Effect of maturation on seed quality in Holoptelea integrifolia

The purpose of these studies was to determine the physical changes that occur during the maturation process of Kanju (Holoptelea integrifolia) seeds. Fruits were harvested at different stages of development and the size, fresh and dry mass, moisture content, percentage germination, desiccation tolerance and colour of both the fruit and seed were determined to identify the optimum harvest date for seed quality based on fruit maturity stage. As the seeds developed, seed moisture content declined from about 72% at 21 days after anthesis (DAA) to about 3% at 51 DAA, whereas dry mass of seeds increased to a maximum level at 42 DAA, when the moisture content was about 16%. Freshly collected seeds had 100% germination at 35 DAA, when less than half of the seed was filled; no seeds germinated before this stage. Desiccation of seeds at different stages of maturity revealed that at 39 DAA they could withstand desiccation to 4-5% moisture content and achieved 100% germination even though only 60% of the dry mass accumulated. However, maximum seed vigour was not achieved until seeds had attained maximum dry mass at 42 DAA; this stage therefore marked physiological maturity. At this stage fruits and seeds started to change to become light brown, a visual indicator for the time of maximum seed quality.