Leaf Traits in Jasminum humile Related to Environmental Factors in the Dry Valley of the Upper Minjiang River
岷江上游干旱河谷矮探春叶片特征与环境因子的关系

The relationship between leaf characteristics and environmental factors was determined in Jasminum humile L. grown in the dry valley of the upper Minjiang River. The leaves were elliptic and leaf mesophyll tissue was distinctively differentiated. Leaf area, leaf thickness, leaf dry weight, leaf saturated water content, spongy tissue thickness, mid-vein thickness and the ratio of mid-vein thickness to collenchyma thickness (the M:C ratio) increased with increasing altitude. The ratio of palisade tissue thickness to spongy tissue thickness (the P:S ratio) declined as altitude increased. No significant differences were found in the ratio of leaf length to leaf width, epidermal thickness, palisade tissue thickness and specific leaf weight along altitude gradient. There were significant and positive correlations among leaf area, leaf dry weight, saturated water content, leaf thickness and spongy tissue thickness, while all of these parameters were negatively correlated with the P:S ratio. Leaf area, leaf dry weight, spongy tissue thickness and the M:C ratio increased mainly with increasing soil water content. However, the P:S ratio decreased with increasing soil water content and annual rainfall. Leaf thickness, leaf saturated water content and mid-vein thickness increased with decreasing temperateness. It is likely that leaf traits in J. humile are affected mainly by soil water content and temperature during the growing period in the habitat.