| In recent years,the excessive quality of heavy metals in farmland and vegetable soils has threatened the quality and safety of vegetables.Choosing appropriate agronomic control measures to repair the contaminated soil is a feasible measure to ensure the safe vegetable production in heavy metal polluted fields.Pepper is the largest seasoning in the world,and it is also a kind of vegetable that Chinese people like to eat.Among the vegetable crops,the scale and benefits of pepper plantation are at the forefront of vegetable crops.However,due to soil cadmium exceeding standards,pepper fruits have successively reported Cd exceeding standards,which severely limited their production and development in the agricultural process.The pot experiment were carried out to study four different genotypes pepper varieties growth,and accumulation of Cd content differences under different Cd leves?0,5,10 mg·kg 1?in the soil.Moreover,the different expression of related genes of peppr were detected by the qRT-PCR analysis techniques.It aims to clarify the accumulation differences and accumulated Cd characteristics of different pepper varieties on Cd-contaminated soil from molecular angle.The main conclusions are as follows:Under Cd stress,the above-ground biomass of pepper was inhibited,and the root dry weight of varieties X15,X45,X55 all increased compared with the control,and X15,X55 increased by8.13%?33.38%,19.54%?63.61%,respectively.When Cd treatment concentration was 10 mg·kg-1,the dry weight of root X45 increased by 17.95%compared with the control..The root of variety X39 was more sensitive to Cd stress,and its root biomass decreased with increasing Cd treatment concentration.Under the same Cd concentration treatment,the Cd content in root,stem,and leaf of variety X39 was significantly higher than that of other varieties.The fruit Cd content of variety X15 was the highest,and in 5 mg·kg-1 Cd treatment,it was higher than that of other varieties.17.42%?45.42%;the Cd content is 10 mg·kg-1,it was higher than that of other varieties 9.18%?35.73%.The content of Cd in the fruit is determined by the ability of Cd transfer to the ground and the distribution of Cd above the ground.The accumulation of Cd in pepper increased with the increase of Cd treatment concentration,and the Cd accumulation capacity in different parts was stem>root>leaf>fruit,and the Cd accumulation amount in different shoots was X15>X45>X55>X39.?2?The Pn value of variety X39,X45 had a downward trend with the increase of Cd treatment concentration.The Pn value of variety X15,X55 increased first and then decreased under Cd stress.The change in Tr Gs of pepper leaves was consistent with Pn as the Cd concentration increased.The Pn value of variety X15 X45 X55 decreased and the Ci value increased,indicating that the decrease of photosynthesis of variety X15 X45 X55 was caused by non-stomatal factors.?3?Under Cd stress,the root POD and CAT enzyme activities of the various varieties were higher than the control.With the increase of the Cd concentration,the POD enzyme activity of the variety X15 X39 leaves,the CAT enzyme activity of the leaves X39 X45 leaves,and the SOD enzyme activity of the root lines of the variety X39 leaves variety X55 increased first and then decreased,except for the variety X39 X55 root systems.Under Cd stress,the MDA content was higher than the control.?4?Under Cd stress,the Cd content of subcellular components in the roots,leaves and fruits of different varieties of pepper was:cytoplasm>cell wall>organelles,and the distribution ratio of cytoplasm,cell wall,and organelles in pepper roots was 52.06%.?82.87%,14.29%?37.65%,2.83%?13.96%,the distribution ratio of cytoplasm,cell wall,and organelles in pepper leaves was:51.29%?65.48%,24.32%?40.11%,7.86%?19.71%,distribution ratio of cytoplasm,cell wall,and organelles in pepper roots was 41.71%?57.64%,27.76%?38.28%,6.06%?27.76%.In the stem,Cd is mainly distributed in the cell walls of varieties X15,X45,X55,accounting for 40.9%?54.52%of the total cell Cd;in variety X39,it is mainly distributed in the cytoplasm,accounting for 53.4%?53.8%of the total Cd amount of cells.With the increase of Cd treatment concentration,the Cd content of each subcellular component in each part of each variety increased?except the content of Cd variety X39 in the organelle?.Compared with other varieties of X39,the cytoplasmic Cd content was highest in all organs,and the distribution ratio of Cd content in subcellular components was the highest,indicating that variety X39 was most affected by Cd poisoning.Variety chemical form of Cd content in pepper fruits increased with the increase of Cd treatment concentration.The main chemical form of Cd in pepper fruits was sodium chloride and acetic acid,accounting for 72.36%?79.79%of the total Cd content in fruits.?5?NRAMP and HMA family genes have different expression patterns among different pepper varieties.In general,the relative expression of NRAMP5 in different parts of cultivar X15 is highest in fruits.The relative expression of NRAMP2 and HMA2 is as follows:stem>root>fruit>leaves.The relative expression of NRAMP2,3,5,6 in variety X39 appeared as stem>root>fruit>leaf in different parts,while in cultivar X45 and X55,the relative expression of NRAMP2,3,5,6 was expressed as root>leaf>stem between different parts.Comparing with Cd concentration in different parts of each pepper variety,It is concluded that the high expression of NRAMP2,3,5,6 in the stem is one of the reasons for the high transport and accumulation of Cd in the shoots.?6?Under Cd stress,the relative expression levels of NRAMP1,2,3,5,6 in the stems of varieties X15?39 were 1.25?682.82,1.3?33,1.15?16.42,3.92?62.37,1.44?17.85 times compared with varieties X45?X55,respectively.The order of Cd concentration among different varieties was X39,X15>X55,X45,indicating that the high expression level of NRAMP and HMA among different varieties is one of the reasons for the content of Cd in plants.The relative expression of NRAMP5 in the stem of variety X15 was 4.47?62.37 times,5.57?11.86 times that of the other varieties,and the relative expression of NRAMP5 in fruits was 55.96?111.93,13.46?48.07 times that of the other varieties,and the TF?fruit-root system?of variety X15 was),TF?fruit-stem?values are 1.9?2,and1.59?1.94 times that of other varieties,indicating that NRAMP5 may be a key gene that causes high Cd transport in pepper plants and high accumulation in fruits. |
PDF Full Text Request