The figure given below is a diagrammatic representation of a part of the cross section of the root in the root hair zone. Study the same and then answer the questions that follow: The figure given below is a diagrammatic representation of a part of the cross section of the root in the root hair zone. Study the same and then answer the questions that follow:
Due to an excess of this pressure sometimes drops of water are found along the leaf margins of some plants especially in the early mornings. What is the phenomenon called?
Topic: Guttation
Answer
GUTTATION.
GUTTATION is the loss of water in LIQUID form, as visible drops, through permanently open pores called HYDATHODES at the tips and margins of leaves.
THE TIMING EXPLAINS THE MECHANISM, and the question supplies the clue: EARLY MORNING. At night the air is humid and the stomata are closed, so transpiration cannot occur — but ROOT PRESSURE goes on pushing water upward. With no escape as vapour, the water is forced out through the hydathodes as droplets.
THE CONTRAST to hold: TRANSPIRATION gives water VAPOUR through STOMATA, mainly by day; GUTTATION gives water DROPS through HYDATHODES, at night and early morning.
Drops on grass in the early morning may be guttation or DEW — dew condenses from the air, guttation comes from inside the plant.