Interactions between seed priming treatments and nine seed lots of carrot, celery and onion. II. Seedling emergence and plant growth

SUMMARY Samples of three seed lots of each of three cultivars of carrot, celery and onion were primed in polyethylene glycol solution for two weeks at 15 °C. Seedling emergence was recorded in the field for carrot and onion and in the glasshouse for celery. Compared to the untreated control, priming increased the percentage seedling emergence in certain poorly‐emerging seed lots of carrot and celery, but had no effect on onion. Mean emergence times were reduced by priming in all seed lots, by 3–5, 5–8 and 3–9 days in carrot, celery and onion respectively. The largest effects occurred in the slowest‐emerging seed lots. There were significant interactions between priming and seed lots within cultivars in carrot and celery and between priming and cultivars in celery and onion. Priming generally reduced the spread of emergence times, but the effects were not statistically significant in carrot. Drying back the primed seeds had no effect on percentage emergence in onion, but reduced it (compared to primed seed which had not been dried‐back) in certain carrot and celery seed lots. Primed and dried‐back seeds emerged later than primed seeds, by up to 1·5, 2·6 and 2·6 days in carrot, celery and onion respectively. The spread of emergence times was generally larger for primed and dried‐back seeds than for primed seeds, but the differences were not always statistically significant. Plant fresh weights were recorded 9, 7 and 12 wk after sowing for carrot, celery and onion, respectively. In each species, mean plant weight was inversely related to seedling emergence time; thus plants grown from primed seed were always heavier than the controls, by up to 33%, 182% and 47% in carrot, celery and onion respectively.