γ辐照对洋葱生长点细胞微结构的影响

The Effects of γ-ray Irradiation on the Ultrastructure of the Shoot Apical Meristem Cellin Onion(Allium cepa L)

洋葱鳞茎生长点细胞呈多边形,截面长径平均为 7.9μm左右,短径为4.92μm左右,细胞核中的染色质丝呈网状分布,核中一般有1～3个核仁.洋葱在整个休眠期间细胞和微结构无明显变化.脱离休眠后,其染色质丝变粗、浓缩,原生质膜内褶形成小液泡,液泡体积增大,数量增多.辐照的洋葱在萌动期才表现明显受损现象,用0.3 kGy辐照的其细胞形状发生畸变,细胞壁加厚,严重的壁破裂,微结构渗漏于胞外,发生严重的质壁分离,液泡变形、变小,而线粒体和核仁外形仍属正常。

The cells of the shoot apical meristem in onion assume a configuration of polyhedron with average long and short diameters of 7.9 and 4.92μm respectively. There was no significant ultra strutural changes in cells of the shoot apical meristem in dormancy. However, after dormancy, the chromatics clustered, the plas- molemma folded into the plasma, leading to the development of small vacuoles which then merged into larger ones. There was significant ultrastructural damages in cells of the shoot apical meristem during sprouting pe- riod. The irradiated cells didn't develop significant visible structural damage until the dormancy ended. The cells irradiated with 0.3kGy developed morphological abnormality, such as thickened cell wall, broaken cell wall, severe plasmolysis, deformed cell wall and broken vacuoles, while the nucleus and mitochondria still remained intact.