Plant-mediated rhizospheric interactions in rice and water spinach intercropping enhance Si uptake by rice

Aims Silicon (Si) plays an important role in rice. Although biodiversity utilization in paddy fields has increased in recent years, Si nutrition of rice in intercropping systems is poorly understood. The present research focused on deciphering the underlying mechanisms involved in rice and water spinach intercropping, which enhance Si uptake by rice. Methods We carried out a series of experiments including field, greenhouse, and incubation experiments to explore the plant-plant-soil interaction mechanisms. Results The field trials showed that rice and water spinach intercropping with different row ratios can increase Si concentration by 9.8 %-52.6 % and Si absorption by 34.7 %-127.8 % in rice leaves at ripening stage compared to rice monoculture. The pot trials further indicated that intercropping can promote rice to increase Si concentration in Si-deficient soil, with a significant increase of 35.9 % in stems and 29.7 % in leaves, and intercropping significantly increased soil CaCl2-Si content by 168.1 % compared to rice monoculture. In-depth research indicated that there was an interspecific rhizosphere interaction under intercropping conditions, which not only induced the up-regulated expression of Si transporter genes in rice roots (OsLsi1, OsLsi2) and stems (OsLsi6), but also stimulated rice roots to secrete more organic acids to increase Si availability in the soil. Moreover, water spinach root exudates helped reduce the polymerization or adsorption of monosilicic acid through proton efflux of roots. Conclusions Rice and water spinach intercropping can greatly enhance Si absorption of rice through several beneficial ways, which will have important practical significance for sustainable rice production, especially in Si-deficient soils.

Automated summary

Intercropping rice and water spinach can enhance silicon uptake by rice through promoting the secretion of organic acids by rice roots and reducing polymerization or adsorption of monosilicic acid through water spinach root exudates, which is significant for sustainable rice production in silicon-deficient soils.