基于垂直方向的色素辣椒氮素诊断敏感叶位筛选

Screening of sensitive leaf sites for nitrogen diagnosis in pigment pepper in vertical direction

探明植物体内氮素水平可以指导农户科学施肥,对减轻环境污染具有实质性意义,SPAD技术能实时、无损且精准的表征植物体内氮素水平。研究分析了色素辣椒氮营养指标与叶片SPAD在不同生育期的变化特征,利用偏最小二乘(partial least square,PLS)方法的VIP(variable importance for projection)值明确了基于SPAD仪的色素辣椒氮素诊断敏感叶层和叶位。结果表明:色素辣椒果实膨大期SPAD值较高,各生育期不同叶层SPAD均在N80处理下较高;SPAD值和氮营养指标表现出上层叶>中层叶>下层叶的特征。PLS分析显示,色素辣椒不同叶层和叶位的SPAD值与氮营养指标的相关决定系数(coefficient of determination,R^(2))和均方根误差(root-mean-square error,RMSE)满足模型精确要求,表明不同叶层和叶位的SPAD值对氮素营养指标具有良好的预测性能,能满足利用SPAD仪对辣椒氮素状况进行无损诊断的需求。VIP分析显示上层叶(UL)完全展开叶中部位置(C)是色素辣椒氮营养诊断的最佳SPAD测定位置。

Irrational application of nitrogen fertilizer is one of the key factors affecting the growth and fruit quality of pepper,which limits the development of pepper industry in Xinjiang.The variation characteristics of nitrogen nutrient indices and leaf SPAD in pepper at different growth stages were studied and analyzed.Using variable importance for projection(VIP)values in partial least square(PLS)model,the location of sensitive leave in plant and sensitive site at leaf of pigment pepper were determined based on SPAD instrument.The results showed that the SPAD value was higher in fruit expansion stage,and the SPAD value in all position of the plant was higher in all growth stages under N80 treatment.SPAD value and nitrogen index showed the characteristics of top of leaf>middle of leaf>base of leaf.PLS analysis showed that the determination correlation coefficient and root-mean-square error between SPAD value and nitrogen nutrition index of pepper in different location along plant height all meet the requirements of accurate diagnosis of the model.VIP analysis showed that the middle part of the fully expanded upper leaf is the best position for diagnosis of nitrogen nutrition in pigment pepper by SPAD.