Heavy metals such as cadmium and arsenic can be naturally found at various concentrations in the environment (e.g. in soil, water and the atmosphere). They may also be present in food, as residues from human agricultural activities: indeed, contaminants in plant food come from the soil, as well as from the soil surface and from substances that are sprayed on the soil. 

In the case of rice, a lot of water is needed to make it grow: so-called submerged cultivation is used so that rice does not suffer from temperature fluctuations.

The issue of climate change is at the centre of attention because of its serious implications for our planet, and its impact on rice farming must also be assessed. In the last decade, cultivation techniques have been promoted and adopted by rice growers to accumulate carbon in the soil and consequently reduce atmospheric emissions of carbon dioxide and other greenhouse gases.

The careful management of crop residues, which aims to favour rapid degradation before rice fields are flooded, intercropping between two rice cycles (green manure) together with the adoption of irrigation practices aimed at limiting fermentation processes in the soil’s organic matter represent concrete and effective tools to mitigate climate change. 

A recent review study conducted by Frontiers Plant Science demonstrated that the co-exposure of salinity and pollution in the pedosphere as well as rising levels of carbon dioxide and increasing temperatures in the atmosphere, as a result of the rapid acceleration of industrialization and global climate change, pose increasingly severe environmental challenges to the health of plants and food.

The objective of the study was to analyse, via a hydroponics-based experiment, the individual and mutual effects of different temperatures and carbon dioxide concentrations on the uptake and translocation of sodium chloride (NaCl) and cadmium nitrate (Cd(NO3)) by rice seedlings.  

The findings showed that exposure to cadmium and sodium hindered plant development significantly, but that the effects on plant growth were reduced by high temperature and a medium/high level of carbon dioxide. Co-exposure tests revealed that cadmium levels in rice roots decline slightly with additional sodium and at high temperatures.  

Overall, the research indicated that changes in the global climate may affect the distribution of heavy metals and contaminants in rice plants as well as the plants’ tolerance. 

More information on the findings of this review study is available at https://www.frontiersin.org/articles/10.3389/fpls.2023.1161334/full.