Amelioration of the Salt-stressed Root Growth of Rice and Normalization of the Na⁺Distribution between the Shoot and Root by (S)-α-Methylbenzyl-2-fluoro-4-methylphenylurea

Abstract

Optically active alpha-methylbenzyl phenyl ureas (MBPUs) show diverse plant physiological properties. Experiments were conducted to evaluate the salt-stress response of just-germinated rice seedlings supplemented with the S-enantiomer of MBPUs by assessing the growth and Na+ content. This study indicates that S-MBPUs served as a unique stress reliever for just-germinated young seedlings of rice injured by salinity. NaCl severely affected the root growth of rice seedlings. Concomitant treatment with S-MBPUs effectively ameliorated the growth inhibition of rice by NaCl. Glycine betaine (GB) did not act as a reliever of the NaCl stress. The addition of S-alpha-methylbenzyl 2-fluoro-4-methylphenyl urea (7, denoted as S-FM) to the saline medium ameliorated not only the root growth but also the protein content and dry weight of roots depending upon its concentration. The protein content, Na+ content and growth rate were correlated to each other with a positive relationship. The Na+ distribution ratio (S/R(Na+)) between the shoot and root increased with increasing concentration of NaCl when added alone, viz. with increasing growth reduction. A concomitant treatment with S-FM (7), however, resulted in the S/R(Na+) value becoming smaller with growth amelioration. This indicates that S-FM (7) controlled the translation of Na+ from the roots to shoots. S-FM (7) would have influenced some inherent functions connected with the Na+ behavior in the rice plant, although details of the mechanism for normalization of the S/R(Na+) ratio are still not clear.

Proteomics Reveals New Salt Responsive Proteins Associated with Rice Plasma Membrane

“…20) The reduction in plant dry matter might have been due to a slower growth rate and slower development as a result of osmotic stress imposed by salinity, or due to inhibition of photosynthesis as a result of direct effects of salinity on the photosynthetic apparatus. 21) The greater reduction in shoot dry matter, in comparison with root, in response to salt stress suggests that the growth of rice root is less Continued on next page.…”

Chiral response of Oryzeae and Paniceae plants in α‐methylbenzyl‐3‐p‐tolyl urea agar medium

“…The chiral urea derivatives enantioselectively affect the functions of chloroplasts (by the ( S )‐enantiomer) and mitochondria (by the ( R )‐enantiomer),20 and exhibit herbicidal activity towards Cyperus paddy weeds (by the ( R )‐enantiomer) 21, 22. They also show stress‐relieving activity towards herbicide and sodium chloride influence (by the ( S )‐enantiomers) 21, 23–25. Two chiral pairs (( R )‐/( S )‐1‐α‐methylbenzyl‐3‐ p ‐tolylureas ( R ‐MBTU and S ‐MBTU) and ( R )‐/( S )‐1‐α‐methylbenzyl‐3‐ m ‐tolylureas) exhibited a cross intergenus selective phytotoxicity 21, 24, 26.…”

Rice OsDOF15 contributes to ethylene‐inhibited primary root elongation under salt stress

“…We therefore asked whether salt‐regulated root growth in rice requires the regulation of ethylene biosynthesis. To address this question, concentrations of NaCl were determined to observe the root phenotype of rice seedling, considering that the roots of young rice seedling are more sensitive to salt stress than shoots, with the half maximum inhibitory concentration of NaCl < 43 mM (Flowers & Yeo, ; Khan et al ., ; Omokawa & Aonuma, ; Nam et al ., ). Thus, we treated three japonica cultivars and three indica cultivars with NaCl treatments of different concentrations.…”