Figure 3.
Heat stress applied during the tetrad stage of pollen development inhibits pollen germination in maize. A and B, In vitro germination assay of pollen isolated from nonstressed (A) and heat-stressed plants (B) show a reduced germination rate and burst of stressed pollen. Arrows indicate nongerminated pollen tubes. Scale bars = 100 μm. C, Percentage of in vitro germination rate of pollen harvested from nonstressed and heat-stressed plants. The asterisk indicates a significant difference at P < 0.001; one-tailed t test comparing heat-stressed samples to nonstressed samples. D and E, Aniline blue staining of nonstressed (D) and heat-stressed (E) pollen germinating on papilla hair cells show lack of pollen tubes and penetration after heat stress application. The star indicates a normal germinating pollen tube. Scale bars = 100 μm. F, Nonstressed cobs were pollinated with both nonstressed pollen (NS × NS) and heat-stressed pollen (NS × HS). Seed set is strongly reduced after using heat-stressed pollen. Data are presented as the mean ± sd. n = 400–500.