Quantifying spatial heterogeneity of chlorophyll fluorescence during plant growth and in response to water stress

• DOI: 10.1186/s13007-015-0067-5
• Publication Date: 2015-03-25T22:48:55Z
• Authors: Justine Bresson; François Vasseur; Myriam Dauzat; Garance Koch; Christine Granier; Denis Vile
• Keywords: 0301 basic medicine; 570; croissance végétale; Photosynthetic performance; fluorescence chlorophyllienne; Plant Science; efficience de la photosynthèse; Modelling; 03 medical and health sciences; Plant survival; Genetics; Chlorophyll fluorescence imaging; [SDV.BV]Life Sciences [q-bio]/Vegetal Biology; photosynthèse; Plant growth; modélisation; 580; Heterogeneity of Fv/Fm values; Vegetal Biology; arabidopsis thaliana; Methodology; tolérance à la sécheresse; 15. Life on land; 6. Clean water; Pixels distribution; Chlorophyll fluorescence imaging;Heterogeneity of Fv/Fm values;Photosynthetic performance;Pixels distribution;Modelling;Plant growth;Plant survival;Sensitivity analysis; écophysiologie végétale; stress hydrique; Sensitivity analysis; Biologie végétale; Biotechnology

Effects of abiotic and biotic stresses on plant photosynthetic performance lead to fitness and yield decrease. The maximum quantum efficiency of photosystem II (F v/F m) is a parameter of chlorophyll fluorescence (ChlF) classically used to track changes in photosynthetic performance. Despite recent technical and methodological advances in ChlF imaging, the spatio-temporal heterogeneity of F v/F m still awaits for standardized and accurate quantification.We developed a method to quantify the dynamics of spatial heterogeneity of photosynthetic efficiency through the distribution-based analysis of F v/F m values. The method was applied to Arabidopsis thaliana grown under well-watered and severe water deficit (survival rate of 40%). First, whole-plant F v/F m shifted from unimodal to bimodal distributions during plant development despite a constant mean F v/F m under well-watered conditions. The establishment of a bimodal distribution of F v/F m reflects the occurrence of two types of leaf regions with contrasted photosynthetic efficiency. The distance between the two modes (called S) quantified the whole-plant photosynthetic heterogeneity. The weighted contribution of the most efficient/healthiest leaf regions to whole-plant performance (called W max) quantified the spatial efficiency of a photosynthetically heterogeneous plant. Plant survival to water deficit was associated to high S values, as well as with strong and fast recovery of W max following soil rewatering. Hence, during stress surviving plants had higher, but more efficient photosynthetic heterogeneity compared to perishing plants. Importantly, S allowed the discrimination between surviving and perishing plants four days earlier than the mean F v/F m. A sensitivity analysis from simulated dynamics of F v/F m showed that parameters indicative of plant tolerance and/or stress intensity caused identifiable changes in S and W max. Finally, an independent comparison of six Arabidopsis accessions grown under well-watered conditions indicated that S and W max are related to the genetic variability of growth.The distribution-based analysis of ChlF provides an efficient tool for quantifying photosynthetic heterogeneity and performance. S and W max are good indicators to estimate plant survival under water stress. Our results suggest that the dynamics of photosynthetic heterogeneity are key components of plant growth and tolerance to stress.