Abstract
Conversion of sunlight into photochemistry depends on photoprotective processes that allow safe use of sunlight over a broad range of environmental conditions. This review focuses on the ubiquity of photoprotection associated with a group of interconvertible leaf carotenoids, the xanthophyll cycle. We survey the striking plasticity of this process observed in nature with respect to (1) xanthophyll cycle pool size, (2) degree and speed of interconversion of its components, and (3) flexibility in the association between xanthophyll cycle conversion state and photoprotective dissipation of excess excitation energy. It is concluded that the components of this system can be independently tuned with a high degree of flexibility to produce a fit for different environments with various combinations of light, temperature, and other factors. In addition, the role of genetic variation is apparent from variation in the response of different species growing side-by-side in the same environment. These findings illustrate how field studies can generate insight into the adjustable levers that allow xanthophyll cycle-associated photoprotection to support plant photosynthetic productivity and survival in environments with unique combinations of environmental factors.
Highlights
Overview of Sources and Roles of CarotenoidsCarotenoids are responsible for the yellow or orange color of egg yolk [1], corn kernels [2], vegetables and fruits [3,4], and flowers [5,6]
A PsbS-deficient Arabidopsis thaliana mutant that lacks rapid changes in thermal energy dissipation did not exhibit any appreciable effect on plant productivity in constant high light under controlled conditions, where A. thaliana used a large fraction of excitation energy via the photochemical route [71]
Our summary aims to illustrate the ubiquity of xanthophyll cycle-based photoprotection and the striking variety found in nature with respect to (i) xanthophyll cycle pool size, (ii) degree and speed of interconversion of its components, (iii) degree as well as onset and relaxation kinetics of excitation energy dissipation as thermal energy, and (iv) flexibility in the association among xanthophyll cycle conversion state, thermal dissipation of excitation energy, and the fraction of absorbed light available for utilization in photochemistry
Summary
Carotenoids are responsible for the yellow or orange color of egg yolk [1], corn kernels [2], vegetables and fruits [3,4], and flowers [5,6]. Carotenoids support a photosynthetic organisms’ unique task of using sunlight to make food, fuels, and other important molecules under the wide range of different, and continuously changing, light environments encountered in nature. Our review summarizes leaf carotenoid levels’ dynamic adjustment in response to a wide of natural environments with leaf different combinations of light and/or resource-efficient crops (see,range e.g., [10]). We refer to others for authoritative reviews on carotenoid function adjustment in response to a wide range of natural environments with different combinations of light in photosynthetic organisms other than plants [11,12,13,14,15]. Since a the light reactions, be consumed That interconvert xanthophyll epoxidesxanthophylls to epoxide-free xanthophylls [17,20,21,22,23]
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