Li Chunyang, Xu Gang, Zang Runguo, Korpelainen Helena, Berninger Frank
Chengdu Institute of Biology, Chinese Academy of Sciences, P.O.Box 416, Chengdu 610041, China.
Tree Physiol. 2007 Mar;27(3):399-406. doi: 10.1093/treephys/27.3.399.
In most woody plants, leaf morphological and physiological characteristics are extremely variable across environmental gradients, particularly across altitudinal gradients. Hippophae rhamnoides L., a dioecious and deciduous shrub species, occupies a wide range of habitats in the Wolong Nature Reserve, southwest China. We measured growth, sex ratio and morphological and physiological characteristics of leaves in male and female H. rhamnoides individuals along an altitudinal gradient. Shoot height (HT), leaf N concentration per unit dry mass (N(mass)), leaf N concentration per unit area (N(area)) and leaf carbon isotope composition (delta(13)C) were higher in males than in females, whereas females had higher specific leaf area (SLA), stomatal length (SL) and stomatal index (SI) (i.e., total stomatal length per unit leaf area) than males along the altitudinal gradient. Females also had higher values of stomatal density (SD) at all altitudes except 2800 m. The male:female ratio (MFR) was biased toward males at all altitudes except at 2800 m. Changes in HT, MFR, SLA, SD, SL, SI, N(mass), N(area) and delta(13)C along the altitudinal gradient were nonlinear. Below 2800 m, HT, SLA, SD, SL and SI increased with increasing altitude, but above 2800 m they decreased with increasing altitude. In contrast, MFR, N(mass), N(area) and delta(13)C showed the opposite patterns with altitude. Consequently, we confirmed our hypotheses: (1) stressful environments have a more negative impact on females than on males in a variety of ways; (2) under optimal growth conditions the sex ratio is even, but becomes male-biased as resources become limited; and (3) there is an optimum altitudinal range at around 2800 m for the growth of H. rhamnoides in the Wolong Nature Reserve.
在大多数木本植物中，叶片的形态和生理特征会随着环境梯度，尤其是海拔梯度发生极大变化。沙棘是一种雌雄异株的落叶灌木物种，在中国西南部的卧龙自然保护区占据着广泛的栖息地。我们沿着海拔梯度测量了雄性和雌性沙棘个体的生长、性别比例以及叶片的形态和生理特征。雄性的枝高（HT）、单位干质量叶片氮浓度（N(mass)）、单位面积叶片氮浓度（N(area)）和叶片碳同位素组成（δ(13)C）均高于雌性，而在海拔梯度上，雌性的比叶面积（SLA）、气孔长度（SL）和气孔指数（SI，即单位叶面积的总气孔长度）高于雄性。除了2800米处，雌性在所有海拔高度的气孔密度（SD）值也更高。除了2800米处，在所有海拔高度上雄雌比例（MFR）都偏向雄性。HT、MFR、SLA、SD、SL、SI、N(mass)、N(area)和δ(13)C沿着海拔梯度的变化是非线性的。在2800米以下，HT、SLA、SD、SL和SI随海拔升高而增加，但在2800米以上则随海拔升高而降低。相反，MFR、N(mass)、N(area)和δ(13)C随海拔呈现相反的模式。因此，我们证实了我们的假设：（1）在各种情况下，压力环境对雌性的负面影响比对雄性更大；（2）在最佳生长条件下，性别比例是均衡的，但随着资源变得有限，会偏向雄性；（3）对于卧龙自然保护区的沙棘生长来说，在大约2800米处存在一个最佳海拔范围。
