Spatiotemporal Heterogeneity of Chlorophyll Content and Fluorescence Response Within Rice (Oryza sativa L.) Canopies Under Different Nitrogen Treatments

Jiafei Zhang; Liang Wan; C Igathinathane; Zhao Zhang; Ya Guo; Dawei Sun; Haiyan Cen

doi:10.3389/fpls.2021.645977

Spatiotemporal Heterogeneity of Chlorophyll Content and Fluorescence Response Within Rice (Oryza sativa L.) Canopies Under Different Nitrogen Treatments

Front Plant Sci. 2021 Mar 25:12:645977. doi: 10.3389/fpls.2021.645977. eCollection 2021.

Authors

Jiafei Zhang^{1

2}, Liang Wan^{1

2}, C Igathinathane³, Zhao Zhang^{4

5}, Ya Guo⁶, Dawei Sun^{1

2}, Haiyan Cen^{1

2}

Affiliations

¹ College of Biosystems Engineering and Food Science, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China.
² Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture and Rural Affairs, Hangzhou, China.
³ Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND, United States.
⁴ Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education of China, China Agricultural University, Beijing, China.
⁵ Key Laboratory of Agriculture Information Acquisition Technology, Ministry of Agriculture of China, China Agricultural University, Beijing, China.
⁶ Key Laboratory of Advanced Process Control for Light Industry, Ministry of Education, Jiangnan University, Wuxi, China.

Abstract

Accurate acquisition of plant phenotypic information has raised long-standing concerns in support of crop breeding programs. Different methods have been developed for high throughput plant phenotyping, while they mainly focused on the canopy level without considering the spatiotemporal heterogeneity at different canopy layers and growth stages. This study aims to phenotype spatiotemporal heterogeneity of chlorophyll (Chl) content and fluorescence response within rice leaves and canopies. Multipoint Chl content and high time-resolved Chl a fluorescence (ChlF) transient (OJIP transient) of rice plants were measured at different nitrogen levels and growth stages. Results showed that the Chl content within the upper leaves exhibited an increasing trend from the basal to the top portions but a decreasing pattern within the lower leaves at the most growth stages. Leaf Chl content within the rice canopy was higher in the lower leaves in the vegetative phase, while from the initial heading stage the pattern gradually reversed with the highest Chl content appearing in the upper leaves. Nitrogen supply mainly affects the occurrence time of the reverse vertical pattern. This could be the result of different nutritional demands of leaves transforming from sinks to sources, and it was further confirmed by the fall of the JI phase of OJIP transient in the vegetative phase and the rise in the reproductive phase. We further deduced that the vertical distribution of Chl content could have a defined pattern at a specific growth stage. Furthermore, the reduction of end acceptors at photosystem I (PSI) electron acceptor side per cross section (RE₀/CS) was found to be a potential sensitive predictor for identifying the vertical heterogeneity of leaf Chl content. These findings provide prior knowledge on the vertical profiles of crop physiological traits, which explore the opportunity to develop more efficient plant phenotyping tools for crop breeding.

Keywords: OJIP transients; chlorophyll a fluorescence; chlorophyll content; heterogeneity; nitrogen; phenotyping; photosynthesis.