Excretion in Plants – Definition, Types & Significance

When you drink a lot of water, you know that in a while, you will need to pee a lot too, right? Do you know why that is? It’s because our kidney filters out our blood and collects all the waste product in our urinary bladder, which we then excrete. Excretion is an extremely important activity as it gets rid of all the toxins from our body as well as any excess material like water that we have. Now, have you ever seen a plant pee? Of course, you haven’t. But then what do plants do with their waste material? Well, even though they don’t excrete it out in the same way as us, they still do excrete. How? Read on to find out

What is Excretion in Plants?

The process of removal of waste products like excess water, exchange of gases, through leaves or leaf margins is called excretion in plants. Excretion of waste products is very simple and much less in plants as compared to animals, and the organs used for the same are very different.

Organs Used During Excretion in Plants

Plants do not have any specialised organs for eliminating waste. The process of excretion in plants takes through plant parts like leaves, roots, stems, ageing tissues, barks, etc.

Different Types of Excretion in Plants

The different types of excretion in plants are as follows:

1. Transpiration: Transpiration is the loss of water vapour from the surface of the plant, mainly from the leaves. This loss of water has the effect of ‘pulling’ water up through the xylem. The amount of water lost by a plant due to transpiration can be surprisingly large. There are mainly three types of transpiration and they are:
   (a) Stomatal Transpiration: The loss of water from leaves through stomata.
   (b) Cuticular Transpiration: The loss of water through the cuticle of a leaf.
   (c) Lenticular Transpiration: The loss of water from lenticels- minute openings on the stem.
2. Guttation: The loss of water as water droplets from the hydathodes of plants is called guttation. In some herbaceous plants, water droplets ooze out through their leaf margins. When the root pressure is high and transpiration is low, water drops ooze out through special marginal structures called Hydathodes or Water Stomata. These drops are rich in mineral salts, organic acids, carbohydrates and nitrogenous compounds. Guttation can be seen in garden nasturtium, grasses, tomatoes, potatoes and colocasia.
3. Bleeding: Bleeding is the exudation of sap from the injured parts of the plants. When an incision is made in the stem of a plant growing in well-watered soil, xylem sap starts oozing out due to root pressure. Oozing of watery sap is very common in mulberry, while oozing of milky latex can be seen in Calotropis and Euphorbia.
4. Respiration: Plants perform a function called photosynthesis which uses carbon dioxide, water, sunlight, and chlorophyll to synthesise food. During photosynthesis, oxygen is given out as a by-product. This oxygen acts as an excretory product and is given out by a process called diffusion. Certain plants perform a process known as photorespiration where oxygen is taken in and carbon dioxide is given out as a waste product.
5. Tannins: Tannins are a group of complex compounds found in the bark and leaves. The presence of tannin in tea leaves makes tea taste bitter if the tea leaves are boiled for a longer time.
6. Latex: Latex is a white milky fluid that can be seen oozing from any cut on the stem of a rubber plant. It is used for making rubber.
7. Gums and Resins: Resins and gums are the waste products that are produced by plants that are basically stored in ageing or old xylem. Resins present in the stem of the pine tree makes the pinewood strong and durable. Resins are also used for preparing varnish.
8. Excretion of Minerals: Plants eliminate the excess minerals and salt in the form of crystals such as calcium carbonate, sodium oxalate crystals, etc. The plant tissue phloem is responsible for transporting minerals and water from the soil to the upper tissues of the plant. The leaves utilise the number of minerals they require while the rest are eliminated.

Excretory Products in Plants

The excretory products in plants are:

1. Waste products of photosynthesis and respiration oxygen, carbon dioxide, water and heat are released into the atmosphere through stomata in the leaves and lenticels in stems. The waste products of one process are, however, usable as raw products in another process.
2. Ammonia is formed as a breakdown product of proteins. Plants use this ammonia to synthesise useful compounds.
3. Some of the waste products of photosynthesis collect in the leaves and bark of trees, plants shed their leaves and bark to get rid of these wastes.
4. Some waste materials keep accumulating within cells. Calcium oxalate crystals, called raphides, are such wastes. Yam (zimikand) is rich in raphides.
5. Several of the plant wastes are useful to us. Latex, gums, resins, tannins, sandalwood oil and eucalyptus oil are such substances.

Summary

Plants do not have any specialised organs for excretion and instead use plant parts like leaves, roots, stems, ageing tissues, barks, etc for the same. Some types of plant excretion are transpiration, guttation, and bleeding. Humans utilise a lot of plant waste products for industrial purposes. Some notable examples are Latex, gums, resins, tannins, sandalwood oil and eucalyptus oil.

Frequently Asked Questions (FAQs) on Excretion in Plants

Q.1. Where are waste products stored in plants?
Ans: Cellular vacuoles are the major part of plants that store waste products. Other than cellular vacuoles the plants store their waste products like resins and gums in old xylem.

Q.2. Which plant gives a tannin?
Ans: Eucalyptus, red mangrove, maples, willows, etc., are a few examples of plants that give a tannin.

Q.3. Which plant wastes are useful to human beings?
Ans: Oxygen is the most important and useful waste of plants that is essential for all living beings on Earth.

Q.4. What are the methods of excretion in plants?
Ans: The plants let out the gaseous wastes like carbon dioxide, oxygen through stomata lenticels during respiration and a few of the waste is excreted through transpiration, etc.

Q.5. What is excretion with an example?
Ans: Excretion is a process in which the waste products are eliminated from the living organisms through various organs is called excretion.
For example: In animals, the metabolic wastes are removed through the nose, skin, kidneys, etc.
In plants, the excretion process takes place through the leaves, roots, bark, etc.

Learn about Domestication of Plants here

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