Abstract:

Camellia pollen was used as the material to study the effects of different substances of plant growth regulators, mineral elements, compound NO and reactive oxygen species (ROS) on pollen germination and pollen tube growth, and the orthogonal method was used to optimize the culture components of C. oleifera pollen germination. The results showed that 0.5-5.0 mg·L^-1 gibberellic acid (GA₃) and 0.5 mg·L^-1 naphthylacetic acid (NAA) could significantly promote pollen germination and pollen tube growth, and the maximum pollen germination rates were 59.07% and 71.29%, respectively. However, at high concentration (50 mg·L^-1), NAA and GA₃were significantly inhibited pollen germination and pollen tube growth. The germination rate of C. oleifera pollen treated with 10-50 mg·L^-1 MgSO₄ ranged from 56.88% to 65.83%, the maximum pollen tube length was 2 809.56 μm at 24 h. The promoting effect of 50-150 mg·L^-1 CaCl₂·2H₂O was significantly different from that of the control group, and the germination rate ranged from 59.91% to 63.28%, the maximum pollen tube length was 2 770.11 μm at 24 h. The pollen germination rate and pollen tube length decreased with increasing concentrations of ethylene glycol tetraacetic acid (EGTA) (inhibitor of Ca²⁺), ethephon and sodium nitroprusside (SNP) (donor of NO). 100-300 μmol·L^-1 Nω-Nitro-L-arginine (L-NNA) (NO inhibitor) promoted pollen germination and pollen tube growth, and the maximum pollen germination rate was 68.12%. The higher the concentration of H₂O₂(ROS donor) and N-Acetyl-L-cysteine (NAC) (ROS inhibitor), the lower the pollen germination rate and pollen tube length, and the maximum pollen germination rates were 48.39% and 45.78%, respectively. The results of orthogonal experiments showed that the optimal composition for promoting C. oleifera pollen germination were 100 g·L^-1sucrose, 10 g·L^-1 agar, 0.1 g·L^-1 H₃BO₃, 50 mg·L^-1 CaCl₂·2H₂O, 10 mg·L^-1 MgSO₄, 0.5 mg·L^-1 NAA and 2 mg·L^-1 GA₃, and the optimal composition for promoting C. oleifera pollen tube growth were 100 g·L^-1sucrose, 10 g·L^-1 agar, 0.1 g·L^-1 H₃BO₃, 50 mg·L^-1 CaCl₂·2H₂O, 10 mg·L^-1 MgSO₄, 0.5 mg·L^-1 NAA and 8 mg·L^-1 GA₃. Ca²⁺, Mg²⁺ and appropriate concentrations of GA₃and NAA promoted pollen germination and pollen tube growth, while ethylene, NO and ROS had opposite effects. This paper can lay the foundation for the in vitro germination test of C. oleifera pollen.

Key words: hormone, reactive oxygen species, Camellia oleifera, pollen germination rate, pollen tube length