Studies on Stigma Receptivity of Grewia Asiatica L. with Reference to Esterase and Peroxidase Activity
Abstract
The present paper deals with the stigma receptivity in terms of in vivo pollen germination of Grewia asiatica L. (Tiliaceae), an economically fruit yielding plant, with a view to find out the stigma receptive period and correlation of stigma receptivity with the activity of esterase and peroxidase on stigmatic surface in order to provide information about reproduction as a basis for fertilization and plant breeding programme. Flowers open at 7.00 hrs to 8.30 hrs. Anther dehisces by longitudinal slits just before flower opening. The non-specific esterase and peroxidase are present densely all over the stigmatic head. Stigma showed maximum receptivity (91.5%) with mean pollen tube of 338µm after 3 hrs of anthesis. Conspicuous presence of esterase and peroxidase was observed during higher receptive period. Prominent presence of peroxidase enzyme was also observed after 3hrs of flower opening (45 oxygen bubbles/minute by using hydrogen peroxide) during maximum receptive period of stigma.
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Introduction
Receptivity of the stigma is a critical factor for successful completion of the post-pollination events (Joshirao and Saoji 1989). Physiological, cytochemical, biochemical and structural features of the stigma are of prime importance in the sexual life of a plant leading to the effective post-pollination events which produce mature fruits and seeds for future generation and other uses. Stigma receptivity refers to the ability of the stigma to support pollen germination and tube growth of viable, compatible pollen grain (Shivanna 1998). Stigma receptivity is a critical stage in maturation of the flower that may greatly influence the success of pollination at different stages in the life cycle of the flower (Barrett, 2002).
Generally receptivity is maximum soon after anthesis, it varies among species and depends upon temperature and humidity (Shivanna and Johri, 1985). Joshirao and Saoji( 1989) also stated that the period of receptivity may vary from species to species. The receptive surface of the stigma contains extracellular proteins either as an extracuticular layer called pellicle in dry stigma or as a component of the exudates in wet stigma (Heslop-Harison and Shivanna, 1977; Heslop-Harrison, 1981; Shivanna and Johri, 1985). Esterase and peroxidase are the important components of the stigma surface proteins and their presence is related to stigma receptivity .Therefore, stigma receptivity in terms of in vivo pollen germination of Grewia asiatica L. belonging to the family Tiliaceae with reference to esterase and peroxidise activity at different times after anthesis is of prime importance in the reproductive biology. These observations were further correlated between esterase and peroxidase activity with stigma receptivity (Stone et .al. 1995; Lavithis and Bhalla, 1995; Bhattacharya et. al 2004; Choudhury et. al. 2008, 2011, 2012).