Klich MG
Departamento de Agronomía, Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur, C.C. 738, 8000-, Bahía Blanca, Argentina
Environ Exp Bot. 2000 Nov 1;44(3):171-183. doi: 10.1016/s0098-8472(00)00056-3.
Elaeagnus angustifolia (Russian olive) is a Eurasian tree that has become naturalized and has invaded zones along watercourses in many arid and semiarid regions of the world. These habitats are characterized by vertical environmental gradients, thus trees must develop some plasticity to adapt to the wide range of site conditions. This study was undertaken to test the hypothesis that variations in leaf anatomy and morphology of E. angustifolia reflect their adaptability to the differences in the microclimate that occur within the canopy of single trees. Foliar architecture, blade and petiole epidermal and internal anatomy were examined in leaves at different canopy positions and related to environmental conditions. Upper sun-leaves are exposed to higher solar irradiance and lower air humidity and are smaller, more slender and thicker than the lower, half-exposed and shade-leaves. Color varies between the leaves at different levels, from silvery grey-green in the upper strata, to dark green in the lower one. Bicolor is more evident in half-exposed and shaded leaves. When compared with the lower half-exposed and shade-leaves, the upper leaves of E. angustifolia have a greater areole density, a higher mesophyll proportion and stomatal density. Trichomes are multicellular, pedestalled, stellate-branched or peltate and their form and density can be associated with leaf color and appearance. The slender petioles of the upper leaves have proportionally more epidermis, collenchyma and phloem and less parenchyma and xylem than those of lower leaves, when observed in transverse sections. Foliar morphological and anatomical variability in E. angustifolia may be considered an adaptive advantage that enables leaves to develop and function in habitats marked by strong variations of solar radiation, air temperature and humidity.
沙枣（俄罗斯橄榄）是一种欧亚树种，已在世界各地许多干旱和半干旱地区的水道沿线区域归化并扩散。这些生境具有垂直环境梯度特征，因此树木必须具备一定的可塑性以适应广泛的立地条件。本研究旨在验证以下假设：沙枣叶片解剖结构和形态的变化反映了其对单株树冠内微气候差异的适应性。研究了不同树冠位置叶片的叶结构、叶片和叶柄的表皮及内部解剖结构，并将其与环境条件相关联。上部的阳生叶接受更高的太阳辐射和更低的空气湿度，比下部的半阴生叶和阴生叶更小、更细长且更厚。不同层次的叶片颜色各异，从上层的银灰绿色到下层的深绿色。双色现象在半阴生叶和阴生叶中更为明显。与下部的半阴生叶和阴生叶相比，沙枣上部叶片具有更大的小区密度、更高的叶肉比例和气孔密度。表皮毛为多细胞，具柄，星状分枝或盾状，其形态和密度与叶片颜色和外观相关。横切观察时，上部叶片细长的叶柄比下部叶片的叶柄具有相对更多的表皮、厚角组织和韧皮部，而薄壁组织和木质部较少。沙枣叶片形态和解剖结构的变异性可被视为一种适应性优势，使叶片能够在太阳辐射、气温和湿度变化强烈的生境中发育和发挥功能。
