b) Write short notes on the following.
i) Transpiration pull:
ii) Root Pressure
iii) Cohesion
iv) Adhesion
Answers
Answer:
Write short notes on the following.
i) Transpiration pull: A transpiration pull could be simply defined as a biological process in which the force of pulling is produced inside the xylem tissue. This force helps in the upward movement of water into the xylem vessels. In this process, loss of water in the form of vapours through leaves are observed.
ii) Root Pressure : Root pressure is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day.
iii) Cohesion : Cohesion is the grammatical and lexical linking within a text or sentence that holds a text together and gives it meaning. It is related to the broader concept of coherence.
iv) Adhesion : Adhesion is the tendency of dissimilar particles or surfaces to cling to one another. The forces that cause adhesion and cohesion can be divided into several types.
hope this answer helps
Answer:
Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves.
Transpiration pull is the force which aids in drawing the water upward from roots to leaves. In leaves, some amount of water is used for photosynthesis and excess water is released into atmosphere. Water molecules stick to one another through cohesion forming a column in the xylem. The negative pressure created by transpiration pull exerts a force on the water particles causing their upward movement in xylem.
Root pressure is osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. Root pressure is caused by active distribution of mineral nutrient ions into the root xylem. Without transpiration to carry the ions up the stem, they accumulate in the root xylem and lower the water potential. Water then diffuses from the soil into the root xylem due to osmosis. Root pressure is caused by this accumulation of water in the xylem pushing on the rigid cells. Root pressure provides a force, which pushes water up the stem to a certain level.
COHESIVE FORCES
Attractive forces between molecules of the same type are called cohesive forces.
ADHESIVE FORCES
Attractive forces between molecules of different types are called adhesive forces.