What is Allelopathy?


-Dr. Prashant Arya 

Animosity is prevalent amongst plants – Trees just like human beings and animals. This speciality has been discovered in a few plants only. Fungi, micro-organism, paramecium and a few angiosperms (the plants which seeds are covered) are a few forms of plant kingdom which have this sort of speciality. Such plants with the salient features/speciality release a particular chemical in soil and the surrounding environment; as a result, it affects the growth and development of other plants. This queer but surprising behaviour of plants has been termed as ‘Allelopathy’ and the released chemical is known as ‘Allelo-chemical’. The effect of the chemical on plants is either positive or negative. The positive effect is termed as ‘positive Allelopathy’ whereas the negative effect is known as ‘negative Allelopathy’. Babul, Garlic, Walnut, Tobacco, Peas, Sorghum grass are such plants which possess the speciality ‘Allelopathy’. 

Austrian Scientist Hans Molish in 1937 used the word - ‘Allelopathy’ in his book written in the German language. In fact, the term ‘Allelopathy’ has been derived from the Greek language which means mutual loss or suffering. Hans Molish used the word ‘Allelopathy’ as ‘It is a biochemical found in plants which hampers the growth of neighbouring plants’ 

If we trace the history of plant development, the readers would know that the Father of Botany Theofrastus has described this speciality of plants in 300 B.C. He further described that a few plants release a chemical which renders soil infertile and destroy weeds. 

Plants scientist– Augustine Piramus Dey Candole, in 1832, expressed that due to release of chemicals by certain crops, the fertile content of soil get decimated and as a result, the soil turns into barren. In 1907-1909, two researchers viz. Shriver and Reid were successful in separating such biochemicals from plants and soil. In 1971, scientists – Whittekar and Fenny discovered and revealed in their exhaustive Research Paper that Allelo chemicals found in plants are similar to bio-chemicals. 

Practically allelochemicals may be present in any part of the plant. These may be located in leaves, flowers, fruits, roots, trunk as well as anywhere in the said areas. These can be traced in the surrounding soil. Allele chemical may target plants; it can stop the growth of trunk/root, can slow down or stop the transportation of nutrients or may affect mutual relations of other inter-dependant plants. 

Allelopathy is a form of chemical competition in the plant community. In the competition, one species of plant compete with other species of plant to secure sunlight, water and other nutrients. Plants which adopt allelopathic behaviour prevent other plants to utilize necessary natural resources for its survival. It is a fascinating behaviour of such plants. 

In the case of social forestry, the Allelopathic characteristics are very useful. Black walnut (juglms Ingra) releases an allelochemical which is known as Juglon and interestingly it affects a lot a few species of plants whereas, in case of species, it does not affect at all. The dry leaves of Eucalyptus and roots of the tree release a set of chemicals which is harmful to soil micro-organisms and plants species. Alenty Tree or Tree of Heaven (Allenthus, Alticeena) releases allelochemicals which hinder the germination and growth of plants in the neighbouring areas. 

The plant breeders have discovered allelopathic characteristics in varieties of rice and the research in this direction is in progress. 

It has been discovered in North Montana, a plant named Kochia possesses the allelopathic characteristics and as a result, it hampers the growth of wheat. Kochia born allele chemicals slow down the growth rate and height of wheat. 

In the contemporary scenario, the scientists of the world are pursuing research – utilization of the natural resource of allelochemical to find out perpetual and substantive growth in agriculture. There are many allelo chemicals available in the market which has the potential of making the agricultural crops weed and pests resistant. Laptospormon is one such example of allelochemical.

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