Nondestructive and intuitive determination of circadian chlorophyll rhythms in soybean leaves using multispectral imaging

Abstract

The circadian clock, synchronized by daily cyclic environmental cues, regulates diverse aspects of plant growth and development and increases plant fitness. Even though much is known regarding the molecular mechanism of circadian clock, it remains challenging to quantify the temporal variation of major photosynthesis products as well as their metabolic output in higher plants in a real-time, nondestructive and intuitive manner. In order to reveal the spatial-temporal scenarios of photosynthesis and yield formation regulated by circadian clock, multispectral imaging technique has been employed for nondestructive determination of circadian chlorophyll rhythms in soybean leaves. By utilizing partial least square regression analysis, the determination coefficients R2, 0.9483 for chlorophyll a and 0.8906 for chlorophyll b, were reached, respectively. The predicted chlorophyll contents extracted from multispectral data showed an approximately 24-h rhythm which could be entrained by external light conditions, consistent with the chlorophyll contents measured by chemical analyses. Visualization of chlorophyll map in each pixel offers an effective way to analyse spatial-temporal distribution of chlorophyll. Our results revealed the potentiality of multispectral imaging as a feasible nondestructive universal assay for examining clock function and robustness, as well as monitoring chlorophyll a and b and other biochemical components in plants.

Correlations between Circadian Rhythms and Growth in Challenging Environments

“…R fd 9 is calculated from F v and F9 and, like the other F measurements, is affected by chlorophyll pigment levels. Both chlorophyll and chlorophyll b have been shown to be under circadian control in soybean (Pan et al, 2015), suggesting that this may be a potential mechanism for the circadian rhythms of R fd 9 and F v /F m that we observed. In the future, it will be interesting to carry out further experiments to understand the mechanism(s) by which the circadian system controls F parameters.…”

Field‐grown soybean transcriptome shows diurnal patterns in photosynthesis‐related processes

“…This pattern in soybean was similar to diurnal chlorophyll a / b ratios in wheat ( Triticum aestivum ; Busheva et al., ). While an earlier study reports no significant diurnal changes in total leaf chlorophyll content of soybean plants grown in greenhouses (Wickliff & Aronoff, ), a more recent study conducted in environmental growth chambers shows chlorophylls a and b in soybean leaves declining early during the light period and increasing after 4–8 h of illumination (Pan et al., ). Thus, by experiencing natural light conditions in the field, which are typically more intense and more varied than in growth chambers, soybean leaves in this study exhibited largely different patterns in diurnal chlorophyll content.…”

Endogenous circadian rhythms in pigment composition induce changes in photochemical efficiency in plant canopies

“…This fact, together with the feasibility of Chl a / b determination, makes this parameter an excellent reporter of the photosynthetic output of circadian oscillations. Furthermore, as Chl a / b can be easily estimated with reflectance indexes (Siebke & Ball, ), it can be used as a non‐invasive reporter of rhythmicity in phenotyping or remote‐sensing platforms using hyperspectral images (Pan et al ., ), complementing other circadian reporters currently available such as delayed chlorophyll fluorescence and transgenic luciferase (Tindall et al ., ).…”