岸基质、根、芽和大气的水通量。 树木水分关系的方面将调查水力传导和脆弱性木质部空化，空气栓塞在木质部血管破坏的能力进行水。这些研究将比较和对比四种加拿大棉白杨叶杨，研究雄性和雌性之间的差异，还将调查来自西南部阿尔伯塔复杂杂交区的自然发生的杨树杂交种和人工交叉杂交种。 这些研究将调查负责适应不同环境的生理过程，我们已经确定了一些“幸存者”，在慢性压力后仍然存在的树木，可能是独特的干旱适应。 植物激素的研究将调查激素赤霉素（GA）的作用，在不断变化的环境条件下的协调棉白杨的生长反应，研究还将调查GA水平和行动的转基因修饰的后果。 这些调查将（1）揭示三角叶杨和杨树的生理生态适应，（2）通过河流调节和水管理促进原生三角叶杨的恢复，（3）确定可遗传的生理性状，使干旱适应杂交杨树的发展。

Cottonwoods are Populus species that are adapted to riparian (floodplain) zones throughout the Northern Hemisphere. Interspecific hybrids occur naturally in zones where species overlap and are also artificially produced to create hybrid poplars, the fastest-growing trees in Canada. Due to the impacts of river damming and diversion and other human influences, cottonwood populations have collapsed across western North America. I propose to further investigate the ecophysiology of riparian cottonwoods and their conservation. Investigations will involve three overlapping areas, hydraulics, hormones and hybridization. Studies of hydraulics will investigate water fluxes linking streams, riparian substrates, roots, shoots and the atmosphere. Aspects of tree water relations will investigate hydraulic conductance and vulnerabilities to xylem cavitation, air embolism in the xylem vessels that destroys the capacity to conduct water. The studies will compare and contrast the four Canadian cottonwood species, study differences between males and females, and will also investigate naturally occurring Populus hybrids from the complex hybrid zone in southwestern Alberta, and artificial intersectional hybrids. The studies will investigate the physiological processes responsible for adaptation to differing environments and we have identified some 'survivors', trees that have persisted after chronic stress and may be uniquely drought-adapted. Plant hormones studies will investigate the roles of the hormone gibberellin (GA) in the coordination of cottonwood growth responses to changing environmental conditions and studies will also investigate consequences of transgenic modification of GA level and action. These investigations will (1) reveal ecophysiological adaptations of cottonwoods and poplars, (2) contribute to the restoration of native cottonwoods through river regulation and water management, and (3) identify heritable physiological traits that may enable the development of drought-adapted hybrid poplars.