FIGURE 1.

Moderate low temperature (MTL) stress at the tetrad stage affects pollen development in tomato. (A) Alexander staining of mature pollen grains from the plants exposed to normal temperature (NT), MLT-stress and returned to normal growing temperature for recovery after moderate low temperature treatment (MLTR). Scale bars = 100 μm. (C) Scanning electron microscopy indicated that MLTR-stress pollen grains were seriously shrunk and collapsed, appearing aggregated. Scale bars c1 = 10 μm; c2 = 3 μm; c3 = 1 μm. (B,D) Quantification of viable mature pollen grains and morphology normal pollen from NT, MLT, and MLTR plants, respectively. Each value is the mean ± SD (n = at least three biological replicates with 15 plants each). *P < 0.05; **P < 0.01 (two-tailed Student’s t- test). (E) Semithin cross sections of anthers in different stages under NT and MLT condition. The tapetum degeneration was postponed under MLTR compare to NT condition. MMC, microspore mother cell; Tds, tetrads; UMsp, uninucleate microspore; BP, binucleate pollen; PG, pollen grains; DUMsp, degenerated uninucleate microspore; DBP, degenerated binucleate pollen; DPG, degenerated pollen grains; T, tapetum. The experiment was repeated three times independently with consistent results. Scale bars = 20 μm.