Homeostasis in Plants:

 

Homeostasis in Plants

                                   Plants respond to environmental changes and keep to their internal conditions constant i.e. homeostasis. They apply different mechanisms for the homeostasis of water and other chemicals (oxygen, carbon dioxide, nitrogenous material etc).

Removal of Extra Carbon dioxide and Oxygen:

In daytime, the carbon dioxide produce during cellular respiration is utilized in photosynthesis and hence it is not a waste product. At night, it is surplus because there is no utilization of carbon dioxide. It is removed from the tissue cells by diffusion. In leaves and young stems, carbon dioxide escapes out through stomata. In young roots, carbon dioxide diffuses through the general root surface, especially through root hairs.

Removal of Extra Water

                                    We know that plants obtain water from soil and it is also produced in the body during cellular respiration. Plants store large amount of water in their cells for turgidity. Extra water is removed from plant body by transpiration.
At night, transpiration usually does not occur because most plants have their stomata closed. If there is a high water content in soil, water enters the roots and is accumulated in xylem vessels. Some plants such as grasses force this water through special pores, present at leaf tips or edges, and form drops. The appearance of drops of water on tips or edges of leaves is called guttation.

Removal of Other Metabolic Wastes
                                                         Plants deposit many metabolic wastes in their bodies as harmless insoluble materials. For example, calcium oxalate is deposited in the form of crystals in the leaves and stems of many plants e.g. in tomato.
In trees which shed their leaves yearly, the excretory products are removed from body during leaf fall. Other waste materials that are removed by some plants are resins (by coniferous trees), gums (by keeker), latex (by rubber plant) and mucilage (by carnivorous plants and ladyfinger) etc.
Osmotic Adjustments in Plants:
                                        On the basis of the available of water and salt, plants are divided into three groups. 

Hydrophytes: are the plants which live completely or partially submerged in freshwater. Such plants do not face the problem of water shortage. They have developed the mechanisms for the removal of extra water from their cells. Hydrophytes have broad leaves with a large number of stomata on their upper surfaces. This characteristic helps them to remove the extra amount of water. The most common example of such plants is water lily.
 Xerophytes: live in dry environments. They possess thick, waxy cuticle over their epidermis to reduce water loss from internal tissue. They have less number of stomata to reduce the rate of transpiration. Such plants have deep root to absorb maximum water from soil. Some Xerophytes have special parenchyma cells in stems or roots in which they store large quantities of water. This makes their stems or roots wet and juicy, called succulent organs.

 Halophytes: lives in sea waters and are adapted to salty environments. Salts enter in the bodies of such plants due to their higher concentration in sea water. On the other hand, water tends to move out their cells into the hypertonic sea water. When salts enter into cells, plants carry out active transport to move out of their cells into the hypertonic sea water. When salts enter into the cells, plants carry out active transport to move and hold large amount of salts in vacuoles. Salts are not allowed to move out through the semi-permeable membranes of vacuoles. So the sap of vacuoles even more hypertonic than sea water. In this way, water does not move out of cells. Many sea grasses are included in this group of plants.