Intensifying heat stress impacts cotton flowering and boll development efficiency

Authors: BISTA, MOHAN - Mississippi State University; NARAYANA, NISARGA - Mississippi State University; CHAKRAVARAM, ALEKHYA - Mississippi State University; PIERALISI, BRIAN - Mississippi State University; DHILLON, JAGMAN - Mississippi State University; REDDY, K - Mississippi State University; BHEEMANAHALLI, RAJU - Mississippi State University

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2025
Publication Date: 7/30/2025
Citation: Bista, M., Narayana, N., Chakravaram, A., Pieralisi, B., Dhillon, J., Reddy, K.R., Bheemanahalli, R. 2025. Intensifying heat stress impacts cotton flowering and boll development efficiency. BMC Plant Biology. 25(984):1-14. https://doi.org/10.1186/s12870-025-06934-8.
DOI: https://doi.org/10.1186/s12870-025-06934-8

Interpretive Summary: Cotton farmers face challenges during hot weather, particularly when plants are flowering and forming bolls. Heat stress can reduce yields and degrade cotton quality. We studied 16 cotton genotypes under normal and elevated temperatures to understand their responses to heat. In hot conditions, cotton plants struggled to cool down despite high transpiration, resulting in hotter leaves and reduced energy for producing cotton bolls. Leaves became thinner with less green pigment, essential for photosynthesis. Heat also hindered pollen growth, crucial for boll formation. While a few cotton types maintained the number of bolls and seeds, overall cotton and lint production decreased, indicating smaller, less dense bolls. Additionally, heat negatively impacted seed oil content and fiber quality.

Technical Abstract: Cotton-growing regions face heat stress (HS) during flowering and boll development, adversely affecting reproductive fitness, yield, and quality. Identifying and incorporating superior physiological and reproductive traits into high-yielding cultivars may improve yield potential under such stress. Thus, this study quantified the effects of heat stress (36/24°C, HS) on 25 trait responses of 16 upland cotton cultivars compared to current growing conditions (32/24°C, control-CNT) during the reproductive stage. Under HS, all cultivars exhibited transpirational cooling with increased stomatal conductance (1-fold) and transpiration (1.6-fold) compared to CNT. However, the leaf temperature of plants under HS was 3.5°C higher than that of CNT plants. The quantum efficiency of photosystem II decreased by 20% under HS compared with CNT. Heat stress also reduced the ratio of reproductive to vegetative dry mass (57%), indicating poor resource partitioning towards reproductive organs. The specific leaf area was increased by 34%, whereas the leaf chlorophyll index dropped by 28% under HS compared with CNT. When exposed to HS, pollen germination was reduced by 71% across cultivars compared to the control. While some cultivars maintained similar boll and seed numbers between CNT and HS, a corresponding tolerance was not observed in seed cotton yield. On average, seed cotton yield and lint yield decreased by 19% and 26% under HS, respectively. In contrast, seed yield remained stable, suggesting a disproportionate reduction in intra-boll components. The seed oil content and fiber quality, except for fiber uniformity, displayed susceptibility to HS. Overall, cultivar responses to heat stress varied, highlighting the importance of understanding genotype interactions with heat stress for effective selection in breeding programs.