Question

Short / Long answer type questions .
Write the short notes on the following
(a)Bulliform cells, (b) Velamen, (c) Periderm, (d) Ring porous wood

Answer 1

A) Bulliform cells: They are large, colourless, empty, bubble-shaped cells that occur in groups on the epidermis of the leaves. These are found in monocots and not in dicots. They generally occur near the midvein of the leaf. They play an important role in the unfolding of the developing leaves and rolling and unrolling of the mature leaves according to the dry and wet periods.

B) Velamen: It is an outer layer of empty cells in the aerial roots of epiphytic orchids. It is a spongy, multiple layered epidermises that protect the vascular tissues in the root cortex and shields the roots from transpirational losses. The velamen arises from the root tip by the division of a special tissue.

C) Periderm: The corky outer layer of a plant stem that is formed during the secondary thickenings or as a response to injury or infection. It serves as a protective layer of many roots and stem that typically consists of phellem, phellogen and phelloderm.

D) Ring-porous wood: They have more numerous vessels and larger in cross-sectional area. They are more or less distinct line between springwood and last season wood.