A field experiment was conducted in Huangping County, Guizhou Province, China, during 2019 using two indica hybrid rice cultivars, Qyou6 and Yixiangyou2115, to investigate the effects of varying nitrogen application rates on photosynthetic pigments, leaf fluorescence characteristics, grain yield, and their interrelationships. Five nitrogen levels were applied: 0 (N0), 75 (N1), 150 (N2), 225 (N3), and 300 kg ha⁻¹ (N4). The results showed that chlorophyll a, chlorophyll b, and carotenoid contents generally increased with higher nitrogen application rates, particularly at the heading and maturity stages, where N4 treatments exhibited significantly greater pigment levels than N0.
Photosynthetic efficiency parameters revealed complex responses. At the booting stage, the maximum quantum yield of PSII (Fv/Fm) first decreased and then increased with rising nitrogen, peaking at N3. At the heading stage, Fv/Fm declined steadily, while PSII followed a similar trend but remained relatively stable across treatments. At maturity, both Fv/Fm and PSII increased after an initial decline.MYL1 Antibody custom synthesis The actual quantum yield of PSII (PSII) and relative electron transfer rate (ETR) initially rose and then fell at heading and maturity stages, with peak values observed in N3 (heading) and N1 (maturity), though differences were not always significant.
Fluorescence quenching parameters indicated dynamic changes. Photochemical quenching (qP) increased with nitrogen up to 300 kg ha⁻¹ at heading and maturity stages, suggesting enhanced opening of PSII reaction centers.SNAI 1 Antibody In Vitro Non-photochemical quenching coefficient (qN) initially rose and then declined across all growth stages, indicating a shift from protective energy dissipation to potential photodamage under excessive nitrogen.PMID:35017069 Quantum yield of regulatory energy dissipation (Y(NPQ)) followed a similar pattern, while non-regulatory energy dissipation (Y(NO)) decreased initially before increasing, reflecting the balance between light protection and damage.
Grain yield exhibited a parabolic relationship with nitrogen rate, peaking at N2 (150 kg ha⁻¹) and declining thereafter. Regression analysis predicted optimal nitrogen application at 168.16 kg ha⁻¹, yielding 11,804.87 kg ha⁻¹. Components such as effective panicle number (EPN) increased with nitrogen, while thousand-grain weight (TGW) and spikelet filling (SF) were highest under low nitrogen (N0).
Significant correlations were found among physiological traits and yield. At heading stage, chlorophyll a and b were negatively correlated with Fv/Fm but positively with qP. Carotenoids correlated positively with EPN at booting and negatively with SPP at heading. At maturity, chlorophyll a and carotenoids were positively linked to EPN but negatively to SF. Notably, qP was negatively correlated with EPN at booting, while Fv/Fm and Y(NO) were negatively related to EPN and SPP, respectively, and positively to SF. At maturity, Fv/Fm showed a strong negative correlation with grain yield.
These findings demonstrate that moderate nitrogen application enhances photosynthetic pigment content, improves photochemical efficiency, increases open reaction center proportion, and boosts self-protection capacity of PSII, ultimately promoting photosynthetic efficiency and yield. Optimal nitrogen input maximizes these benefits without triggering photoinhibition or metabolic imbalance.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com