Question

Which layer of cell wall has simple and border pit and why

Answer 1

Cavities or thin areas within the thick secondary wall are called pits.

During the development of pits, the secondary cell wall may over arch the pit cavity forming a border, leaving an inner opening called pit-aperture. Such pits with borders are called bordered pits. Two opposite bordered pit are called bordered pit pair. Pits which lack the borders are called simple pits. Two opposite simple pits are called simple pit pair. Simple pits are formed on the secondary cell wall of extra xylary fibres (fibers present outside xylem).

Pits basic

Pits are the characteristic depressions on the cell walls of plant cells. They act as the channels for the transport of water and minerals between adjacent cells. Pits of two neighboring cells are usually located opposite to each other and these opposite pits together are called pit pair. Each pit has a cavity called pit cavity. Pit cavity opens internally to the lumen of the cells. The pit cavities of a pit pair are separated by a thin membrane called pit membrane. Pit membrane composed of the middle lamella and the primary cell wall of corresponding cells.