Jane Dearman

Effects of osmotic priming on seed germination and seedling growth in leek

Abstract Priming four seed-lots of leek ( Allium porrum L.) cultivar ‘Winterreuzen’ in PEG solution significantly improved the rate and uniformity of seed germination, particularly in the slower-germinating lots. In both field and glasshouse conditions, priming improved the rate and generally improved the uniformity of seedling emergence. Earlier emergence after priming gave rise to higher mean plant weights 10 weeks after sowing. There was no effect of priming on seedling relative growth rate under controlled conditions. Drying-back the primed seeds slightly delayed germination and emergence (compared with seeds which had been primed but not dried-back) because of the time taken for the seeds to re-imbibe water. Most of the beneficial effect of priming was retained after drying-back.

The effect of photon flux density on distribution of assimilate between shoot and storage root of carrot, red beet and radish

Abstract Growth and 14C distribution were measured in carrot, red beet and radish exposed to different photosynthetic photon flux densities (PPFD) in controlled environments to permit a comparison with their responses to varying plant density. Growth studies revealed that red beet maintains its leaf area, shoot fresh and dry weights at a range of PPFD while its storage organ weight is markedly reduced as PPFD decreases. Experiments with 14C showed that the beet shoot apex was a strong sink for assimilates and mobilised 14C at the expense of the storage root. In carrot, leaf area and shoot fresh weight were also maintained across a range of PPFD, though shoot and storage root dry matter were reduced at lower PPFD. The distribution of 14C suggested that in carrot there was a tendency to mobilise 14C to the apex at the expense of the leaf lamina at lower PPFD. In radish, leaf area and the fresh and dry weights of both shoot and storage organ decreased as PPFD decreased, but with the storage organ affected to a greater extent. The tendency in red beet and radish to mobilise assimilate to the shoot at the expense of the storage organs at lower PPFD (in contrast to carrot) is consistent with the response of these species to increasing density.

Priming and pre-germination of parsnip (Pastinaca sativa L.) seed

SummarySeedling emergence and growth responses to priming seeds in polyethylene glycol solutions, to germinating them before sowing and to a combined priming and pre-germination treatment were examined in the field and growth rooms using several stocks of seed. Priming or priming and pre-germinating seeds of a slowly germinating stock improved the percentage seedling emergence compared with untreated and pre-germinated seeds. In rapidly germinating stocks all three seed treatments showed similar levels of emergence which were higher than those of untreated seeds. Both priming and pre-germinating seeds reduced the mean emergence time and, in general, the effect of the combined treatment was greater than either treatment alone. Priming alone generally had no effect on the spread of emergence time or on seedling or plant weight variability, but pre-germinating seeds increased variability, particularly in a slowly germinating stock. Priming seeds before pre-germinating them reduced this variability.