Abstract
The response of crop photosystem activity to a certain level of
[CO2] elevation have been widely concerned. However,
long-term effects of elevated [CO2] over
multi-generations of crops received little attention. Using open-top
chambers, we set up two treatments of elevated [CO2]
from 2016 to 2019 in rice (Oryza sativa) growing seasons. One treatment
was stepwise increase (SI) of +40 µmol mol-1 per season, the other was
constant increase (CI) of +200 µmol mol-1. Rice seeds harvested in each
[CO2] environment was planted successively. Seeds
from ambient [CO2] were also planted in SI and CI
OTCs in next year to study the short-term effect. We measured the
diurnal change in PSII functionality of leaf in 2019. Results showed
that both SI and CI promoted PSII function. SI was more beneficial to
improve efficiency of electron trapping and transporting in PSII and
performance index of leaf. The maximal photochemical efficiency of PSII
decreased linearly with increasing photosynthetic photon flux density
throughout the day. Predawn efficiency decreased dramatically with the
development of growth stages. Together, we found PSII efficiency benefit
from multi-year [CO2] elevation, which could help to
better understand the response of electron transport to elevated
[CO2].