Question

Epithem cells are
(a) Loosely arranged mass of parenchyma in hydathodes
(b) Large intercellular spaces of hydathodes
(c) Xylem elements of hydathodes
(d) Phloem below the air chamber

Answer 1

Hint: The hydathode is a pore that is found in the angiosperms. It secretes water through the pores present in the leaf margins. Epithem cells lie above the vein endings and are connected to the external atmosphere through water stomata. These cells are located just below the epidermis.

Complete answer:
Epithem cells are loosely arranged masses of parenchyma cells in hydathodes. These cells are thin-walled and have numerous intercellular spaces which are filled with water but very few or no chloroplast. The sub-epidermal chambers bear the opening of these Epithem cells. These cells lie above a vein ending and through a pore, in the epidermis, it is connected with the external atmosphere. This pore in the epidermis is called the water stomata. These cells together constitute the hydathode is a type of pore normally found in angiosperms. These pores are responsible for the secretion of water in the leaf margin.
The hydathodes are present in the leaves of submerged aquatic plants such as water lettuce, water hyacinth, and also in some herbaceous such as rose, balsam, etc.
Hydathodes are involved in guttation which is a process in which water or liquid ooze out of the pores due to positive xylem pressure. This xylem pressure is caused due to the root pressure.
The process of guttation occurs only when the soil is moist that is during night hours and the roots absorb water.
The root pressure increases due to plenty of water absorbed causing water to squeeze out of the plant and onto the tips of the leaves or the blades of the plant.
There found two types of hydathodes : passive hydathodes and active hydathodes. When a leaf vein terminates in an epithem the passive hydathodes are formed and when water is lost by epidermal cells actively the active hydathodes are formed.

Hence, the correct answer is option (a).

Note:
The primary function of hydathodes is that they discharge water from the interior of the leaf to its surface. The process they occupy is known as guttation. The process of guttation allows the absorption of solutes when transpiration is suppressed.