Analysis of heavy metal stressed plants by fluorescence imaging

Abstract

Chlorophyll fluorescence has been widely applied as a non-invasive technique for the in vivo analysis of plant stress. In this work, the two-dimensional image analysis of the fluorescence signal was used to evaluate the physiological status of heavy metal stressed leaves, based on their photosynthetic capacity. Chlorophyll fluorescence (>650nm) emission of control and heavy metal treated plants registered at different times during the blue light illumination of the leaves show abnormal patterns of non-homogeneous spatial distribution of the fluorescence emission from metal-treated plants. This is correlated to an altered photosynthetic functionality in different parts of the leaves. Quantitative evaluation of the photosynthetic activity can be made on data extracted after simple arithmetical pixel-point processing of fluorescence images taken at different time during the illumination process. The altered fluorescence emission was observed in absence of other visual symptoms that could testify problems at the level of the photosynthetic apparatus. This indicates that chlorophyll fluorescence imaging is a suitable tool for the early, pre-visual detection of plant stress also in the case of heavy metal stress.