Plants, on the whole, continue to develop throughout their lives. Plants, like other multicellular animals, grow through cell division and growth. Cell division (mitosis) multiplies the number of cells, whereas cell expansion expands the size of the cells. Plant cells specialise in several cell types as they grow through cellular differentiation. Once cells have differentiated, they can no longer divide. How do plants develop or replace destroyed cells after that?
The meristem is necessary for the growth and repair of plant cells. Meristem is a type of plant tissue made up of undifferentiated cells that can grow and proliferate indefinitely.
Apical Meristem
Apical meristems are found in the apex, or tip, of roots and buds, and they allow roots and stems to grow taller and leaves and flowers to differentiate. The meristem continues to add tissue “behind” it, forcing itself deeper into the ground (for roots) or the air (for stems) (for stems). The apical meristem of a single branch will commonly become dominant, inhibiting the growth of meristems on other branches and eventually leading to the establishment of a single trunk. Meristems around the base of grass leaf blades allow for regeneration after animal grazing or lawnmower mowing.
The protoderm generates a new epidermis, the ground meristem generates new ground tissue, and the procambium generates new xylem and phloem. Apical meristems differentiate into three fundamental types of meristem tissue that correspond to the three types of tissue: protoderm generates new epidermis, ground meristem generates ground tissue, and procambium generates new xylem and phloem. Because they allow for primary growth in length or height, these three types of meristems are referred to as primary meristems.
Secondary Meristem
Secondary meristems enable woody plants to grow in size (secondary growth). Herbaceous plants do not have secondary growth. Cambium, which means “changing” or “exchange,” refers to both types of secondary meristems. The vascular cambium produces secondary xylem (towards the centre of the stem or root) and phloem (towards the outside of the stem or root), which increases the plant’s diameter. This process produces wood and aids in the growth of strong trunks in trees. The cork cambium replaces the epidermis of roots and stems with bark, of which one layer is cork, between the epidermis and the phloem.
Primary growth has five components: The epidermis is the skin’s outermost layer. The inside is formed of ground tissue. The vascular cambium is a ring that runs through the ground tissue. The primary phloem and primary xylem are connected to the vascular cambium. There are a few more components to secondary growth.
Woody plants can grow in two ways. Apical meristem tissue at the terminals of roots and shoots mediates initial growth, which is difficult to portray clearly in cross-sectional diagrams. Secondary growth increases the diameter of a stem or root; vascular cambium adds xylem (inward) and phloem (outward), whereas cork cambium replaces the epidermis with bark.
Plant Growth Regulators
Plant Growth Regulators are modest, basic substances that plants create spontaneously to control their growth and development.
Characteristics
Plant growth regulators can be gases (ethylene), terpenes (gibberellic acid), or carotenoid derivatives with a variety of chemical compositions (abscisic acid). Plant growth compounds, phytohormones, and plant hormones are other names for them. They are classed as follows based on their actions:
Cell division, cell expansion, flowering, fruiting, and seed development are all promoted by plant growth promoters. Auxins, gibberellins, and cytokinins are examples.
Plant Growth Inhibitors – These compounds stop plants from growing and encourage them to go dormant or abscise. Abscisic acid is a good example
CONCLUSION
Plants, for the most part, continue to grow for as long as they live. They grow by a combination of cell division and growth (mitosis). Meristem, a form of plant tissue made up of undifferentiated cells that can divide and differentiate, is essential for plant growth. Meristem enables plant stems and roots to grow longer and wider (primary growth) (secondary growth).