Pollen Germination and Storage of Melastoma Linn

There are nearly 100 species of Melastoma Linn. (Melastomaceae) in the world, among which 9 species and a variety are native in China. Pollen viability and suitable storage conditions for pollens of M. affine, M. candidum and M. sanguineum were investigated. Pollen viability was measured using medium culture and three staining techniques, I₂-KI, 2,3,5-triphenyltetrazolium chloride (TTC), and benzidine-H₂O₂. In culture medium study, an orthogonal test with four factors was conducted, sucrose (5, 10, and 20 g·L^-1), boric acid (50, 100, and 200 mg·L^-1), calcium chloride (50, 100, and 200 mg·L^-1), and temperature (20, 25, and 30℃). Pollen tube germination of pollens from both long and short stamens was examined under microscope 2 h after being placed on medium. In vitro pollen germination of M. affine and M. candidum at 25 ℃ and 30 ℃ was higher than these at 20 ℃. The best culture medium for the pollen germination of M. affine, M. sanguineum, and M. candidum are 20 g·L^-1 sucrose + 200 mg·L^-1 H₃BO₃ + 100 mg·L^-1 CaCl₂+30 ℃, 20 g·L^-1 sucrose + 50 mg·L^-1 H₃BO₃ + 100 mg·L^-1CaCl₂+20 ℃, and 10 g·L^-1 sucrose + 100 mg·L^-1 H₃BO₃ + 50 mg·L^-1 CaCl₂+30 ℃, respectively. For three pollens staining studies, I₂-KI could not separate the viable and non-viable pollens; pollen viability determined by TTC and benzidine-H₂O₂ was similar to pollen germination method. For pollen storage study, pollens were enclosed in silica gel and preserved at room temperature, 4 ℃, -23 ℃, or -80 ℃, and pollen viability measured on 1, 5, 10, 15, 30, 60, 90, 120 days after storage. The results indicated that the lower preserved temperature, the higher pollen viability. -80℃ was the best pollen storage temperature, and after 120 days, the pollen viability of the three species still remained high.