AGEING TESTS AS A BASIS FOR EVALUATING SEED QUALITY

S. Matthews
In the production of vegetables seed quality is especially important. The mass marketing of vegetables requires size standards in the produce that can only be achieved by specific plant spacings which in turn require high quality seed for uniformity in crop establishment and seedling growth. Furthermore costly hybrid seed and modular transplant production methods have created a demand from growers for consistently reliable seed well above the minimum germination standards. In this paper the consequences of poor seed quality for vegetable production are exemplified.

In terms of the seed survival curve seed ageing begins well before germination falls to below what in earlier times has been regarded as an acceptable level. The earliest evidence that commercially available seed lots contained a wide range of physiological quality that was not clearly detected by the laboratory germination test came from work in Mississippi where the response of seeds to what is termed "accelerated ageing" was related to longevity in seed stores. In "accelerated ageing" seeds are placed in humid atmospheres at temperatures as high as 45°C which increases the rate of deteriorative processes as revealed by the subsequent germination after just a few days in the ageing treatment. An alternative method, so-called "controlled deterioration", has been developed in which all seed moisture contents are raised to one level more rapidly by imbibition on moist germination papers before deterioration at elevated temperatures for 24 hours. Germination following such treatments has been related to field emergence and seed longevity in storage. These relationships not only provide the basis for a test of seed quality but also suggest that natural ageing prior to testing and sowing is a major cause of quality differences. A more refined method of determining quality using at least three periods of deterioration at a constant seed moisture and temperature has been suggested. This method determines what is termed the initial germination or potential longevity (Ki) of a seed lot.

The evidence for the practical value of ageing tests in the determination of seed quality in vegetable seeds is discussed in relation to the seed survival curve. Some of the problems of standardisation and interpretation associated with the various methods are illustrated.

Matthews, S. (1994). AGEING TESTS AS A BASIS FOR EVALUATING SEED QUALITY. Acta Hortic. 362, 251-262
DOI: 10.17660/ActaHortic.1994.362.31
https://doi.org/10.17660/ActaHortic.1994.362.31

Acta Horticulturae