Ethylene modulates peanut (Arachis hypogaea L.) growth and yield in response to planting depth

Temperature may affect ethylene production in plant tissues. Due to temperature variations in the soil depth profile, planting depth can potentially affect ethylene production at the seed germination phase and postgermination growth phase. We hypothesized that in the field, altered ethylene biosynthesis in response to planting depth affect peanut growth and development. Ethylene production in peanut seedlings of the cultivars 'Tatu-53' and 'IAPAR 25' showed a positive correlation with soil temperature at different planting depth. In response to shallow (1.0-2.5 cm) planting depth, ethylene biosynthesis is increased, leading to low shoot/root ratio, whereas in in deep (10-15 cm) planting treatments, ethylene production is repressed, resulting in high shoot/root ratio. In both cases, peanut yield is lower than in the medium depth (5 cm) sowing treatment. These results indicate that ethylene alters shoot/root ratio in early postembryonic development in both shallow and depth planting, leading to negative effects in long-term adult plant development. Ethylene production in response to the 5-cm depth allows seedlings to balance shoot and root growth, avoiding the detrimental effects of planting depth response on yield. Moreover, sowing at 5 cm depth raises the concentration of Ca, S, and Zn in the seeds of the next generation. Together, these findings indicate that planting depth couples soil temperature with seedling ethylene production, and this plays a significant role in priming the future development of the peanut plant and conditioning its yield.