What are thickening. Give an account of various types of thickneings.
Answers
Answer:
contrast to primary wall, secondary wall is thicker and more rigid due to lignin deposition. The deposition of secondary wall materials occurs in such a way that various patterns are formed on the cell wall.
The following patterns are commonly noted (Fig. 3.17):
Types of thickening of Cell Wall in Longitudinal View
1. Annular thickening:
ADVERTISEMENTS:
These are ring like thickening present on the inner side of primary wall. The rest of the wall is thin. Ex. Protoxylem.
2. Spiral or helical thickening:
These are spiral or helical thickening of secondary wall materials. There may be more than one helix. Ex. Protoxylem.
3. Scalariform thickening:
The thickenings appear as parallel transverse bands like the rungs of a ladder. Ex. Protoxylem.
4. Reticulate thickening:
The secondary wall appears as a network as the meshes remain thin. Ex. Metaxylem.
5. Pitted thickening:
These are more or less circular areas, called pit, where secondary wall materials are not deposited. Ex. Metaxylem.
Answer:
Examples of thickening agents include: polysaccharides (starches, vegetable gums, and pectin), proteins (eggs, collagen, gelatin, blood albumin) and fats (butter, oil and lards). All purpose flour is the most popular food thickener, followed by cornstarch and arrowroot or tapioca.