Radiation Use Efficiency among Cotton Cultivars

Abstract Cotton ( Gossypium hirsutum L.) cultivars have diverse growth rates and fruiting characteristics that may be due to differences in radiation use efficiency. Potential growth rates were measured to see if differences could be attributed to radiation use efficiency or canopy light transmission coefficients. An irrigated field study was conducted at the Blackland Research Center using three diverse cotton cultivars; Acala SJ‐2, Deltapine 5O, and Tamcot CD3H. Plant densities ranged from 10 to 14 plants m −2 . Transmitted, incoming, and reflected photosynthetically active radiation and leaf area index were measured weekly from 3 wk after emergence to boll opening. Dry matter accumulation and leaf area index were significantly different among cultivars both years. Light transmission coefficients were not different, but cultivars differed in radiation use efficiency through the reproductive period. Values for radiation use efficiency ranged from 1.5 g MJ −1 photosynthetically active radiation for Acala to 1.3 g MJ −1 for Tamcot. Values were not significantly different during the vegetative period. These differences during the reproductive period are likely due to differences in boll number and photosynthetic efficiency among cultivars. Tamcot had 50 to 100% more bolls than Acala both years. These results suggest that crop models should account for these cultivar differences in radiation use efficiency.

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