Figure 1 . Changes of viability and phenolics in tomato pollen subjected to heat stress, expressed as the percentage of pollen grains with positive cytochemical reaction . Series 1 - Control .   Series 2 - t o 1 - Pollen variability; 2 - Total phenolics; 3 - Flavonoids; 4 - Flavonols; 5 - Condensed tannins