poonam allelopathy –a tool for weed mgt
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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
JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYAJAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYAJABALPUR(M.P.)JABALPUR(M.P.)
PRESENTED BY
POONAM CHOURASIYAEnrl. no. 160111009
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.
3)3)Increased crop- weed interferenceIncreased crop- weed interference
4)4)Growing susceptibility of plants to disease/ pestsGrowing susceptibility of plants to disease/ pests
5)5)Reduced nitrification and biological nitrogen fixationReduced nitrification and biological nitrogen fixation
6)6)Reduced nutrient uptakeReduced nutrient uptake
7)7)Weed seed decomposition delayed/ preventedWeed seed decomposition delayed/ prevented
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
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
S.No. Crops Weed species
1 Maize Chenopodium album, Amaranthus retroflexus
2 Sorghum Setaris viridis, Bromus pectinatus, Amaranthus hybridus
3 Cucumber Echinochloa crusgalli
4 Sweet potato Cyperus rotundus, Cyperus esculentus
Crops Weeds Cause/source released from crop plant
Effect on weeds
Coffea arabica (Coffee)
Amaranthus spinosus (Spiny amaranth)
1,3,7-trimethylxanthin
Inhibit germination
Zea mays (Maize) Agropyron repens Setaria viridis
Increased Catalase and Peroxidase activity by root extract
Inhibit growth
Oat, pea, wheat Chenopodium album (Lamsquarter)
Root exudates Suppress growth
Weed against crops:Weed against crops:S.No. Weeds Crops
1 Cyperus rotundus Sorghum , soybean
2 Imperata cylindrical Several crops
3 Chinopodium album Alfalfa, cucumber, oat, maize
4 Cirsium arvense Several crops
5 Avena fatua Several crops
•
Weeds Crops Cause/source released from weeds
Effect on crops
Agropyron repens (Quack grass)
Maize, potato Ethylene produced by the activity of microorganism on rhizomes of weeds
Decrease uptake of manures (N,K) followed by yield reduction of crop
Avena fatua (Wild oat)
Wheat, barley, oat Root exudates Growth of leaves and roots of wheat
Cynodon dactylon (Bermuda grass)
Barley Decayed grass residues of weeds
Seed germination, root and top growth of crop
Cyperus esculentus (Yellow Nut sedge)
Grain crops, soybean, orchard
Vanillic acid, Hydrobenzoic acid in sedge extract
Root and shoot growth of maize and soybean
Weeds Weeds Cause/source released from weeds
Effect on weeds
Impereta cylindrica (Cogon grass)
Borreria hispada (Button weed)
Exudates of inhibitory substances through rhizomes
Inhibits the emergence and growth
Sorghum halepense (Johnson grass)
Setaria viridis (Giant foxtail), D. sanguinalis (Large crabgrass)
Living and decaying rhizomes and leaves
Inhibit growth
WEEDS AGAINST WEEDS
PLANT CHEMICALS REFERENCES
Secale cereal L.
(Rye)
Avena sativa L.
Sorghum bicolor L.
(Sorghum),
Barley
Mungbean
Medicago sativa L.
Chenopodium
Cucumis sativus L. (Cucumber)
2,4-dihydroxy-1,4(2H)benzoxazin-3-
one (DIBOA) 2(3H)-
benzoxazolinone (BOA)
Ferulic acid
P-cumaric acid
Hydroxamic acid
Saponins
Ascaridole, alpha-terpinene
Gamma-linolenic acid,
Alpha-asarone
Benzoic and Cinnamic acids
Barnes & Putnam (1987)
Rice (1984)
Perez ( 1990)
Corcurea et al. (1992)
Krol et al. (1995)
Corcurea et al. (1992)
Yu and Matsui, 1994
Crops Weeds Allelochemicals Referrences
Rice Echinochloa colona
Phenolic acids Rimando et al., 2001
Wheat Avena fatua Hydroxamic acids Niemeyer, 1988
Cucumber Impereta cylindrica Benzoic and Cinnamic acids
Yu and Matsui, 1994
Black mustard Phalaris paradoxa Allyl isothiocyanate Weston, 1996
Buck wheat Canada thistle Fatty acids Weston, 1996
Clovers and Sweet clover
Echinochloa crusgalli
Isoflavonoids andPhenolics
Weston, 1996
Oat Chenopodium album
Phenolic acids& Scopoletin
Weston, 1996
Cereals Hydroxamic acids Weston, 1996
Sudangrass - Phenolic acidsand Dhurrin
Weston, 1996
Sorghum Echinochloa colona
Sorgoleone Netzley and Butler(1986)
AJEA,2010
Factors affecting Allelopathic effect Factors affecting Allelopathic effect
• 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
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