Study On Cold Tolerance And Cold Tolerance Mechanism Of Eight Ornamental Plants

Low temperature is a kind of disaster often encountered in plant growth.In order to choose a cold-tolerant ornamental plant and provide a theoretical basis for the cultivation of cold-tolerant plants,the experiment selects Pachysandra terminalis Sieb.et Zucc,Licheng Ophiopogon japonicus,Lonicera japonica,Laoyu Carex,Qinglv Carex,Gutonghong Iris tectorum Maxim,Jinwawa Hemerocallis fulva and Licheng No.6 Hemerocallis fulva as the test materials.Natural conditions overwintering.The cold resistance of the eight ornamental plants was studied by field observation and subordinate function values analysis.In order to explore the physiological mechanism of cold-tolerant plants,the most cold-resistant materials obtained from the previous tests were subjected to outdoor natural low-temperature treatment,and the indicators of their cold resistance were determined by correlation analysis and principal component analysis.The application of CaCl₂ and calcium ion chelating agent EGTA,through the determination of physiological indicators,explored the effect of Ca²⁺ on its cold tolerance.In order to reveal the molecular mechanism of cold-tolerant plants,the leaves and roots of the most cold-tolerant materials were subjected to transcriptome sequencing after cold treatment,and the differences between expressed genes before and after treatment were analyzed to understand the molecular mechanism of low-temperature response.The test results are as follows:1 Through field observation and chilling injury index determination of eight ornamental plants,it is concluded that the degree of damage to the eight ornamental plants from low to large is Licheng Ophiopogon japonicas < Pachysandra terminalis Sieb.et Zucc < Lonicera japonica < Laoyu Carex <Qinglv Carex < Gutonghong Iris tectorum Maxim < Jinwawa Hemerocallis fulva < Licheng No.6 Hemerocallis fulva.The cold resistance of eight ornamental plants was evaluated by subordinate function values analysis.The cold tolerance of the eight plants was as follows: Pachysandra terminalis Sieb.et Zucc > Licheng Ophiopogon japonicas > Lonicera japonica > Laoyu Carex > Qinglv Carex > Gutonghong Iris tectorum Maxim > Jinwawa Hemerocallis fulva > Licheng No.6 Hemerocallis fulva.From the field observation results and the subordinate function values analysis,the cold resistance of Licheng Ophiopogon japonicus and Pachysandra terminalis Sieb.et Zucc was stronger.2 With the persistence of low temperature stress,soluble protein content,chlorophyll content,SOD activity,relative conductivity and MDA content increased,and calcium ion concentration increased first and then decreased.Principal component analysis and correlation analysis showed that the six indicators of chlorophyll a,chlorophyll b,chlorophyll content,carotenoid content,soluble protein content and relative conductivity are 0.983?0.907?0.967?0.991?0.985 and 0.956,they are larger eigenvectors,it is indicated that Pachysandra terminalis Sieb.et Zucc.mainly resists low temperature by regulating its physiological metabolism such as chlorophyll content,soluble protein content and relative conductivity.3 Spraying CaCl₂ and its inhibitor EGTA,after low temperature treatment,the relative conductivity and MDA content of the leaves of Pachysandra terminalis Sieb.et Zucc with only exogenous CaCl₂ sprayed were lower than those of EGTA,SOD activity,soluble protein content and the chlorophyll content was higher than that of EGTA.After spraying EGTA and spraying CaCl₂,the results of each index were between EGTA and only CaCl₂.This result indicates calcium ions participated in the low temperature response of Pachysandra terminalis Sieb.et Zucc.The process confirmed that the low temperature stress response of Pachysandra terminalis Sieb.et Zucc was closely related to calcium ion signaling.4 The transcriptome sequencing of the low-temperature treated Pachysandra terminalis Sieb.et Zucc was carried out,and the GO function analysis was carried out on the differentially expressed genes.The low temperature stress mainly affected the cell membrane of Pachysandra terminalis Sieb.et Zucc,concluding the response to stress and chemical reaction of Pachysandra terminalis Sieb.et Zucc on low temperature.The pressure reaction also affects antioxidase activity,transcription factor activity and specific DNA sequence binding,and nucleic acid binding transcription factor activity.The KEGG enrichment pathway of the differentially expressed genes showed that the Pachysandra terminalis Sieb.et Zucc improved its cold tolerance mainly through plant hormone transduction,starch and sucrose metabolism,oxidative phosphorylation,plant pathogen interaction,photosynthesis pathway,MAPK signaling pathway,etc.5 This experiment screened 10 genes related to cold tolerance of plants based on differential gene function annotation information,including WRKY transcription factor,AP2/ERF transcription factor,MYB transcription factor,NAC transcription factor,coding dehydration reaction element binding protein and anion peroxidase genes.Quantitative Real-time PCR was performed on the selected 10 genes,and the expression of the gene was consistent with the results of transcriptome sequencing,indicating that WRKY transcription factor,AP2/ERF transcription factor,MYB transcription factor,NAC transcription factor,coding dehydration reaction element binding protein and anion peroxidase gene play an important role in the regulation of gene expression under the low temperature stress of Pachysandra terminalis Sieb.et Zucc.