A HOLISTIC APPROACH TO QUANTIFICATION OF SEED VIGOUR THROUGH INTEGRATION OF MORPHOLOGICAL AND PHYSIOLOGICAL-BIOCHEMICAL PARAMETERS

摘要

In response to certain queries on an earlier paper on quantification of seed vigour, published in the Indian Biologist, 36(2), 2004, this rejoinder-cum-reappraisal paper reaffirms the benefits of integration of germination factor (GF) with physiological-biochemical seed vigour test scores (all mathematically converted to positive score values in the percentage scale), such as lipid peroxidation resistance score, LPRS; electrical conductivity resistance score, ECRS; volatiles emanation resistance score, VERS; jute seedling bioassay score, JSBS (originally positive), on their correlations with germination and asserts that the integration of score values with the germination factors of seed lots is simply an attempt to mathematically eliminate the contribution of nonviable seeds to the vigour test scores. As such, those arithmetic conversions, needed to make the correlations with germination more meaningful, are different from the conventional statistical transformations in correlation-regression analysis. The confirmation of the efficacy of GF incorporation comes from materials that are botanically, biochemically and agriculturally of diverse nature and includes soybean, cabbage, maize, peas, wheat and sunflower from different provenances, storage conditions, invigoration treatments, etc. implying thereby that the effect of integration cuts across cultivar, species and genus barriers and are also equally effective in seed lots differing in natural vigour levels as well as in variously invigorated (physico-chemically treated) seeds. Besides GF, another factor, seedling factor (seedling growth factor), SF, calculated from data on early seedling growth in the laboratory and a combined germination-cum-seedling factor (GSF, through integration of germination and seedling growth) have been introduced in this paper both of which when incorporated into vigour test scores show substantial improvements of correlations with germination, field emergence, yield and 1000-seed weight. The evidences presented in the text suggest that the morphological factors (GF, SF and GSF) when integrated with vigour test scores act in a complementary manner to improve their correlations with field performance parameters most often raising the statistical significance of the correlation coefficients to 0.01P, especially when both the variates in the bivariate linear regressions are integrated with the same morphological factor. In soybean, unification of vigour scores (LPRS, ECRS, VERS and JSBS) into a unified physiological-biochemical score (UPBS) by taking the average of the four revised scores, confers little additional benefit possibly because the revised test scores show no significant differences between them. However, integration of UPBS with GF, SF and GSF demonstrates the same complementary nature of the amalgamating components in improving the correlations with the field performance data. The improved predictive value of the regression equations based on integration of laboratory germination test and early seedling growth data with any one of the easily practicable vigour tests, such as electrical conductivity (data to be converted to ECRS prior to integration), with a minimum of five seed lots and at least three replications for each of the parameters, may prove to be very useful in crop husbandry in general and seed production in particular, especially when seed lots with relatively high germination percentages but differing vigour levels are used for the purpose.