Growth and in vitro flowering of Gomphrena globosa

To clarify the mechanism of growth and in vitro flowering induction of Gomphrena globosa, the shoots with apical bud were used as explants on modified Murashige and Skoog (MS) medium to explore the effects of different concentrations (0, 20, 40, 60, or 80 g·L-1) of sucrose, and different combinations of cytokinins N6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA) and auxin polar transport inhibitors TIBA and NPA on nitrogen-regulated growth and flowering in vitro. The results indicated that sucrose was the key factor in floral morphogenesis and growth, and that treatments without sucrose (modified MS supplied with 6.5 g·L-1 agar) produced no flowers and few roots. An increasing concentration of sucrose could promote flowering, and the highest percentage of flowering (80.72%) was obtained on medium containing 80 g·L-1 sucrose. The height, leaf number, and particularly the root volume of G. globosa were all higher in treatments with 20~40 g·L-1 sucrose. L9(34) orthogonal experiment results showed that BA was more effective than NAA in promoting growth and flowering induction, with the highest percentage of flowering (60.14%) and growth being obtained on media containing 1.0 mg·L-1 BA. Auxin polar transport inhibitors prevented flowering and rooting of G. globosa, with the inhibition effects of TIBA being stronger than those of NPA at the same concentrations, although auxin itself did not induce flowering. Therefore, sucrose is indispensable for the growth and in vitro flowering of G. globose. BA also plays an important role, and the effect was also regulated by endogenous hormones.