Physiological and biochemical changes during seed development and maturation in onion (Allium cepa L.)

Abstract

Onion (Allium cepa L.) is one of the important commercial bulb vegetables. Harvesting a seed crop at the correct stage not only aims at preserving the viability and vigour potential of the seeds but also eliminates the field damage. The present study was made to know physiological and biochemical changes associated during seed development and the right stage of harvest for quality seeds. The samples were collected from the tagged umbles starting from 5th day after 50% flowering up to 45th day. Dry weight of the seeds increased and reached the maximum (0.27g) at 40 DAA (days after anthesis) after which the values remained constant. Dehydrogenase and alpha amylaseactivity increased progressively with accumulation of seed reserves. Peroxidase activity was almost unaltered from 20 to 40 DAA and later decreased at 45 DAA. SDS-PAGE profile of Tris soluble storage proteins showed synthesis and accumulation of several polypeptides during the course of seed maturation. The seed quality in terms of germination and vigour were similar and their maximum at 40 and 45th DAA. The seed attained physiological maturity between these stages and 45th DAA with seed moisture content of 16.6% was found to be the right stage for harvest