Cotton responses to nitrogen, carbon dioxide, and temperature interactions

Abstract

Several studies were conducted to evaluate how increases in the global atmospheric carbon dioxide concentration [CO2] and temperature affect growth and development rates, dry matter production, photosynthesis, and water use efficiency of cotton and how these responses are influenced by leaf N levels. In one study, cotton (cv. DPL 50) plants were grown at four temperatures (20/12, 25/17, 30/22, and 35/27°C day/night) until harvest at 70 days after emergence (DAE). Each temperature treatment was combined with [CO2] of 350 or 700 μL L-1. In another study, cotton (cv. DES 119) grown at two [CO2] received five N treatments (0, 1, 2, 6, and 10 mM NO3- in Hoagland's nutrient solution) at 17 DAE and every 2 days thereafter. Canopy gross photosynthetic rates increased with increasing [CO2] and temperature. The increased photosynthesis resulted in higher plant growth and dry matter accumulation rates except at the highest temperature. At 70 DAE, the maximum canopy dry matter accumulation rate occurred in 30/22°C. The 35/27°C treatment induced fruit abortion, resulting in greater dry matter accumulation in vegetative structures. Increases in plant dry weights by CO2 enrichment were greater in the two high temperature regimes than in the two lower temperature regimes. Water-use efficiency increased with increased [CO2] and decreased with increased temperature. Increases in water-use efficiency were due mainly to increased photosynthesis and partly to reduced canopy transpiration. Increase in leaf N concentration increased cotton photosynthesis and vegetative growth rates, and the increases were higher at 700 μL L-1 than at 350 μL L-1 [CO2].