Effects of High Night Temperatures On Cotton During Squaring and Flowering.

Cotton growth areas across United States are facing several changes in temperatures year after year and as a consequence yields are variables. High night temperatures increases respiration and decreases carbohydrates content, however, it is unclear which development stage is more sensitive. The experiment was conducted in growth chambers located at Altheimer Laboratory, University of Arkansas, Fayetteville, Arkansas, USA. Treatments were high night temperatures (29 °C for 4 hours) at squaring and flowering and a control treatment (24°C), in a randomized complete block  design with 10 replications. High night temperatures (29°C) had lower respiration than control treatment (24°C) only at the second week of squaring. In addition, at the third week of flowering high night temperature stress raised respiration. Photosynthesis decreased in the 2^nd week in high night temperature treatment during squaring, but no differences occurred at flowering stage. High night temperatures increased shedding rates both squaring and flowering stages. However, the boll number per plant diminished in high night temperature at squaring, but no effect of high night temperature at flowering was observed. Also, total reproductive dry matter production decreased under HNT during squaring, despite the individual reproductive weight.