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Background Nitrogen (N) is a crucial element for increasing photosynthesis and crop yields. The study aims to evaluate the photosynthetic regulation and yield formation mechanisms of different nodulating peanut varieties with N fertilizer application. Method The present work explored the effect of N fertilizer application rates (N0, N45, N105, and N165) on the photosynthetic characteristics, chlorophyll fluorescence characteristics, dry matter, N accumulation, and yield of four peanut varieties. Results The results showed that N application increased the photosynthetic capacity, dry matter, N accumulation, and yield of peanuts. The measurement of chlorophyll a fluorescence revealed that the K-phase, J-phase, and I-phase from the OJIP curve decreased under N105 treatment compared with N0, and W OI , ET 0 /CS M , RE 0 /CS M , ET 0 /RC, RE 0 /RC, φPo, φEo, φRo, and Ψ0 increased, whereas V J , V I , W K , ABS/RC, TR 0 /RC, DI 0 /RC, and φDo decreased. Meanwhile, the photosystem activity and electron transfer efficiency of nodulating peanut varieties decreased with an increase in N (N165). However, the photosynthetic capacity and yield of the non-nodulating peanut variety, which highly depended on N fertilizer, increased with an increase in N. Conclusion Optimized N application (N105) increased the activity of the photosystem II (PSII) reaction center, improved the electron and energy transfer performance in the photosynthetic electron transport chain, and reduced the energy dissipation of leaves in nodulating peanut varieties, which is conducive to improving the yield. Nevertheless, high N (N165) had a positive effect on the photosystem and yield of non-nodulating peanut. The results provide highly valuable guidance for optimizing peanut N management and cultivation measures.

Background Drought stress poses a critical constraint to plant growth by impairing photosynthetic efficiency in crops. Results Through transcriptome profiling of two peanut cultivars with contrasting drought tolerance, Fuhua18 (drought-sensitive, FH18) and Nonghua5 (drought-tolerant, NH5), we identified significant enrichment of differentially expressed genes in photosynthesis-related pathways. Notably, these genes were predominantly downregulated in FH18. Subsequent physiological analysis revealed cultivar-specific responses: Chlorophyll content decreased in FH18 but increased in NH5 after 24 h of drought treatment, accompanied by significant reductions in net photosynthetic rate (Pn) and water use efficiency (WUE) in both cultivars. The drought-induced physiological perturbations were further evidenced by elevated electrolyte leakage and activated antioxidant systems. To dissect photosynthetic apparatus dynamics, we implemented JIP-test analysis of chlorophyll fluorescence kinetics. Both cultivars exhibited substantial increases in Vj and Vi parameters at 24 h, while FH18 demonstrated a pronounced elevation in Vk during the O-J phase transition, suggesting severe impairment of the oxygen-evolving complex. Quantitative evaluation of photosynthetic performance indices revealed marked declines in PI abs and PI total , indicating systemic damage to both PSI and PSII under drought stress. Comparative analysis identified 11 traits showing significant inter-cultivar variation, particularly in PSII reaction center parameters including PI abs , DI 0 /RC, RE 0 /RC, ABS/RC, and TR 0 /RC. Conclusion These findings provide mechanistic insights into cultivar-dependent photosynthetic responses to drought stress, offering potential biomarkers for breeding drought-resilient peanut varieties.

The consequences of climate change, and the increased accumulation of metalloids, like arsenic (As), in the environment, are significantly affecting crop performance and yield. Arsenic interferes with various plant biochemical and physiological processes, which result in diminished plant growth and development. Magnesium oxide nanoparticles (MgO-NPs) can improve plant growth and contribute to plant tolerance of heavy metal/metalloid toxicity. During current research, the efficacy of MgO-NPs was assessed for lessening arsenic (As) toxicity in soybean plants. In our experiment As uptake, plant growth, antioxidant enzyme activity, nutrient content, photochemical efficiency and photosynthetic performance were evaluated with/without exogenous application of 500 mg L−1 MgO-NPs in the presence/absence of 150 µM As in soybean plants. Foliar application of MgO-NPs, in the presence of As, enhanced plant height and dry weight by 17% and 15% respectively, and improved net photosynthetic rate by 12.9%, stomatal conductance by 13.4%, intercellular CO2 concentration by 15.3% and transpiration rate by 14.7%, as well as nutrient uptake and photosystem II (PSII) efficiency. In contrast, it decreased As uptake and oxidative stress as evaluated with hydrogen peroxide (H2O2) and lipid peroxidation (MDA). Hence, field tests may be implemented to formulate MgO-NPs use in agriculture, in order to obtain sustainable crop production in arsenic-contaminated soils.

Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis characterized by improved water use efficiency mediated by major nocturnal CO fixation. Due to its inherent metabolic plasticity CAM represents a successful physiological strategy for plant adaptation to abiotic stress. The present study reports on the impact of drought stress and different light intensities (PPFD 50 and 200 μmol m s ) on the photosynthetic performance of the obligate CAM orchid \"Edessa\" by integrating diel gas exchange patterns with assessments of the light reactions by analyzing fast chlorophyll fluorescence induction. Parameters such as PI (performance index), different energy fluxes per active reaction centre (RC) reflecting the electron flow from photosystem II to photosystem I and the energetic communication between PSII complexes defined as connectivity were considered for the first time in a CAM plant. A higher PS II connectivity for plants grown under low light ( ∼ 0.51) compared to plants grown under high light ( ∼ 0.31) brought about similar specific energy fluxes of light absorbance, dissipation and processing through the electron transport chain, irrespective of the light treatment. With a 25% higher maximum quantum yield and comparable biomass formation, low light grown plants indeed proved to process light energy more efficiently compared to high light grown plants. The performance index was identified as a very reliable and sensitive parameter to indicate the onset and progress of drought stress. Under restricted CO availability (due to closed stomata) leaves showed higher energy dissipation and partial inactivation of PSII reaction centres to reduce the energy input to the electron transport chain and as such aid in avoiding overexcitation and photodamage. Especially during CAM idling there is a discrepancy between continuous input of light energy but severely reduced availability of both water and CO , which represents the ultimate electron acceptor. Taken together, our results show a unique flexibility of CAM plants to optimize the light reactions under different environmental conditions in a dual way by either attenuating or increasing energy flux.

In maize-soybean intercropping system, soybean plants will be affected by the wide light-fluctuation, which resulted from the shading by maize plants, as the shading of maize the light is not enough for soybean in the early morning and late afternoon, but at noon, the light is strong as the maize shading disappeared. The objective of this study is to evaluate the photosynthetic response of soybean leaf to the wide light-fluctuation. The data of diurnal variation of photosynthetic characters showed that the photosynthetic rate of intercropped soybean was weaker than that of monocropped soybean. The chlorophyll content, ratio of chlorophyll a/b, and AQE (apparent quantum efficiency) were increased and (dark respiration rate) was decreased for the more efficient interception and absorption of light and carbon gain in intercropping. δ (The efficiency/probability with which an electron from the intersystem electron carriers was transferred to reduce end electron acceptors at the PSI acceptor side) and φ (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) in intercropped soybean leaf were lower compared to those in monocropped one, which showed that the acceptor side of PSI might be inhibited, and also it was the main reason that soybean plants showed a low photosynthetic capacity in intercropping. ψ (the efficiency/probability with an electron moves further than Q ) in monocropping and intercropping decreased 5.8, and 35.7%, respectively, while φ (quantum yield for electron transport) decreased 27.7 and 45.3% under the high radiation at noon, which suggested that the acceptor side of PSII was inhibited, while the NPQ became higher. These were beneficial to dissipate excess excitation energy in time, and protect the photosynthetic apparatus against photo-damage. The higher performance index on the absorption basis (PI ) and lower δ , φ , ψ , and φ of intercropped soybeans compared to monocropping under high radiation indicated that the electron transfer of intercropped soybean was inhibited more seriously and intercropped soybean adjusted the electron transport between PSII to PSI to adapt the light-fluctuation. Higher NPQ capacity of intercropped soybeans played a key role in keeping the leaf with a better physiological flexibility under the high radiation.

Magnetopriming has emerged as a promising seed-priming method, improving seed vigor, plant performance and productivity under both normal and stressed conditions. Various recent reports have demonstrated that improved photosynthesis can lead to higher biomass accumulation and overall crop yield. The major focus of the present review is magnetopriming-based, improved growth parameters, which ultimately favor increased photosynthetic performance. The plants originating from magnetoprimed seeds showed increased plant height, leaf area, fresh weight, thick midrib and minor veins. Similarly, chlorophyll and carotenoid contents, efficiency of PSII, quantum yield of electron transport, stomatal conductance, and activities of carbonic anhydrase (CA), Rubisco and PEP-carboxylase enzymes are enhanced with magnetopriming of the seeds. In addition, a higher fluorescence yield at the J-I-P phase in polyphasic chlorophyll a fluorescence (OJIP) transient curves was observed in plants originating from magnetoprimed seeds. Here, we have presented an overview of available studies supporting the magnetopriming-based improvement of various parameters determining the photosynthetic performance of crop plants, which consequently increases crop yield. Additionally, we suggest the need for more in-depth molecular analysis in the future to shed light upon hidden regulatory mechanisms involved in magnetopriming-based, improved photosynthetic performance.

Background Proline can promote growth of plants by increasing photosynthetic activity under both non-stress and abiotic stress conditions. However, its role in non-stressed conditions is least studied. An experiment was conducted to assess as to whether increase in growth of wheat due to seed priming with proline under non-stress condition was associated with proline-induced changes in photosystem II (PSII) activity. Seeds of four wheat varieties (S-24, Sehar-06, Galaxy-13, and Pasban-90) were primed with different concentrations of proline (0, 5, 15 and 25 mM) for 12 h and allowed to grow under normal conditions. Biomass accumulation and photosynthetic performance, being two most sensitive features/indicators of plant growth, were selected to monitor proline modulated changes. Results Seed priming with proline increased the fresh and dry weights of shoots and roots, and plant height of all four wheat varieties. Maximum increase in growth attributes was observed in all four wheat varieties at 15 mM proline. Maximum growth improvement due to proline was found in var. Galaxy-13, whereas the reverse was true for S-24. Moreover, proline treatment changed the Fo, Fm, Fv/Fo, PI ABS , PI Tot in wheat varieties indicating changes in PSII activity. Proline induced changes in energy fluxes for absorption, trapping, electron transport and heat dissipation per reaction center indicated that var. Galaxy-13 had better ability to process absorbed light energy through photosynthetic machinery. Moreover, lesser PSII efficiency in var. S-24 was due to lower energy flux for electron transport and greater energy flux for heat dissipation. This was further supported by the fact that var. S-24 had disturbance at acceptor side of PSI as reflected by reduction in ΔV IP , probability and energy flux for electron transport at the PSI end electron acceptors. Conclusion Seed priming with proline improved the growth of wheat varieties, which depends on type of variety and concentration of proline applied. Seed priming with proline significantly changed the PSII activity in wheat varieties, however, its translation in growth improvement depends on potential of processing of absorbed light energy by electron acceptors of electron transport chain, particularly those present at PSI end.

Drought is a global problem limiting plant growth and productivity by hampering the physiological and biochemical processes. Acetylcholine (ACh), a potential neurotransmitter found in lower and higher plants, has the potential to promote growth. However, little is known about ACh-mediated physiological and biochemical changes that promote plants’ growth under drought stress conditions. Current experiments were undertaken to assess the effect of ACh (0.01 and 0.1 mM ACh) supplementation on the growth performance of tobacco under drought stress (10%, PEG 6000). The current findings exhibit that drought stress substantially reduced the physiological and biochemical parameters. However, the ACh application enhanced the growth and biomass of tobacco plants. Moreover, ACh application significantly enhanced the activity of PSII and chlorophyll fluorescence under normal and drought stress treatment, respectively. Furthermore, PEG treatment increases reactive oxygen species and oxidative damage; however, ACh application reduced H 2 O 2 , O 2 − and lipid peroxidation. In addition, exogenous application of ACh improved plant water status by improving the accumulation of proline and regulating the stomatal opening and closing. Besides, ACh-induced amelioration of oxidative stress was related to the up-regulation of antioxidant enzyme activities like SOD, POD, CAT, and APX. Hence, it can be concluded that ACh treatment improved photosynthesis in tobacco by regulating the stomatal and non-stomatal factors and up-regulation of the antioxidant system.

To clarify the genotypic-dependent alternation in D1 protein turnover and PSII repair cycle and its relation to light intensity in senescent leaves of rice, two rice genotypes, namely, the psf mutant and its wild type, were used to determine their temporal differences in terms of the net photosynthetic rate (Pn), chlorophyll fluorescence parameters of PSII, and transcriptional levels of genes that participated in D1 protein turnover during leaf senescence. The results showed that compared to its wild type, the psf mutant had lower Pn, solar energy transmitting efficiency (Fv/Fm), and performance index on absorption basis (PIabs) than its wild type. Moreover, our results showed that the emergence of leaf senescent symptoms for psf mutant mainly depends on light intensity, instead of light quality in the field. The prevention of leaves from sugar starvation and oxidative damage contributes to the regulation of shaded-delayed leaf senescence in the psf mutant. Both non-phosphorylated and phosphorylated D1 proteins in leaves of the psf mutant were found decreasing with leaf senescence, while the non-phosphorylated one had more decrease. The initiation and subsequent progresses of leaf senescence induced by light were closely related to the D1 protein turnover in the leaves of the psf mutant. Partial shading treatment within an intact leaf concomitantly alleviated or even repaired the leaf premature senescent symptoms of the shaded area, which also suppressed D1 protein from being degraded. The key genes (OsPsbA and OsFtsHs) participated in D1 protein de novo synthesis and PSII repair cycle had lower expression during leaf senescence. Among different OsFtsH isoforms, OsFtsH2 exhibited the highest transcriptional levels, and it was also the isoform gene with the largest decline in the light treatment. Meanwhile, OsFtsH5 and OsFtsH7 were only down-regulated in conditions with high light intensity. Therefore, the inhabitation of D1 de novo synthesis and photo-damaged D1 degradation are mainly due to the down-regulation of OsPsbA and OsFtsH2. Other OsFtsH isoforms may play synergistic or complementary roles in D1 protein turnover and PSII repair cycle in light-induced leaf senescence.

Water deficit limits plant growth and yield. Arbuscular mycorrhizal (AM) symbiosis is viewed as one of the several methods to improve growth under water deficit. The present study investigated the growth performance in relation to water deficit in two cultivars (“H2” and “660”) of AM treated macadamia ( Macadamia tetraphylla L.) plants. AM treatment significantly improved the growth in macadamia plants that have been subjected to water deficit (7 % soil water content) for 14 days. Leaf water content (LWC) and maximum quantum yield of PSII (F v /F m ) in AM-associated plants were maintained better than those in the control (well-watered) plants. A positive correlation was observed between LWC and F v /F m in “H2” cultivar. AM treatment enhanced proline and soluble sugar content in “H2” cultivar under water deficit stress. In contrast, only soluble sugars were accumulated in the AM-associated plants of “660” cultivar under water deficit stress. The study concludes that soluble sugars and proline are involved as key signals of osmoregulation defense response, improve water relation in plant tissues, and thereby resulting in improved growth in AM-associated macadamia plants.