ALLELOPATHY –A TOOL FOR WEED MANAGEMENT Credit Seminar SEMINAR INCHARGE & GUIDE DR. M. L. KEWAT PROFESSOR Department of Agronomy, JNKVV ,Jabalpur(M.P.) Department of Agronomy, JNKVV ,Jabalpur(M.P.) COLLEGE OF AGRICULTURE COLLEGE OF AGRICULTURE JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYA JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYA JABALPUR(M.P.) JABALPUR(M.P.) PRESENTED BY POONAM CHOURASIYA Enrl. no. 160111009
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ALLELOPATHY –A TOOL FOR WEED MANAGEMENT
Credit Seminar
SEMINAR INCHARGE & GUIDE
DR. M. L. KEWAT PROFESSOR
Department of Agronomy, JNKVV ,Jabalpur(M.P.)Department of Agronomy, JNKVV ,Jabalpur(M.P.)COLLEGE OF AGRICULTURECOLLEGE OF AGRICULTURE
ConceptConceptConceptConcept• The phenomenon of one plant having detrimental effect on
another through the production and exertion of toxic chemical compounds is called allelopathy. Allelopathy is the indirect harmful effect through exertion of chemical substances.
• Allelopathy is existent in the natural ecosystem and it occurs widely in the natural plant communities. Allelopathy is possibly a significant factor in maintaining the present balance among the various plant communities. Allelopathic substance was first detected by Davis (1928) in black walnut tree (Juglans nigra) whose foliar leachate containing Juglone was found to damage germination and seedling growth of crops beneath the tree.
ALLELOPATHIC PROBLEMS IN AGRICULTURE, HORTICULTURE AND FORESTRY
1)1)Soil sicknessSoil sickness
2)2)Auto toxicity under same crop monocropping.Auto toxicity under same crop monocropping.
8)8)Poor success on replanting of tree cropsPoor success on replanting of tree crops
9)9)Failure of vegetative propagation (e.g. grafting, budding)Failure of vegetative propagation (e.g. grafting, budding)
10)10)Suppression effect from treesSuppression effect from trees
INTRODUCTIONINTRODUCTION
• Allelopathy is derived from two Greek words “allelon” Allelopathy is derived from two Greek words “allelon” means “of each other” and “pathos” means “to suffer”, means “of each other” and “pathos” means “to suffer”, and means the “injurious effect of one organism upon and means the “injurious effect of one organism upon the other” the other”
• Hans Molisch (1937)Hans Molisch (1937), plant physiologist, University , plant physiologist, University of Vienna, Austria, coined the term allelopathyof Vienna, Austria, coined the term allelopathy
• It was first reported in alfa-alfa, and the first It was first reported in alfa-alfa, and the first allelochemical was extracted from walnut.allelochemical was extracted from walnut.
• Actually, it is the process involving secondary Actually, it is the process involving secondary metabolites, produced by algae, bacteria, plants , metabolites, produced by algae, bacteria, plants , which influence the growth of the other or same which influence the growth of the other or same species.species.
• The central principle in Allelopathy arises from the fact that plants and microorganisms collectively produce thousands of chemicals, and many of these chemicals are released from the producing organism by leaching, exudation, volatilization, or decomposition processes. Subsequently, some of these compounds (known as allelochemicals) alter the growth or physiological functions of organisms that encounter them during growth.
• For example, almost pure droplets of sorgoleone (a quinone) are exuded from the roots of Sorghum species, which inhibits growth
in plants that contact it by blocking photosynthesis and respiration.
• Cinnamic and benzoic acids, flavonoids , and various terpenes are the most commonly found allelochemicals,. A few allelo-chemicals have been developed as herbicides and pesticides.
Allelopathic ChemicalsAllelopathic Chemicals
• Phenolic acid
• Coumarins – block mitosis in onion by forming multinucleate cells
• Terpinoids • Flavinoids • Scopulatens – inhibits photosynthesis without
significant effect on respiration
Ways of releasing allelochemicals Ways of releasing allelochemicals
Allelopathic chemicals are released from the plants as:
• Vapour – from root and leaf (through stomata)
• Foliar leachate
• Root exudate • Breakdown/ decomposition product of dead plant parts • Seed extract
SOURCES OF ALLELOPATHY
. TYPES OF ALLELOPATHY
True allelopathy Functional allelopathy
Crop against other crops:
Examples:Examples:• Sunflower has been foundSunflower has been found allelopathic to groundnut underallelopathic to groundnut under intercropping situationintercropping situation• Tree crops like Tree crops like EucalyptusEucalyptus also shows some allelopathic also shows some allelopathic
interactions to vegetables and some field crops grown interactions to vegetables and some field crops grown as intercrop with it.as intercrop with it.
• Crop residues of lentil are phytotoxic to wheat and of Crop residues of lentil are phytotoxic to wheat and of sunflower and mustard to several cropssunflower and mustard to several crops
• Sorghum is allelopathic to wheat and sweet potato to Sorghum is allelopathic to wheat and sweet potato to cowpea.cowpea.
• Mung/ green gram and cowpea are stimulatory to the Mung/ green gram and cowpea are stimulatory to the growth of wheat.growth of wheat.
FORMS OF ALLELOPATHIC INTERACTIONS
Crop against weeds: Crop against weeds: Examples:Examples:• Sorghum releases hydrocynic acid (HCN) and suppresses many Sorghum releases hydrocynic acid (HCN) and suppresses many
weeds growing in vicinity. weeds growing in vicinity. • Barley produces “gramine” an alkaloid, which inhibits weed growth Barley produces “gramine” an alkaloid, which inhibits weed growth
• Allelopathic effects might also depend on a number of other factors that might be important in any given situation:
• VarietiesVarieties:: There can be a great deal of difference in the strength of allelopathic effects between different crop varieties.
• SpecificitySpecificity: There is a significant degree of specificity in allelopathic effects. Thus, a crop which is strongly allelopathic against one weed may show little or no effect against another.
• AutotoxicityAutotoxicity:: Allelopathic chemicals may not only suppress the growth of other plant species, they can also suppress the germination or growth of seeds and plants of the same species. Lucerne is particularly well known for this and has been well researched. The toxic effect of wheat straw on following wheat crops is also well known
• Crop on crop effectsCrop on crop effects: Residues from allelopathic crops can hinder germination and growth of following crops as well as weeds. A sufficient gap must be left before the following crop is sown. Larger seeded crops are effected less and transplants are not affected.
• Environmental factorsEnvironmental factors: Several factors impact on the strength of the allelopathic effect. These include pests and disease and especially soil fertility. Low fertility increases the production of allelochemicals. After incorporation the alleopathic effect declines fastest in warm wet conditions and slowest in cold wet conditions.
CONCLUSION• Allelopathy plays an important role in investigations of appropriate
farming systems as well as in the control of weeds, diseases and insects, the alleviation of continuous cropping obstacles, and allelopathic cultivar breeding.
• Furthermore, allelochemicals can act as environmentally friendly
herbicides, fungicides, insecticides and plant growth regulators, and can have great value in sustainable agriculture.
• With increasing emphasis on organic agriculture and environmental protection, increasing attention has been paid to allelopathy research, and the physiological and ecological mechanisms of allelopathy are gradually being elucidated. It is obvious that allelopathy requires further research for widespread application in agricultural production worldwide.
ReferencesReferences
• Abrahim D., Takahashi L., Kelmer-Bracht A. M., Ishii-Iwamoto E. L. (2003b). Effects of phenolic acids and monoterpenes on the mitochondrial respiration of soybean hypocotyl axes. Allelopathy J. 11, 21–30
• Anaya A. L. (1999). Allelopathy as a tool in the management of biotic resources in agroecosystems. Crit. Rev. Plant Sci. 18, 697–739. 10.1080/07352689991309450
• Belz R. G. (2007). Allelopathy in crop/weed interactions–an update. Pest. Manag. Sci. 63, 308–326. 10.1002/ps.1320
• Bhadoria P. (2011). Allelopathy: a natural way towards weed management. Am. J. Exp. Agric. 1, 7–20