Analysis of Factors Determining Yield in Crop Plants. II. The Influence of Photoperiodic Treatments on Characters Determining Yield in Wheat with Special Reference to the Temperature of the Ripening Period.

Abstract

Investigations on the effect of seedling and post-seedling photoperiodic treatments on characters determining grain yield in 3 varieties of wheat (Triticum vulgare vars. N.P. 165, N.P. 52 and P.C. 591). The number of ears per plant, the length of the ear, the number of spikelets and grains per ear and the thousand grain weight are all reduced under both SD and LD post-seedling treatments. The seedling treatments also affect the yield characters, though the effect is not so pronounced. The interactions between seedling treatment and variety and post-seedling treatment and variety are also significant. Highly significant positive correlations have been found to exist between grain yield and the characters determining yield and also between these yield characters and growth characters, namely the number of tillers and plant height, which are reduced under LD and SD post-seedling treatments. Reduction in these characters is reflected in the number of ears produced, the length of the ears, the number of spikelets and grains per ear and, ultimately, in the grain yield. The lack of significance of correlation coefficient that was found between the temperature of the ripening period and the grain yield in these experiments was considered to be due to the masking effect of growth characters. But even after elimination of the effect of these characters determining yield, the correlation between the yield per ear and the mean maximum temperature of the ripening period lacked significance. This is ascribed to sterility of pollen grains, which increases both under SD and LD treatments, resulting in a reduction in the fertility ratio and consequently in the grain yield under these treatments.