Galls in Trewia Nudiflora L. - Contextual Divergence Toward Plant Defense Tropism

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Research Article

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Biopesticides International


Trewia nudiflora (Euphorbiaceae), commonly known as false white teak, is one of the important medicinal plants and also reported as a host of foliar gall caused by Trioza fletcheri. Gall-inducing insects have profound effects on their hosts as they inject some elicitors and lead to the synthesis of different type of enzymes and some secondary metabolites at high amount in the plant which plays an important role in plant defense tropism. To understand the actual mechanism of gall formation by T. fletcheri on T. nudiflora leaves, we have studied the sequential morphological, anatomical, and biochemical profile changes during gall formation. Morphological study showed numerous simple gall pouches covering the upper surface of the leaf blades. Anatomical study revealed the presence of completely deformed cells compressed to form a hollow cavity (0.5-2.0 cm). In mature galls, adult fly with hard covering was seen within the gall cavity, whereas in perforated galls, Brachymyrmex depilis ants of the family Formicidae were observed. Biochemical studies revealed a positive correlation between activity of antioxidant enzymes and phenolics with different stages of gall formation, whereas chlorophyll content decreased with gall maturation. IR spectra of the cuticular layer of both fresh and infected galls showed significant differences, which suggested that leaf cuticle played a key role in plant-insect interaction. At the latter developmental stages, the sugar content increased, which attracted the ants for further infestation. However, there is no report about ant infestation in T. nudiflora leaf galls. Ants have a series of ecological relationships with gallmakers, as predators, mutualists, or successori. The entering-exiting behavior of ants to galls is simply from their own searching attitude or from a situation of reward coming from the gall in the form of exudates which confer an additional defense against predation and/or parasitism of the galls through the attraction of such predatory ants. This apparently helps in the release of mature fly by rupturing the hard outer covering.

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