Phenotyping of Arabidopsis Drought Stress Response Using Kinetic Chlorophyll Fluorescence and Multicolor Fluorescence Imaging

Abstract

Plant responses to drought stress are complex due to various mechanisms of drought avoidance and tolerance to maintain growth. Traditional plant phenotyping methods are labor-intensive, time-consuming, and subjective. Plant phenotyping by integrating kinetic chlorophyll fluorescence with multicolor fluorescence imaging can acquire plant morphological, physiological, and pathological traits related to photosynthesis as well as its secondary metabolites, which will provide a new means to promote the progress of breeding for drought tolerant accessions and gain economic benefit for global agriculture production. Combination of kinetic chlorophyll fluorescence and multicolor fluorescence imaging proved to be efficient for the early detection of drought stress responses in the Arabidopsis ecotype Col-0 and one of its most affected mutants called reduced hyperosmolality-induced [Ca2+]i increase 1. Kinetic chlorophyll fluorescence curves were useful for understanding the drought tolerance mechanism of Arabidopsis. Conventional fluorescence parameters provided qualitative information related to drought stress responses in different genotypes, and the corresponding images showed spatial heterogeneities of drought stress responses within the leaf and the canopy levels. Fluorescence parameters selected by sequential forward selection presented high correlations with physiological traits but not morphological traits. The optimal fluorescence traits combined with the support vector machine resulted in good classification accuracies of 93.3 and 99.1% for classifying the control plants from the drought-stressed ones with 3 and 7 days treatments, respectively. The results demonstrated that the combination of kinetic chlorophyll fluorescence and multicolor fluorescence imaging with the machine learning technique was capable of providing comprehensive information of drought stress effects on the photosynthesis and the secondary metabolisms. It is a promising phenotyping technique that allows early detection of plant drought stress.

Transcriptome Profiling, Biochemical and Physiological Analyses Provide New Insights towards Drought Tolerance in Nicotiana tabacum L.

“…Reduction in Fv/Fm values present characteristics of photoinhibition and the small decrease can be interpreted as photo-protection [54]. In our study, a small decline in Fv/Fm values only occurs upon 72 h of drought stress which are agreeable with [16,30]. The maximal quantum efficiency of PSII was almost unaffected until the last time point of drought stress considering generally an insensitive and might not be a good indicator for short term of drought stress.…”

“…The increase in blue, green and red fluorescence may due to the higher content of phenolic compounds and accumulation of intermediary compounds during chlorophyll breakdown, as it is considered as an adaptation mechanism of the photosynthetic apparatus to drought stress [58]. Conversely, IrF values of all the three varieties were reduced in response to drought stress which was due to the lack of reabsorption of the emitted chlorophyll fluorescence [30]. Similarly, we witnessed an increase in the values of F690/F740 in the drought-stressed plants of the three varieties earlier on 48 h (Table S2) than the symptoms appears in plants upon 72 h of drought stress which caused a significant reduction in chlorophyll content ( Figure 2C).…”

“…The leaf chlorophyll fluorescence was measured on the second fully expanded leaf from the apex in dark-and light-adopted leaves using a PAM (Pulse amplitude modulated) fluorescence imaging system (FluorCam FC 800, Photon Systems Instruments, Brno, Czechia). The protocol of [30] was essentially followed to obtain the kinetic chlorophyll fluorescence parameters and images at various time intervals upon the onset of drought stress. Based upon the basic chlorophyll signals the maximal photochemical efficiency (Fv/Fm), steady-state PSII quantum yield (ΦPSII_Lss) and steady-state non-photochemical quenching (NPQ_Lss) were calculated.…”

“…Additionally, the explanation of spatial heterogeneity under drought is that the chlorophyll fluorescence images could display spatial variations. Different fluorescence signals of leaf tips and edges at the whole leaf might imply a greater potential restriction in photosynthesis and suppression of the protective ability in these areas [30].…”

Robotic Assay for Drought (RoAD): An Automated Phenotyping System for Brassinosteroid and Drought Response

“…typing under controlled environments (Bao et al, 2019b;Granier et al, 2004;Skirycz et al, 2011;Serrand et al, 2013;Fujita et al, 2018). Various advanced sensor technologies have been successfully integrated into phenotyping systems, including visible RGB imaging (Minervini et al, 2014;Clauw et al, 2015), chlorophyll fluorescence imaging (Rousseau et al, 2013;Yao et al, 2018), thermal imaging (Zia et al, 2013;Klem et al, 2017), and hyperspectral imaging (Ge et al, 2016;Behmann et al, 2018). While both commercial (Skirycz et al, 2011;Neumann et al, 2015) and custom-built platforms (Apelt et al, 2015;Tisne et al, 2013) have been created, most current systems are limited to two-dimensional (2D) imaging and lack flexibility to administer different types of treatments.…”