Objective Effects of low temperature and plant growth regulator on the growth, bolting, and flowering of Isatis indigotica plants were investigated.
Method Seeds of Isatis. indigotica Zhongqing No. 1 were exposed to 2, 4, or 6 ℃ in a climate-controlled chamber for vernalization to observe the bolting and flowering of the emerged seedlings. Endogenous hormones in the shoot apex and effects of gibberellin and uniconazole on the bolting rate of the plants under 25 ℃ and 4 ℃ were determined.
Result (1) Low temperature vernalization promoted the process of bolting, flowering, and bud differentiation of the plants. The seedlings emerged from a 40 d/4 ℃ vernalization began to flower at 27 d after planting ,which had 12 leaves on a plant. and It's 4 nodes earlier than that of 2 ℃ or 6 ℃ vernalization. (2) The low temperature treatment increased the contents of IAA, GA, and ABA in the seedling stem tips. and under 4 ℃ and 25 ℃ treatment, the IAA and GA content slowly increased and followed by a decline ,IAA peaked 40 d after germinating, while GA 50 d, and the IAA and GA content was lower than that before bolting, while ABA continued to rise throughout the growing season. (3) The combined low temperature and GA treatment showed additive positive effect, and which accelerated the plant bolting and flowering, not only due to the GA induction at the stem tip but also the interaction between low temperature and hormone. Uniconazole treatment significantly reduced the bolting rate of Isatis indigotica, while GA could break this inhibition
Conclusion Low temperature vernalization promotes bolting and flowering of Isatis indigotica. It promoted the GA, IAA, and ABA generation in the seedlings. Exogenous GA could induce flowering of the plants without a low temperature treatment, but uniconazole would retard bolting.
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