Plant Adaptations to Extreme Environments - Class IX

Xerophytes are plants specifically adapted to survive in environments with little liquid water, such as deserts or ice-covered regions. Lithophytes grow on rocks, mesophytes in moderate conditions, and hydrophytes in water.

The succulent stem of the cactus plants usually store water and carry out photosynthesis also. The cactus stem contains a tough and waxy outer layer, called cuticle. The cactus plants possess modified leaves shaped like thin spines or thorns that decrease water loss through transpiration. 

Stomata in xerophytes open in night and remain close during day to prevent loss of water through transpiration.

"Patther phul" or stone flower or rock moss is a xerophytic plant or xerophytic shrub occurring wild on rocky ground( not much water present) As it is a plant which needs very little water it is called a xerophyte and occurs in the region of Gujarat 

One of the most commonly found plants in deserts is opuntia. it is a type of cactus. It is also called prickly pear. It is used to treat burns, diabetes, ulcers, inflammation, etc.

Xerophytes have very small leaves or spines to reduce loss of water.

The osmotic concentration of cell sap is higher in xerophytes to allow them to absorb water in an otherwise water deficient environment. The higher osmotic concentration would mean a lower water potential. A lower water potential will be advantageous to xerophytes as water always flows from a higher water potential to lower water potential.

Most species of desert plants have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis.

The cuticle is a waxy coating over the surface of leaves and plants. It forms a waterproof coating over the surface of leaves and plants. It prevents water loss from plants and also prevents the plants from getting desiccated. It also prevents the intake of gases into the plants. 

In cacti, the succulence is mostly in the stems because the leaves of the cacti are reduced to thrones to minimize the surface areas and therefor the water evaporation through them. the cacti have a shallow widespread network of roots that enables them to absorb water, therefore the roots are not succulent. the cacti have thick stems that store maximum amount of water in the entire plant. So, the correct answer is 'Stem'.

A phreatophyte is a deep-rooted plant that obtains a significant portion of the water that it needs from the phreatic zone (zone of saturation) or the capillary fringe above the phreatic zone. Phreatophytes are plants that are supplied with surface water and often have their roots constantly in touch with moisture. These plants have very deep roots that are able to reach the water table. So the correct answer is ' Very deep reaching ground water fringe'. 

Drought endurers are plants that can survive drought periods by maintaining their physiological functions, typically through deep root systems or water storage, and are usually perennial. Annuals are typically drought escapers.

The xerophytic plants are the plants present in the desert and other dry environments. The rate of transpiration is high in xerophytic plants due to high temperatures. In order to minimize the rate of transpiration, they have sunken stomata.

Ephemeral xerophytes are drought escapers that complete their entire life cycle very quickly during the short rainy season, remaining as seeds during the dry periods.

Lamina is reduced in xerophytic plants. In xerophytes, the petiole is modified into expanded green structure which carries out photosynthesis in case of reduced lamina.  For example, in Australian acacia.

While many plants have spines or stipular leaves, a long tap root system is a classic, primary adaptation in many xerophytes to reach deep groundwater sources in arid environments.

Physiological xerophytes are plants that grow in saline soils (halophytes) where water is present but physiologically unavailable due to high osmotic pressure, making them appear xerophytic. Salicornia is a classic example.

Xerophytes are the plants that survive in an environment having little supply of water or moisture. To survive with limited water supply they have anatomical modifications such as-

In non-succulent Perennial have extensive root systems, roots penetrate deep into the soil and establish contact with sub-soil water. 

• Some trees have deep, extensive root systems that anchor them to hillsides. Shrubs service berry is a deep-rooted deciduous shrub or small tree that grows best in well-drained, slightly acidic, moist soil. Ground covers, Vetiver Grass.

Xerophytes employ multiple strategies to conserve water, including sunken stomata to reduce transpiration, deep root systems to access water, and a thick waxy cuticle to prevent water loss.

Ephemerals are classified as drought escaping plants because they avoid the drought period entirely by existing as dormant seeds.

Acacia arabica is xerophyte because it is seen in desert places.

Xerophytes minimize water loss by reducing the number of stomata or having them sunken. A larger number of stomata would increase transpiration, which is detrimental to a plant in a dry habitat.

Calotropis is a non-succulent xerophyte that features thick, leathery leaves covered in a white, waxy, or hairy coating to reduce water loss and reflect sunlight.

Xerophytes are made up of thick cuticles and contains parenchymal tissues. It does not contain Aerenchyma.

In many xerophytes, leaves are reduced to spines to prevent water loss. Consequently, the stem becomes green and photosynthetic (cladode or phylloclade) to perform the function of leaves.

Halophytes grow in saline environments where water uptake is difficult due to high salt concentrations, leading to physiological drought. Thus, they often develop xerophytic adaptations.

Agave is a well-known succulent xerophyte that stores water in its thick, fleshy leaves.

Capparis is a genus of shrubs that are well-adapted to dry, arid environments, making them true xerophytes.

Mechanical tissues (like sclerenchyma) are highly developed in xerophytes to provide structural support and prevent wilting in the absence of high turgor pressure.

Sunken stomata are a specific adaptation in xerophytes to create a micro-environment of higher humidity around the pore, thereby reducing the rate of transpiration.

• Water storage in stem and tubers is an adaptation of plants to thrive in harsh environments with high temperatures and scarce water. Such plants called xerophytes usually develop succulent stems that can store water.
• They have a very extensive root system to absorb the maximum amount of water from the soil.
• Other adaptations include thick waxy cuticle, reduced leaf size, densely packed leaves, reduced number of stomata in pitted and grooved positions.

Vegetation of geographic region with low rainfall, high temperature, loose and sandy soil is of the type called xerophytic vegetation. It consists of spiny shrub, cactus. Caatinga is a type of xerophytic vegetation.

A xerophyte is the species of plants, that has the special characters to adapt in the environment with little water. Xerophytes plant have a thick waxy cuticle on the stem and leaves. This waxy cuticle reduces the water evaporation. In xerophytic plants, sunken stomata are present. which open during the night to prevent the water loss. To adapt in this environment, xerophytic plants leaves reduces into spines, which reduces the surface area of the leaf and reduces the amount of transpiration. The xerophytic plant makes their food through the CAM pathway.

Lithops (stone-faced as the plants appear stone-like)  is a genus of succulent plants in the ice plant family, Aizoaceae. They avoid being eaten by blending in with surrounding rocks and are often known as pebble plants or living stones. These are small succulent plants that survive in their harsh environment by having much of the plant body below ground. Each individual plant consists of two succulent leaves fused together in the shape of an inverted cone (although some species will produce multi-headed plants). The fissure at the top of the plant is the division between the two leaves and is spine-like. 

Ceiba (specifically species like Ceiba pentandra) is known for having succulent stems and roots, which helps it survive in its native habitats.

Xerophytes are defined as plants that have adapted to survive in environments with limited water availability, commonly referred to as dry areas.

Vegetation of Rajasthan is xerophytic. It is a geographic region with low rainfall, high temperature, loose and sandy soil. It consists of spiny shrub, cactus. Caatinga is a type of xerophytic vegetation.

When forests are destroyed, the soil often loses its moisture-retaining capacity and becomes exposed to harsh sun, leading to the development of xerophytic vegetation.

Proline is a common compatible solute (osmolyte) accumulated by plants, especially xerophytes and halophytes, to maintain osmotic balance and protect cellular structures under drought stress.

Heliophytes are plants that require or thrive in full, direct sunlight, as opposed to sciophytes which prefer shade.

Sciophytes are plants that are adapted to grow in low-light conditions, such as the shade provided by the canopy of other plants.

Heliophytes (sun plants) typically exhibit adaptations to high light intensity, including thicker leaves to store more chlorophyll and shorter internodes to maintain a compact structure. Sciophytes (shade plants) generally have thinner leaves to maximize light absorption in low-light conditions and longer internodes to reach for light.

Hence, option A is correct.

Shade plants (sciophytes) are adapted to low-light environments, which results in lower overall metabolic rates, including reduced photosynthetic and respiratory activity compared to sun-loving plants. Because they operate at lower energy levels, all these metabolic processes are typically lower.

Desert plants often develop sclerenchymatous tissues, which are rigid, dead cells that provide significant mechanical strength and structural support. This reinforcement helps the leaves withstand high wind velocities without tearing.

Sun plants (heliophytes) are adapted to high-light environments and typically possess more mechanical tissue for structural integrity, extensive root systems to support high transpiration rates, and often show more vigorous growth and flowering compared to shade plants.

Heliophytes are specifically defined as plants that thrive in direct sunlight. Sciophytes are shade-loving, halophytes grow in saline soils, and autotrophs are organisms that produce their own food.

Sciophytes are plants that are adapted to grow in low-light or shaded conditions. Psammophytes grow in sand, mesophytes in moderate water, and xerophytes in dry conditions.

Lithops plants or Pebble plant consist of one or more pairs of bulbous, almost fused leaves opposite to each other and hardly any stem. The slit between the leaves contains the meristem and produces flowers and new leaves. The leaves of Lithops are mostly buried below the surface of the soil, with a partially or completely translucent top surface known as a leaf window which allows light to enter the interior of the leaves for photosynthesis.