Oxygen consumption and transportation in rice roots are highly dependent on leaf area and root dry weight ratio

Abstract

As rice is cultivated under diverse moisture conditions from paddy to field, the internal morphology of their roots may be diverse within species. This study aimed to investigate which traits affect the root oxygen consumption and transportation ability using rice varieties with different root anatomical traits. First, the CSR of seminal roots of six rice varieties was used to identify a variety with a low CSR. Results showed that the CSR in Sensho was the lowest in both aerated and stagnant solutions. Second, the shoot morphological traits, root anatomical traits, and root oxygen consumption and transportation of four rice varieties, including Sensho, were examined in preaerated and deoxygenated agar solutions. Results showed that deoxygenated conditions did not have any negative effects on the growth of the rice varieties. The root oxygen consumption rates were strongly positively correlated with the leaf area/root dry weight (LA/RDW, r = 0.90). The root oxygen transportation rates were also positively correlated with LA/RDW (r = 0.57). The percentage of root oxygen consumption compensated by oxygen transportation was highest in IR42, which had a low LA/RDW. Multiple regression using stomatal conductance, LA/RDW, and shoot dry weight as explanatory variables explained only 65.0% of oxygen transportation. We concluded that further studies on gas movements inside the shoots and roots are needed to clarify the mechanism that provides more sufficient oxygen to the roots.