Effects of Plant Growth Regulating Substances on Catalpa bungei Pollen Germination and Pollen Tube Growth

The effect of four types of plant growth regulating substances on pollen germination and pollen tube growth of different Catalpa bungei provenances was studied by in-vitro pollen cultivation in liquid media. The results showed that low concentration of GA3stimulated pollen germination and pollen tube growth,whereas the high concentration of GA3had inhibition effect. The most suitable concentration to stimulate the pollen germination and pollen tube growth was 300 mg / L. The effect of IAA and 2,4-D varied with the C. bungei provenances,but the general law was that the low concentrations could promote but the high concentrations would inhibit the pollen germination and pollen tube growth. The maximum pollen germination rate was obtained by 15 mg / L IAA concentration,there was significant difference in the pollen germination rate among two provenances and the control. Regarding to 2,4-D,the maximum pollen germination rate was obtained by 200 mg / L concentration. When the concentrations of both IAA and 2,4-D were over the most suitable values,these two types of plant growth regulators would inhibit the pollen germination and pollen tube growth. NAA had an inhibition effect on the pollen germination and pollen tube growth of C. bungei at different concentrations,the higher NAA concentration was,the sronger the inhibition effect would be.