Soybean Pollen Anatomy,Viability and Pod Set under High Temperature Stress

High temperature (HT) stress is one of the major environmental factors influencing yield of soybean (Glycine max L. Merr.) in the semi‐arid regions. Experiments were conducted in controlled environments to study the effects of HT stress on anatomical changes of pollen and their relationship to pollen function in soybean genotype K 03‐2897. Objectives of this study were to (a) quantify the effect of HT stress during flowering on pollen function and pod set and (b) observe the anatomical changes in pollen grains of soybean plants grown under HT stress. Plants were exposed to HT (38/28 °C) or optimum temperature (OT, 28/18 °C) for 14 days at flowering stage. HT stress significantly decreased in vitro pollen germination by 22.7 % compared to OT. Pollen from HT stress was deformed; it had a thicker exine wall and a disintegrated tapetum layer. HT stress decreased pod set percentage (35.2 %) compared to OT. This study showed that decreases in pollen in vitro germination by HT stress were caused by anatomical changes in pollen, leading to decreased pod set percentage under HT stress.