Control of floral size and scent profiles by the plant circadian clock

The success of many ornamental plants relies on having attractive flowers. An additional trait of interest is scent, considered in many cases an added value. The plant circadian clock controls a large number of internal processes, including growth. Scent emission displays a circadian pattern in many species such as snapdragon. Here we show that knocking down LATE ELONGATED HYPOCOTYL in Antirrhinum majus causes a significant decrease in some floral size parameters. In order to gain understanding of the growth kinetics, we took a phenomic approach using in-house artificial vision systems, obtaining time-lapse videos. Wild type flowers showed a higher growth speed than knockdown plants. The maximal growth rate was decreased by 22% in plants with lower LHY expression. Floral volatiles were differentially affected as iRNA plants showed changes in the phase of emission of ocimene, linalool and 3,5-dimethoxytoluene, while others such as acetophenone or methyl benzoate were not affected. Plants with low LHY expression produced lower levels of methyl benzoate, acetophenone and linalool, higher levels of myrcene and nonanal while ocimene was not modified. Overall, transgenic lines produced roughly 18% less aroma and displayed a modified scent profile. Our results show that the plant circadian clock plays an important role in the quantitative and qualitative control of floral growth and scent emission. The differential effect on floral proportions and scent components suggests a biotechnological potential of the plant circadian clock to manipulate floral traits.