Drought Induced Structural Changes in Developing Chloroplasts of Jalapeno Pepper (Capsicum annuum)

Abstract

Chloroplasts, present in leaves of higher plants have an extensive, folded network of photosynthetic membranes. These membranes have closely appressed (grana) and non-appressed (stroma) regions and they are responsible for the conversion of solar energy into biochemically useful forms. Light plays an important role for the development of mature chloroplasts from proplastids. However, when seeds germinate in the dark, the proplastids do not form mature chloroplasts and instead they form etioplasts. The etioplasts contain a compact, highly regular lattice of inner membranes called prolamellar body. Exposure of dark grown seedlings to light induces formation of fully mature chloroplasts from etioplasts. Plant growth and development is dependent on various environmental factors and drought has profound effect on plant metabolism. Leaves depend on adequate water for both turgor pressure and photosynthesis. Turgor pressure enables nutrients in the form of carbon and minerals to be transported from soil to leaves where they are needed for synthesis of organic compounds. in this study we evaluated the influence of drought on the ultrastructure of developing chloroplasts in pepper plants.

Jalapeno pepper plants were grown from seeds in the dark and drought was induced to experimental group of plants after they developed the first pair of primary leaves. The dark grown control plants received water throughout the drought induction period. At the end of tenth day of drought, plants in both control and experimental groups were exposed to light for up to 48 hours and leaf samples from both groups were obtained at various time intervals after exposure to light. The samples were fixed, dehydrated and embedded for transmission electron microscopy. Ultrathin sections were made, observed under a Hitachi H7000 TEM and data were collected for ultrastructural study. The mature chloroplast and etioplast structures were compared between experimental and control group of plants.