Early Vegetative Growth of Cotton as Influenced by Leaf Type1

Abstract

Cotton (Gossypium hirsutum L.) plants with mutant Okra (L0) and Super Okra (L5) leaves have several desirable characteristics in production systems with narrow rows and with standard rows where humidity and boll rot are high. These leaf types cause a modified fruiting expression in cotton plants. This investigation was conducted to determine the effect of the mutant leaves on rate of dry matter production, rate of leaf area development, assimilation efficiency, and dry matter partitioning during early growth of cotton plants. Three near‐isogenic lines of ‘Stoneville 7A’ (normal, Okra, and Super Okra leaves) were grown spaced field plantings during 2 years. The two mutant leaf types had significantly lower dry matter accumulation than the normal‐leaf type during both years. Values for Okra leaf‐plants were intermediate to the normal and Super Okra‐leaf plants. Initial size of cotyledons, mean net assimilation rate, and C exchange rate were similar among the leaf types and were not major factors causing the differential growth rates. The mutant types, especially Super Okra‐leaf plants, had low dry matter partitioning into leaf area. Relative leaf area growth rate of the Super Okra‐leaf plants was 12 to 20% lower than that of the normal‐leaf plants. The leaf area partition coefficient of the Super Okra‐leaf plants was 11 to 17% less than that of the normal‐leaf plants. Values for the Okra‐leaf plants were generally intermediate and frequently not significantly different from normal‐leaf plants. These factors are primarily responsible for the low growth rate of Super Okra‐leaf plants and probably to a lesser extent affect the growth of Okra‐leaf plants in a similar manner.