Mechanism Of Different Photoperiod On Flower Bud Differentiation And Secondary Flowering Of LC6 Hemerocallis

Hemerocallis fulva,originated in China and cultivated for thousands of years in China,is the mother flower of China.It is a perennial hosta of the Hemerocallis L.in the family Asphodelaceae Dumort.,with a variety of varieties and bright colors,and has high ornamental value.Hemerocallis fulva is internationally recognized as one of the world’s three largest perennial perennial flowers,with many breeders and over 2500 varieties registered internationally each year.It is one of the most diverse flowers in the world.There are many studies on breeding,mainly focusing on flower color,flower type,population flowering period,and other aspects of Hemerocallis fulva,but relatively few studies on its flowering period regulation.In order to reveal the effect of photoperiod on the secondary flower bud diffe rentiation of Hemerocallis fulva,four photoperiods of natural light CK(14h/10h),P h12(12h/12h),Ph10(10h/14h),and Ph8(8h/16h)were used to study the effect of photoperiod on the secondary flower bud differentiation of Hemerocallis fulva LC6.The results show that:(1)In the CK group,the scaping time was normal in late August,with Ph 12 being23 days later than CK,Ph 10 being 26 days later than CK,and Ph 8 being 34 days later than CK.Compared with CK,the number of scapes in each treatment group was significantly reduced,with 76 scapes in CK and 3,6,3 in the other three treatments,respectively.In the CK group,flowering was normal at the beginning of September,while Ph 12 had 3 but not flowering,Ph 10 had 6 but not flowering,and Ph 8 had 3 but not flowering.Shortening the photoperiod affected the secondary flowering and flowering of Hemerocallis fulva LC6.(2)The results of paraffin section showed that under natural photoperiod conditions,Hemerocallis fulva LC6 entered reproductive growth on June 30,with Ph12 being 15 days later than CK,and Ph10 and Ph8 being 30 days later than CK,indicating that shortening the photoperiod delayed the initiation time of secondary flower bud differentiation of Hemerocallis fulva LC6.The photoperiod treatment group did not complete flower bud differentiation,and the process of flower bud differentiation in Ph12 treatment ended at the flower primordium differentiation stage,while Ph10 treatment remained at the flower primordium differentiation stage of flower bud differentiation,and Ph8 treatment remained at the inflorescence primordium differentiation stage.Shortening the photoperiod delayed the initiation of flower bud differentiation in Hemerocallis fulva LC6,delayed the process of flower bud differentiation,and thus interrupted flower bud differentiation.(3)Under the photoperiod treatment,the soluble sugar content in the leaves and roots of the three treatment groups was lower than CK,with both fructose and sucrose decreasing,with sucrose having a higher decrease.The starch content in the root was higher than CK,and the amylase activity was lower than CK,indicating that shortening the photoperiod affected the soluble sugar and starch content and distribution during flower bud differentiation of Hemerocallis fulva LC6.The above results indicate that different photoperiods ultimately affect the flower bud differentiation of Hemerocallis fulva LC6 by affecting the content and distribution of carbohydrates in leaves,roots,and stem tips.(4)During the secondary flower bud differentiation of Hemerocallis fulva LC6,the expression of Hf CO in CK group showed a trend of first increasing and then decreasing,reaching a peak at the second stage of collection,significantly higher than that in Ph8 treatment group.Flower bud differentiation showed that CK entered the inflorescence primordium differentiation stage at collection stage II;However,the expression of Hf CO in the Ph8 treatment group showed a "downward-upward-downward" trend,significantly higher than CK at the collection stage IV,while the flower bud differentiation in the Ph8 treatment group entered the inflorescence primordium differentiation stage.In summary,both CK and Ph8 treatment groups entered the inflorescence primordium differentiation stage at the highest level of Hf CO gene expression,completing the transition from vegetative growth to reproductive growth.Therefore,the increased expression of Hf CO may serve as a molecular marker for the transformation of secondary flower bud differentiation from vegetative growth to reproductive growth in Hemerocallis fulva LC6.Shortening the photoperiod significantly changed the expression trend of Hf CO during flower bud differentiation in the Ph8 treatment group,affecting the initiation of secondary flower bud differentiation in Hemerocallis fulva LC6.