A) remain closed at night
B) remain closed during day
C) remain always open
D) do not show any specificity in opening and closing
Correct Answer: C
Solution :
Guttation, is the loss or excretion of water in form of liquid droplets from the leaves and other parts of an uninjured or intact plant. It occurs only in some plants (345 genera) such as cucurbits, potato, tomato, garden nasturtium, Luffa, Balsam, Colocasia and many grasses. Guttation takes place through special structures on margins and tips of leaves called hydathodes. Hydathodes or water pores, unlike stomata, are always open, as their guard cells are immobile. The guard cells enclose a water pore or water stoma. It over lies the area of a vein ending or terminal trachieds. The vein ending is surrounded by a mass of loosely arranged achlorophyllous or colour less and parenchymatous cells called epithem. Epitehm cells are specialized cells, called transfer cells, which help in absorbing a good percentage of inorganic and organic solutes present in the exudate. Exudation of liquid of liquid from the water pore or stoma is due to development of a positive pressure in the xylem present in the vein ending. The pressure forces the liquid from vein ending into epithem and then to outside through the hydathode.
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