AUTHOR=Zhang Damao , Chen Qianru , Zhang Xia , Lin Ling , Cai Ming , Cai Wenqi , Liu Yang , Xiang Lili , Sun Ming , Yu Xiaoying , Li Yanlin 

TITLE=Effects of low temperature on flowering and the expression of related genes in Loropetalum chinense var. rubrum

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1000160

DOI=10.3389/fpls.2022.1000160

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p><italic>Loropetalum chinense</italic> var. <italic>rubrum</italic> blooms 2-3 times a year, among which the autumn flowering period has great potential for exploitation, but the number of flowers in the autumn flowering period is much smaller than that in the spring flowering period.</p></sec><sec><title>Methods</title><p>Using ‘Hei Zhenzhu’ and ‘Xiangnong Xiangyun’ as experimental materials, the winter growth environment of <italic>L. chinense</italic> var. <italic>rubrum</italic> in Changsha, Hunan Province was simulated by setting a low temperature of 6-10°C in an artificial climate chamber to investigate the effect of winter low temperature on the flowering traits and related gene expression of <italic>L. chinense</italic> var. <italic>rubrum</italic>.</p></sec><sec><title>Results</title><p>The results showed that after 45 days of low temperature culture and a subsequent period of 25°C greenhouse culture, flower buds and flowers started to appear on days 24 and 33 of 25°C greenhouse culture for ‘Hei Zhenzhu’, and flower buds and flowers started to appear on days 21 and 33 of 25°C greenhouse culture for ‘Xiangnong Xiangyun’. The absolute growth rate of buds showed a ‘Up-Down’ pattern during the 7-28 days of low temperature culture; the chlorophyll fluorescence decay rate (Rfd) of both materials showed a ‘Down-Up-Down’ pattern during this period. The non-photochemical quenching coefficient (NPQ) showed the same trend as Rfd, and the photochemical quenching coefficient (QP) fluctuated above and below 0.05. The expression of <italic>AP1</italic> and <italic>FT</italic> similar genes of <italic>L. chinense</italic> var. <italic>rubrum</italic> gradually increased after the beginning of low temperature culture, reaching the highest expression on day 14 and day 28, respectively, and the expression of both in the experimental group was higher than that in the control group. The expressions of <italic>FLC</italic>, <italic>SVP</italic> and <italic>TFL1</italic> similar genes all decreased gradually with low temperature culture, among which the expressions of <italic>FLC</italic> similar genes and <italic>TFL1</italic> similar genes in the experimental group were extremely significantly lower than those in the control group; in the experimental group, the expressions of <italic>GA3</italic> similar genes were all extremely significantly higher than those in the control group, and the expressions all increased with the increase of low temperature culture time.</p></sec><sec><title>Discussion</title><p>We found that the high expression of gibberellin genes may play an important role in the process of low temperature promotion of <italic>L. chinense</italic> var. <italic>rubrum</italic> flowering, and in the future, it may be possible to regulate <italic>L. chinense</italic> var. <italic>rubrum</italic> flowering by simply spraying exogenous gibberellin instead of the promotion effect of low temperature.</p></sec>