基于 U 弦长曲率的番茄氮肥调控目标区间获取方法. (Chinese)

Artificial nitrogen fertilizer has been one of the most essential supplements for plant growth. Nitrogen can be an indispensable element for chlorophyll synthesis of most crops. However, the high nitrogen application rate in tomato production has posed a serious threat to the nitrogen utilization rate and ecological environment in recent years. In this study, data acquisition was proposed to obtain a suitable range of nitrogen concentration for tomato growth using chlorophyll fluorescence under the requirements of precision fertilization. Seven test groups were set with the nitrogen concentration gradient (3.5, 7.0, 10.5, 14.0, 17.5, 21.0, and 24.5 mmol/L), according to the nitrogen content in the formula of Japanese garden test nutrient solution (17.5 mmol/L). The contents of other elements were the same as the formula in the experiment. The parameters of chlorophyll fluorescence and dry matter were obtained for the leaves of tomatoes that were treated with seven nitrogen concentrations. A systematic analysis was made to determine the change of dry weight, leaf nitrogen, phosphorus, and potassium concentration with the nitrogen concentration. As such, the nitrogen concentration of the nutrient solution was between 7.0-10.5 mmol/L suitable for the tomato plant growth. A correlation analysis of chlorophyll fluorescence parameters was carried out for the appropriate nitrogen concentration range using the maximum mutual information coefficient. The results showed that there were the most correlated parameters of chlorophyll fluorescence with the nitrogen concentration, including ABS/RC (absorbed flux absorbed by reaction center), PI ABS (Performance Index based on ABS), ET o /RC (electron transport flux captured by reaction center), and F v /F o (Potential activity of photosystems), whose Maximum Information Coefficient (MIC) values were all greater than 0.4. The F v /F o was found to be the most suitable chlorophyll fluorescence parameter in the proper nitrogen concentration range for plant growth. The response curve of F v /F o to nitrogen concentration was obtained by the polynomial fitting the discrete points of F v /F o response to nitrogen concentration. The curvature curve was calculated using the u-chord curvature of the curve, and the point at which the curvature began to increase was taken as the curvature characteristic point. The curvature characteristic point and the maximum point were used as the lower limit and upper limit for the regulation interval of nitrogen concentration. The suitable nitrogen concentration range was 7.2-9.8 mmol/L for tomato growth. In this case, the dry matter and physiological amounts remained at a high level, and the coefficient of variation was the lowest, indicating that there was little effect of nitrogen concentration on the tomato growth. Specifically, the tomato dry weight, P and K concentration in the leaves increased by 33.8%, 10.2%, and 11.3% on average, respectively, the N concentration in the leaves decreased by 0.8% on average, and the nitrogen application decreased by 51.4%, compared with Japan garden test nutrient solution treatment. There was also a higher plant dry weight, as well as the leaf N, P, and K contents, indicating balanced nutrient absorption. Consequently, a reasonable and accurate interval of nitrogen concentration can be achieved for crop growth. This finding can provide a theoretical basis for the accurate regulation of nitrogen application rate, further realizing the long-term monitoring of leaves without destructive physical and chemical testing [ABSTRACT FROM AUTHOR]

针对中国现有设施番茄生产中氮肥施用量过高，利用率低，环境污染严重等问题，该研究面向设施番茄精量施 肥需求，提出一种基于叶绿素荧光技术的设施番茄生长氮素浓度适宜区间获取方法。该研究利用不同氮浓度水培液进行 番茄栽培，获取叶片荧光参数和干物质等生理指标，采用最大互信息系数值（Maximum Information Coefficient，MIC） 筛选叶绿素荧光参数，确定最适的荧光参数进行水培液氮调控研究目的是区间确定。结果表明，叶绿素荧光参数 F v /F o （光 系统潜在活性）的整体表现效果较优。以 F v /F o 的响应曲线提出基于 U 弦长曲率特征点为分界点的适宜氮素浓度区间获 取技术。采用此方法的番茄生长的适宜氮素浓度区间为 7.2~9.8 mmol/L，同时干物质等生理指标都保持在较高水平，变 异系数最小。与日本园试营养液对照组相比，番茄干质量平均提高 33.8%，叶片磷浓度平均提高 10.2%，叶片钾浓度平均 提高 11.3%，叶片氮浓度平均降低 0.8%，而氮肥用量减少了 51.4%。因此，基于 U 弦长曲率特征点的方法是确定番茄施 氮目标区间调控有效的技术。 [ABSTRACT FROM AUTHOR]

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