甜菊叶愈伤组织诱导过程中叶绿体的超微结构变化

观察了甜菊(Stevia rebaudiana Bertoni)叶外植体愈伤组织诱导过程中叶绿体的超微结构变化。结果表明,当叶外植体转移到培养基上培养后,叶绿体的片层结构逐渐退化。在叶绿体发生退化的过程中伴有叶绿体出芽和原质体的形成。推测新产生的原质体来自叶绿体产生的芽状体。而叶绿体本身最后完全解体消失。叶绿体超微结构的这种变化与高度液泡化的叶肉细胞脱分化至分生状态是平行的。随着培养的进行,分生状态的细胞发生液泡化变为薄壁细胞时,在愈伤组织表层的细胞中,质体重新形成片层结构,而内部细胞的质体则充满淀粉粒。

ULTRASTRUCTURAL CHANGES OF CHLOROPLAST DURING CALLUS INDUCTION IN LEAF EXPLANTS OF STEVIA REBAUDIANA BERTONI

Ultrastructural changes of chloroplasts were observed during callus induction in the leaf explants of Stevia rebaudiana Bertoni. Transfer of the leaf explants into the culture medium brings about the gradual degeneration of the chloroplast lamellar structures. The process is frequently accompanied by the occurrence of chloroplast gemma-like extension (here called plastid bud)and the formation of proplastids; presumably the newly proplastids originate from the gemma-like extensions, while the chloroplasts themselves ultimately disintegrate completely and then disappear. The changes in the ultrastructure of the chloroplasts parallel with the highly vacuolated mesophyll cells from a dedifferentiation to a less differentiated, meristematic state. Subsequent growth results in the reformation of large central vacuoles in the cells both within and on the periphery of callus. Transforming the meristematic callus cells into the highly vacuolated parenchymatous cells, the plastid lamellar structures are reformed in the cells close to the periphery of the callus, while the plastids in the cells from the interior, which are often devoid of lamellar structures, are filled with starch grains.