Question

Discuss the factors responsible for ascent of xylem sap in plants.

Answer 1

Hint: Cell is the smallest and basic unit of living organisms.
Tissue is a group of cells that have similar structure and that function together as one unit.
Plant tissue is of two types:
1. Meristematic tissue and 2. Permanent tissue.
The ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root.
There are many factors on which the ascent of xylem sap is dependent.

Complete answer:
Plant tissue: It is a collection of similar cells performing an organized function for the plant.
Each plant tissue is specialized for a special purpose, and can be combined with other tissues to create organs such as leaves, flowers, stems and roots.
Plant tissues are further divided into two types of tissues on the basis of their cell division.
1. Meristematic Tissue.
2. Permanent Tissue
Meristematic tissue: Meristematic tissue cells are either undifferentiated or incompletely differentiated.
Permanent tissue consists of plant cells that lack the property of dividing.
Such cells take on specific roles and lose their ability to divide further.
Permanent tissue is further of two types:
1. Simple: It includes parenchyma, sclerenchyma and collenchyma.
2. Compound: It includes xylem and phloem.
The factors responsible for ascent of xylem sap are:
1. Transpiration pull: It is carried out in the upper regions of the plant which causes a continuous loss of water further causes a negative pressure to develop which drives the water upwards.
2. Root pressure: It is the positive pressure developed in the roots due to absorption of water and minerals from the soil which forces the water upwards to a certain range as well as prevents the formation of air bubbles.
3. Capillary action: It is the ability of water to rise up in tubes or columns.
4. Imbibition: It is the phenomenon in which colloidal particles attract a large amount of water.

Note: Transpirational pull: It refers to the suction, force, or pull that draws water up through a plant. It is a process where the water molecules and ions are absorbed up from the root and then evaporation occurs within the leaves and thus spreading water throughout the plant.
The whole mechanism of transpiration pull in plants could be visualized to a person drawing a bucket full of water from a well when he is in need of water.