Question

Pulvinus is found in
a. Calotropis
b. Legume plants
c. Alstonia
d. Ficus
e. All of the above

Answer 1

Leaf bases are part of the leaf attached to the stem or branch. Pulvinus is defined as the swollen leaf base. It is a joint-like thickening at the base of a leaflet or plant leaf that occurs due to change in the turgor pressure.

Complete answer:
- Leaves are the food manufacturing organs of the plant and they have several parts like leaf stalk or petiole, blade or lamina, pulvinus, stipules, etc
- Leaf is the organ of plants that forms food by photosynthesis.
- It also helps in gaseous exchange during respiration and transpiration process for cooling the plant temperature.
- The leaf base or pulvinus helps in the attachment of the leaf at the node. It also helps in the growth-independent movement.
- It has a core of vascular tissue with the flexible bulky cylinder of thin walled parenchyma cells.
- Leaves of family Fabaceae and Marantaceae have pulvinus leaves.
- Alstonia is a tree of the family Apocynaceae. It is native to Africa, Australia, Central America, Polynesia and Southeast Asia.
- Calotropis belongs to the family Apocynaceae and it is native tree of North Africa and Southern Asia. They usually produce latex and are milkweeds.
- Ficus belongs to the family Moraceae and these are common in tropics and some parts of temperate regions. It has trees, shrubs, vines, epiphytes and hemi epiphytes.
- So among all the given options only legume plants have pulvinus leaves.
- The other type of leaf base is sheathing leaf base. The leaf base in the monocot stem becomes broad and flat and covers a part of the node stem, this is called sheathing leaf base.

Hence, the correct answer is option (B).

Note: Pulvinus is responsible for sleep movements in Mimosa pudica, also called sensitive plant. It involves closing leaflets of plants at night and opening in the morning. Generally the function of pulvinus is to protect the young axillary buds.