Chlorophyll fluorescence imaging as a tool for analyzing the effects of chilling injury on tomato seedlings

Abstract

The effect of chilling injury on leaves was studied by chlorophyll fluorescence imaging, which was mainly investigated from spatial heterogeneity, histogram distribution and texture features of chlorophyll fluorescence grayscale images, as a means to detect the impact of chilling injury. The fluorescence images used in the experiment were the gray images acquired by Imaging-Pam under dark adaptation. Firstly, the images of fluorescence parameters Fo, F, Fm, Fm', Fv/Fm, Y (II), Y (NPQ), Y (NO), NPQ/4, qN, qP, qL and their respective heterogeneity curves were analyzed, in which the chilling injury in the parameter image of F, Y(II), Y(NPQ), Y(NO), qP, qL exhibited good spatial heterogeneity. With the impact of low temperature, F value raised while susceptible to leaf vein, Y (NO) continued to rise but insensitive to the initial stage of chilling injury, Y (NPQ) increased first and then decreased, qP and qL declined rapidly only sensitive to leaf vein, however Y (II) not only fell continuously but was sensitive to initial cold damage and was not affected by leaf veins. Secondly, the histogram of the Y (II) fluorescent grayscale image was analyzed. In the experiment, the Y (II) data shifted to the left, when the leaf suffered cold damage, and the number of peaks changed from one to two. Finally, by calculating the mean and standard deviation of the gray level co-occurrence matrices ASM, ENT, INE, COR, it is found that the energy values and the correlation values on the Y (II) grayscale map of the leaf gradually reduced, and the entropy and inertia expanded. The results of this study indicate that: (i) chlorophyll fluorescence imaging is a useful technique to evaluate cold stress in tomato leaves; (ii) F, Y(Ⅱ), Y(NPQ), Y(NO), qP, qL show good spatial heterogeneity in chilling stress of leaves ; (iii) Histogram and texture features of gray image are good indicators for evaluating chilling damage. Fluorescence imaging can be used for non-destructive diagnosis of plant chilling injury, which has good development prospects.