63 - Plant Cell Physiology

Abstract

This chapter discusses the physiological aspects of plant cell. Plant cells and animal cells are connected evolutionarily, sharing a common ancestor, but separated by over half a billion years of evolution. Throughout the plant's life, new cells are typically produced in localized regions of relatively high mitotic activity called meristems. Morphological and physiological specialization of plant cells occurs primarily through modifications of the cell wall and plastids. Consisting of cellulose microfibrils embedded in a polysaccharide and protein matrix, the cell wall of plants both supports and protects the protoplast. Cell walls provide a physical barrier to insects and microbial pathogens and also allow plants to take up water. Plant cell division cannot occur without the formation of a new cell wall, which also determines the morphology of the cell during growth and differentiation. The other important structures of the plant cell, such as endomembrane systems, vacuoles, lipid bodies, plastids, microbodies, glyoxysomes, peroxisomes, cytoskeleton, and plasmodesmata are discussed. The discussion on cell-to-cell communication in plants includes intercellular transport via plasmodesmata, plant hormones, defensive signals, and interactions between plants and other organisms. Plant cells maintain a substantial resting potential across their plasma membrane, mainly through electrogenic, proton-translocating ATPases. This primary active transport mechanism drives most of the other secondary transport systems in plasma membrane. Plants can perceive subtle changes in light quality and quantity through at least two different kinds of photoreceptors—phytochrome and a blue-light photoreceptor.