Optimization of hormone combinations for root growth and bud germination in Chinese fir (Cunninghamia lanceolata) clone leaf cuttings

In order to ascertain the optimal hormone combination for Chinese fir (Cunninghamia lanceolata) leaf cuttings, an L(16)(4)(4) orthogonal test of 6-benzylaminopurine (6-BA), 1-naphthaleneacetic acid (NAA), and indole-3-butyric acid (IBA) (0, 10, 30, or 50 mg · L(−1) of each exogenous hormone) immersion for 5, 10, 15, or 20 min was conducted. Callus initiation rate and rooting promotion rate were mainly affected by treatment time, root length increase by 6-BA concentration, and bud germination rate and plantlet formation rate by NAA concentration. The expected optimal combination for callus initiation rate was 50 mg · L(−1) 6-BA + 0 mg · L(−1) NAA + 30 mg · L(−1) IBA + 10 min; for rooting promotion rate, it was 0–10 mg · L(−1) 6-BA + 10 mg · L(−1) NAA + 30 mg · L(−1) IBA + 20 min; for bud germination rate, it was 50 mg · L(−1) 6-BA + 0–10 mg · L(−1) NAA + 0–30 mg · L(−1) IBA + 20 min; and for seedling formation rate for No. 4, it was 10 mg · L(−1) 6-BA + 10 mg · L(−1) NAA + 0 mg · L(−1) IBA + 20 min. Light microscopy image analysis revealed that a cluster of primordial cells was produced 40 days after cutting, and mastoid cells developed into peninsula cells in calli that were cultured for 50 days.