Respiratory Rates and Alternative Pathway Capacity during Early Germination of Soybean

Seed respiratory rate generally correlates well with seed quality and germination performance. Alternative pathway respiration has been measured in germinating soybean [ Glycine max (L.) Men.] seeds, and has been documented and theorized to play a role under cool temperatures in other species. This study was conducted to determine whether differences in respiratory rates and alternative pathway capacity (determined by sensitivity to salicylhydroxamic acid in the presence of cyanide) of germinating seeds could be detected among soybean lines at different germination temperatures. Respiratory rates and alternative pathway capacity in germinating seeds of four soybean lines of similar maturity paired into two coldtolerant vs. ‐intolerant line comparisons were evaluated at 25 and 10 °C. Neither of the two genotype comparisons showed significant differences in 25 °C‐respiratory rates or alternative pathway capacity. At 10 °C, cold‐tolerant PI 290138 exhibited significantly higher respiratory rates and alternative pathway capacity than coldintolerant PI 189947. Differences in early field establishment between cold‐tolerant PI 290138 and cold‐tolerant PI 189947 but not between the other cold‐tolerant and cold‐intolerant genotypes could be explained, in part, by respiratory characteristics. At 25 °C, alternative pathway capacities of cold‐tolerant and cold‐intolerant genotypes represented approximately 20% of their uninhibited rates. At 10 °C, both cold‐tolerant genotypes retained their capacity for alternative pathway respiration, but the capacity of cold‐intolerant genotypes was severely reduced. The data suggest that the capacity for alternative respiration among germinating seeds from soybean lines differing in cold tolerance may not be affected at warm temperatures, but that differences may exist at low temperatures, possibly influencing soybean seed germination under suboptimal temperatures.