Question

Due to availability of less water, how does the plant cope up with lack of water in desert conditions?

Answer 1

Desert plants or xerophytic plants are adapted to desert conditions as they have modified leaves and modified stems. Their leaves are modified into spines, which reduces transpiration to almost nil. The stem is modified into succulent stems, which appear as broad leaf. These modified stems have stomata but they remain closed during day time to reduce transpiration. At night, these stomata opens and takes CO2 in. Other things required for photosynthesis like H2O absorbed through out day and night and chlorophyll is already present. Since they take CO2 at night, half of photosynthesis process takes place at night thus forming an intermediate sugar product which are stored in chloroplast and next day, in presence of sunlight, that intermediate product changes to starch, thus completing the photosynthesis (CAM pathway).

Answer 2

The plants that grow in desert conditions are adapted to survive the extreme heat and lack of water by means of modified leaves and stems. In succulents, the leaves are fleshy which store water; if their leaves are cut, they contain spongy fluid which is protected by waxy layer. 

Cacti have leaves modified to spikes which restrict transpiration. They conduct photosynthesis, collect dew in the morning, and reflect light to reduce water loss. During rainy weather, they grow temporary roots for absorption of water which dry up after the rainy season.

Desert deciduous plants, in comparison with temperate deciduous plants that annually shed their leaves,  shed leaves as many as five times a year. The leaves in such plants are reduced to very small size and they have a waxy layer to avoid water loss.  During the dry period, they remain dormant to cope with the absence of water