Arsenic Accumulation in Different Parent Materials of Rice (Oryza Sative L.) are Affected by Root Morphology

Revealing the response of rice root systems to varying concentrations of arsenic (As) stress is pivotal for elucidating the uptake mechanism of arsenic in rice. To determine whether there is a general stress response of rice roots to As, here we utilized 54 varieties of rice parent materials to conducted hydroponic experiments under different As stress. We investigated at the changes in biomass, As content, root length, root surface area and root volume of rice. The findings demonstrate that: (i) Under the stress of As2 and As8, T14 exhibits the least susceptibility to arsenic stress, whereas T3 shows the opposite trend. (ii) Compared to the CK, the biomass, total root length, total root volume, and total root surface area of rice were significantly inhibited under As treatments with different concentration. Notably, under treatments with 2 and 8 mg L⁻¹As, the drop in shoot biomass (decreased by 55.9 and 85.9%, respectively) was greater than root biomass (decreased by 9.6 and 72.9%, respectively). (iii) The total root length, total root volume, total root surface area, and number of root tips with D ≤ 0.10 mm were significantly higher than those of root tips with D > 0.10 mm in all treatments. Moreover, as the concentration of As increased, the average ratio of total root length and average ratio of total root surface area between D ≤ 0.10 mm and D > 0.10 mm initially increased but then decreased. In summary, the shoot of rice exhibited greater inhibition than the root with increasing As concentration. The correlation between As accumulation and root morphology confirmed that under low-As treatment, rice alleviated As toxicity primarily through enhanced fine root (D ≤ 0.10 mm) development. Conversely, under high-As treatment, there was a tendency for similar average total root surface area in both groups of roots, indicating inhibited fine root (D ≤ 0.10 mm) development and coarse root (D > 0.10 mm) development was found to be a potential mechanism by which rice mitigates As toxicity.