03005nam a2200265 a 450000100080000000500110000800800410001910000220006024500930008226000580017530000090023350000240024252023280026665000160259465000240261065000160263465000160265065000120266665000090267865300080268765300150269565300090271065300120271965300080273114444422006-06-01       1982    bl uuuu  m   00u1 u    #d1 aPEREIRA, L. A. G.  aPlanting dates and maturation relationships in soybean [Glycine max (L.) Merrill] seeds.  aMississippi State: Mississippi State Universityc1982  a99p.  aPh.D. Dissertation.  aTwo commercial soybean cultivars and a hardseeded breeding line-- 'Hill', 'Bragg' and D-67-5677-1 ('D-1'), respectively, were planted in April, May, June and July during 1980 and 1981 to study the effects of planting dates on some seed quality characteristics. Harvests were made from leaf yellowing to field maturity. Seed were evaluated for moisture content, dry weight, carbohydrate leachates and electrical conductivity. Standard germination was performed after completing all harvests and storing the seed under ambient laboratory conditions. Delaying planting from May to June caused a 10-day maturation delay of Hill which could result in the seed escaping adversely high temepratures at maturity. There were no substantial differences in germination among seeds from different plantings. However, D-1 showed generally lower values for seeds from early planting in 1980 which might indicate that it is more sensitive to high temperature/low moisture stress which was particularly severe in that year. Such results were not evident dor D-1 seeds of the late 1980 plantings as well as during 1981. Within planting dates germinations of Hill and D-1 were usually low for the first harvests, increased towards physiological maturity and declined somewhat at field maturity. Bragg, however, showed tittle variability and was generally high up to field maturity. At full maturity carbohydrate leachates were usually high for seed from early plantings, but this was not constant in both years. Within plantings carbohydrate leachates responded quadratically with a minimum at or near physiological maturity except for D-1 seeds which exudated in a decreasing linear fashion in 1980. In 1981, however, the linearity did not hold true. After physiological maturity, leachates from Hill and Bragg seeds increased, probably as a result of disorganization of membranes as dehydration progressed. Electrical conductivity measurements exhibited similar patterns to the carbohydrate leachates. Seeds of Hill showed higher readings than did seeds of the other two cultivars. The increase in leachates (carbohydrates and electrolytes) after physiological maturity might indicate that progressive damage to membranes and release of substrates for microorganisms are potential hazards to be considered before field maturity is reached.  asowing date  aÉpoca de Semeadura  aGlycine Max  aMaturação  aSemente  aSoja  aEUA  aMaturation  aSeed  aSoybean  aUSA