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Background Caryopsis development consists of several processes in the production of grain yield in field crops. This study evaluated the effect of silicon (Si) on spikelet formation, spikelet fertility, and grain filling and its impact on grain yield in rice. Results Applying Si increased grain yield by 44% in Chainat 1( CNT1) and by 23% in Pathumthani 1 (PTT1). With no Si application, CNT1 had fewer total spikelets, and the fertilized and filled spikelets responded more strongly to Si than PTT1 did. Grain yield in both genotypes increased with increasing number of spikelets and filled fertilized grains. There were close relationships between Si concentration in the shoots, flag leaf, and the husk, which were positively correlated with grain yield, the number of spikelets, and fertilized and filled grains. Applying Si fertilizer also increased the expression level of Lsi6 in both CNT1 and PTT1 by 202% and 144% respectively compared with the expression of plants with no Si supplied. Conclusion This study has shown how rice grain yield can be limited by Si deficiency through the spikelet formation, fertilization, and grain filling processes. Applying Si fertilizer could improve rice grain yield through increasing spikelet formation, fertilization, and grain filling, which is in parallel with Lsi6 gene expression. This information can be used for improving rice productivity by Si fertilization management. © 2020 Society of Chemical Industry.

Rice is the main staple crop for one-third of the world population. To maximize yields, large quantities and constant input of fertilizers containing essential nutrients such as phosphorus (P) and iron (Fe) are added. Rice can germinate in both aerobic and anaerobic conditions, but the crosstalk between oxygen (O₂) and nutrients such as P and Fe on plant growth remains obscure. The aim of this work was to test whether such interactions exist, and, if so, if they are conserved between up- and lowland rice varieties. To do so, we assessed shoot and root biomass as well as inorganic phosphate (Pi) accumulation in four rice varieties, including two lowland rice varieties Nipponbare and Suphanburi 1 (SPR1) (adapted to non-aerated condition) and two upland rice varieties CMU122 and Sew Mae Jun (SMJ) (adapted to aerated condition) under various conditions of Pi and/or Fe deficiencies, in aerated and non-areated solution. Under these different experimental conditions, our results revealed that the altered shoot biomass in Nipponbare and SPR1 was O₂-dependent but to a lesser extent in CMU122 and SMJ cultivars. In this perspective, discovering the biological significance and molecular basis of these mineral elements and O₂ signal interaction is needed to fully appreciate the performance of plants to multiple environmental changes.