Plant cells are eukaryotic cells that differ in several key aspects from the cells of other eukaryotic organisms. Their distinctive features include:
A large central vacuole, a water-filled volume enclosed by a membrane known as the tonoplast that maintains the cell'sturgor, controls movement of moleculesbetween the cytosol and sap, stores useful material and digests waste proteins andorganelles.A cell wall composed of cellulose andhemicellulose, pectin and in many caseslignin, is secreted by the protoplast on the outside of the cell membrane. This contrasts with the cell walls of fungi (which are made ofchitin), and of bacteria, which are made ofpeptidoglycan. Cell walls perform many essential functions: they provide shape to form the tissue and organs of the plant, and play an important role in intercellular communication and plant-microbe interactionsSpecialized cell-to-cell communication pathways known as plasmodesmata, pores in the primary cell wall through which theplasmalemma and endoplasmic reticulumof adjacent cells are continuous.Plastids, the most notable being thechloroplast, which contains chlorophyll, a green-colored pigment that absorbs sunlight, and allows the plant to make its own food in the process known as photosynthesis. Other types of plastids are the amyloplasts, specialized for starch storage, elaioplastsspecialized for fat storage, and chromoplastsspecialized for synthesis and storage ofpigments. As in mitochondria, which have a genome encoding 37 genes, plastids have their own genomes of about 100–120 uniquegenes and, it is presumed, arose asprokaryotic endosymbionts living in the cells of an early eukaryotic ancestor of the land plants and algae.