Analysis Of Growth Characters And Stress Resistance Of Populus Davidiana Dod

Polyploid induction is one of the important methods to create new species of forest.In this study,we studied the creation,identification,growth traits,physiological indexes and photosynthetic characteristics of polyploid Populus davidiana Dod,which laid the foundation for ploidy breeding of Populus davidiana Dod.At the same time,the changes of phenotypes,physiological and biochemical indexes were observed under drought and salt stress treatments to study their drought and salt tolerance.The main results are as follows:（1）Polyploid Populus davidiana Dod was obtained by treating diploid populus davids with 0.1%-0.2%colchicine for 2 to 4 days.Tetraploid Populus davidiana Dod were quickly screened by morphological observation,fluorescence in situ hybridization and ploidy analyzer.（2）Compared with diploid Populus davidiana Dod,tetraploid Populus davidiana Dod had some growth advantages.The ground diameter of tetraploid Populus davidiana Dod increased12.35%higher than diploid Populus davidiana Dod,but there was no significant difference in seedling height.The leaf area of tetraploid Populus davidiana Dod also increased 18.28%compared with diploid Populus davidiana Dod,which was mainly caused by the increase of leaf width.In addition,the results of paraffin sections of tetraploid aspen leaves showed that the upper epidermis cells were thicker,palisade tissues were more developed,stomata were larger,stomata density was smaller,and guard cells were larger.（3）The analysis of photosynthetic characteristics showed that the total chlorophyll content,net photosynthetic rate（Pn）,stomatal conductance（Cond）,intercellular CO₂concentration（Ci）,transpiration rate（Tr）increased in tetraploid Populus davidiana Dod.The non-photochemical fluorescence quenching（NPQ）of tetraploid tetraploid Populus davidiana Dod was lower than diploid Populus davidiana Dod,while the maximum photochemical efficiency（Fv/Fm）,the central non-cyclic electron transport quantum yield of PSⅡ（ΦPSⅡ）,photochemical fluorescence quenching（q P）,and the non-cyclic photosynthetic electron transport rate（ETR）of PSⅡwere higher than diploid Populus davidiana Dod.The results showed that compared with diploid Populus davidiana Dod,tetraploid Populus davidiana Dod can capture and use light energy better,have higher light energy conversion rate,stronger potential photosynthetic capacity,and stronger resistance to external adverse environment.（4）By observing and comparing the performance of different ploidy Populus davidiana Dod under drought and salt stress,it was found that compared with diploid Populus davidiana Dod,tetraploid Populus davidiana Dod had lower leaf damage degree,and better performance in growth state and leaf damage index than diploid Populus davidiana Dod.Under stress conditions,compared with diploid tetraploid Populus davidiana Dod,the relative conductivity was lower,MDA accumulation was less,and Pro content was higher.The enzyme activities of SOD,POD and CAT in tetraploid Populus davidiana Dod were significantly higher than those in diploid Populus davidiana Dod.These results indicated that under drought and salt stress,the oxidation damage degree of cell membrane of tetraploid Populus davidiana Dod was lower than diploid Populus davidiana Dod,the cell membrane was more stable,and the stress adaptability was stronger.Based on the above analysis,it is concluded that tetraploid Populus davidiana Dod have growth advantages.Under short-term drought and salt stress,tetraploid Populus davidiana Dod has stronger drought and salt tolerance than diploid Populus davidiana Dod.The results of this study provide valuable reference for populus polyploid breeding.