The Functions of Lymph (or Lymphatic System)

1. Lymph (or lymphatic system) takes part in the nutritive process of the body. For example, it puts into circulation large protein molecules by carrying them from the tissues into the blood stream (which could not be absorbed by blood capillaries due to their large size). Lymph also carries digested fat for the nutritive process.

2. Lymph (or lymphatic system) protects the body by killing the germs drained out of the body tissues with the help of lymphocytes contained in the lymph nodes, and by making antibodies.

3. Lymph (or lymphatic system) helps in removing the waste product;

Excretion :

All the organisms (plants and animals) are made up of cells. These cells work all the time for sustaining the life of the organism. Most of the work of the cells is in the form of biochemical reactions which they carry out all the time.

The biochemical reactions taking place in the cells of an organism may produce toxic wastes (poisonous wastes) in the body. The accumulation of toxic wastes in the body harms an organism.

So, for an organism to lead a normal life, the toxic wastes being produced in its body must be removed continuously. The process of removal of toxic wastes from the body of an organism is called excretion. Excretion takes place in plants as well as in animals.

Excretion in Plants :

Like animals, plants also produce a number of waste products during their life processes. As compared to animals, the plants produce waste products very slowly and in very small amounts. The plants have no special organs for waste removal like the animals. The plants remove their waste products by different methods. Some of the important plant wastes and the methods by which they are removed are described below.

The main waste products produced by plants are carbon dioxide, water vapour and oxygen. Carbon dioxide and water vapour are produced as wastes during respiration by plants whereas oxygen is produced as a waste during photosynthesis. The gaseous wastes of respiration and photosynthesis in plants (carbon dioxide, water vapour and oxygen) are removed through the ‘stomata’ in leaves and ‘lenticels’ in stems and released to the air.

The plants excrete carbon dioxide produced as a waste during respiration only at night time. This is because the carbon dioxide produced during respiration in day time is all used up by the plant itself in photosynthesis.

The plants excrete oxygen as a waste only during the day time (because oxygen is produced by photosynthesis only during the day time when the sunlight is there). Water vapour produced as a waste by respiration is, however, excreted by plants all the time (day as well as night). This waste water is got rid of by transpiration.

The plants also store some of the waste products in their body parts. For example, some of the waste products collect in the leaves, bark and fruits of the plants (or trees). The plants get rid of these wastes by shedding of leaves, peeling of bark and felling of fruits.

So, when the dead leaves, bark and ripe fruits fall off from a tree, then the waste products contained in them are got rid of. Some of the plant wastes get stored in the fruits of the plant in the form of solid bodies called raphides. These wastes are removed when the fruits get detached from the plant.

For example, the fruit called ‘yam’ (zamikand) has needle-shaped raphides on its surface. The plants secrete their wastes in the form of gum and resins from their stems and branches. The plants also excrete some waste substances into the soil around them.

From the above discussion we conclude that the various methods used by the plants to get rid of their waste products are the following:

(i) The plants get rid of gaseous waste products through stomata in leaves and lenticels in stems.

(ii) The plants get rid of stored solid and liquid wastes by the shedding of leaves, peeling of bark and felling of fruits.

(iii) The plants get rid of wastes by secreting them in the form of gums and resins.

(iv)Plants also excrete some waste substances into the soil around them.