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Inoculation with Arbuscular Mycorrhizal Fungi Alleviates the Adverse Effects of High Temperature in Soybean
High temperature is foremost abiotic stress and there are inadequate studies explicating its impact on soybean. In this study, a pot experiment was done in a greenhouse maintained at a day/night temperature of 42/28 °C with a mean temperature of 35 °C to examine the effects of high temperature in soybean plants inoculated with and without arbuscular mycorrhizal fungi (AMF).Various parameters were taken in soybean plants treated with AMF (+) and AMF (−) such as growth analysis, chlorophyll content, canopy temperature, number of stomata, gas exchange, chlorophyll fluorescence, seed yield, and its attributes. It was observed that growth parameters like leaf area, stem height, root length, shoot and root dry biomass were increased in AMF (+) as compared to AMF (−) plants. Chlorophyll content, the number of stomata, photosynthesis rate, stomatal conductance, transpiration rate, and water use efficiency increased in AMF (+) as compared to AMF (−) plants. Chlorophyll fluorescence parameters such as Fv/Fm, Fv/Fo, PhiPSII, fluorescence area, performance index, photochemical quenching, linear electron transport rate, and active reaction centres density of PSII were also found to be enhanced in AMF (+) plants. However, canopy temperature, intercellular CO2, Fo/Fm, and non-photochemical quenching were higher in AMF (−) as compared to inoculated plants. An increase in growth and photosynthesis ultimately enhanced the seed yield and its attributes in AMF (+) as compared to AMF (−). Thus, AMF (+) plants have shown much better plant growth, photosynthesis parameters, and seed yield as compared to AMF (−) plants under high temperature. Thus, it is concluded that heat stress-induced damage to the structure and function of the photosynthetic apparatus was alleviated by AMF inoculum. Therefore, AMF can be used as a biofertilizer in alleviating the adverse effects of heat stress in soybean.
Enhancing UV-B Tolerance in Radish and Mung Bean Plants Using Magnetic Iron Oxide Nanoparticles Foliar Application
ABSTRACTThis study investigates the potential of magnetic iron oxide nanoparticles (MIONPs) in mitigating ultraviolet‐B radiation (UV‐B) induced physiological damage in radish (Raphanus sativus L.) and mung bean (Vigna radiata). Screening of the seed vigour indices identified 1500 mg L−1 MIONPs as the optimal concentration for radish and 100 mg L−1 for mung bean for seed vigour improvement. After the first true leaf appeared (~15 days), plants were exposed to different UV‐B intensities: control (UV0, 0 mW m−2), moderate (UV1, 26 mW m−2), and high (UV2, 53 mW m−2), with or without foliar MIONPs application. Results showed that UV‐B significantly decreased the net photosynthesis rate (Pn) by 32% in radish and 65% in mung bean after UV2 exposure. Fluorescence parameters, including photosystem II (PSII) efficiency and photosynthetic performance (PIabs), were also impaired by UV‐B. UV‐B stress led to a decline in plant growth, leaf area, biomass accumulation, and chlorophyll content while increasing antioxidant enzyme activities, flavonoids, anthocyanins, malondialdehyde (MDA), and hydrogen peroxide (H2O2) levels. However, MIONPs treatment enhanced UV‐B tolerance by improving pigment content, PSII efficiency, Pn, leaf area, and biomass accumulation while reducing MDA and H2O2 levels, thus improving overall plant physiological health. In the leaf model of energy flux, MIONPs‐treated plants showed more active reaction centers and improved electron transport. The OJIP curves differed under UV‐B stress, with increasing UV‐B stress showing decreased fluorescence intensity at the IP phase. However, plants treated with MIONPs showed higher fluorescence intensity specifically at the IP phase, suggesting their protective effect. The UV sensitivity index (UV‐SI) revealed that mung bean is more UV‐sensitive than radish. MIONPs treatment increased UV‐SI values and enhanced the plant tolerance towards UV‐B. The results suggest that the application of MIONPs could improve UV‐B resistance in future agricultural practices.
Interplay among photoreceptors determines the strategy of coping with excess light in tomato
SUMMARYThis study investigates photoreceptor's role in the adaption of photosynthetic apparatus to high light (HL) intensity by examining the response of tomato wild type (WT) (Solanum lycopersicum L. cv. Moneymaker) and tomato mutants (phyA, phyB1, phyB2, cry1) plants to HL. Our results showed a photoreceptor‐dependent effect of HL on the maximum quantum yield of photosystem II (Fv/Fm) with phyB1 exhibiting a decrease, while phyB2 exhibiting an increase in Fv/Fm. HL resulted in an increase in the efficient quantum yield of photosystem II (ΦPSII) and a decrease in the non‐photochemical quantum yields (ΦNPQ and ΦN0) solely in phyA. Under HL, phyA showed a significant decrease in the energy‐dependent quenching component of NPQ (qE), while phyB2 mutants showed an increase in the state transition (qT) component. Furthermore, ΔΔFv/Fm revealed that PHYB1 compensates for the deficit of PHYA in phyA mutants. PHYA signaling likely emerges as the dominant effector of PHYB1 and PHYB2 signaling within the HL‐induced signaling network. In addition, PHYB1 compensates for the role of CRY1 in regulating Fv/Fm in cry1 mutants. Overall, the results of this research provide valuable insights into the unique role of each photoreceptor and their interplay in balancing photon energy and photoprotection under HL condition.
The role of potassium on drought resistance of winter wheat cultivars under cold dryland conditions: Probed by chlorophyll a fluorescence
Silicon-induced photosynthetic adaptations in common buckwheat under salt stress revealed by prompt chlorophyll a fluorescence analysis
Abstract This study aimed at investigating the protective role of silicon (Si) in mitigating salt-induced damage in common buckwheat plants (Fagopyrum esculentum cv. Smuga). Twenty one-day-old seedlings were subjected to salt stress by irrigating 50 mM sodium chloride solutions for seven days, with or without Si (two foliar applications with 1 mM sodium metasilicate nonahydrate). Salt stress significantly altered the chlorophyll a fluorescence transient (OJIP) curve, disrupting energy flow and electron transport in photosystem II (PSII), as reflected in the O-J, J-I, and I-P phases, along with the emergence of a positive K-band indicating damage to the oxygen-evolving complex (OEC). Silicon application mitigated these effects, stabilizing the OEC and thylakoid membrane integrity while improving JIP test parameters and reducing excessive energy absorption, dissipation, and unregulated energy loss per reaction center. Silicon-treated plants under salt stress exhibited enhanced photochemical quenching, reduced regulatory energy dissipation, and decreased photosystem I (PSI) over-reduction. A significant increase in open PSI centers was observed, improving the balance and functionality between PSI and photosystem II. The application of Si resulted in significant photosynthetic improvements, which were also paired with enhanced morphological traits, such as increased root length and leaf thickness in saline conditions. Overall, findings indicate that exogenous Si helps to reduce salt-induced stress by enhancing photosynthetic efficiency in plants, positioning it as a promising strategy for improving crop performance in saline environments.
Artificial neural network (ANN)-based algorithms for high light stress phenotyping of tomato genotypes using chlorophyll fluorescence features
Effects of Seed Priming with Gamma Radiation on Growth, Photosynthetic Functionality, and Essential Oil and Phytochemical Contents of Savory Plants
Gamma radiation has been suggested to have post-effects on emerging plants when applied to the seeds. In the present study, we aimed to induce alterations in photosynthetic functionality and subsequent modifications in secondary metabolites of summer savory following seed priming with gamma radiation. Savory seeds were treated with 0, 50, 100, 200, and 300 Gy gamma radiation in a completely randomized design with ten replications for morphological and photosynthetic parameters and three for phytochemical assessments. The results showed that gamma radiation on seeds adversely affected photosynthetic performance, especially at the highest doses. It negatively influenced the growth, while increasing the shoot branching, the number of nodes, and the diameter of the stem. Gamma radiation on seeds generally reduced pigmentation in savory leaves, such as chlorophylls, carotenoids, and anthocyanins. However, soluble sugar, starch, total phenolics, and total flavonoid contents were elevated in the leaves of plants that emerged from gamma-primed seeds. Gamma radiation priming reduced essential oil’s percentage and yield. Carvacrol and limonene components of essential oil were diminished, whereas linalool and thymol were increased. In conclusion, due to its inherent stress-inducing effects, and despite some positive effects on phytochemicals, seed priming with gamma radiation adversely influenced growth, photosynthesis, and quantity and quality of savory essential oils. Further research is still needed to target the use of gamma radiations before harvesting the seeds or determine the cytogenetic characteristics of irradiated plants.
A Multi-Model Gap-Filling Strategy Increases the Accuracy of GPP Estimation from Periodic Chamber-Based Flux Measurements on Sphagnum-Dominated Peatland
Gross primary productivity (GPP), the primary driver of carbon accumulation, governs the sequestration of atmospheric CO2 into biomass. However, GPP cannot be measured directly, as photosynthesis and respiration are simultaneous. At canopy level in plot-scale studies, GPP can be estimated through the closed chamber-based measurements of net ecosystem exchange (NEE) and ecosystem respiration (Reco). This technique is cost-effective and widely used in small-scale studies with short vegetation, but measurements are periodic-based and require temporal interpolations. The rectangular hyperbolic model (RH) was the basis of this study, developing two temperature-dependent factors following a linear and exponential shift in GPP when the temperature oscillates from the optimum for vegetation performance. Additionally, a water table depth (WTD)-dependent model and an exponential model were tested. In the peak season, modified RH models showed the best performance, while for the rest of the year, the best model varied for each subplot. The statistical results demonstrate the limitations of assuming the light-use efficiency as a fixed shape mechanism (using only one model). Therefore, a multi-model approach with the best performance model selected for each period is proposed to improve GPP estimations for peatlands.
Photosynthetic Responses of Peat Moss (Sphagnum spp.) and Bog Cranberry (Vaccinium oxycoccos L.) to Spring Warming
The rising global temperature makes understanding the impact of warming on plant physiology in critical ecosystems essential, as changes in plant physiology can either help mitigate or intensify climate change. The northern peatlands belong to the most important parts of the global carbon cycle. Therefore, knowledge of the ongoing and future climate change impacts on peatland vegetation photosynthesis is crucial for further refinement of peatland or global carbon cycle and vegetation models. As peat moss (Sphagnum spp.) and bog cranberry (Vaccinium oxycoccos L.) represent some of the most common plant functional groups of peatland vegetation, we examined the impact of experimental warming on the status of their photosynthetic apparatus during the early vegetation season. We also studied the differences in the winter to early spring transition of peat moss and bog cranberry photosynthetic activity. We have shown that peat moss starts photosynthetic activity earlier because it relies on light-dependent energy dissipation through the winter. However, bog cranberry needs a period of warmer temperature to reach full activity due to the sustained, non-regulated, heat dissipation during winter, as suggested by the doubling of photosystem II efficiency and 36% decrease in sustained heat dissipation between the mid-March and beginning of May. The experimental warming further enhanced the performance of photosystem II, indicated by a significant increase in the photosystem II performance index on an absorption basis due to warming. Therefore, our results suggest that bog cranberry can benefit more from early spring warming, as its activity is sped up more compared to peat moss. This will probably result in faster shrub encroachment of the peatlands in the warmer future. The vegetation and carbon models should take into account the results of this research to predict the peatland functions under changing climate conditions.
Photoinhibition in horticultural crops: an overview of the effect of light quality and signaling in the underlying photoprotection mechanisms
The interactive effect of high temperature and water deficit stress on nitrogen fixation, photosynthesis, chlorophyll fluorescence, seed yield and quality in soybean (Glycine max)
Response to Cadmium Toxicity: Orchestration of Polyamines and microRNAs in Maize Plant
Cadmium (Cd) is a heavy metal that is widely contaminating the environment due to its uses in industries as corrosive reagents, paints, batteries, etc. Cd can easily be absorbed through plant roots and may have serious negative impacts on plant growth. To investigate the mechanisms utilized by plants to cope with Cd toxicity, an experiment was conducted on maize seedlings. We observed that the plant growth and photosynthetic mechanism were negatively influenced during 20 days of Cd stress. The expression levels of ornithine decarboxylase (ORDC) increased in the six seedlings under Cd exposure compared to the control. However, Cd toxicity led to an increase in putrescine (Put) content only on day 15 when compared to the control plants. In fact, with the exception of day 15, the increases in the ORDC transcript levels did not show a direct correlation with the observed increases in Put content. Spermidine and Spermine levels were reduced on day 6 by Cd application, which was parallel with suppressed Spermidine synthase gene. However, an increase in Spermidine and Spermine levels was observed on day 12 along with a significant elevation in Spermidine synthase expression. On day 6, Cd was observed to start accumulating in the root with an increase in the expression of microRNA 528; while on day 15, Cd started to be observed in the shoot part with an increase in microRNA 390 and microRNA 168. These results imply that different miRNAs may regulate polyamines (PAs) in maize under Cd toxicity, suggesting a plant-derived strategy to commit a PAs/miRNA-regulated mechanism/s in different developmental stages (time points) in response to Cd exposure.