2-3oc Elevated Temperature from Ambient Temperature Regime (30.1/25.8oC) during Flowering and Boll Formation Stage Was Beneficial to Cotton Production on Distal Fruiting Positions.

Temperature has increased approximately 0.8°C since the early 20th century and is likely to rise 1.8-4°C by the end of the 21st century due to global warming. The increase will consequently significantly affect cotton production. To investigate the effect of elevated temperature on source-sink metabolism of cotton boll on different fruiting positions (FPs), field experiments were conducted under ambient temperature regime (30.1/25.8°C) and elevated temperature regime (32.6/28.6°C, ambient temperature plus2-3°C) during flowering and boll formation stage in 2011 and 2012 in Nanjing (118°50'E, 32°02'N), China. We found that elevated temperature increased boll number by around 20% and cotton yield by around 10%, but decreased boll weight and lint percentage. Further analyze showed that elevated temperature decreased yield distribution rate and increased boll number on FP1 and FP2, but notably increased yield distribution rate by around 17% and boll number by around 40% on FP3 and FP above 3. Whereas boll weight and lint percentage were decreased by elevated temperature due to decreased sucrose content of cotton fiber and the subtending leaf on all FPs. This indicated that the increased boll number on FP3 was the main contributor to the yield increase. For cotton fiber, elevated temperature increased callose content and decreased cellulose content on FP1, but decreased the callose content and increased cellulose content on FP3. In addition, fiber length decreased, fiber strength and micronaire increased by elevated temperature on all FPs. But the decrease was slighter and the increase was bigger on FP3 than on FP1, which related to the different response of fiber callose and cellulose content to elevated temperature between different FPs. Results suggested that 2-3°C elevated temperature from ambient temperature regime (30.1/25.8°C) during flowering and boll formation stage can enhance cotton yield by around 17% and improve fiber quality on distal FPs.