Preliminary Study On Plant Growth Regulators On The Flowering Physiology And Flowering Period Regulation Of Hydrangea Paniculata ’Vanillaaw Berry’

In this paper,the effects of foliar spraying gibberellin(GA3),salicylic acid(SA)and ethephon(ETH)on flowering and physiological indexes of Hydrangea paniculata ’Vanillaawberry’ were studied,and the optimum plant growth regulators and corresponding concentrations were selected.The flower buds of the best treatment group and the control group were analyzed by transcriptional sequencing.It provides a theoretical reference for revealing the flowering regulation mechanism of Hydrangea.The main results are as follows:(1)Effects of plant growth regulators on flowering of Hydrangea paniculata.100 mg·L-1 SA treatment advanced the flowering stage by 5 days,prolonged the total flowering time by 10 days,and increased inflorescence length,width and sepal area by 22.76%,26.74%and 27.45%,respectively,compared with CK.Different concentrations of GA3,ETH and 1000 mg·L-1 SA significantly delayed the initial flowering stage and shortened the total flowering time.The delayed flowering days of GA3 and SA groups increased with the increase of treatment concentration,and the total flowering period shortened with the increase of treatment concentration.The inflorescence length,width and sepal area of GA3 and SA treatment groups decreased with the increase of treatment concentration,and the inflorescence number increased with the increase of treatment concentration,while the change rule of ETH treatment group was the opposite.(2)Determination of physiological indexes of Hydrangea paniculata were determined.It was found that the three plant growth regulators could increase the contents of photosynthetic pigment,soluble sugar,soluble starch and soluble protein in leaves.The contents of soluble sugar and soluble protein in 100 mg·L1SA group were significantly higher than those in CK in the later stage of flower bud differentiation.The MDA content of all treatments showed an upward trend,and the MDA content after foliar spraying of 100 mg·L-1GA3 was significantly lower than that of CK;100 mg·L-1SA,500 mg·L-1GA3 and 150 mg·L-1ETH,which significantly decreased the MDA content after flowering.The activities of antioxidant enzymes increased continuously during the growth of Hydrangea paniculata.Different concentrations of GA3,SA and ETH could increase the activities of SOD and POD in leaves,in which the activities of antioxidant enzymes decreased with the increase of GA3 and SA concentration,and increased with the increase of ETH concentration.(3)Determination of endogenous hormones in Hydrangea paniculata.Under the treatment of GA3 and SA,the contents of endogenous GA3 and IAA increased with the increase of treatment concentration,while the contents of endogenous ABA and ZR decreased with the increase of treatment concentration.The change of endogenous hormones in ETH treatment group was opposite to that of GA3 and SA.During the critical period of flower bud differentiation,the ratio of ABA/IAA,ABA/GA3,ZR/IAA and ZR/GA3 in the 100 mg·L-1SA treatment group was significantly higher than that in the control group at the flower bud differentiation stage,and increased by 10.98%,22.72%,12.50%and 23.49%respectively on the 20th day,and increased by 27.37%,17.36%,15.38%and 13.97%respectively after 30 days.The ratios of 500,1000 mg·L-1GA3 and SA and 25,75 mg·L-1ETH at flower bud differentiation stage were significantly lower than those of CK.(4)Transcriptome sequencing of flower bud samples from the early and late stages of flower bud differentiation in the optimal treatment group(100 mg·L-1 SA)and CK groups showed that:In the early stage of flower bud differentiation,there were 2110 differential genes,of which 550 genes were up-regulated and 1560 genes were down-regulated,while in the later stage of flower bud differentiation,there were 287 genes,14 genes were up-regulated and 273 genes were down-regulated,indicating that SA had a great effect on flower bud differentiation of Hydrangea paniculata in the early stage.30 differentially expressed genes related to flowering,37 genes related to hormone signal transduction,6 genes related to sucrose and starch metabolism,3 differentially expressed genes related to chlorophyll synthesis and metabolism and 5 genes involved in the defense mechanism of oxidative stress were obtained.it provides a reference for revealing the molecular mechanism of flowering regulation of Hydrangea paniculata.Nine gene fragments were randomly selected for qRTPCR verification,and the qRT-PCR results were consistent with the sequencing results,indicating that the transcriptome sequencing data were reliable.In summary,spraying 100 mg·L-1SA on the leaves of Hydrangea paniculata could significantly promote inflorescence growth,early flowering,increase sepal area and prolong florescence,etc.100 mg·L-1GA3 treatment could significantly promote the growth of Hydrangea paniculata,but the florescence was shortened and the number of flower branches decreased significantly;1000 mg·L-1GA3,500,1000 mg·L-1SA and 75,150 mg·L-1ETH treatments all led to delayed florescence and poor inflorescence quality.