Phototropism is a classic adaptive growth response that helps plants to enhance light capture for photosynthesis. It was shown that hydrogen peroxide (H2O2) participates in the regulation of blue light-induced hypocotyl phototropism; however, the underlying mechanism is unclear. In this study, we demonstrate that the unilateral high-intensity blue light (HBL) could induce asymmetric distribution of H2O2 in cotton hypocotyls. Disruption of the HBL-induced asymmetric distribution of H2O2 by applying either H2O2 itself evenly on the hypocotyls or H2O2 scavengers on the lit side of hypocotyls could efficiently inhibit hypocotyl phototropic growth. Consistently, application of H2O2 on the shaded and lit sides of the hypocotyls led to reduced and enhanced hypocotyl phototropism, respectively. Further, we show that H2O2 inhibits hypocotyl elongation of cotton seedlings, thus supporting the repressive role of H2O2 in HBL-induced hypocotyl phototropism. Moreover, our results show that H2O2 interferes with HBL-induced asymmetric distribution of auxin in the cotton hypocotyls. Taken together, our study uncovers that H2O2 changes the asymmetric accumulation of auxin and inhibits hypocotyl cell elongation, thus mediating HBL-induced hypocotyl phototropism.

Fire is a common disturbance in many biomes, with both beneficial and detrimental effects on soil biology, which largely depend on fire intensity. However, little is known about the impact of fire on soil nematode communities in terrestrial ecosystem. In the present study, we investigated the effects of short‐term prescribed fire on soil nematode communities and soil properties in an old‐field grassland in Northern China. The results showed that burning significantly increased soil nematode abundance by 77% and genus richness by 49% compared to the control. Burning also decreased taxon dominance by 45% (Simpson's D ) and increased nematode diversity by 31% (Shannon‐Weaver H '). However, burning increased plant parasites (particularly genera Cephalenchus and Pratylenchus ) and shifted community to more bacterial‐feeding genera (i.e., decreased Channel Index). Generally, burning increased soil bio‐available nitrogen (NH 4 + –N and NO 3 − –N) content, which would be the main drivers causing nematode community to flourish via a “bottom‐up” effect. These results suggest that prescribed fire increases nematode diversity and alters community composition toward more plant parasites and bacterial feeders. Our findings highlight the importance of prescribed fire management in shaping short‐term nematode community structure and function, but the long‐term effects and impacts of these changes on soil nutrient and carbon cycling remain unknown.

No abstract

No abstract