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ISHS Acta Horticulturae 607: IX International Symposium on Timing of Field Production in Vegetable Crops

SEED ENHANCEMENTS

Author:   D.J. Cantliffe
Keywords:   emergence, longevity, osmoconditioning, priming, seed quality, solid matrix priming (SMP)
Abstract:
Essential prerequisites to optimize stand establishment are rapid and uniform field emergence under all environmental conditions. Over the past two decades seed enhancement through seed priming has led to great improvements in a grower=s ability to routinely achieve this goal in both the field and greenhouse. Numerous vegetable and ornamental crop species have been primed successfully. In order to maintain a superior product, seed companies have to maintain seed quality and longevity in the primed seed. Rapid and uniform field emergence are two essential prerequisites to increase yield, quality, and ultimately profits in crops. Uniformity and percentage of seedling emergence of direct-seeded crops have a major impact on final yield and quality. Rate and uniformity of emergence are inherent to seed quality and environmental conditions during seedling emergence. Slow emergence results in smaller plants and seedlings, which are more vulnerable to soil-borne diseases. Extended emergence periods predispose the planting bed to deterioration and increased soil compaction, particularly under adverse environmental conditions. In the last two decades, seed priming has become a common seed treatment to increase the rate and uniformity of emergence in many vegetable and flower species. Heydecker acknowledged the use of the term Apriming@ of seeds to describe a presowing seed treatment to enhance germination and increase seedling emergence uniformity under adverse environmental conditions. Terms such as halopriming (soaking in salt solutions) or osmopriming (soaking in other osmotic solutions) were proposed as alternatives to priming. The use of a salt as an osmoticum can lead to an increase in fresh weight of a seed. In this case, germination is delayed through increased solute potential of the embryo. Osmoconditioning or osmotic conditioning are also used to describe the same treatment when materials such as polyethylene glycol (PEG) are used as the osmoticum. Solid matrix priming (SMP) is a term used for a presowing seed treatment in which a solid-matrix instead of an osmotic solution is used to enhance germination. It is a process that uses solid matrix materials, water, and seed in combinations to control water, oxygen, and temperature effects on germination. The process controls the hydration of seed to a level that allows Apre-germination@ activity but that prevents radicle emergence. Matriconditioning was proposed as an alternative term to SMP, to distinguish seed conditioning by matric and osmotic forces. Biopriming is a treatment where sweet corn seeds are coated with a bacteria and soaked in warm water until the seed moisture content increases to 35-40%. In the discussion, the terms priming and solid matrix priming will be used. The cadre of other terms has actually led to confusion of what seed priming is and what is needed to obtain consistent positive effects from priming, and thus, these terms will not be used.
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