THE DELAY IN ARTIFICIAL DRYING AND THE PHYSIOLOGICAL QUALITY OF MAIZE SEED

Abstract

The moisture content of maize (Zea mays L.) ears at harvest time and the delay of artificial drying may decrease seed physiological quality. In Montecillo, State of Mexico, 2000 ears from the female parent of a three-way cross hybrid HS2 were harvested at 47, 39, 31, 24, and 17 % moisture content (Harvests 1, 2, 3, 4 and 5, respectively), and placed into three containers without ventilation. At 0, 12, 24, 36, and 48 h of drying delay, seeds were removed from 15 ears at three phases: 1) At the end of each drying delay period (before artificial drying), to evaluate changes in moisture content, temperature, respiration, and germination; 2) At the end of artificial drying (12 % moisture content); and 3) After six months of storage. Germination and vigor were evaluated in both phases. Before artificial drying, temperature and respiration increased after 12 h for Harvest 1 and after 24 h for Harvests 2, 3 and 4, but seed germination and vigor did not decrease. At the end of artificial drying, the speed of germination decreased (Harvests 1, 2 and 5) as the drying delay time increased; however, germination was maintained above the limit required for seed certification (85 %). After storage the germination speed increased, although the percentage of germination declined (no treatment decreased below 85 %); electrical conductivity and imbibition rates also increased, and seed germination in the accelerated ageing test decreased, especially when the harvest moisture content was above 24 % and the drying delay was prolonged. It is concluded then that the drying delay did not reduce germination below the minimum required for seed certification even after six months of storage, and
that vigor declined only after six months of storage when the seed was harvested above 24 % of moisture content.