Question

What are for ways (anatomical or physiological) plants in dry environments conserve water?

Answer 1

Xerophytes are the plant which store water in extreme dry condition like desert .

The Xerophytes have very high osmotic pressure, which increases the turgidity of the cell sap.

Morphological Adaptations	Anatomical Adaptations	Physiological Adaptations
The root system is very well developed with root hairs and rootcaps. e.g. Calotropis.	Root hairs and root caps are well developed in Opuntia	The stomata of these plants open during night hours and remain closed during the day. This unusual feature is associated with metabolic activities of these plants.
The roots are fasciculated as in Asparagus.	Roots may become fleshy to store water as in Asparagus	In xerophytes, the chemical compounds of cell sap are converted into wall forming compounds (eg) Cellulose, Suberin etc.
Stems are stunted, woody, dry, hard, ridged, and covered with thick bark, may be underground, e.g. Saccharum. In Opuntia phylloclade is covered with spines	In succulent xerophytes, stems possess a water storage region (thin walled parenchyma cells)	Some enzymes, such as catalases, perioxidases are more active in xerophytes than in mesophytes.
Stem is covered with thick coating of wax and silica in Equisetum or dense hairs as in Calotropis	Stems of non-succulent xerophytes show a very thick cuticle, well developed epidermis with thickened cell wall, several layered and sclerenchymatous hypodermis e.g. Casuarina.	The capacity of xerophytes to survive in long period of drought is due to the resistance of the hardened protoplasm to heat and desiccation.
Stems may be modified into a thorn e.g. Ulex or cladodes e.g. Asparagus.	The stems have sunken stomata and well developed vascular and mechanical tissues.
Leaves are very much reduced, small scale-like, appearing only for a brief period (Caducous) sometimes modified into spines or scales as in Casuarina, Ruscus, Asparagus	Mesophyll is well differentiated and vascular tissues and mechanical tissues are well developed.
Lamina may be narrow or needle like as in Pinus or divided into many leaflets as in Acacia or succulents as in Aloe	Leaves show well developed cuticle, succulent leaves in Aloe, multilayered epidermis in Nerium, sclerenchymatous and several layered hypodermis in Pinus, bulliform cells in Sugarcane.