自然干旱梯度下的酸枣表型变异

表型变异是植物应对环境变化的一种策略。酸枣植物从中国东部沿海到内陆腹地均有分布,其表型性状的变异可能解释其对自然干旱梯度的适应机制。为验证这一假说,以烟台、石家庄、银川、吐鲁番4个自然干旱梯度生境中生长的酸枣三年生植株的12个表型性状为调查研究对象,采用变异系数和巢式方差分析对酸枣的表型变异进行分析。结果表明:(1)从烟台到银川,叶面积、叶长、叶周长和叶柄长总体呈减小的趋势,而比叶面积呈增大的趋势;(2)随着干旱程度的增强,二次枝的长度、二次枝的基部粗、二次枝的枣吊数、茎比密度和茎水分含量均呈减小趋势,并且种子重和种子短轴长也均呈减小的趋势;(3)对沿干旱梯度分布的4个酸枣种群而言,叶性状的平均变异系数(33.70%)枝性状的平均变异系数(32.41%)种子性状的平均变异系数(9.07%),并且酸枣性状间存在很强的协变。结果表明酸枣的地上部分形态性状沿干旱梯度表现出很强的变异,推测在未来的气候变化下,酸枣将通过这种表型变异的有效组合来适应环境变化。

Phenotypic variation in Ziziphus jujuba var. spinosa along a natural drought gradient

Phenotypic variation is a strategy used by some plants to cope with fluctuations in environmental factors. Ziziphus jujuba var. spinosa is widely distributed from the east coast to the inland hinterland in North China, and variations in its phenotypic traits may represent an adaptive mechanism used by this species to adapt to natural drought gradients. In order to test this hypothesis, 12 phenotypic traits of 3-year-old plants from four natural populations along an aridity gradient (Yantai, Shijiazhuang, Yinchuan, and Turpan) were examined. Variations in the phenotypic traits of Z. jujuba var. spinosa were determined by the coefficient of variation and nested analysis of variance. The results showed that (1) leaf area, leaf length, leaf perimeter, and leaf stalk length all showed decreasing trends from Yantai to Turpan, whereas an adverse trend was observed in specific leaf area; (2) as the drought gradient increased, the secondary branch length and basal diameter, bearing branch number of the secondary branch, stem-specific density, stem water content, seed mass, and length of the short axis of the seed, all decreased; and (3) the average coefficient of variation was the highest for leaf traits (33.70%) in the four populations along the natural drought gradient. This was followed by branch traits (32.41%) and seed traits (9.07%), and all the measured traits showed strong covariance. Our results suggest that high levels of variation in the aboveground morphological traits of Z. jujube var. spinosa are expressed along a drought gradient, which indicates that Z. jujube var. spinosa should be able to cope well with future climate change by exploiting effective combinations of these phenotypic variations.