ALLELOPATHY ABDON, Demiel Kaye BAUTISTA, Laiza MELEGRITO, Jodelyn MONTALLA, Venus TAROMA, Neil

ALLELOPATHY

v refers to beneficial or harmful effects of one plant to another plant by release of chemicals from plant parts via:

-leaching -root exudation -volatilization -residue decomposition -other processes in both natural and agricultural systems

• Common effect: reduced seed germination & seedling growth

• Allelopathic compounds may have originally evolved as compounds that deter pathogens or herbivores

ALLELOPATHIC COMPOUNDS v Like other herbicides, action of most allelopathic

compounds is unknown v However, known action sites of allochemicals are in:

• Cell division • Pollen germination • Nutrient uptake • Photosynthesis • Specific enzyme function

EXAMPLES OF ALLOCHEMICALS

v mixture with other compounds may lead to enhanced allolepathic effect, than when it is alone:

• Phenolic compounds: through ion uptake or respiration • Flavonoids • Terpenoids: can inhibit cell division • Alkaloids • Steroids • Carbohydrates • Amino acids

PLANTS PARTS HAVING ALLELOPATHIC ACTIVITY v may vary over a growing season

• Flowers • Leaves • Leaf litter • Stems • Bark •  root

ECOLOGICAL EFFECTS

v Autotoxicity -allolepathy between oraganims of the same species Ex. Trifolium spp. (clovers) and Asparagus officinalis

(asparagus) v Control of weeds in agriculture

- some genetically modified crops are allelopathic to weed, increasing the rate of production

PLANTS EXHIBIT ALLELOPATHY

v Miracle tree • Used in india •  Inhibits growth of other trees but not its own seedlings • Reduce yield of yeast but increased yield of rice

v Pine trees • Pine needle droppings causes the soil around pine

trees to be acidic

BLACK WALNUT v Black walnut causes neighboring plants to turn yellow, wilt

and die • Hydrojuglone

-Non toxic, colorless chemical -In leaves, stems, fruit hulls, inner bark and roots, -When exposed in air and soil compounds, turns

into allochemical “juglone”

• Juglone -Higly toxic -Exuded from all parts of the tree -Affect other plants through: Root contact Leakage or decay in the soil Falling and decaying leaves Rain -Although low water solubility, small amounts can

cause injury to sensitive plants

CONTROL

v Soil micro organisms -Ingest juglone as energy sources and metabolic composition can turn juglone as non toxic -Well drained, aerated soils accelerate microbial activity -Urban soils on the other hand decrease microbial growth making plants in the urban area high risk for these chemicals

v  Adheres to soil rather than in plants causing favorable environment for microbial growth

v  Mycorrhizal fungi -necessary for normal uptake functions -Allelochemicals can disrupt the uptake process by damaging the root hairs or by inhibiting mycorrhizal populations in the soil

REFERENCES

•  James J. Ferguson, a. (2015). HS944/HS186: Allelopathy: How Plants Suppress Other Plants. Edis.ifas.ufl.edu. Retrieved 24 November 2015, from https://edis.ifas.ufl.edu/hs186

• Appleton, B. B. (2015). The Walnut Tree: Allelopathic Effects and Tolerant Plants. Virginia Cooperative Extension.