No abstract

The primary objective was to examine hybrids and their parents throughout their life span to detect the onset of heterotic behavior and its cumulative effect. Four single‐cross hybrids of Upland cotton, Gossypium hirsutum L., and their parents were studied. No heterotic effects were detected during the embryonic stage of development. Neither did hybrids appear to be any more vigorous than their parents during the first 7 days of seedling growth following germination. The first significant divergence of hybrids from their parents was recorded at approximately 6 weeks after planting. Relative rates of dry matter production continued to diverge for a period of about 3 weeks and then proceeded at comparable rates in both parents and hybrids to maturity. Hybrids thus maintained their vegetative superiority throughout the period of fruition with the result that hybrid plants were larger than parental plants and produced a greater yield of fruit.

In Korea, the seeds of Brassica rapa ssp. pekinensis are sown in the winter and spring months. Cold stress can result in irregular seed germination and poor seedling establishment in some cases. Priming seeds with salicylic acid (SA) can reduce the likelihood of poor seedling establishment when exposed to cold stress conditions, which is beneficial for many plant species. The present study was carried out to determine the effectiveness of seed priming with SA on seed germination and seedling establishment in B. rapa ssp. pekinensis under cold stress conditions. Seeds were soaked in different SA concentrations (0.5 and 1.0 mM) for 12 and 24 hours, respectively, and then both primed and unprimed seeds germinated at 5 oC. Using SA treatment, seed germination was improved, as was root and shoot length, which were both longer in SA primed seeds than in unprimed seeds. Based on the findings, it is possible to use SA priming as one of the most effective ways to maintain productivity in B. rapa ssp. pekinensis while it is exposed to low temperatures.