Morphological Studies of Insect-Induced Galls in Flower and Fruit of Alstonia scholaris (L.) R. Br
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RESEARCH ARTICLE
Morphological Studies of Insect-Induced Galls in Flower and Fruit of Alstonia scholaris (L.) R. Br Seema Chauhan1 • Nisha Singh1 • Shyam Vir Singh Chauhan1
Received: 25 April 2019 / Revised: 26 August 2019 / Accepted: 29 August 2019 Ó The National Academy of Sciences, India 2019
Abstract Morphological changes in insect-induced galls in flowers and fruits of Alstonia scholaris (L.) R. Br. (Apocynaceae) were recorded. The insect Pauropsylla tuberculata Crawford (Homoptera: Psyllidae) penetrates the thalamus of young flowers inducing hypertrophy and hyperplasia in the parenchymatous tissue resulting in the formations of green galls of various sizes and shapes. The reproductive organs, stamens, and pistil of galled flowers are sterile. Pollen sterility was associated with abnormal behaviour of endothecium and the tapetum. In young anthers of severely infested flowers, the sporogenous tissue and tapetum degenerate. In anthers of some infested flowers, the callose wall surrounding pollen mother cells was thick although tapetal cells showed normal signs of degeneration. In anthers of a few infested flowers, the microspores were formed but they degenerated along with tapetal cells. Anthers of some diseased flowers contained thick-walled vacuolated and sterile microspores surrounded by degenerated tapetum layer and radially elongated endothecial cells which lacked the usual fibrous thickenings. The size of gynoecium and the size and number of ovules were reduced in galled flowers. Ovules failed to differentiate and represented by a globular undifferentiated mass of cells. A large number of green, conical galls are formed on fruits by hypertrophy and hyperplasia in the
Significance Statement The paper is based on the light and scanning electron microscopic study of the anatomy of the insect-induced galls in the flowers of Alstonia scholaris, an ornamental tree cultivated in gardens, parks and road sides all over India. & Shyam Vir Singh Chauhan [email protected] 1
Academy of Life Sciences, 8/13 I Kaushalpur, Bye Pass Road, Agra 282005, India
parenchymatous pericarp. Size of severely infested fruits was reduced, and they became thick, circular and seedless. As a consequence, sexual reproduction of the host tree was completely inhibited. Keywords Alstonia scholaris Floral galls Hypertrophy Hyperplasia Pollen Ovular sterility
Introduction Alstonia scholaris (L.) R. Br., commonly called ‘saptaparna’ or satpatiya’ or devil’s tree, is a beautiful mediumto large-sized evergreen tree, native to India [1]. It is planted in the gardens and avenues for its dense umbrellalike canopy of dark green foliage. A large number of small, creamish-white, fragrant flowers are borne in bunches. The beauty of this ornamental tree is marred by profuse leaf galls formed by the insect, Pauropsylla tuberculata Crawford (Homoptera: Psyllidae). The infestation spreads to flowers and fruits as well [2]. Plant galls are abnormal outgrowths of plant tissues. It is common knowledge today that a gall is a cumulative expres
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