| Curcuma kwangsiensis S.G.Lee&C.F.Liang can be popularized as bulbous hydroponic flowers in Chinese Lunar New Year Fair.The inflorescence is developed from lateral buds on the rhizome,with bright color and controllable flowering period.Previous studies have observed that lateral buds can develop into flowers directly after low temperature storage and high temperature treatment,but the flowering rate needs to be improved.In order to improve the flowering rate of lateral buds of C.kwangsiensis and understand its flowering regularity and influencing factors,the rhizomes of C.kwangsiensis at high temperature sprouting stage were treated with drought stress,and the effect of drought stress on lateral buds flowering was analyzed.The physiological and biochemical indexes of buds during drought stress were determined,and the transcriptome sequencing of buds at drought stress stage was performed.Combined with physiological and biochemical analysis and transcription level analysis,the mechanism of drought stress promoting the flowering of lateral buds of C.kwangsiensis was explored.In addition,reagent treatment was applied to improve the inflorescence quality after drought stress,which provided a theoretical basis for the production of hydroponic flowers of C.kwangsiensis.The main research results are as follows:1.After 4 d of drought stress at the high temperature flowering stage,the flowering rate of buds reached 43.3%,which was 20.0%higher than that of the control group（continuous water culture）.Moreover,the inflorescence spike extraction time was earlier.the interval from flowering to growing leaves and the inflorescence life are longer,but the flower branches were shorter.2.During drought stress,the contents of soluble protein,soluble sugar and starch in the lateral buds of the treatment group were increased basically,which were different from those in the control group,and the total nitrogen content in the treatment group and the control group showed a law of increase-decrease-increase.Under drought stress for 4 d,proline content and C/N ratio in treatment group were higher than those in control group.3.Drought stress changed the endogenous hormone balance of buds.The ratios of CTK/IAA and ABA/IAA in buds were higher than that in the control group at 4 d,but returned to the same level or slightly lower than that in the control group at 8 d.4.Transcriptome sequencing was performed on the bud samples before drought stress（PDT）,4 d after drought stress（DT）and 4 d after rewatering（RWT）.A total of 2000 genes were screened out in the two differential expressed genes sets of PDT-vs-DT and PDT-vs-RWT.KEGG enrichment analysis revealed that 2000 genes were mainly involved in metabolic pathways,biosynthetic pathways of secondary metabolites,photosynthesis and carbon metabolism.)5.Some differential genes were selected for q-PCR verification,and the expression trends of the two results were consistent generally,confirming that the transcriptome data were reliable.Further analysis of the differential expressed genes showed that the expression levels of NCED,the key enzyme gene for ABA synthesis,and CYP707A7,the metabolic enzyme gene,were increased and decreased in the DT group,respectively.The expression levels of ABA signal transduction pathway response element ABF and photoperiod flowering pathway gene GI were increased in the DT group,and the flowering integration factors FT,SOC1,LFY,and AP1 were highly expressed in the DT or RWT group.6.Under drought stress,when the bulbs were cultured in 5 mg/L lanthanum nitrate solution,the main roots of lateral buds germinated most and the root activity increased significantly.Under the treatment of 5 mg/L GA3solution,the length of flower branches reached 23.25 cm,which was 7.52 cm longer than that of control group.When 500 mg/L magnesium sulfate solution was used in bud expansion period,the anthocyanin content of crown bracts was the highest during the flowering period.When these reagents were used at the same time,except that the number of main roots had no significant change,they played a certain role in promoting inflorescence elongation and crown bract color depth. |
