The Stem and Its Functions - Practice Questions & MCQ

The Stem and Its Functions

• Stem is a major organ of the shoot system of plant body.
• It arises through the elongation of plumule of the embryo.
• Stem is negatively geotropic, negatively hydrotropic and positively phototropic.
• Stem differs from root because it shows a clear demarcation of nodes and internodes.
• Nodes are the regions of the stem where leaves are borne.
• Internode is the region between two nodes.
• Stem bears vegetative buds that are responsible for the growth of the plant.
• The apical bud adds to the height of the plant while the axillary bud allows the growth of lateral branches.
• Stem also bears floral buds.
• Young stem is generally green due to the presence of chlorophyll. Hence, young stem is photosynthetic.
• Older stem of trees becomes woody and dark brown.

Types of Stems:

1. Aerial Stem: Erect, rigid, strong and upright as can be seen in herbs, shrubs and trees.
2. Sub-aerial Stem: Weak, cannot stay upright as seen in creepers and climbers.
3. Underground Stem: It stays buried in the soil and produces aerial branches under favourable conditions.

Functions of the Stem:

• Its main function is to spread out branches bearing leaves, flowers and fruits.
• It conducts water, minerals and photosynthates.
• Modified stems serve for perennation, vegetative propagation, storage of reserve food, support, climbing and clinging.
   

Buds

• Buds are the lateral or terminal outgrowths on the stems of vascular plants.
• These buds may develop into a flower, leaf or shoot.
• Buds can be classified on the basis of their function and position.

Types of buds on the basis of their functions:

1. Vegetative buds: These contain embryonic leaves or branches. They grow into leaves or branches. These can be terminal or axillary.

2. Floral buds: These are also called reproductive buds as they contain embryonic flowers. They grow into flowers.

3. Tendrillar buds: They grow into tendrils.

Types of buds of the basis of their position:

1. Terminal or apical buds: They develop at the apex of the main stem or at the apex of branches. For example, cabbage is a large apical bud.

2. Lateral buds: They can develop into lateral branches or flowers. These are further classified into the following types:

• Axillary buds: they arise in the axils of the leaf.
• Accessory buds: more than one bud that arise in the axils of the leaf.
• Sub Petiolar buds: these are covered with the leaf base. They remain dormant for a long period.

3. Adventitious buds: These buds arise at any position except for their normal position. For example, epiphyllous or foliar buds present on the leaf margins in case of Bryophyllum; radical buds present on roots in case of sweet potato, dahlia, etc.