Pollen viability assessed by FDA staining. A, Histogram of pollen fluorescence, with white bars representing positive FDA-stained fluorescent (live) pollen and gray bars representing nonfluorescent (dead) pollen from nontreated (no SlPRALF), treated (1 μm SlPRALF), and heat-killed pollen. FDA staining was done 1 h after the start of pollen to germination, ±sd, n ≥ 100 pollen grains. B, Micrograph of stained untreated pollen. C, Micrograph of stained SlPRALF-treated pollen.