03881nam a2200421 a 450000100080000000500110000800800410001910000240006024500680008426000580015230000100021050000240022052028850024465000110312965000160314065000210315665000090317765000160318665000130320265000160321565000170323165000140324865000120326265000090327465000110328365000160329465000120331065300200332265300140334265300080335665300260336465300150339065300130340565300120341865300090343065300120343965300080345114443992009-06-01       1980    bl uuuu  m   00u1 u    #d1 aKRZYZANOWSKI, F. C.  aFactors affecting the germination and emergence of cotton seed.  aMississippi State: Mississippi State Universityc1980  a106p.  aPh.D. Dissertation.  aFactors affecting the germination and emergence of cotton seed were studied in the laboratory and field, and with a Soil Microenvironment Simulator (SMS). The factors emphasized were level of seed quality, temperature, and the moisture content of the seed and soil. Three commercially processed lots of the Deltapine 55 variety, representative of high, medium and low quality seed, were used. Field emergence tests were made on the Plant Science Farm, MAFES, Mississippi State, MS during the period April - July in 1978 and 1979. The Soi Microenvironment Simulator used for the major portion of the research had a capacity for twenty-four emergence boxes (plastic crispers) 8 X 11 X 4 in. It was capable of reproducing diurnal temperature cycles recorded in the field or synthesized from several recordings. The seed were planted in a soil/sand mixture adjusted to various moisture contents expressed as a percentage of saturation. Immediately after planting the seed were subjected to various soil temperature regimes (STR) after which they were transferred to a 25C room for completion of germination and emergence. In a thermogradiente plate study, the optimal temperature zone for germination was determined to be 28 - 30C. As temperature decreased from the optimal zone rate of germination decreased but germination percentages obtained during the 10 day period were significantly lower only below 20C. As temperature increased above the optimal zone the rate of germination decreased and the percentage of germination was sharply decreased above 32 - 34C. The rate and percentage of emergence in field plantings were affected by seed quality and time of planting (soil temperature). The most rapid emergence occurred under the warmest soil temperature during the germination and emergence period. Rate of germination decreased, and in some plantings, emergence percentage decreased, as soil temperature decreased, which generally corresponded to earliness of planting. Pre-conditioning the seed to moisture contents up to 14-16% slightly increased rate of emergence but had no effect on final emergence percentage. Results from five experiments using the SMS indicated that: (a) low quality cotton seed are more adversely affected by low temperature stress than high quality seed; (b) the detrimental effects of low temperature stress on germination and emergence increase as soil moisture level increases; (c) high quality seed are more resistant to low temperature stress at relatively low soil moisture levels than are low quality seed; and (d) a 24 hour period at a favorable soil temperature level before the onset of low temperature stress greatly reduces the detrimental effects of low temperatue. The SMS proved to be an excellent system for rigorous and carefully controlled research on the effects of the soil microenvironment on germination and emergence of seed.  acotton  agermination  aseed germination  asoil  atemperature  aAlgodão  aEmergência  aGerminação  aQualidade  aSemente  aSolo  aStress  aTemperatura  aUmidade  aDesenvolvimento  aEmergence  aEUA  aGerminacao de semente  aInfluencia  aMoisture  aQuality  aSeed  aStresse  aUSA