The rare species Magnolia wufengensis frequently suffers from freezing injury in northern China. To investigate the influence of exogenous abscisic acid (ABA) application on the natural cold acclimation of M. wufengensis, physiological and biochemical changes in field-grown M. wufengensis seedlings subjected to foliar ABA treatments at four concentrations (0, 300, 600, and 900 mg·L−1) were evaluated from Sept. 2012 to Jan. 2013. The optimum foliar application concentrations of ABA for M. wufengensis were between 600 and 900 mg·L−1, which led to faster shoot growth cessation, leaf senescence, and development rates of bud endodormancy level and shoot freezing tolerance. The improved freezing tolerance under exogenous ABA application was associated with promoted dehydration and accumulation of proline, soluble protein, and certain soluble sugars such as glucose and fructose. Foliar ABA treatments initiated a cascade of steps for advancing the cold acclimation process of M. wufengensis. We suggest that exogenous ABA application may be used on M. wufengensis grown in northern China, where there are short growing seasons and early fall frost events.
Yang Yang, Zhongkui Jia, Faju Chen, Ziyang Sang, and Luyi Ma
Yuyu Wang, Faju Chen, Yubing Wang, Xiaoling Li, and Hongwei Liang
High-frequency somatic embryogenesis and plant regeneration were achieved from immature cotyledonary-stage embryos in the endangered plant, Tapiscia sinensis Oliv. Plant growth regulators with different concentrations and combinations on embryogenesis capacity were studied. The optimal explants for in vitro somatic embryogenesis were immature embryos in T. sinensis. A high callus induction rate of 100% was achieved on Murashige and Skoog (MS) basal medium supplemented with 1.0 mg·Ll−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5% (w/v) activated charcoal. Alternatively, a high induction rate (96.16%) of somatic embryogenesis was obtained on MS basal medium supplemented with the combination of 0.05 mg·L−1 α-naphthaleneacetic acid (NAA) and 0.2 mg·L−1 6-benzylaminopurine (6-BA), and somatic embryos proliferated fastest on the mentioned medium supplemented with 0.5% (w/v) activated charcoal and 3% (w/v) sucrose, inoculation of explants proliferating 21 times in the 23-day subculture. Of the 100 plantlets transferred to field after the acclimation, 95 (95%) survived. Based on the histocytological observations, the development of somatic embryos was similar to that of zygotic embryos. There were two accumulation peaks of starch grains in the embryogenic calli and in the globular-stage embryos, both closely related to the energy supply, and the embryoids were of multicelluar origin.