基于动态荧光指数的草莓干旱胁迫分析

Analysis of drought stress in strawberry based on dynamic fluorescence index

为了探究干旱胁迫与草莓幼苗荧光图像参数的关系,设计了草莓幼苗叶绿素荧光图像采集系统,研究利用460 nm波长LED光源主动激发不同胁迫组分下的草莓幼苗,采集从激发开始到稳态阶段的荧光图像.提出基于最大类间方差法的阈值分割及图像去背景方法进行图像预处理,并根据每幅图像的像素均值绘制荧光淬灭曲线,分析荧光衰减比率、动态荧光指数与胁迫天数相关关系.结果表明:离体叶片的荧光淬灭曲线衰减变化较大,荧光衰减比率与干旱胁迫时间高度相关,决定系数R^(2)=0.98;活体草莓幼苗荧光衰减比率在干旱胁迫7 d内相比对照组存在较明显变化,荧光淬灭曲线550 s处的动态荧光指数与干旱胁迫天数存在较高相关性(决定系数R^(2)=0.84),可以作为模型分析草莓幼苗干旱状况;经过数字处理的荧光图像可以直观地分析叶片荧光二维分布、进行不同胁迫天数之间的荧光比对.结合图像的叶绿素荧光分析相较传统的荧光检测手段更加经济直观,可以作为一种农业生产监测手段来实现干旱胁迫预警.

A chlorophyll fluorescence image acquisition system of strawberry seedlings was designed for investigating the relationship between drought stress and fluorescence image parameters of strawberry seedlings.The strawberry seedlings under different stress components were actively excited by using a 460 nm LED light source,and the fluorescence images from excitation to the steady-state stage were collected.Based on maximum interclass variance method,a threshold segmentation method and image de-background method were proposed for image preprocessing.The fluorescence quenching curve was plotted according to the mean pixel value of each image.The correlation between fluorescence decay ratio,dynamic fluorescence index and stress days was analyzed.The results show that the fluorescence quenching curve of isolated leaves has a large variation in decay,and the fluorescence decay ratio is highly correlated with the time of drought stress with a coefficient of determination R^(2)=0.98.Comparing with the control group,the fluorescence decay ratio of living strawberry seedlings changes significantly within 7 days of drought stress.The dynamic fluorescence index at 550 s of the fluorescence quenching curve has a high correlation with the number of days of drought stress(coefficient of determination R^(2)=0.84),which can be used as a model analyzing the drought condition of strawberry seedlings.The digitally processed fluorescence images can directly analyze the two-dimensional fluorescence distribution of leaf fluorescence and compare fluorescence information of leaves between different stress days.The chlorophyll fluorescence analysis combined with the digital images is more economical and intuitive than the traditional fluorescence detection method.It can be used as an agricultural production monitoring method to realize drought stress early warning.