Osmoregulation in plants | Osmoregulation in Animals |

Osmoregulation in plants.

Plants are distributed in different habitats. These habitats may be aquatic, moderate, severely dry or terrestrial. Thus plants are divided into three groups on the basis of nature of the habitat. These are:

1. Hydrophytes:

The aquatic plants are called hydrophytes. They have the adaptation to save themselves from excessive water in the freshwater environment. These plants have large surface area. So transpiration takes place excessively. They have a large number of stomata on their upper surface. These stomata open in the atmosphere. So they promote loss of water or transpiration.

2. Mesophytes:

The plants, living in the moderate environment are called mesophytes. These plants have moderate water availability. When there is sufficient supply of water, the stomata are opened to promote the loss of excessive water. When there is less supply of water, the stomata are closed to prevent the loss of water e. g. Brassica, rose, mango etc.

3. Xerophytes:

The plants living in the severely dry terrestrial environment are called xerophytes. They have following adaptation to reduce the rate of transpiration.

(i). Many xerophytes posses small, thick leaves. It reduces the surface are proportional to the volume of the plants. Thus it reduces the loss of water by transpiration.

(ii). They have thick, waxy and leathery cuticle.

(iii). The stomata are on the lower surface of the leaves. These stomata are present in depressions.

(iv). Some plants like cacti shed their leaves during the dry seasons. Therefore, the transpiration is stopped completely. They have stem as their photosynthetic organ. Their stem store water in the rainy season and use it in dry condition.

Osmoregulation in Animals

The animal cells require more critical balance of water and solutes in the body. They cannot survive without water gain or water loss. Water continuously enter or leave the cell. However, the quantity of water and the solute is kept in balance. There are two approaches in maintaining this balance:

1. Osmoconformers:

The animals which do not require to actively adjust their internal osmotic state are called osmocoformers. These animals keep their body fluid isotonic to the external environment. They even keep their body fluid isotonic to marine and salt water environment.

2. Osmoregulation:

The animals which actively adjust their internal osmotic state according to external environment are called osmoregulator. Their body fluid concentration differs greatly with outside environment. They discharge excess water in a hypotonic environment and excrete salt in a hypertonic environment. The animals living in a different environment have a distinct adaptation to regulate osmotic balance. These environments may be the marine, freshwater and terrestrial environment.

Osmoregulation in Different Environment

Marine

1. Marine invertebrates:

Most marine invertebrates are osmocoformers.

2. Hag fishes:

The hag fishes keep their envrinment isotonic to the surrounding sea water.

3. Cartilaginous fishes:

Most of the cartilaginous fishes maintain lower internal salt concentration than the sea water. Their kidneys and gills excrete salts for osmoregulation. Additionally, they also passes salt secreting organs like rectal glands. These fishes use active transport mechanism to remove salts against the osmotic concentration gradient.

4. Urea retaining marine fishes:

Some fishes have relatively low salts in the body fluid. But they retain urea in adequate concentration for making this fluid hypertonic to the sea water. Urea is harmful in high concentration. So these fish retain another chemical Called trimethylamine oxide. This compound protects the fishes against the harms of urea. 

5. Boney fishes:

Bony fishes have formed from the fresh water ancestors. But later, they become marine. They constantly lose water form their hypotonic body fluid into hypertonic environment. These fishes are adapted to drink a large amount of sea water. They excrete concentrated urine. So they excrete maximum salts but loss minimum water.

Fresh water

Fresh water animals constantly face the problem of flooding of body fluid. So they lose salts. Fresh water protozoa like Amoeba, Paramecium pump out excess water by contractile vacuole. Many fresh water fishes remove excess water by excreting large volume of very dilute urine: They

compensate this loss of salt by these adaptations.

➤ They eat salt containing foods.

➤ They also uptake salts by active transport through gills and skin.

Terrestrial environment

The terrestrial animals loss water by evaporation. It leads to dehydration. It is major problem for the terrestrial animals. The arthopods and vertebrates have successfully adapted to terrestrial life. They have following adaptations to solve the problem of dehydration:

1. The body surface of the terrestrial animals is covered with structures.

These structures reduce the loss of water:

➤ Waxy exoskeleton of insects

➤ The terrestrial vertebrates have dead multilayered skin. These layers of skin are composed of keratinized skin cells.

2. They drink and eat moist foods to compensate the loss of water.

3. These animals also show metabolic and behavioral adaptations. Some desert mammals like kangaroo rat survive without drinking water. It feeds on seeds of desert plants. These seed contains more carbohydrates. The metabolism of carbohydrates produces water.

4. The terrestrial animals possess kidneys. Kidney absorbs most of the filtered water in the process of excretion. So they produce concentrated urine.

5. These terrestrial animals have developed different methods to tolerate dehydration. The toleration of dehydration is called anhydrobiosis.