Ethylene coordinates seed germination behavior in response to low soil pH in Stylosanthes humilis

Low soil pH modulates ethylene biosynthesis and germination response of Stylosanthes humilis seeds

“…ACC concentrations were increased by the reduction of soil pH in hypocotyl. 5 Moreover, soil pH did not influence the concentration of IAA in hypocotyl. 5 It is also interesting that the ACC concentrations were lower in hypocotyls than in roots of S. humils seedlings grown in soil with pH < 5.0.…”

“…5 Moreover, soil pH did not influence the concentration of IAA in hypocotyl. 5 It is also interesting that the ACC concentrations were lower in hypocotyls than in roots of S. humils seedlings grown in soil with pH < 5.0. 5 Presumably, ethylene concentrations that occur in hypocotyl under acidic conditions are not enough to maintain the curvature of apical hook for a long period of time.…”

“…In our original research article 5 we showed that low soil pH increased ethylene biosynthesis during germination of S. humilis seed, facilitating root penetration into the soil. Soils with pH < 5.0 effectively increases 1-aminocyclopropane-1carboxylic acid (ACC) concentration and the subsequent biosynthesis of ethylene by the enzymes ACC synthase (ACS) and ACC oxidase (ACO) ( Figure 1).…”

“…Acidic condition-induced root penetration into the soil is also dependent on the synthesis of the auxin indole-3-acetic acid (IAA). 5 Exactly how low pH soil induces auxin biosynthesis is still unclear, but it may involve alterations in ethylene concentration. Of note, our results revealed changes in tryptophan concentrations in root of seedlings grown in pH 5.8 soil compared with pH 3.9 soil.…”

“…Of note, our results revealed changes in tryptophan concentrations in root of seedlings grown in pH 5.8 soil compared with pH 3.9 soil. 5 In this context, ethylene concentration could trigger a generation of IAA by modifying the activity of tryptophan aminotransferase (TA)/TA-related (TARs) converting tryptophan to indole-3-pyruvic acid (3-IPA), while flavin-containing monooxygenase family proteins (YUCCA) convert 3-IPA to IAA (Figure 1). 13 Interestingly, ethylene and IAA accumulation under soil with pH < 5.0 decreases radicle elongation, allowing root penetration into the soil.…”