干旱胁迫下4种锦鸡儿属植物叶脉密度与最低水势关系

以内蒙古中间锦鸡儿(Caragana intermedia)、小叶锦鸡儿(Caragana microphylla),新疆北部粉刺锦鸡儿(Caragana pruinosa)、多刺锦鸡儿(Caragana spinosa)为材料,探讨4种植物叶脉特征是否存在差异,是否促进干旱胁迫下叶忍耐的最低水势的分化。结果表明:中间锦鸡儿、小叶锦鸡儿叶忍耐的最低水势分别为-6.0 MPa和-6.5 M Pa,粉刺锦鸡儿、多刺锦鸡儿忍耐的最低水势分别为-4.0 M Pa和-4.4 M Pa;最低水势与一级脉密度、二级脉密度无线性关系,但随三级叶脉密度和细脉密度的增加而线性增加;最低水势随一级脉、二级脉、三级脉和细脉导管壁厚与导管腔直径比值的三次方(t/b)3增加而增加,但只与细脉(t/b)3显著线性相关。和新疆分布种相比,内蒙古分布种三级脉和细脉密度的增加,细脉抗塌陷能力的增强促进了叶干旱胁迫下忍耐的最低水势的下降。

Relationship between Leaf Vein Density and the Lowest Water Potential under Drought Stress in four Caragana Species

A comparison of the closely-related species Caragana intermedia and C. microphylla from Inner Mongolia to C. pruinosa and C. spinosa from Xinjiang was conducted to examine whether lowest predawn leaf water potential(Ψ_leaf) measured under severe drought stress was associated with variation in vein architecture(1°, 2°, 3° and minor vein density(t/b)³). The results showed that the lowest leaf water potential(Ψ_leaf) of C. intermedia and C. microphylla respectively was -6.0 MPa and -6.5 MPa, while C. pruinosa and C. spinosa respectively was -4.0 MPa and -4.4 MPa. The lowest water potential had no linear relation with 1° and 2° vein densities, while increasing with the 3°-order vein and minor vein densities; The lowest water potential incresed with the(t/b)³ of the ratio of conduit wall thickness to lumen diameter in 1°, 2°, 3° and minor vein. The research suggested that the increased density of tertiary veins, minor veins in Inner Mongolia species and the enhanced ability of minor veins to resist collapse promoted the decline of lowest water potential under leaf drought stress. compared with Caragana species growing in Xinjiang,