| Potassium is the essential element in plant growth and fruit development,which is closely related to fruit quality.In this study,‘Jinhua No.1’ was used as material.Which were treated with four potassium level treatments,including control group(CK),low potassium(K1),medium potassium(K2)and high potassium(K3).Through the determination of sucrose,fructose,glucose and organic acid content in Loquat fruit.The results showed the physiological effects of potassium on Loquat.On the basis of physiology,transcriptome sequencing was used to explore genes related to the key metabolic pathways.Furthermore,we used sucrose-related genes sequences to clone and analyze.This experiment preliminarily suggested the sugar synthesis genes expression characteristics in Loquat fruit.The main results are described as follows:1.Potassium application increased the Loquat fruit weight and soluble solid content,and decreased content of titratable acid.Meanwhile,the thickness of leaves were thicker,and the lower epidermis of leaves presented a "wavy" structure.When potassium was K2 treatment,the which above had the best effect.When potassium was K3 treatment,compared with K2 treatment,the mass of fruit became lighter,and the leaf thickness was thinner.Therefore,K2 treatment improved the fruit quality of Loquat,and promoted the accumulation of soluble sugar,accelerated the degradation of acid,and improved the sugar-acid ratio of fruit.2.Potassium can significantly improve the mineral content of fruit.With increasing of potassium,the content of K,Zn and Mn in Loquat fruit increased first and then decreased,the Ca content in fruit decreased first,then increased and then decreased,and K2 treatment was the most significant than others.Meanwhile,with increasing of potassium,Fe content in pulp and leaves decreased,but the content of N element in pulp and leaves increased first and then decreased.Therefore,excessive potassium application was not conducive to the accumulation of N element.3.In the early period of fruit,the fructose was the main sugar in fruit,and K3 treatment was significantly higher than others.In the veraison period,the contents of sucrose and fructose were higher than CK.In the fructescence,the sucrose contents of K2 and K3 treatment were significantly higher than that of CK,meanwhile,the total sugar and sucrose contents were the highest at K2 treatment.In the early period of fruit,the quinine acid,malic acid and lactic acid had a high content in fruit,the content of malic acid was the highest.At CK treatment,oxalic acid content was significantly higher than that potassium treatment,and under K3 treatment was the lowest.In the veraison period and fructescence,the malic acid was main acid,and the total acid content in the fructescence was the lowest in development of fruit.With potassium treatment,the contents of oxalic acid,tartaric acid,lactic acid and quinine acid were significantly lower than that of CK treatment.4.With increasing of potassium,the variation trends of Gs and Pn of leaves were basically the same,rising first and then decreasing.At K2 treatment,the Pn and Gs were the largest,which were significantly higher than the CK treatment.In the fructescence,the change trend of Tr was contrary to the Gs,which was the lowest at K2 treatment,but at CK treatment was the highest.In addition,the Tr under the CK treatment was significantly higher than potassium treatment.5.The activity of antioxidant enzyme was the highest in the early period of fruit.With the development of fruit,in the fructescence,the enzyme activity of APX was significantly higher than that of CK after potassium treatment.Meanwhile,with increasing of potassium,the activity of CAT and POD first increased and then decreased,and the enzyme activity was the highest under K1 treatment.But the activity of SOD showed a decreasing trend,and the activity under potassium treatment was significantly lower than CK treatment.6.In the rapid growth period of fruit,different concentrations of potassium and the same concentration of nitrogen were applied,then determined the concentrations of N,P and K of soil.The results showed the change of alkaline N content of soil was significant.The concentration of alkaline N at CK treatment was significantly higher than potassium treatment,and the concentration of alkaline N of soil decreased significantly with increasing of potassium.Therefore,potassium can improve the absorption of alkaline N in soil.7.Compared with Potash fertilizer treatment,sugar content was significantly higher than that of CK treatment,and the organic acid content decreased significantly.In order to explore the molecular mechanism of potassium influence on sugar and organic acid,the fruits of K2 and CK treatment were selected as materials,transcriptome sequencing by RNA-seq technology,attained the Loquat fruit transcription,from which we can get 660 up-regulated genes,and 1368down-regulated genes.These genes were mainly enriched in pathways such as glycolysis,pentose phosphate pathway,sucrose metabolism,TCA cycle,nitrogen metabolism.Meanwhile,transcription factors such as b HLH,C2H2,ERF and WRKY.Which were related to the regulation of potassium to affect Loquat growth and fruit development.8.By homologous cloning,obtained the EjUGD1 gene and the two-pore potassium channel protein gene EjTP3,which were related to the synthesis of sucrose.The ORF of EjUGD1 gene was 1443 bp,encoding 480 amino acids.The analysis of the molecular system showed,EjUGD1 and Pp UGD1 had a high homology and got together into a branch.q RT-PCR analysis showed,in the rapid growth period,veraison period and fructescence,the relative expression of EjUGD1 gene decreased with increasing of potassium.The ORF of EjTP3 gene was 1203 bp,encoding 400 amino acids and one termination codon.The analysis of molecular phylegenesis and protein sequence alignment showed,the protein of EjTP3 and Pb TP3 had a high similarity and got together into a branch.q RT-PCR analysis showed,the relative expression of EjTP3 gene was significantly higher in fruits than in leaves,and the expression in Loquat leaves increased with increasing of potassium. |
