Effects Of Boron On Chinese Cabbage Quality And Glutamine Synthetase Family Gene Expression

More and more people are paying attention to the nutritional value and flavor of vegetables,because of the change in the domestic vegetable supply situation and the improvement of people’s living standard,how to improve the nutritional and flavor quality of vegetables has become a hot topic of research today.The content of vitamin C,sugars,amino acids and volatile compounds has far-reaching implications for the nutritional and flavor quality of vegetables.To investigate the mechanism of action of these substances on the nutritional and flavor substances of vegetables,it is necessary to study the key enzymes and genes related to the metabolism of these substances.Boron is one of the six essential trace elements for higher plants and plays an important role in the growth and development of crops.There have been numerous studies showing that boron fertilisation helps to improve the nutritional and flavor quality of vegetables,but the optimum boron concentration and its mechanism of action in Chinese cabbage growth are still unclear.Therefore,in this study,Chinese cabbage "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" were used as test materials,cultivated in substrates,and measured under different boron concentration treatments(0,0.5,1,2 and 4 mg·L-1 H3BO3)Physiological indicators of Chinese cabbage growth and the nutritional and flavor quality of the above-ground parts.At the same time,the expression of glutamine synthetase family genes that are closely related to nitrogen metabolism and amino acid metabolism are measured,and the growth of Chinese cabbage under different boron concentrations And the role of quality and its biological mechanism.The main findings of the study are as follows.(1)Appropriate application of boron fertilizer(0.5～2 mg-L-1 H3BO3)promoted the growth and development of Chinese cabbage,but there were some differences in the performance of different varieties:the biomass of "Hua Liang Zao Wu Hao" increased and then decreased with the increase of boron concentration,and the root,above-ground and total biomass of each treatment increased by 3.32%-39.66%,0.48%～36.93%and 3.27%～36.61%respectively compared with the control.The biomass of "Cui Tian Bai 2 Hao" increased with increasing B concentration,with the root,above-ground and total biomass of each treatment increasing by 18.16%～40.08%,12.12%～36.51%and 18.07%～40.03%.Overall,the growth of Chinese cabbage under B2(1 mg·L-1 H3BO3)treatment was the best and was the optimum concentration for Chinese cabbage growth.(2)The application of boron fertilizer significantly increased the above-ground reducing sugar content of Chinese cabbage,with the reducing sugar content of "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" increasing by 8.51%～20.03%and 5.95%～16.76%,respectively,compared with the control.The maximum values of reducing sugars were reached at 0.68%and 0.67%under B4 treatment.The nitrate content of above-ground cabbage was significantly reduced after the application of B fertilizer,with the lowest nitrate content in "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" under B4(4 mg-L-1 H3BO3)and B2(1 mg·L-1 H3BO3)treatments,respectively,with minimum values of 957.53 mg-kg-1 and The Vc content of Chinese cabbage could be improved by appropriate B concentration,except for "Hua Liang Zao Wu Hao" t B3(2 mg-L-1 H3BO3),"Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" at B3(2 mg·L-1 H3BO3).The Vc content of "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" increased by 0.27%～16.58%and 8.35%～62.47%,respectively,compared with the control.(3)Appropriate concentration of boron fertilizer significantly increased the above-ground N,P and K content of Chinese cabbage,and the above-ground N,P and K content of "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" reached the maximum under B2(1 mg·L-1 H3BO3),B3(2 mg·L-1 H3BO3)and B2(1 mg～L-1 H3BO3)treatments respectively,increasing by 10%,16.03%,11.44%and 8.56%,12.79%and 6.16%respectively compared with the control.The effect of B on the P content of Chinese cabbage was better than that of N and K.The effect of B on the mineral element content of "Hua Liang Zao Wu Hao" was better than that of "Cui Tian Bai 2 Hao".The water-soluble B,semi-bound B and bound B contents of Chinese cabbage roots,petioles and leaves all increased with increasing B concentration,and were all maximised at the highest B concentration treatment.The relative content of boron in different forms of Chinese cabbage showed different trends with increasing B concentration:the relative content of bound boron in roots,petioles and leaves were the largest,and the proportion decreased continuously with increasing B concentration;the relative content of semi-bound boron in roots increased more than water-soluble boron,and the relative content of water-soluble boron and semi-bound boron in petioles and leaves increased differently depending on the variety of Chinese cabbage.(4)The application of boron fertilizer(1～2 mg·L-1 H3BO3)increased the proportion of essential amino acids to total amino acids in Chinese cabbage,and the appropriate amount of boron fertilizer also increased the above-ground essential amino acids and total amino acids in "Hua Liang Zao Wu Hao".The main indicators of the nutritional value of amino acids in cabbage are aspartic acid(Asp),glutamic acid(Glu),glycine(Gly),isoleucine(Ile),lysine(Lys),threonine(Thr),proline(Pro)and methionine(Arg).The amino acid nutritional values of the treatments of "Hua Liang Zao Wu Hao"and "Cui Tian Bai 2 Hao" under the principal component analysis were B2>B3>CK>B1>B4 and CK>B4>B1>B2>B3 in descending order,and in the amino acid ratio coefficient method The SRC of"Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" were B1>B2>B4>CK>B3 and B3>B4>CK>B2>B1 in descending order.The above two methods were used to evaluate the nutritional value of above-ground amino acids in cabbage under different boron concentrations from two perspectives.The RCT of gustatory amino acids in "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao" at different B concentrations were,in descending order:B2>B3>B1>CK>B4,CK>B4>B1>B3>B2.(5)The characteristic volatile compounds of Chinese cabbage were trans,cis-2,6-nonadienal,isopropyl isothiocyanate,methyl salicylate,(3-viologenone,phenylacetonitrile,decanal and(E)-2-hexenal.Appropriate concentrations of boron(0.5～2 mg·L-1 H3BO3)increased the total amount of aldehydes,nitrile and volatile compounds in "Hua Liang Zao Wu Hao" and "Cui Tian Bai 2 Hao",reaching maximum values of 878.155μg·kg-1,680.358 μg·kg-1 and 59.311 μg·kg-1 at B2 treatment.1 and 59.311 μg·kg-1,115.149 μg·kg-1.(6)The expression of GLN family genes in Chinese cabbage petioles and leaves is higher than that in roots.Application of boron fertilizer has different effects on the expression of GLN family genes in Chinese cabbage roots,petioles and leaves:the expression of GLN1;2 and GLN2 in Chinese cabbage roots is up-regulated,GLN1;1 And the expression of GLN1;4 was down-regulated."Hualiangzao 5" petiole GLN1;1;GLN1;4 expression was up-regulated,"Cuitianbai 2" petiole GLN2 expression was up-regulated,GLN1;2 expression was down-regulated;leaf GLN family gene expression was up-regulated overall.In summary,under the condition of boron deficiency,proper application of boron fertilizer(1 mg·L-1 H3BO3)increased the relative and absolute content of semi-bound water-soluble boron in Chinese cabbage roots and aerial parts and improved the structure,stability and stability of the cell wall.Root vitality promotes the growth and development of Chinese cabbage plants.Appropriate application of boron fertilizer may increase/decrease the expression of some genes of the GLN family in the regulation roots,and increase the nitrate assimilation ability of Chinese cabbage,thereby promoting the absorption and utilization of nitrogen and the synthesis of amino acids by plants;at the same time,it promotes the production of photosynthetic products of plants.And transhipment.Therefore,the content of amino acids,carbohydrates and aromatic compounds derived from the above-ground of Chinese cabbage is increased,and the nutrition and flavour quality of Chinese cabbage is improved.