The effects of water or 1% K3PO4 priming at 5°, 15° and 25°C for short durations on ‘Minetto’ lettuce (Lactuca sativa L.) seed germination at high temperatures were studied. Germination percentage and rate at 35° of seeds primed in K3PO4 were significantly higher than that of seeds soaked in water. Aeration improved the results of priming at 15° and 25°. A priming temperature of 15° was generally best. The effects of light during priming of ‘Mesa 659’, ‘Minetto’ and ‘Ithaca’ seeds in water, K3PO4, polyethylene glycol (PEG) or PEG + K3PO4 solutions at 15° for 6 or 9 hr and drying methods for primed seeds were also studied. Imbibition rates were higher with K3PO4. Primed seeds germinated more rapidly at 35° with K3PO4 alone or in combination with PEG. Air drying of primed seeds was better than oven drying. Seed priming in light increased germination percentage and rate of ‘Minetto’ and ‘Ithaca’, although neither cultivar is photosensitive.
Seeds of hairy indigo, a tropical legume cover crop, are dormant due to hard seed coats. Immersion of the seed in concentrated H2SO4 for 20 or 30 minutes or hot water at 70° to 80°C for 2 minutes, significantly increased the germination percentage and rate. H2SO4 was more effective than hot water. Redrying the seed after treatment improved the effectiveness of the treatments slightly.
‘Minetto’ lettuce seeds (Lactuca sativa L.) were germinated at 35°C after different initial imbibition periods at 20°. No germination occurred at 35° in untreated seeds when the imbibition period was less than 6 hours. Maximum germination occurred after the seeds were imbibed for 16 hours. Most seeds primed in 1% K3PO4 at 15° for 9 hours then redried, germinated at 35°. However, germination increased gradually by increasing the time of early imbibition exposure to 9 hours. The endosperm membrane of seeds primed for 9-18 hours in a 1% K3PO4 solution did not rupture. Rupture of the membrane was evident after 21 hours of priming. A progressive loosening of the membrane after 9 hours of priming may be indicative of membrane weakening, possibly enhancing seed germination at high temperature.