Pit (botany)

Pits' are parts of plant cell walls which allow the exchange of fluids. In the case of pressure changes in the cell lumen pit aspiration can occur.

Types Of Pits

There are following types of pits:.

1. Simple pits: The diameter of the pit cavity remains uniform in simple pit. Pit cavity trpens in the lumen of the cell. Therefore, the pits of the two sides of the common wall form a simple pit.

2. Bordered pits: In this case, secondary wall border over the cavity of the pits. Thus the pit opening become narrow than the pit diameter. Bordered pits of the opposite cells form bordered pit pair. The cavity in the thick secondary wall is called pit chamber. The bordered pit opens in the cell lumen by pit aperture. The pit aperture is circular and much narrower than ihe diameter of pit chamber. In certain cases, the pit apertures are lenticular or linear or mai. ‘the pi.t membrane of bordered pit develops an oval thickening in the middle. It is called torus. Pit membrane is flexible. The liquid in cell put pressure on torus membrane. Pit membrane pushes the torus. Thus the torus closes the bordered pit. It slums that torus control the passage of pit through bordered pit. Bordered pits are more complex than simple pits. These are found in the vessels. tracheids and fibers of xylem.

3. Half bordered pit pair: In some cases, bordered pit has a complimentary simple pit. Such a pit pair is called half bordered pit pair.

4. Blind pits: Some pits do not hate ally complimentary pit. Such pits are called blind pits.

5. Compound pits: Sometimes, there is one pit on side. But there are two or more complimentary pits on opposite side. Such pits are called compound pits.

The cell wall is not totally complete around the cell. It is interrupted by narrow pores carrying fine strands of cytoplasm, which interlink the contents of the cells. They are called plasmodesmata (singular: plasmodesma). They form a protoplasmic continuum called symplast which consists of a canal, lined by plasma membrane. It has a simple or branched tubule known as desmotubule. The desmotubule is an extension of endoplasmic reticulum. Plasmodesmata serve as a passage for many substances to pass through. It is also believed that they have a role in the relay of stimuli.

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