Non-photochemical Quenching Plays a Key Role in Light Acclimation of Rice Plants Differing in Leaf Color

Guanfu Fu,Caixia Zhang,Tingting Chen,Shaobing Peng,Longxing Tao,Baohua Feng,Xiufu Zhang,Xia Zhao

doi:10.3389/fpls.2016.01968

Abstract

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in rice; however, little is known regarding its role in the photosynthetic response of rice plants with differing in leaf color to different irradiances. In this study, two rice genotypes containing different chlorophyll contents, namely Zhefu802 (high chlorophyll) and Chl-8 (low chlorophyll), were subjected to moderate or high levels of light intensity at the 6-leaf stage. Chl-8 possessed a lower chlorophyll content and higher chlorophyll a:b ratio compared with Zhefu802, while Pn, Fv/Fm, and ΦPSII contents were higher in Chl-8. Further results indicated that no significant differences were observed in the activities of Rubisco, Mg2+-ATPase, and Ca2+-ATPase between these genotypes. This suggested that no significant difference in the capacity for CO2 assimilation exists between Zhe802 and Chl-8. Additionally, no significant differences in stomatal limitation were observed between the genotypes. Interestingly, higher NPQ and energy quenching (qE), as well as lower photoinhibitory quenching (qI) and production of reactive oxygen species (ROS) was observed in Chl-8 compared with Zhefu802 under both moderate and high light treatments. This indicated that NPQ could improve photosynthesis in rice under both moderate and high light intensities, particularly the latter, whereby NPQ alleviates photodamage by reducing ROS production. Both zeaxanthin content and the expression of PsbS1 were associated with the induction of NPQ under moderate light, while only zeaxanthin was associated with NPQ induction under high light. In summary, NPQ could improve photosynthesis in rice under moderate light and alleviate photodamage under high light via a decrease in ROS generation.

Highlights

Rice (Oryza sativa L.) is one of the most important food crops and is consumed by more than 3 billion people worldwide (Fageria, 2007)
It has been reported that non-photochemical quenching (NPQ) exerts an effect on the rate of photosystem II (PSII) photochemistry by increasing the dissipation of excitation energy by non-radiative processes in the pigment matrices of PSII, which results in a decrease in the efficiency of delivery of excitation energy for PSII photochemistry in low light conditions (Genty et al, 1990)
The light harvesting complex (LHC) consists of chlorophyll a, chlorophyll b, and carotenoids, which primarily transfer absorbed light energy to the reaction center complexes of photosystem I (PSI) and PSII, respectively

Summary

INTRODUCTION

Rice (Oryza sativa L.) is one of the most important food crops and is consumed by more than 3 billion people worldwide (Fageria, 2007). High light intensities saturate photosynthetic rates in the leaves of rice, and excess light can cause photoinhibition of photosystem II (PSII) resulting in a decrease in quantum yield. Membrane reorganization was reported to occur in intact chloroplasts exposed to high light, resulting in clustered domains of LHCII and PSII reaction centers (Johnson and Ruban, 2011; Goral et al, 2012). In full sunlight there is much excessive light energy and it is vitally important to switch to specific antenna states and trigger NPQ (Pascal et al, 2005) This suggests that light acclimation contributes to the different photosynthetic properties of leaves. NPQ regulates photosynthetic processes, and gives insight for breeding cultivars with high photosynthetic efficiency

MATERIALS AND METHOD

RESULTS

DISCUSSION