Assessing Physiological Contributions of the First True Leaf to Seedling Vigor for Cotton Under Field Conditions.

Previous research has indicated that seed characteristics such as seed mass and composition can influence seedling vigor and possibly seedling growth response to temperature. Rapid development of the first true leaf has been suggested as a reliable indicator of seedling vigor in cotton, yet studies demonstrating a relationship between the photosynthetic response of the first true leaf to growth temperature and early season crop growth are limited. It was hypothesized that large seeded cotton cultivars or species would demonstrate greater early season vigor, especially under cool early season temperatures, thereby facilitating physiological development of the first true leaf and promoting early season seedling and whole-crop growth. To address this, a small (72 mg seed^-1) and large (94 mg seed^-1) seeded Upland cotton cultivar and a Pima cultivar (138 mg seed^-1) will be planted on three different dates to generate differences in temperature conditions. Stand establishment will be assessed at 3, 5, 7, 14, 21, and 35 DAP, first true leaf area at 21, 35, and 49 DAP, and classical crop growth analysis and physiological processes of the first true leaf at 21 and 35 DAP. This study will contribute to our understanding of the importance of the first true leaf in determining early season growth and allow for a more detailed understanding of the underlying component processes contributing to early season vigor in cotton.