Excess and deficient nitrogen (N) inhibit photosynthesis in the leaves of rice plants, but the underlying mechanism is still unclear. N can improve the chlorophyll content and thus affect photon absorption, but the photosynthetic rate does not increase accordingly. To investigate this mechanism, three concentrations of N treatments were applied to two rice varieties, Zhefu802 and Fgl. The results indicated increased chlorophyll content of leaves with an increased N supply. Little discrepancy was detected in Rubisco enzyme activity and Non-photochemical quenching (NPQ) in the high nitrogen (HN) and moderate nitrogen (MN) treatments. The model that photoinhibition occurs in Zhefu802 due to a lack of balance of light absorption and utilization is supported by the higher malondialdehyde (MDA) content, higher H₂O₂ content, and photoinhibitory quenching (qI) in HN treatment compared with MN treatment. A lower proportion of N in leaf was used to synthesize chlorophyll for Fgl compared with Zhefu802, reducing the likelihood of photoinhibition under HN treatment. In conclusion, HN supply does not allow ideal photosynthetic rate and increases the likelihood of photoinhibition because it does not sustain the balance of light absorption and utilization. Apart from Rubisco enzyme activity, NPQ mainly contributes to the unbalance. These results of this study will provide reference for the effective N management of rice.

The inherent chemical composition of different rice varieties can significantly influence the quality of sweet rice wine. However, most studies on sweet rice wine overlook varietal characteristics, resulting in slow progress in breeding rice varieties specialized for sweet rice wine production. To investigate the relationship between the inherent chemical composition of various rice varieties, such as starch, protein, and crude fat content, and their corresponding rice wines, 16 rice varieties with significant compositional variation were used in this study. The results revealed that screening solely for glutinous or non-glutinous rice is insufficient to select suitable raw materials for sweet rice wine production. Correlation analysis showed that the total sugar content of sweet rice wine was primarily associated with starch properties. In contrast, the formation of alcoholic strength and juice yield was more complex, exhibiting close correlations with multiple rice components, including amylose, albumin, globulin, crude fat, tannin content, and others. Furthermore, interactions among these components were also significantly correlated with these quality traits. In conclusion, amylose content, the ratio of amylose to amylopectin, gel consistency, and albumin content are important indicators for the rapid screening of high-quality rice lines, as they strongly correlate with sweet rice wine quality. These results will facilitate the development of rice varieties specialized for sweet rice wine production.

Introduction: Colored rice is recognized for nutritious function due to its flavonoid compounds. Flavonoid aglycones are conjugated with various sugar moieties. Iron (Fe) is an essential mineral nutrient for plants; however, the regulatory mechanisms by which Fe influences flavonoid accumulation dynamics and sugar metabolism remain unclear. Methods: FeSO ₄ was foliar-applied to black rice cultivar Nanheinuo and red rice cultivar Yuhongdao 5815 to study regulatory mechanisms by which Fe influences flavonoid accumulation dynamics and sugar metabolism. Results and discussion: The content of anthocyanins, proanthocyanidins, and total flavonoids in the grains decreased throughout the later filling stages. Fe application delayed their degradation during this phase. The differential expression of numerous genes associated with flavonoid transformation may be the primary reason. Genes annotated as key enzymes involved in phenylpropanoid and flavonoid biosynthesis were significantly upregulated in Nanheinuo. Additionally, foliar Fe application significantly impacted sugar and sugar alcohol content by regulating the expression of genes involved in polysaccharide decomposition, phosphorylation and dephosphorylation processes, and sugar interconversion. A close relationship was observed between sugar content and flavonoid-related compound content in the grains of colored rice. Multiple hub genes annotated as glycoside hydrolases in KEGG occupied central nodes within the co-expression network, suggesting that glycoside hydrolases may mediate the crosstalk between sugar and flavonoid metabolism in colored rice grains under Fe treatment, although glycosyltransferases primarily function in flavonoid glycosylation. Foliar Fe application delays flavonoid degradation during the later filling stage and regulates sugar metabolism in colored rice, thereby influencing flavonoid enrichment and eating quality.

The flavor variation among different tea plant cultivars significantly influences their economic value. ‘Huangjinya’ (HJY), a typical light-sensitive etiolated tea cultivar, is prized for its fresh and mellow taste with low bitterness and astringency, and commands a high market value, serving as excellent germplasm for breeding superior-flavor tea varieties. Previous studies have largely focused on the mechanisms underlying fresh and umami tastes, whereas the regulatory mechanisms underlying bitterness and astringency remain poorly understood. In this study, two tea plant (Camellia sinensis (L.) O. Kuntze) cultivars with distinct bitterness and astringency phenotypes, namely ‘Fuxuan 9’ (FX) and HJY, were used to investigate the formation mechanism of reduced bitterness and astringency through integrated metabolomic and transcriptomic analyses. Metabolomic profiling identified 601 differentially accumulated metabolites between the two cultivars, which were significantly enriched in the flavonoid biosynthesis pathway. Notably, although the total flavonoid content was higher in HJY, the accumulation of non-esterified catechins (C, EC, EGC), which are key contributors to bitterness, was significantly lower than in FX. By contrast, the levels of esterified catechins (EGCG, GCG) showed no marked differences between cultivars. This distinct accumulation pattern provides a metabolic basis potentially associated with the reduced bitterness and astringency in HJY. Transcriptomic analysis revealed that the catechin biosynthetic gene CsLAR was significantly down-regulated in HJY, consistent with the reduced accumulation of non-esterified catechins. Promoter cloning and functional validation confirmed that the CsLAR promoters in both cultivars were active, which differed by only one regulatory element. Under shading treatment, CsLAR expression in HJY was more sensitive to light and decreased more markedly, suggesting that the expression of CsLAR may be regulated by transcription factors. Furthermore, 385 differentially expressed transcription factors were identified, with predicted binding sites in the CsLAR promoter region, implying their potential involvement in modulating catechin accumulation through modulation of CsLAR expression. Together, these multi-omics findings reveal molecular features potentially contributing to the low bitterness and astringency of HJY, providing a theoretical basis and candidate regulators for breeding tea cultivars with improved flavor profiles.