Osmotically primed seed and seedling reactions to variations in day night temperature

The effects of alternating day/night temperatures, varying in maxima and mi nima but all averaging 30 degrees C, on germination and seedling characteri stics of Sorghum bicolor L. (Moench) were investigated. Seeds of sorghum CS V IS were soaked in 2, 4 or 6 g NaCl l(-1) solutions for 2 days at 25 degre es C, soaked in water for 1 day at 25 degrees C, or untreated. After treatm ent, drying and storage, seeds were germinated at 30/30 (day/night), 35/25, 40/20 or 41/19 degrees C temperature regimes under a polyethylene glycol-i nduced drought level of -3 bar. Results revealed no advancement of germinat ion percentage but a partial increase in germination speed by osmotic seed treatments. All three osmotic treatments also reduced the plumule/radicle r atio owing to a speculated increase in root over shoot growth. Temperature regimes significantly influenced both germination and seedling characterist ics with the optimum temperature appearing to be 35/25 degrees C. Increasin g the temperature amplitude from 30/30 to 35/25 degrees C increased germina tion speed, which was reduced by incremental increases in temperature ampli tude to 40/20 or 41/19 degrees C.