Yield variability is a major problem in cotton production that has been associated with high temperature stress during flowering and boll development. Our research has shown a strong negative correlation between high temperature and low yields during the first four weeks of boll development. However, insufficient information exists about how these high temperatures influence yield. Reports in the literature indicate that high temperatures adversely affect pollination, fertilization and seed set resulting in reduced seed numbers and lower yields. It is well documented in horticultural crops that polyamines are indispensable for the development of fruit. In the current study, it was hypothesized that because pollination and seed set are a problem in cotton production and because polyamines are needed for the development of fruit, the addition of certain PGRs that stimulate increased levels of polyamines may have a very direct benefit of improving pollination and seed set in cotton. This benefit may thereby enhance yields, especially under conditions of extreme temperatures at mid summer. The objectives of these studies were to investigate the effect of temperature and plant growth regulators on fertilization, seed set, and yield of a diverse set of cotton genotypes. In addition, we wanted to quantify the physiological and biochemical responses of Goemar BM86 on the ability of the cotton plant to tolerate high temperature stress.