When does temperature matter? Response of rice arsenic to heat exposure during different developmental stages

PurposeArsenic is a frequent contaminant of rice. Recent studies show that elevated temperatures, like those from climate change, can further increase arsenic concentrations in rice. It is still unclear if the timing of heat exposure relative to plant development influences the magnitude and allocation of arsenic accumulation in rice plants.MethodWe grew potted rice plants from seedlings until maturity in growth chambers with different temperature regimes: baseline (26 & DEG;C/22 & DEG;C, day/night), continuously elevated (30 & DEG;C/27 & DEG;C), baseline with a 20-day heat spike during the vegetative stage, and baseline with a 20-day heat spike during the ripening stage. Heat spikes mimicked the elevated temperature.ResultsConcentrations of arsenic in both porewater and plant tissues were uniformly higher in the continuously elevated treatment relative to the baseline treatment. A heat spike during the ripening stage caused a marked increase in arsenic mobilization into porewater. A heat spike in the vegetative stage caused a short-term increase in arsenic concentrations in plant tissue but this relative increase did not persist to maturity. Plants that experienced a heat spike in the ripening stage had an increase in arsenic concentrations within various tissue types at maturity.ConclusionDifferential responses to the two heat spikes may be due to less soil microbial and plant biomass during the vegetative stage, as well as reduced root biomass caused by heat stress during the vegetative stage. Our results demonstrate that both continuous and short-term increases in temperature later in plant development can heighten dietary arsenic exposure to rice consumers.

Automated summary

Recent studies have shown that elevated temperatures caused by climate change can increase arsenic concentrations in rice. It is still uncertain whether the timing of heat exposure affects the accumulation of arsenic in rice plants. Results indicate that continuous heat exposure and heat spikes during the ripening stage can increase the arsenic content in rice.