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

Abstract

Aims Although biodiversity utilization in paddy fields has increased in recent years, silicon (Si) nutrition of rice in intercropping systems is poorly understood. On the basis of our previous study, 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 underlying mechanisms.Results The field trials showed that rice-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 an increase of 35.9% in stems and 29.7% in leaves, and intercropping significantly increased soil water-soluble Si content by 168.1% compared to rice monoculture. Further research indicated that there was an interaction between rice roots and water spinach roots 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 the mobilization of Si in soil through proton efflux of roots. Conclusions Rice-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.

Nitrogen availability and plant–plant interactions drive leaf silicon concentration in wheat genotypes

“…The central horizontal bar in each box shows the median, the box represents the interquartile range (IQR), the whiskers show the location of the most extreme data points that are still within a factor of 1.5 of the upper or lower quartiles, and black points are values that fall outside the whiskers. Results of ANOVA (F-values) Ning et al, 2021). Our results suggest that both competition and facilitation for Si uptake might exist at the intraspecific level with durum wheat genotypes.…”

“…So far, facilitation for Si uptake in the rhizosphere has been demonstrated at the interspecific level with functionally contrasting species (e.g. contrast in Si demand and/or nutrient‐acquisition strategies; Ning et al, 2021). Our results suggest that both competition and facilitation for Si uptake might exist at the intraspecific level with durum wheat genotypes.…”

“…Height gain following Si fertilisation is, however, also associated with straighter leaves with lower leaf insertion angle (Zanão Júnior et al, 2010), which might in turn reduce the light extinction coefficient inside the canopy (Ando et al, 2002). In any case, this finding opens up new research directions on Si and plant-plant interactions in both natural and agroecosystems which remain strikingly scarce to date (but see Garbuzov et al, 2011;Ning et al, 2017Ning et al, , 2021.…”

“…Future research should identify which root chemical and physical traits characterise these facilitators, for the future development of productive and stress-resistant genotypes mixtures, that is, ideomixes (Litrico & Violle, 2015). Furthermore, facilitation/competition for plant Si uptake should be tested for different soil types with contrasting Si availability because the effect of plant-plant interactions on plant Si uptake is influenced by soil Si availability (Ning et al, 2021).…”

“…production of multiple phenotypes from a single genotype depending on environmental conditions; Miner et al, 2005) of leaf [Si] in response to N fertilisation might differ among genotypes, but this has not yet been tested. So far, the influence of plant-plant interactions on plant Si nutrition has received surprisingly little attention in the literature (but see Garbuzov et al, 2011;Ning et al, 2017Ning et al, , 2021, especially compared with other nutrients (Li et al, 2014). At the interspecific level, Ning et al (2021) showed that rice accumulates significantly more Si when grown with water spinach (Ipomoea aquatica Forsk)-a low Si-accumulating species-compared with a rice monoculture, possibly through the effect of root exudates on soil Si mobilisation (de Ning et al, 2021).…”