NEET Biology Notes Morphology of Flowering Plants Stem
It is the ascending part of the axis bearing branches, leaves, flowers and fruits. It develops from the plumule of embryo of a germinating seed and bears nodes and internodes. Node is the region, where leaves arise and intemode is the region between two nodes.
Main functions of stem are as follow:
- It bears leaves, fruit, flowers and seeds in position.
- Transport water and minerals among leaves, flowers, fruits and roots.
- Stem store food as reserve food material, bears flowers for reproduction and provide support and protection to plant.
- Stem synthesize hormone, e.g. auxin.
Special features of stem are as follows:
- In many xerophytic plants like Opuntia, stem becomes green, flattened or fleshy, which carries out photosynthesis. It is called phylloclade or cladophyll.
- In some plants, short, green, cylindrical (e.g. Asparagus) or some times flattened (e.g. Ruscus) branches, limited in growth, develop from the node of stem or branch in the axil of a leaf, which are reduced to small scales which perform the functions of photosynthesis. It is called cladode.
- Some stems are thin, weak and lie prostrate on soil.
- Tendril is a thread-like, green, leafless, spirally coiled structure sensitive to touch. These help in the climbing of weak stem.