REVIEW OF BIOCHEMICAL APPROACHES TO RATING SEED VIGOR.

"Seed vigor is the sum total of those properties of the seeds which determine the level of activities and performance of the seed lot during germination and seedling emergence".

Specifying particular aspects of possible measured activities, the definition goes on as follows:

1. Biochemical processes and reactions during germination as enzyme reactions and respiratory activity.
2. Rate and uniformity of seed germination......etc. (Perry, 1978).

Regardless of what measurements are used for seed vigor, the vigor level must finally represent the relative performance of seed lots in the field environment.

The conclusion is that any biochemical examination for comparative activities in seeds may represent seed vigor only if the seeds differ in their field performance. Thus, a positive correlation between biochemical activities and seed germination or seedling development under stress conditions should be considered only as a possible measurement of seed vigor and should be confirmed by the correlation with field performance.

This makes the entire project of a biochemical measurement of seed vigor time-consuming and expensive. In an attempt to facilitate the work, the important question, is which biochemical activities should be examined preferentially, having a reasonable chance to be involved in the expression of field performance.

A review of the experiments done on this subject revealed two basic methods that were used to measure seed vigor, and which may reflect biochemical activities directly:

1. the tetrazolium (TTZ) test (Lakon, 1950; Germ and Kietreiber, 1954; Lindenbein and Bulat, 1955; Ader 1965; Moore, 1973; Steiner and Werth, 1974; Kietreiber, 1975; Anon., 1976).and
2. the electrical-conductivity test (Matthews and Whitbread, 1968; Bradnock and Matthews, 1970; Bedford, 1974; Scott and Close, 1976).

The TTZ test was originally designed as a "topographical" test, namely the quantitative reduction of tetrazolium in certain parts of the seed or embryo reflected the embryo integrity.

The reduction of TTZ is a result of reducing activities and reducing compounds in the seed; thus, their rate of TTZ reduction may represent biochemical activities related to seed vigor (Perl, et al., 1978: Gelmond et al., 1978). However, since the reductive activity represents dehydrogenase activities and primarily malate-dehydrogenase

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