The flowering of SDP chrysanthemum in response to intensity of supplemental or night-interruptional blue light is modulated by both photosynthetic carbon assimilation and photoreceptor-mediated regulation

Abstract

The photoreceptor-mediated photoperiodic sensitivity determines the obligate short-day flowering in chrysanthemum (Chrysanthemum morifolium Ramat.) when the night length is longer than a critical minimum, otherwise, flowering is effectively inhibited. The reversal of this inhibition by subsequent exposure to a short period of supplemental (S) or night-interruptional (NI) blue (B) light (S-B; NI-B) indicates the involvement of B light-received photoreceptors in the flowering response. Flowering is mainly powered by sugars produced through photosynthetic carbon assimilation. Thus, the light intensity can be involved in flowering regulation by affecting photosynthesis. Here, it is elucidated that the intensity of S-B or NI-B in photoperiodic flowering regulation of chrysanthemums by applying 4-h of S-B or NI-B with either 0, 10, 20, 30, or 40 mmol•m −2 •s −1 photosynthetic photon flux density (PPFD) in a 10-h short-day (SD10) [SD10 + 4B or + NI-4B (0, 10, 20, 30, or 40)] or 13-h long-day (LD13) condition [LD13 + 4B or + NI-4B (0, 10, 20, 30, or 40)] provided by 300 ± 5 mmol•m −2 •s −1 PPFD white (W) LEDs. After 60 days of photoperiodic light treatments other than the LD13 and LD13 + NI-4B (40), flowering with varying degrees was observed, although the SD10 gave the earliest flowering. And the LD13 + 4B (30) produced the greatest number of flowers. The flowering pattern in response to the intensity of S-B or NI-B was consistent as it was gradually promoted from 10 to 30 mmol m −2 s −1 PPFD and inhibited by 40B regardless of the photoperiod. In SD conditions, the same intensity of S-B and NI-B did not significantly affect flowering, while differential flowering inhibition was observed with any intensity of NI-B in LDs. Furthermore, the 30 mmol•m −2 •s −1 PPFD of S-B or NI-B up-regulated the expression of floral meristem identity or florigen genes, as well as the chlorophyll content, photosynthetic efficiency, Frontiers in Plant Science frontiersin.org 01

Blue Light Supplemented at Intervals in Long-Day Conditions Intervenes in Photoperiodic Flowering, Photosynthesis, and Antioxidant Properties in Chrysanthemums

“…CmFTL1 in chrysanthemum may operate as an LD florigenic gene, comparable to RFT1 in rice. Under photoperiod-unfavorable conditions, it may be anticipated that residual CmFTL3 and enhanced CmFTL1 eventually cause flowering, which was also proved by our pervious study exploring the LD florigenic-like gene CmFTL1 involved in photoperiodic flowering in SDP chrysanthemum [ 13 ]. That might be one of the regions to induce more flowers in “60 days-(LD13 + 4B)” and “30 days-(LD13 + 4B)” treatments ( Figure 2 and Table 3 ).…”

“…Based on previous studies [ 12 , 13 ], 10-h short-day (SD10) and 13-h long-day (LD13) treatments without any supplemental blue light (S-BL) were established as the two control groups in the current study. The light duration was started every day at 8:00 a.m. Plants were grown with daily light at an intensity of 300 ± 5 μmol·m −2 ·s −1 PPFD provided by white (W) MEF50120 LEDs (More Electronics Co. Ltd., Changwon, Korea) with a wide spectrum ranging from 400 to 720 nm and a distinct peak at 435 nm in blue ( Figure 1 A).…”

“…The light duration was started every day at 8:00 a.m. Plants were grown with daily light at an intensity of 300 ± 5 μmol·m −2 ·s −1 PPFD provided by white (W) MEF50120 LEDs (More Electronics Co. Ltd., Changwon, Korea) with a wide spectrum ranging from 400 to 720 nm and a distinct peak at 435 nm in blue ( Figure 1 A). Because the photoperiodic flowering and physiology of chrysanthemums are sensitive to the 30 μmol·m −2 ·s −1 PPFD of S-BL [ 13 ], the B LEDs (450 nm) ( Figure 1 B) were used to provide 4-h supplemental blue light (30 μmol·m −2 ·s −1 PPFD) at the end of LD13 (LD13 + 4B) ( Figure 1 C) at different intervals. The detailed description and abbreviation of the light treatments and the proportion of S-BL days in the 60 days of experimental duration are shown in Table 1 .…”

“…SDPs, as previously said, are unable to flower when the day is too long. However, short-day plants, chrysanthemum and kalanchoe, flowered in long-day conditions when supplied with low levels of monochromatic blue light [ 10 , 11 , 12 , 13 , 14 ]. In these situations, blue light supplementation did not impair the blossom initiation.…”

“…Flowering is primarily driven by sugars created from photosynthetic carbon assimilation [ 13 ]. Plant flowering is also affected by light quality-related photosynthetic efficiency and carbon absorption, which is related to altered carbon and nitrogen metabolism [ 31 , 32 ].…”