Multiyear CO2 elevation improves PSII efficiency in a japonica rice cultivar

Abstract

AbstractResponses of crop photosystem activity to the short‐term elevation of carbon dioxide concentration ([CO2]) have been studied extensively. However, long‐term effects of elevated [CO2] (e[CO2]) over multiple cropping generations have received little attention. Using open‐top chambers (OTCs), we set up ambient [CO2] (CK) and two multigeneration e[CO2] treatments during rice (Oryza sativa L.) growing seasons in 2016–2019: a stepwise increase (SI) up to +160 μmol mol−1 in 2019 and a constant increase (CI) of +200 μmol mol−1 above CK over four generations. Beginning in 2017, grains harvested from the previous year in different [CO2] treatments were used as seeds. Seedlings derived from CK OTCs in 2018 were transplanted into both SI and CI OTCs in 2019 to simulate single‐generation abrupt elevation of [CO2]. We measured the diurnal changes in photosystem II (PSII) functionality of leaves in 2019. Single‐generation elevation of [CO2] had no effects on PSII efficiency. However, a stepwise increase of [CO2] over four generations significantly enhanced predawn maximum photochemical efficiency of PSII (Fv/Fm), the efficiency that trapped exciton moves an electron beyond QA− (ψo), and the quantum yield of electron transport (φEo) in PSII at jointing stage. The constant increase of [CO2] over four generations dramatically improved predawn Fv/Fm, ψo, φEo, perform index, and reaction center at grain‐filling stage. Moreover, the multigeneration elevation of [CO2] weakened the depression of Fv/Fm relative to single‐generation elevation at midday. All of these results indicated that e[CO2] had transgenerational effects on PSII functionality.