采用树脂包埋块半薄/超薄切片技术，通过光镜（LM ）、扫描电镜（SEM ）和透射电镜（TEM ）方法，研究了轻度、中度和严重干旱胁迫对楸子（Malus prunifolia）、新疆野苹果（M ．sieversii）和平邑甜茶（M ．hupehensis）叶片组织解剖结构、表皮微形态特征（气孔密度、大小及角质层厚度）及叶绿体超微结构的影响。光镜观察结果表明，与对照相比，干旱胁迫条件下3种苹果属植物叶片厚度、栅栏组织厚度及叶肉组织结构紧密度（CTR ）都显著减小（ P＜0．05），而海绵组织厚度与叶肉组织结构疏松度（SR ）均显著增加（ P＜0．05）。扫描电镜观察结果显示，3种苹果属植物幼叶气孔密度在干旱胁迫下显著增大（ P＜0．05），而气孔宽度、开张比及其开张度明显下降。透射电镜观察结果表明，在干旱胁迫下，楸子和新疆野苹果上下角质层厚度逐渐增加，而平邑甜茶的随干旱胁迫程度增加呈先增后减的变化；在轻度和中度水分胁迫下，叶绿体膨胀变形，淀粉粒变小消失，基粒片层排列松散减少，类囊体腔扩大；在严重胁迫条件下，叶绿体膨胀近圆形，叶绿体膜破裂，类囊体严重泡化开始解体。与平邑甜茶相比，严重水分胁迫下楸子和新疆野苹果叶绿体超微结构损伤较小，能较好地保持细胞结构的完整性。%The changes of leaf anatomical structure and several micro-morphology features (stomatal density and size ,and the upper and lower cuticle thickness ) as well as chloroplast ultrastructure were observed for three Malus plants ,drought-tolerant M . prunifolia and M . sieversii , and drought-sensitive M . hupehensis , grown under mild , moderate and severe water deficit ,using the semi-thin/ultrathin section ,light microscope ,scanning electron microscopy (SEM ) ,and transmission electron microscopy (TEM ) methods . For the three genotypes , compared with well watered plants ,the leaf mesophyll contents and palisade tissue thickness as well as cell tightness rate (CTR) in drought-stressed plants significantly decreased ( P<0 .05 ) ,while the sponge tissue thickness and scattered rate (SR ) significantly in-creased ( P<0 .05 ) .SEM photos indicated that the stomatal density in young leaves of drought-stressed plants increased ( P<0 .05 ) ,while the stomata width ,stomatal opening rate ,and the relative opening degree of stomata decreased .TEM analysis showed that the upper and lower cuticle thickness of M . prunifolia and M . sieversii increased ,whereas those of M . hupehensis increased first and then decreased with prolonged drought treatment ,swelling chloroplast ,decreased the number of larger starch granules ,and loosing grana and thylakoid were the typical leaf ultrastructure for medium water stress .Under severe water deficit ,the chloroplasts were round in a shape ,with more damaged structure of membranes , and an extensive vacuolization and disorganization of thylakoid . However , the degree of drought-induced damage was smaller in M . prunifolia and M . sieversii plants as compared to M . hupehensis plants ,duo to the ability to maintain cell integrity .
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