Because air offers substantially less support than water, land plants incorporated more rigid molecules in their stems (and later, tree trunks). The evolution of vascular tissue for the distribution of water and solutes was a necessary prerequisite for plants to evolve larger bodies.

Four major adaptations are found in all terrestrial plants: the alternation of generations, a sporangium in which the spores are formed, a gametangium that produces haploid cells, and apical meristem tissue in roots and shoots.

The evolution of seeds allowed plants to decrease their dependency upon water for reproduction. Seeds contain an embryo that can remain dormant until conditions are favorable when it grows into a diploid sporophyte.

Plants have evolved several adaptations to life on land, including embryo retention, a cuticle, stomata, and vascular tissue.

Here are four important adaptations:

• The Cuticle.
• Leaf Hairs.
• Stomata.
• Partnerships with microorganisms.
• Plants form symbiotic relationships with soil microorganisms like endo and ecto mycorrhizae fungi.

Leaf adaptations

Xerophytes have thick cuticles, lost or finely divided leaves, reduced stomata, and CAM photosynthesis. Water storage adaptations include succulence and protective coverings of color, wax, hair, and/or spines.

Plant adaptations – xerophytic

• Small leaves – these ensure that less water is lost from the plant by transpiration because the leaf has a smaller surface area.
• Tap roots – these are long roots (7-10 metres long) that reach deep under the ground to access water supplies.
• Spines – some plants have spines instead of leaves eg cacti.

In xerophytes the stomata open in night and remain closed during day as an adaptation to conserve water. During day time the stomata are closed and organic acids are decarboxylated to release carbon dioxide, which is fixed into sugars by RuBisCo and Calvin cycle.

Xerophytes are a group of plants that live in very dry regions. They can survive in these areas because they possess adaptations that keep them from drying out. Plants can have waxy stomata, few stomata or stomata that open only at night.

Popular examples of xerophytes are cacti, pineapple and some Gymnosperm plants. The structural features (morphology) and fundamental chemical processes (physiology) of xerophytes are variously adapted to conserve water, also common to store large quantities of water, during dry periods.

Xerophyte survival characteristics:

• Thick cuticle.
• Stomatal closure.
• Reduction in # of stomata.
• Stomata hidden in crypts or depressions in leaf surface (less exposure to wind and sun).
• Reduction in size of transpiration surface (lower leaf only).
• Increased water storage.

Other xerophytic adaptations include waxy leaf coatings, the ability to drop leaves during dry periods, the ability to reposition or fold leaves to reduce sunlight absorption, and the development of a dense, hairy leaf covering.

Hairy leaves – minimise water loss by reducing air flow and creating a humid microclimate which reduces evaporation rate and the water potential gradient. Curled leaves – minimises water loss within a microenvironment with no air flow creating a humid microclimate reducing evaporation rate and water potential gradient.

The sunken stomata trap moist air which reduces diffusion and reduces water loss…. Xerophytes contain sunken stomata. because sunken stomata is a stoma in a small pit, which protects the escaping water vapour from air currents and also decreases the water loss from the leaf…

Some desert plants have sunken stomata in order to reduce the rate of transpiration. Sunken stomata means that the stomata on the surface of the leaves releases water vapour a lttle less as the some amount of water vapour is stopped.So water is retained in the plant and therfore minimizing the deficiencyof water.

Sunken stomata ensure less water loss, thus reduces the rate of transpiration. In order to reduce transpiration, a maximum number of stomata in a dorsiventral leaf are present on the lower surface. Hence, the answer is C.

The stomata of many cacti lie deep in the plants’ tissues. This adaptation helps cacti reduce water loss by keeping the hot, dry wind from blowing directly across the stomata. The leaves and stems of many desert plants have a thick, waxy covering.

Sunken means hidden stomata or stomata those which are not directly exposed to surface. It is in a small pit, which protects the escaping water vapour from air currents, decreasing water loss from the leaf.

The stomata are embedded into inner leaf layers rather than on the surface of the leaf. This is quite helpful in controlling the excessive water loss due to transpiration.

Sunken stomata are usually found in crassulacean acid metabolism plants. Such stomata remain situated below the epidermis and open at night.

Hint: The presence of sunken stomata is a characteristic feature of xerophytic plants to prevent water loss through respiration. Mango and Guava are mesophytic plants, whereas the hydrilla is a hydrophytic plant. Correct step by step answer: Sunken stomata are found in Nerium to control the rate of transpiration.

Xerophytes are the plants which are found in extreme dry conditions. They have very less number stomata present in sunken pits and therefore called sunken stomata.

Complete Answer: Option A: Nerium is a xerophyte it has sunken stomata to curtail the water loss by transpiration. To reduce water loss through transpiration Xerophytic plants such as Nerium have sunken stomata. Therefore, this is the correct option.