Our experiments explored the effects of far-red (FR) light on cucumber (Cucumis sativus L. ‘Zhongnong No. 26’) seedling growth. Our results indicated that FR light significantly promoted the growth of cucumber seedlings. Specifically, it promoted the accumulation of shoot biomass and the elongation of internodes and leaves (except the first leaf at the bottom). Further analysis showed that FR light had no effect on the accumulation contents of abscisic acid (ABA) and auxin (IAA) in seedling leaves. Still, it significantly caused the increase of the gibberellin (GA3, GA4, and GA7) contents and the decrease of GA1 content, which suggested that the leaf expansion progress under FR light may be primarily related to GA. Therefore, the cucumber seedling leaf expansion response to GA was evaluated under different light sources. The exogenous spraying of different GA4/7 contents significantly promoted the leaf expansion of cucumber seedlings under white light, while the GA biosynthesis inhibitor paclobutrazol (PAC) significantly promoted the expression of GA hydrolytic genes (GA2ox2 and GA2ox4) and decreased the content of endogenous active GA, which inhibited the leaf expansion induced by FR light. As expected, the combination of exogenous GA4/7 and PAC restored the growth promotion effect of FR light on cucumber seedling leaves. It increased the contents of endogenous active GA (GA1, GA3, GA4, and GA7), and the expression trend in GA synthetic/hydrolytic-related genes was the opposite of that of PAC was applied alone. All of the above results indicated that FR light regulates leaf expansion progress in cucumber seedlings through GA.

我们的实验探讨了远红（FR）光对黄瓜（Cucumis sativus L.'中农26号'）幼苗生长的影响。我们的结果表明，FR光显着促进了黄瓜幼苗的生长。具体来说，它促进了地上部生物量的积累和节间和叶片（底部第一片叶除外）的伸长。进一步分析表明，FR光对幼苗叶片中脱落酸（ABA）和生长素（IAA）的积累含量没有影响。尽管如此，它仍显着引起赤霉素（GA3、GA4和GA7）含量的增加和GA1含量的减少，这表明FR光下的叶片扩展过程可能主要与GA有关。因此，评价了不同光源下黄瓜幼苗对GA的展叶响应。外源喷施不同GA4/7含量显着促进白光下黄瓜幼苗的展叶，而GA生物合成抑制剂多效唑(PAC)则显着促进GA水解基因GA2ox2和GA2ox4的表达，降低内源活性物质的含量。 GA，抑制 FR 光诱导的叶片扩张。正如预期的那样，外源GA4/7与PAC的组合恢复了FR光对黄瓜幼苗叶片的促生长作用。它增加了内源活性GA（GA1、GA3、GA4和GA7）的含量，并且GA合成/水解相关基因的表达趋势与单独施用PAC相反。以上结果均表明FR光通过GA调控黄瓜幼苗的展叶进程。