A plant cell is a eukaryotic cell present in green plants. It performs photosynthesis and stores starch, a large vacuole that regulates turgor pressure, the absence of flagella or centrioles, except in the gametes, and a unique method of cell division involving the formation of a cell plate or phragmoplast that separates the new daughter cells.
The plant cell is rectangular and comparatively larger than the animal cell. Even though plant and animal cells are eukaryotic and share a few cell organelles, They are quite distinct when compared to animal cells as they perform different functions. Some of these differences can be clearly understood when the cells are examined under an electron microscope.
Structure of Plant Cell
- Cell Wall: It is located outside the cell membrane. The primary function of the cell wall is to protect and provide structural support to the cell. The plant cell wall is also involved in protecting the cell against mechanical stress and to provide form and structure to the cell. It also filters the molecules passing in and out of the cell. The primary cell wall is formed by cellulose laid down by enzymes.
- Cell membrane: The cell membrane plays an important role in regulating the entry and exit of specific substances within the cell. For instance, the cell membrane keeps toxins from entering inside, while nutrients and essential minerals are transported across.
- Nucleus: The nucleus is a membrane-bound structure that is present only in eukaryotic cells. The vital function of a nucleus is to store DNA or hereditary information required for cell division, metabolism and growth.
- Plastids: They are membrane-bound organelles that have their own DNA. They are necessary to store starch, to carry out the process of photosynthesis. It used in the synthesis of many molecules, which form the building blocks of the cell.
- Leucoplasts: They are found in the non-photosynthetic tissues of plants. They are used for the storage of protein, lipid and starch.
- Chloroplasts: It is an elongated organelle enclosed by a phospholipid membrane. Each chloroplast contains a green coloured pigment called chlorophyll required for the process of photosynthesis. The chlorophyll absorbs light energy from the sun and uses it to transform carbon dioxide and water into glucose.
- Chromoplasts: Chromoplasts have red, orange and yellow coloured pigments which provide colour to all ripe fruits and flowers.
- Ribosomes: They are the smallest membrane-bound organelles that comprise RNA and protein. They are the sites for protein synthesis, hence, also referred to as the protein factories of the cell.
- Mitochondria: They are the double-membraned organelles found in the cytoplasm of all eukaryotic cells. They provide energy by breaking down carbohydrate and sugar molecules, hence they are also referred to as the “Powerhouse of the cell.”
- Lysosome: They perform the function of cellular waste disposal by digesting worn-out organelles, food particles and foreign bodies in the cell.
- Central Vacuole: It occupies around 30% of the cell’s volume in a mature plant cell. The vital function of the central vacuole apart from storage is to sustain turgid pressure against the cell wall. The central vacuole consists of cell sap. It is a mixture of salts, enzymes and other substances.
- Golgi Apparatus: They are found in all eukaryotic cells which are involved in distributing synthesized macromolecules to various parts of the cell.
Types of Plant Cell
Following are some of the different types of plant cells:
- Collenchyma Cells: They are hard or rigid cells, which play a primary role in providing support to the plants when there is restraining growth in a plant due to lack of hardening agent in primary walls.
- Sclerenchyma Cells: They are more rigid compared to collenchyma cells and this is because of the presence of a hardening agent. These cells are usually found in all plant roots and mainly involved in providing support to the plants.
- Parenchyma Cells: Parenchyma cells play a significant role in all plants. They are the living cells of plants, which are involved in the production of leaves. They are also involved in the exchange of gases, production of food, storage of organic products and cell metabolism. These cells are typically more flexible than others because they are thinner.
- Xylem Cells: Xylem cells are the transport cells in vascular plants. They help in the transport of water and minerals from the roots to the leaves and other parts of the plants.
- Phloem Cells: Phloem cells are other transport cells in vascular plants. They transport food prepared by the leaves to different parts of the plants.