Study On The Cold-resistance Mechanism And Effective Components Of Lavandula Angustifolia Mill.

Lavandula angustifolia Mill.is a kind of fragrant plant with remarkable economic value,and we obtained a low-temperature tolerant lavender variety in our previous work.In order to systematically study the cold tolerance mechanism of offspring and explore cold tolerance genes in L.angustifolia,this study conducted in-depth analyses of seed germination characteristics,physiological and biochemical response and molecular regulation mechanisms under different temperatures（30℃,20℃,10℃and0℃）.In addition,the bioactive components and the allelopathy effect of lavender on inhibition algal growth were studied.The main results are as follows:（1）The interactive treatment of GA₃ and NaOH on L.angustifolia seeds could break dormancy and promote germination.The germination indexes were comprehensively evaluated by membership function method,and 2%NaOH+50 mg/L GA₃,2%NaOH+100 mg/L GA₃and 2%NaOH+200 mg/L GA₃ were selected as the optimal treatment combinations,respectively,which significantly improved the seed germination and seedling vigorous for the seeds storage one year and two years.And the highest germination percentage were 83.33%.Using the above three combinations treat seeds stored from one to four years revealed that the seeds of L.angustifolia had the storability.While the seeds vigorous decreased with the extension of storage time.（2）For cold stress treatment of L.angustifolia,the enhance of the contents of soluble sugars and proteins as well as the activity of antioxidant enzymes helped L.angustifolia to reduce membrane damage to adapt to low temperature.Under freezing stress,L.angustifolia performed the protective function mainly by accumulating large amounts of proline and improving superoxide dismutase activity.Both 150 mg/L SA and 200μmol/L JA could significantly improve the content of osmotic substances and antioxidant enzyme activity at-10℃,effectively alleviate the cold damage symptoms of L.angustifolia leaves,and provided a certain protection.The results have practical significance for the cultivation of L.angustifolia in alpine regions.（3）Through transcriptomic and bioinformatics analysis,four positive upstream CBF genes（LaICE1,LaCAMTA3,LaEBF1,LaCCA1）,seven LaCBFs and 11 LaCORs were found in L.angustifolia leaves,all significantly differentially expressed under cold treatment.The above genes jointly formed a cold signal regulatory network and played an important role in L.angustifolia against low temperature.In addition,by activating LaSTAD,LaFADs,LaGPATs,LaBAMs,LaSPSA2,LaLEAs,LaP5CR,LaSODs,LaPODs and other related functional gene expression,the plant guided the synthesis of fatty acid desaturase,soluble sugars,late embryogenesis abundant protein,superoxide dismutase,peroxidase.And then the plant improved cold resistance through a series of physiological response enhancing membrane stability,providing osmoprotection and improving antioxidant level,and accumulating secondary metabolites such as flavonoids,phenylpropann.（4）GC-MS of L.angustifolia essential oil and extracts contained lots of alcohol,esters,phenol,and terpenoid-allelopathy active ingredient.The residue immersion filtrate was added to the Microcystis aeruginosa solution at 2.5%,5%,and 10%concentrations.The results showed that algal inhibition effect of residual leaching filtrate exhibited obvious concentration effect and 10%filtrate could persistently and effectively inhibit M.aeruginosa growth.The concentration of the algae density and contents of chlorophyll were continuously lower than the initial value during the 21-day experiment.The inhibition rate of algae was up to 96.02%,indicating that the L.angustifolia residue filtrate owned the excellent chemosensory algae inhibition.This study found that the residue after extracting essential oil from L.angustifolia has the potential to act as environment-friendly algae suppressors,which provides a scientific basis for realizing the efficient utilization of L.angustifolia and alleviating algal bloom pollution.