Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 1997
Publication Date: N/A
Interpretive Summary: Global atmospheric carbon dioxide levels and temperature are expected to continuously increase in the future. As carbon dioxide and temperature increases, nutrient requirements, including nitrogen, of crop plants may change due to changes in plant growth. The experiments were conducted to evaluate how increases in carbon dioxide and temperature affect growth, photosynthetic production, and water use efficiency of cotton and how these responses are influenced by leaf nitrogen levels. Our results indicate that doubling the current carbon dioxide levels (i.e., increase from 350 to 700 ppm) increases plant photosynthetic production and reduces water loss, therefore increasing cotton water use efficiency. However, increase in temperature increases water loss and thus decreasing plant water use efficiency. The influences of carbon dioxide and temperature on cotton growth depend on leaf nitrogen levels. First, increase in leaf nitrogen level increases cotton photosynthesis and growth rates. Second, doubling the current carbon dioxide level augments this increase. Based on our results, we believe as atmospheric carbon dioxide rises, the rates and time of fertilizer application for plants growing in a warmer climate will need reassessment to obtain maximum growth, development, and yield responses. Reliable predictions of growth will help to enable the most productive farming and environmental quality to be maintained.
Technical Abstract: Global atmospheric CO2 concentration and temperature are expected to increase in the future. Many of the specific relationships required for modeling the response under increased [CO2] and temperature conditions have not been quantified. The experiments were conducted in growth chambers to evaluate how increases in [CO2] and temperature affect growth biomass 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 35/27C day/night) from 15 days after emergence (DAE) until harvest at 70 DAE. Each temperature treatment was combined with [CO2] of 350 or 700 uL L-1. In another study, cotton (cv. DES 119) grown at two [CO2] (350 and 700 uL L-1) 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 photosynthesis increased with increasing [CO2] and temperature. The increased photosynthesis resulted in higher plant growth and dry matter accumulation rates except at the highest temperature. The 35/27C 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 higher than in the two lower temperatures. 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 than at 350 uL L-1 [CO2].