Heat Damage and Drying Effects on Seed Quality

Heat damage to seed can occur as a result of the cumulative effects of respiration and fungal heating, and by the accumulation and retention of radiant heat within the seed mass following harvest both situations being collectively referred to as ‘field heating’. Another type of heating damage occurs in heated air drying systems. Excessive drying air temperature can have deleterious effects on seed quality this is generally referred to as “drying damage”. Both ‘field heating’ and ‘drying damage’ result in loss of quality due to the thermosensitivity of seeds. This is a characteristic which is markedly influenced by the seed moisture content, by the extent and duration of heat production, and by the retention of heat within the seed mass. The role of the thermophilic fungi, Aspergillus spp., in accentuating heat damage, and the effects of both ‘field heat’ and ‘drying damage’ on the market acceptability and quality of seed is also discussed.