| Improving the quality of vegetables（especially nutrition and flavor quality）has become an important goal in today’s vegetable production.Amino acids,sugars,organic acids and volatile metabolites have been used as important indicators for evaluating the nutritional and flavor quality of vegetables.It is important to study the key enzymes and key genes involved in the synthesis of these compounds.As one of the essential nutrients for plant growth and development,potassium is involved in many metabolic processes of plants and is essential for the formation of vegetable quality.However,there is a lack of potash resources in China.Potassium-ion soil deficiency is prevalent in China and Asia,and there is an urgent need to find a solution.Nanomaterials have certain effects in improving fertilizer utilization and improving the quality of agricultural products.As an economically important vegetable crop,Chinese cabbage and cucumber are widely cultivated in various regions of China and are very popular among consumers.In this study,pot experiment and field experiment were used to investigate the effects of nano potassium silicate on nutrition and flavor quality of two vegetable amino acid components,sugar components,organic acid components and volatile metabolites.Chinese cabbage and cucumber were used as representative of leafy vegetables and solanaceous vegetables to explore the effects of potassium nanosilicate on the expression of glutamine synthetase gene related to amino acid metabolism and nitrogen metabolism in two kinds of vegetables;clarify the physiological and molecular biological mechanisms of nano potassium fertilizer in regulating nutrition and flavor quality of vegetables.This will provide a theoretical basis for the efficient use of potash resources and the production of high quality vegetables.The main results of this study are as follows:（1）When the application amount of ordinary potassium silicate（OKSi）and nano potassium silicate（NKSi）is 150-300 kg·hm-2,the yield of Chinese cabbage and cucumber can be increased.The increase of root biomass of Chinese cabbage and cucumber by NKSi was larger than that of aboveground.In the pot experiment,the biomass of the aboveground and root of the two varieties of Chinese cabbage（measured in fresh weight）was the largest when 250 mg·kg-1 NKSi was applied,which was（58.1%,71.8%）and（7.11%,31.0%）higher than that of the control（CK）.In the field experiment,the yield of Chinese cabbage and cucumber was the highest with NKSi-300 treatment,which was 21.0% and 21.3% higher than CK.Under the same application amount,the yield of cucumber treated with NKSi increased by 8.30-12.2% compared with that treated with OKSi.（2）OKSi and NKSi promoted the transfer of sugar components from stem to leaf in Chinese cabbage.After treatment with OKSi and NKSi,the sugar content in “Liang Qing” leaves was significantly increased and higher than that in stems.The total sugar content in OKSi-300 leaves was the highest,which was 17.6% higher than that in stems with the same application amount.OKSi is better than NKSi in improving the content of sugar components in Chinese cabbage leaves.The total sugar and reducing sugar in the fruits of “Ke Xi Jie Jie Zao” were higher in NKSi treatment than in OKSi treatment.The components of organic acid treated with OKSi in “Liang Qing” was lower than that of NKSi treatment,which was 19.3%-29.3% lower than that of CK,while the change trend of “Ke Xi Jie Jie Zao” cucumber was opposite.NKSi treatment was higher than OKSi treatment,which was 4.96%-23.7% higher than CK.（3）NKSi is better than OKSi in improving the amino acid components of vegetables.OKSi and NKSi increased the total amount of essential and non-essential amino acids in the shoot of Chinese cabbage and cucumber fruits,but decreased the proportion of non-essential amino acids in the total amount of amino acids.The total amount of essential amino acids in “Liang Qing” was the highest with NKSi-300,which was 41.1% higher than that of CK,followed by OKSi-450,which was 31.0% higher than CK.The proportion of non-essential amino acids（BD/BT）was the lowest with NKSi-300,which was 11.3% lower than that of CK.Compared with CK,the proportion of total essential amino acids（CI/CT）in OKSi and NKSi treated in “Ke Xi Jie Jie Zao” cucumber fruits increased by 3.21-8.16% and 6.71-14.9%,respectively.NKSi-300 has the highest proportion of treatments.The proportion of total non-essential amino acids in total amino acids（CD/CT）decreased by 1.67%-4.26% and 3.50%-7.76%,respectively,with NKSi-300 as the lowest treatment.（4）NKSi increased the total amount of volatile metabolites（VMs）in shoots of Chinese cabbage and cucumber fruits in the field experiment,with the largest increase in NKSi-450.Principal component analysis showed that NKSi improved better than OKSi.（E）-2-hexenal,（E）-4-hexen-1-ol and butyl isothiocyanate were the highest in all treatments.Under the same application amount,NKSi treatment of aldehydes,alcohols,esters,ketones,acids,nitriles and phenols was 42.6%-95.5%,19.2%-205%,174%-175%,115%-158%,22.0%-112%,630%-1212% and 12.8%-43.5% higher than OKSi treatment,respectively.Total VMs of NKSi-450 was the highest,followed by NKSi-300,which was 56.0% and 11.1% higher than CK,respectively.The content of（E,Z）-2,6-nonadienal and（E）-2-nonenal of “Ke Xi Jie Jie Zao” cucumber fruits was the highest in all treatments.Under the same application amount,NKSi treated cucumber alcohols were 75.2%-84.7% higher than OKSi treatment.（5）Compared with OKSi,NKSi can improve the fertilizer use efficiency,but fertilizer use efficiency decreases significantly with the increase of application amount.Fertilizer use efficiency of NKSi fertilizer was between 20.6%-34.0% at 150-300 kg·hm-2,which was significantly higher than 17.8%-25.4% of OKSi.（6）NKSi has a significant up-regulation effect on the GLN family genes in roots and stems of Chinese cabbage,and the up-regulation effect is significantly better than OKSi,the NKSi-300 treatment has the largest increase.The relative expression level of GLN family genes in “Liang Qing” Chinese cabbage treated with NKSi-300 was up to 34.4-120 times higher than that of CK.The relative expression level of “Liang Qing” GLN family genes in leaves was highest by OKSi-450,which was 3.19-59.7 times higher than that of CK.The relative expression level of “Ke Xi Jie Jie Zao” GLN family genes in cucumber fruits was the highest in NKSi-450 treatment,which was 6.62-10.3 times higher than CK.NKSi may be more suitable for regulating the nutritional and flavor quality of rhizomes and solanaceous vegetables. |
