Plant growth happens through a combination of cell division, cell differentiation, and cell elongation, all carefully managed by plant hormones.
The Fundamentals of Plant Growth
Plants don't grow uniformly; instead, growth is concentrated in specific areas. Here's a breakdown:
- Cell Division: New cells are created, increasing the overall number of cells in the plant.
- Cell Differentiation: These newly formed cells specialize, taking on specific roles like transporting water or carrying out photosynthesis.
- Cell Elongation: Cells increase in size, contributing to the overall growth of the plant.
Growth Zones: Meristems
These processes primarily occur in meristems, which are regions of actively dividing cells. Meristems are found at the tips of shoots and roots (apical meristems) allowing for growth in length and in lateral buds (axillary meristems) allowing for growth in width and the formation of new shoots.
Hormonal Control of Plant Growth
Plant growth isn't random; it's tightly regulated by plant hormones. According to the provided reference, three key hormones involved in plant growth are:
- Auxin: Promotes cell elongation and is involved in phototropism (growth towards light) and gravitropism (growth in response to gravity).
- Gibberellin: Stimulates stem elongation, seed germination, and flowering.
- Cytokinin: Promotes cell division and differentiation, and also plays a role in delaying senescence (aging).
Here's a table summarizing these hormones:
| Hormone | Primary Function |
|---|---|
| Auxin | Cell elongation, phototropism, gravitropism |
| Gibberellin | Stem elongation, seed germination, flowering |
| Cytokinin | Cell division, cell differentiation, delaying aging |
Examples
- The bending of a seedling towards sunlight is largely due to auxin accumulating on the shaded side of the stem, causing those cells to elongate more and bend the stem towards the light.
- Gibberellins are used commercially to increase the size of grapes and improve fruit set.
- Cytokinins are sometimes used to prolong the shelf life of cut flowers and vegetables by delaying their senescence.
