Deacon Nicholas J, Grossman Jake J, Cavender-Bares Jeannine
Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul Minnesota.
Present address: Minneapolis Community and Technical College 1501 Hennepin Avenue Minneapolis 55403 MN.
Ecol Evol. 2019 Jun 25;9(14):8062-8074. doi: 10.1002/ece3.5364. eCollection 2019 Jul.
We assessed the vulnerability of an isolated, relictual Pleistocene hybrid aspen population of conservation interest () and the nearest populations of its parent species ( and ) to springtime post-bud break freezing and growing season drought stress. Response to these stressors in the three taxa was compared in terms of avoidance and tolerance.
North American Midwest; USA.
Unique genets from the hybrid Niobrara River population and from the two parental populations were propagated in a common garden from rhizome cuttings. We tracked their phenology before and after bud break and measured their vulnerability to freezing (stem electrolyte leakage and leaf chlorophyll fluorescence) and to drought (stem hydraulic conductance, leaf osmotic potential, stomatal pore index, and gas exchange).
was slower to leaf out, showed lower vulnerability to stem freezing and drought-induced cavitation, but exhibited a lower capacity to tolerate drought stress through leaf resistance traits compared to . Hybrids were similar to in their overwintering strategy, exhibiting later bud break, and in their higher resistance to stem freezing damage, but they were more similar to in their higher vulnerability to drought-induced cavitation. The hybrids shared various leaf-level gas exchange traits with both parents. All aspens showed limited loss of leaf photosynthetic function following moderate freezing.
The Niobrara River hybrid population is vulnerable to drought due to its combination of inherited drought avoidance and tolerance traits. As climate changes, will likely suffer from increased drought stress, while being unaffected by frost during warmer springs. The two parental species contrast in their survival mechanisms in response to climatic stress, with tending toward freezing tolerance but drought avoidance and tending toward freezing avoidance and drought tolerance.
我们评估了一个具有保护价值的孤立的、残留的更新世杂交山杨种群（）及其亲本物种（和）的最近种群对春季芽后冻害和生长季干旱胁迫的脆弱性。比较了这三个分类群对这些胁迫因子在避害和耐受方面的反应。
北美中西部；美国。
从杂交的尼奥布拉拉河种群以及两个亲本种群中选取独特的基因型，通过根茎插条在一个共同园圃中进行繁殖。我们追踪了它们在芽萌发前后的物候，并测量了它们对冻害（茎电解质渗漏和叶片叶绿素荧光）和干旱（茎水力导度、叶片渗透势、气孔孔隙指数和气体交换）的脆弱性。
与相比，叶片展开较慢，对茎冻害和干旱诱导的空化的脆弱性较低，但通过叶片抗性性状耐受干旱胁迫的能力较低。杂种在越冬策略上与相似，表现出较晚的芽萌发，对茎冻害的抗性较高，但在对干旱诱导的空化的较高脆弱性方面与更相似。杂种与两个亲本共享各种叶片水平的气体交换性状。所有山杨在中度冻害后叶片光合功能的损失都有限。
尼奥布拉拉河杂交种群由于其遗传的避旱和耐旱性状的组合而容易受到干旱影响。随着气候变化，在温暖的春季不受霜冻影响的同时，可能会遭受日益增加的干旱胁迫。两个亲本物种在应对气候胁迫的生存机制上形成对比，倾向于耐冻但避旱，而倾向于避冻和耐旱。
