张娟 吴晓颖 许娜 杜沙沙 张彦 马兴华

摘 要：为研究油菜素内酯（Brassinolide， BR）对烟草主茎生长的影响，利用外源2， 4-表油菜素内酯（2， 4-Epibrassinolide， EBR），设置0.5×10-7 mol/L（T1）、0.5×10-5mol/L（T2）两个浓度，以蒸馏水（CK）为对照对烟草幼苗进行喷施。分析了不同处理的烟草幼苗株高，节距及解剖结构特征，检测了茎中与细胞分裂和细胞大小调控相关基因以及与油菜素内酯（BR）、生长素（IAA）和赤霉素（GA）合成相关基因的表达量。结果表明，喷施EBR对烟草幼苗节距和株高有显著促进作用，并随处理浓度升高，促进作用增强。观察石蜡切片发现EBR处理后茎皮层薄壁细胞数目增多，单细胞面积减小。EBR处理后，细胞周期调控基因NtCYCD3表达上调，细胞大小调控基因NtARF6、NtARF16表达下调;BR信号受体基因NtBRI1，NtBIN2表达上调，BR转录因子NtBES1T表达下调;BR、IAA和GA的关键生物合成基因NtDWF4、NtYUCCA8、NtGA3ox-2表达量均上调。说明喷施EBR可促进内源BR、IAA和GA的合成基因表达，通过促进节间细胞分裂、抑制细胞大小促进烟草幼苗茎的生长。

关键词：2， 4-表油菜素内酯;烟草;茎伸长生长;解剖结构;基因表达量

Abstract： To study the effect of brassinolide （BR） on tobacco stem growth and elongation， the tobacco seedlings were treated with 2，4-epibrassinolide （EBR） of two different concentrations 0.5×10-7 mol/L （T1）， 0.5×10-5 mol/L （T2） and distilled water was used as control （CK）. Plant height， internode distance， and stem anatomical structure were analyzed. Genes related to cell division and cell size regulation， and genes related to biosynthesis of BR， auxin （IAA）， and gibberellin （GA） were also analyzed. The results showed that the application of EBR increased the seedling pitch and plant height， the promotion effect on stem growth was enhanced with increment of EBR concentrations. Stem anatomical study revealed an increase in the number of parenchyma cells and a decrease in its area after EBR treatment. EBR upregulated cell cycle-related gene NtCYCD3 while downregulated NtARF6 and NtARF16 genes that are related to cell size. Similarly， BR signaling receptor genes NtBRI1 and NtBIN2 were upregulated while the BR transcription factor NtBES1T was downregulated in response to EBR application. The expression of key biosynthesis genes NtDWF4， NtYUCCA8， and NtGA3ox-2 of BR， IAA， and GA， respectively， were all upregulated. The results showed that the application of EBR promoted the expression of endogenous BR， IAA and GA biosynthesis genes， and helped in the growth and elongation of tobacco seedling stem by promoting the division of internode cells and inhibiting cell expansion.

Keywords： 2， 4-epibrassinolide; Nicotiana tabacum; stem elongation; anatomical structure; gene expression;

莖是植物的三大营养器官之一，具有支持、运输、储存、繁殖和光合的功能，在植物的生长发育过程中起着不可替代的作用[1]。株高是指植株主茎基部到顶部之间的距离，由植株的茎节数目和节间长度决定，是农作物重要的生物学性状之一，与作物经济产量密切相关。适当的株高能抗倒伏，还有利于CO2的分布，提高光能利用率[2]。

植物株高的增长包括主茎节数的增多以及各节间的伸长[3]。细胞的分裂和伸长是植物茎伸长生长的主要原因，这一过程受多种内外因素的调节和控制。……