青藏高原草地主要单子叶植物的叶表面特征

Leaf epidermis characteristics of the main grassland monocotyledonous plant species on the Tibetan Plateau

采用光学显微镜对青藏高原草地主要单子叶植物的叶表面特征进行观测,并运用one-way ANOVA、Pearson相关及线性回归分析,研究了气孔数量指标的物种间差异性以及气孔数量特征与海拔、生长季均温及生长季降水之间的关系。结果表明:(1)青藏高原草地主要单子叶植物长期受高原气候环境的筛选,形成了一些特有的叶表面共性特征,(a)叶表面细胞有长细胞与短细胞两种类型。长细胞呈规则长方形,排列紧密,纵向相接成行;短细胞呈长方形、方形、近圆形或马鞍形,随机散生、单生或孪生,短细胞形态与分布方式因植物种类而异。(b)气孔多分布于叶片下表面,属于单面分布型气孔。气孔选择性地分布在下表面,可在不影响CO_2同化率的情况下,一定程度上起到限制水分蒸发,避免造成生理干旱的作用。(c)不同物种气孔器形态、保卫细胞及副卫细胞形态表现出较为明显的多态性。保卫细胞近方形、半月形或哑铃形;副卫细胞呈低圆顶形、圆顶形或高圆顶形;气孔器为椭圆形、宽椭圆形或近圆形。(d)气孔器类型均是平列型(paracytic type),由两个副卫细胞与保卫细胞共同构成;副卫细胞与保卫细胞平行,并完全包围保卫细胞。气孔器等间距或不等间距呈直线排列形成"气孔带"。(2)青藏高原草地单子叶植物叶表面的气孔密度(SD)较大,平均为(194.07±4.74)个/mm^2,气孔长度(SL)较小(34.50±0.28)μm,气孔指数(SI)为(18.13±0.31)%,其中SD的变异系数(CV)最大(53.02%),SI的变异系数次之(37.23%),SL的变异系数最小(17.94%)。不同物种间叶表面的SL、SD与SI差异极显著(P<0.01)。(3)青藏高原草地单子叶植物叶表面气孔数量特征与环境生态因子显著相关。海拔与叶表面气孔特征呈显著正相关(P<0.01),生长季均温与SL之间呈弱正相关(P<0.05),与SD、SI之间呈显著负相关(P<0.01),生长季降水与SL之间呈显著负相关(P<0.01)。具体表现为随海拔升高SL、SD与SI增加,随生长季均温降低SL减小、SD与SI显著增大,而随着生长季降水减少SL变大、SD与SI显著降低。(4)海拔、生长季均温与生长季降水对SL、SD与SI的回归方程分别为Y=0.005X_1+0.878X_2-0.021X_3+12.278、Y=0.046X_1-11.688X_2+0.466X_3-46.391与Y=0.003X_1-0.363X_2+0.009X_3+7.394,回归方程统计检验显著(P<0.01);环境生态因子对SD的决定系数最大(R=0.690),SL次之(R=0.557),而对SI的贡献率(R=0.342)相对最小。

The characteristics of the leaf epidermis of the main monocotyledonous plant species from grasslands on the Tibetan Plateau were investigated using optical microscopy. The differences in stoma quantitative indices among plant species was studied using one-way ANOVA and the relationships between stoma quantitative indices and environmental factors, such as altitude, and average temperature and precipitation in the growing season, were analyzed using the Pearson correlation and linear regression analysis. The results indicated that ： （ 1 ） The main monocotyledonous plant species on the grassland shared many special leaf epidermis characteristics, due to long-term adaptation to the plateau environment. These characteristics included： （a） Two types of cells on the leaf epidermis： long ceils were generally rectangular and closely arranged in rows; and short cells were rectangular, square, suborbiculate, or saddle-shaped, and their distribution was randomly scattered, solitary, or twinned among species. （b） Most stomas were distributed in the lower epidermis and belonged to the single-sided type. This pattern might play an important role not only in maintaining high CO2 assimilation rates but also to limit water evaporation and avoid physiological drought. （c） Morphologies of stomatal apparatus, guard cells, and subsidiary cells showed obvious polymorphism. Guard cells were nearly square, half-moon, or dumbbell-shaped. Subsidiary cells were low-dome, dome, or high-dome shaped. The stomatal apparatus appeared in an ellipse, wide-ellipse, or intimate circle. （d）The stomatal apparatus was paracytic, containing two guard and two subsidiary ceils, and was further aligned into stomatal bands with equal or unequal intervals. Subsidiary cells were surrounded by and parallel to guard cells. （2） Average stomatal density （ SD）, length （ SL）, and index （SI） were （194.07±4.74） units/mm2, （34.50±0.28） μm, and （ 18.13±0.31 ） %, respectively. The coefficient of variation （CV） of SD （ 53.02% ） was largest, followed by those of SI （37.23%）, and SL （17.94%）. There were significant differences among species in these three stoma quantitative indices （P 〈 0.01 ）. （3） Stoma quantitative indices of monocotyledonous plants of grasslands on the Tibetan Plateau were distinctly correlated with environmental factors. Altitude was significantly associated with stomatal characteristics of the leaf epidermis （P 〈 0.01 ）. Average temperature in the growing season had a weak positive correlation with SL （P 〈 0.05）, and a notable negative correlation with SD and SI （P 〈 0.01 ）. Precipitation in the growing season was significantly negatively correlated to SI （P 〈 0.01 ）. Specifically, SL, SD, and SI increased with increasing altitude; SL decreased, and SD and SI increased as average temperature in the growing season decreased; SL increased, and SD and SI decreased with reduced precipitation in the growing season. （4） The linear regression equations of SL, SD, and SI from altitude, average temperature, and precipitation in the growing season were Y = 0.005X1＋ 0.878X2- 0.021X3＋ 12.278; Y = 0.046X1- 11.688X2＋ 0.466X3- 46.391; and Y = 0.003X1- 0.363X2＋ 0.009X3＋ 7.394, respectively, which were extremely significant （P 〈 0.01）. The relationship between environmental factors and the leaf epidermis characteristics showed that the coefficient of SD was the largest （R = 0.690）, followed by those of SL （R = 0.557）, and SI （R = 0.342）.