Objective Additives in culture medium to promote germination of Camellia magniflora pollens were studied.

Method Pollens were collected from 4 elite lines of C. magniflora for morphological observation under a scanning electron microscope (SEM). In vitro culture medium was supplemented with a combination of H₃BO₃, NAA, and GA₃ in varied concentrations to determine the effects of the addition on pollen germination. Orthogonal experiments were conducted to optimize the formulation.

Results (1) In a polar view, C. magniflora pollens were triangular-lobed and suborbicular, and in equatorial view, prolate with relatively large grains of the polar axis ranging from 57.59 μm to 69.17 μm long. The pollens of HHCM-6, HHCM-8, and HHCM-9 had a rugulate exine ornamentation, while those of HHCM-7 were foveolate-reticulate. (2) Although the additions of H₃BO₃, NAA, and GA₃ in the test ranges of concentration could all stimulate germination and elongate tubes of the pollens, the combination of 50-200 mg·L⁻¹ H₃BO₃, 0.05-0.5 mg·L⁻¹ NAA, and 0.5-5 mg·L⁻¹ GA₃ significantly enhanced them. (3) The optimal formulation of these additives varied for the different lines of C. magniflora.

Conclusion The pollens of the 4 superior lines of C. magniflora were similar morphologically. The optimal combinations of the additives were 100 mg·L⁻¹ H₃BO₃+0.05 mg·L⁻¹ NAA+1.5 mg·L⁻¹ GA₃ for the pollens of HHCM-6 and HHCM-7, 200 mg·L⁻¹ H₃BO₃+0.05 mg·L⁻¹ NAA+2.5 mg·L⁻¹ GA₃ for those of HHCM-8, and 100 mg·L⁻¹ H₃BO₃+0.5 mg·L⁻¹ NAA+0.5 mg·L⁻¹ GA₃ for those of HHCM-8.