Like all organisms, plants have cells. Plant cells have a nucleus with chromosomes and DNA, and they have mitochondria. Those are common to all eukaryotic cells. But in some ways they are different from animal cells and the cells of other eukaryotes.
- They have cell walls composed of cellulose and some other compounds. Pectin, and sometimes lignin, is secreted on the outside of the cell membrane. This is different from the cell walls of fungi (which are made of chitin), and of bacteria (which are made of peptidoglycan). The cell wall gives the cell a definite shape.
- There are special cell-to-cell communication pathways known as plasmodesmata. These are pores in the cell wall through which the cell content of adjacent cells (including endoplasmic reticulum) are continuous.
- They have plastids. The most notable are the chloroplasts, which contain chlorophyll. This green-colored pigment absorbs sunlight, and allows the plant to make its own food by photosynthesis. Other types of plastids are the amyloplasts, which store starch, elaioplasts for fat storage, and chromoplasts for making and storing pigments. Like mitochondria, plastids have their own genomes of about 100–120 unique genes. It is thought they started as prokaryotic endosymbionts living in the cells of an early eukaryotic ancestor of the land plants and algae.
- They have a large central vacuole, a water-filled volume enclosed by a membrane. The vacuole keeps the cell's turgor (stiffness), controls movement of molecules between the cytosol and sap, stores useful material and digests waste proteins and organelles.
- Cell division by construction of a 'cell plate' late in cytokinesis is characteristic of land plants and a few groups of algae.
- The sperm of bryophytes and pteridophytes, cycads and Ginkgo have flagella similar to those in animals. However, higher plants (including gymnosperms and flowering plants) lack the flagella and centrioles that are present in animal cells.
References[change | change source]
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