Morphogenesis of galls induced by Pauropsylla depressa Crawford (Hemiptera-Psyllidae) on Ficus glomerata Roxb. leaves
Keywords:
Pauropsylla depressa, Ficus glomerata, galls colour, size of galls, morphologyAbstract
Pauropsylla depressa Crawford (Homoptera : Psyllidae) infests Ficus glomerata Roxb. and produces galls on its leaves, causing extensive damage to the foliage of the plant. The gall formation by Pauropsylla depressa causing the changes in the histomorphology of the host plant.
Galls are pathologically developed cells, tissue and organs of plants, which have risen mostly by hypertrophy and hyperplasia (excessive cell division) usually under the influence of parasitic organism. Galls are epiphyllous, simple, globular, sessile, per foliate unilocular. Usually also in large fleshy, multilocular agglomerate masses. The physiology of gall formation is still obscure and it is generally believed that a secretion from nymph emerges out of the gall and moults into adult. Thickness of wall depending upon the size of gall and gall cavity. External surface of gall is shiny greenish, brown or pinkish developing upon the depending stage of P. depressa inside the gall. Outer layer is made of cuticle.
Newly formed galls are green in colour, but as the gall grows due to the metaplacia induced by the feeding of instars in it, gall colour changes pale green. Later on, it develops brownish spots. The colour of galls changes with the development of instars (from 1st instar nymph to 5th instar) inside the galls. After some time, greenish colour turns brown. During winter, mature gall turns pinkish due to the formation of some phenolic compounds. Mature gall contains a lacerated opening on the lower surface (ventral side) of the gall from which fifth instar nymph escapes out for moulting into imago. With the development of instar, the size of the galls also increases (Plate 1). As the size of the nymph increase, subsequently size of the gall also increases. Newly formed gall (young gall) measures 1.5 to 2.0 mm in diameter mature gall measures 10 to 12 mm in diameter and all gall measures 11 to 13 mm in diameter. Attains maximum size of 20 to 30 mm in diameter. However whenever entire leaf turned gallinaceous, then agglomerated mass measured 8 to 12 cm. Agglomerated masses may reach up to 14 to 53 mm in diameter.
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