• Background and Aims High-temperature environments with >30 °C during flowering reduce boll retention and yield in cotton. Therefore, identification of cotton cultivars with high-temperature tolerance would be beneficial in both current and future climates. • Methods Response to temperature (10–45 °C at 5 °C intervals) of pollen germination and pollen tube growth was quantified, and their relationship to cell membrane thermostability was studied in 12 cultivars. A principal component analysis was carried out to classify the genotypes for temperature tolerance. • Key Results Pollen germination and pollen tube length of the cultivars ranged from 20 to 60 % and 411 to 903 µm, respectively. A modified bilinear model best described the response to temperature of pollen germination and pollen tube length. Cultivar variation existed for cardinal temperatures (T_min, T_opt and T_max) of pollen germination percentage and pollen tube growth. Mean cardinal temperatures calculated from the bilinear model for the 12 cultivars were 15·0, 31·8 and 43·3 °C for pollen germination and 11·9, 28·6 and 42·9 °C for pollen tube length. No significant correlations were found between pollen parameters and leaf membrane thermostability. Cultivars were classified into four groups based on principal component analysis. • Conclusions Based on principal component analysis, it is concluded that higher pollen germination percentages and longer pollen tubes under optimum conditions and with optimum temperatures above 32 °C for pollen germination would indicate tolerance to high temperature.

Plant reproduction is highly vulnerable to global climate change components such as carbon dioxide concentration ([CO₂]), temperature (T), and ultraviolet-B (UV-B) radiation. The objectives of this study were to determine the effects of season-long exposure to treatments of [CO₂] at 360 (control) and 720 μmol mol⁻¹ (+CO₂), temperature at 30/22 °C (control) and 38/30 °C (+T) and UV-B radiation 0 (control) and 10 kJ m⁻² d⁻¹ (+UV-B) on flower and pollen morphology, pollen production, germination, and tube lengths of six soybean genotypes (D 88-5320, D 90-9216, Stalwart III, PI 471938, DG 5630RR, and DP 4933RR) in sunlit, controlled environment chambers. The control treatment had 360 μmol mol⁻¹ [CO₂] at 30/22 °C and 0 kJ UV-B. Plants grown either at +UV-B or +T, alone or in combination, produced smaller flowers with shorter standard petal and staminal column lengths. Flowers so produced had less pollen with poor pollen germination and shorter tube lengths. Pollen produced by the flowers of these plants appeared shrivelled without apertures and with disturbed exine ornamentation even at +CO₂ conditions. The damaging effects of +T and +UV-B were not ameliorated by +CO₂ conditions. Based on the total stress response index (TSRI), pooled individual component responses over all the treatments, the genotypes were classified as tolerant (DG 5630RR, D 88-5320: TSRI >−790), intermediate (D 90-9216, PI 471938: TSRI <−790 to >−1026), and sensitive (Stalwart III, DP 4933RR: TSRI <−1026). The differences in sensitivity identified among genotypes imply the options for selecting genotypes with tolerance to environmental stresses projected to occur in the future climates.