Quantum Yield Of Photosynthesis Research Articles

Photoperiod and temperature interactions drive the latitudinal distribution of Laminaria hyperborea (Laminariales, Phaeophyceae) under climate change.

Due to global rises in temperature, recent studies predict marine species shifting toward higher latitudes. We investigated the impact of interacting abiotic drivers on the distribution potential of the temperate kelp Laminaria hyperborea. The ecosystem engineering species is widespread along European coasts but has not yet been observed in the High Arctic, although it can survive several months of low temperatures and darkness. To investigate its ability to extend northward in future, we conducted a long-term multifactorial experiment with sporophytes from Porsangerfjorden, Norway-close to the species' documented northernmost distribution margin. The samples were exposed to three different photoperiods (PolarDay, LongDay, and PolarNight) at 0°C, 5°C, and 10°C for 3 months. Optimum quantum yield of photosynthesis (Fv/Fm), dry weight, pigments, phlorotannins, and storage carbohydrates were monitored. Both physiological and biochemical parameters revealed that L. hyperborea was strongly influenced by the different photoperiods and their interaction with temperature, while temperature alone exerted only minor effects. The Fv/Fm data were integrated into a species distribution model to project a possible northward expansion of L. hyperborea. The combination of extended day lengths and low temperatures appeared to be the limiting reason for northward spread of L. hyperborea until recently. However, with water temperatures reaching 10°C in summer, this kelp will be able to thrive also in the High Arctic. Moreover, no evidence of stress to Arctic winter warming was observed. Consequently, L. hyperborea has a high potential for spreading northward with further warming which may significantly affect the structure and function of Arctic ecosystems.

The usage of physiological methods in the creation of soybean varieties

The results of a study of the operation of photosystem II in the leaves of nine soybean varieties bred by the All-Russian Research Institute of Soybean are presented in order to identify genotypes with increased photosynthetic activity for inclusion in the breeding process when creating highly productive varieties of a new generation. A comparative assessment of varieties is given in terms of effective quantum yield of photosynthesis (Y) and chlorophyll fluorescence (F0), relative electron transport rate (ETR) and photochemical energy conversion depending on light saturation. The soybean varieties Gracia, Sonata and Kitrossa had the highest indicators for the studied parameters, significantly exceeding the standard variety Lydia. The effective quantum yield of photosynthesis, which shows the degree of absorption of solar energy, in the Gracia and Sonata varieties during the entire growing season was at the level of 0.80–0.83 rel. units, with this indicator exceeding for the Lydia variety by 0.09–0.13 rel. units depending on the phase of plant growth and development. The quantum yield of fluorescence (F0) in the leaves of the Lydia variety during the flowering phase exceeded the Gracia, Sonata and Kitrossa varieties by 60, 56 and 63%, respectively, which indicates a reduced activity of photosystem II in this variety. The efficiency of photochemical conversion of photosynthetic energy during the flowering phase was most stable in the leaves of the Sonata variety at light levels from 600 to 1500 µmol quanta/(m2∙s). Using the soybean variety Gratsia as the maternal form (♀) when crossed with the hybrid Am.2146, which was obtained with the inclusion of the Sonata variety in the hybridization, which also has a high degree of absorption of light quanta, the Radiant variety was create. Variety passed testing in 2021–2022, and in 2023 included in the State Register of Breeding Achievements for cultivation in the Far Eastern (12) region.

Efficacy of chlorophyll a fluorescence kinetics and JIP test for early detection of leaf-gall disease in Cordia dichotoma

Gall-induced oxidative stress impairs photosynthesis and ultimately negatively affects a plant’s productivity and yield. Cordia dichotoma is an economically important plant that suffers from galls produced by the insect Aceria gallae. So we investigated how plants deal with such biotic stress by studying chlorophyll fluorescence OJIP transient analysis. The results indicate the intensive variations in minimum-maximum fluorescence, electron transport, light-harvesting efficiency and density of active reaction centers. When reaction centers become inactive in severely infected leaves a significant rise in ABS/RC and TR/RC indicates the expanded antenna size of Photosystem-II which shows the plant's efforts to enhance photon absorption. But the electron transport was blocked due to OECs deactivation, remarkably altered ET/RC and phenomenological fluxes (ABS/CS, TR/CS and ET/CS). The J-curve distortion confirms blockage of electron transport towards PS-I since PQ is fully reduced and unable to grape electrons from QB. Leaf galls carry out noteworthy alterations in Kp, Kn, and primary and secondary photochemistry. But more severe infection causes complete obstruction for electron transport which finally diminishes performance indices (PIabs and PIcs) quantum yield of photosynthesis (φPo), and electron transport (φEo) which increases dissipation and eventually causes the death of the most severely infested leaf. Present studies reveal that measurement of FV/F0, PIabs, and PIcs may be used as a physiological marker for the early diagnosis of gall stress in C. dichotoma. Our results also suggest that repetitive detection of photosynthetic performance through chlorophyll a fluorescence analysis and a JIP-test can be used as potent tools to prevent plants from appearing the visible symptoms of any pathogenic infection.

Activation of stress reactions in the dinophyte microalga Prorocentrum cordatum as a consequence of the toxic effect of ZnO nanoparticles and zinc sulfate

According to the results of the experimental study, the main regularities of changes in morphological, structural-functional and fluorescent indices of P. cordatum were established when zinc oxide nanoparticles ZnO NPs (0.3–6.4 mg L−1) and Zn in form of salt (0.09–0.4 mg L−1) were added to the medium. The studied pollutants have cytotoxic (growth inhibition, development of oxidative stress, destruction of cytoplasmic organelles, disorganization of mitochondria) and genotoxic (changes in the morphology of nuclei, chromatin condensation) effects on microalgae, affecting almost all aspects of cell functioning. Despite the similar mechanism of action of zinc sulfate and ZnO NPs on P. cordatum cells, the negative effect of ZnO NPs is also due to the inhibition of photosynthetic activity of cells (significant decrease in the maximum quantum yield of photosynthesis and electron transport rate), reduction of chlorophyll concentration from 3.5 to 1.8 pg cell−1, as well as mechanical effect on cells: deformation and damage of cell membranes, aggregation of NPs on the cell surface. Apoptosis-like signs of cell death upon exposure to zinc sulfate and ZnO NPs were identified by flow cytometry and laser scanning confocal microscopy methods: changes in cell morphology, cytoplasm retraction, development of oxidative stress, deformation of nuclei, and disorganization of mitochondria. It was shown that the first signs of cell apoptosis appear at 0.02 mg L−1 Zn and 0.6 mg L−1 ZnO NPs after 72 h of exposure. At higher concentrations of pollutants, a dose-dependent decrease in algal enzymatic activity (up to 5 times relative to control) and mitochondrial membrane potential (up to 4 times relative to control), and an increase in the production of reactive oxygen species (up to 4–5 times relative to control) were observed. The results of the presented study contribute to the disclosure of fundamental mechanisms of toxic effects of pollutants and prediction of ways of phototrophic microorganisms reaction to this impact.

Improving nitrogen content in the carboxylation and electron transfer component can boost the reproductive biomass of filmless cotton in arid areas

AbstractDeep drip irrigation combined with high‐density planting is one of the most economical and effective ways to address residual film pollution. This study aimed to explore the photosynthetic potential of and achieve water‐saving and high‐yielding filmless cotton (Gossypium hirsutum L.) by optimizing the irrigation amount. We analyzed the effect of source leaf activity on leaf nitrogen allocation and photosynthetic nitrogen utilization efficiency (PNUE) under different irrigation amounts (mm, 375 (W5), 348 (W4), 320 (W3), 293 (W2), and 265 (W1)) in a 2‐year field experiment under this planting mode. The photosynthetic pigment content, leaf mass per area, and light compensation point all decreased with increasing amounts of irrigation, while the apparent quantum yield of photosynthesis, light saturation point, maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax), triose phosphate utilization rate (VTPU), nitrogen content in the electron transfer component (NB), and nitrogen content in the carboxylation component (NC) showed opposite trends. At the later full boll stage, the W3 and W4 treatments increased the leaf area of a whole plant (LA) by 10.4% and 19.4%, respectively, compared to that in the W1 treatment, while the PNUE increased by 20.2% and 20.8%, respectively, compared to that in the W5 treatment. In addition, principal component analysis found that the factor variables total nitrogen content in the photosynthetic apparatus (NT), net photosynthetic rate (Pn), stomatal conductance (Gs), light‐saturated net photosynthetic rate (Amax), NC, and Vcmax had higher loadings and were all positively correlated with PNUE; LA had a higher loading and was positively correlated with reproductive organ biomass. Therefore, we recommend using an irrigation rate of 320 mm in this cultivation system to increase nitrogen in carboxylation and electron transport components, enhance photosynthetic capacity, and thereby improve PNUE to increase reproductive organ biomass and reduce the irrigation amount in arid areas.

Roles for leakiness and O2 evolution in explaining lower-than-theoretical quantum yields of photosynthesis in the PEP-CK subtype of C4 plants.

Theoretically, the PEP-CK C4 subtype has a higher quantum yield of CO2 assimilation ( ) than NADP-ME or NAD-ME subtypes because ATP required for operating the CO2-concentrating mechanism is believed to mostly come from the mitochondrial electron transport chain (mETC). However, reported is not higher in PEP-CK than in the other subtypes. We hypothesise, more photorespiration, associated with higher leakiness and O2 evolution in bundle-sheath (BS) cells, cancels out energetic advantages in PEP-CK species. Nine species (two to four species per subtype) were evaluated by gas exchange, chlorophyll fluorescence, and two-photon microscopy to estimate the BS conductance (gbs) and leakiness using a biochemical model. Average gbs estimates were 2.9, 4.8, and 5.0 mmol m-2 s-1 bar-1, and leakiness values were 0.129, 0.179, and 0.180, in NADP-ME, NAD-ME, and PEP-CK species, respectively. The BS CO2 level was somewhat higher, O2 level was marginally lower, and thus, photorespiratory loss was slightly lower, in NADP-ME than in NAD-ME and PEP-CK species. Differences in these parameters existed among species within a subtype, and gbs was co-determined by biochemical decarboxylating sites and anatomical characteristics. Our hypothesis and results partially explain variations in observed , but suggest that PEP-CK species probably use less ATP from mETC than classically defined PEP-CK mechanisms.

Iron oxide nanoparticles improving multimetal phytoextraction in Helianthus annuus

This study assessed the phytotoxicity of a mixture of five different trace elements (TEs) frequently found as pollutants in soils: arsenic, cadmium, copper, lead and zinc. On the other hand, the plant response to a magnetite (Fe3O4) nanoparticle amendment on this mixture as well as nanomagnetite remediation potential has been tested. Sunflower (Helianthus annuus) plants were grown for 90 days in soil contaminated with the five mentioned TEs at the limit levels of TEs in soils likely to receive sludge established by French legislation. Depending on the conditions, experimental set-ups were amended or not with 1% dry weight nanomagnetite (NPsMagn), citric acid-coated nanomagnetite (NPsMagn@CA) or micro-sized magnetite (μPs) in order to assess the behavior of nanomagnetites in a TEs-contaminated water-soil-plant system under repeated water-deficiency stress. The mixture of TEs did not induce phytotoxicity as estimated by plant growth, pigment content, maximum quantum yield of photosynthesis, oxidative impact and antioxidant response. Furthermore, both nanomagnetites treatments in a TEs-contaminated soil significantly increased biomass production by 64 % compared to control and antioxidant enzyme activities compared to control and TEs-treated plants. NPsMagn and NPsMagn@CA particularly enhance phytoextraction of Cd and Cu, increasing the amounts of TEs in aerial parts from 1.5 to 4.5 times compared to set-ups without nanomagnetites. Based on Cd, Cu, Pb and Zn contents in soil solutions, both nanomagnetites treatments improved TEs phytoextraction without increasing groundwater contamination. On the contrary, nanomagnetites significantly reduce arsenic uptake by plants and solubilization in dissolved phase. Our results show that modifying surface physicochemical properties of NPsMagn with citric acid coating does not improve their effects compared to bare NPsMagn. NPsMagn and NPsMagn@CA also appear to mitigate the effects of drought stress. This work highlights several positive environmental aspects related to the use of nanomagnetites in phytoremediation.

Diurnal, Seasonal, and Vertical Changes in Photosynthetic Rates in Cinamomum camphora Forests in Subtropical China

The increase in the global atmospheric CO2 concentration is expected to increase the productivity of forests, but the dynamic processes of such increased productivity in the forest canopy remain unclear. In this study, diurnal and seasonal variations and vertical changes in photosynthetic rates were investigated in Camphor tree (Cinnamomum camphora) forests in subtropical China. The effect of photosynthetically active radiation (PAR) and CO2 concentrations on photosynthetic rates were also examined in the studied forests. Results showed the diurnal patterns of photosynthesis exhibited two peaks on sunny days, but only one peak on cloudy days. The daily average photosynthetic rate on cloudy days was approximately 74% of that on sunny days. The photosynthetic rate decreased along the vertical forest canopy profile. If the photosynthetic rate in the upper canopy layer was 100%, the corresponding rates were 83% and 25% in the middle and lower canopy layers, respectively. The rates of dark respiration derived from the PAR response curve were 1.73, 1.25, and 1.0 µmol m−2 s−1 for the upper, middle, and lower canopy layers, respectively. The apparent quantum yield of photosynthesis was 0.0183, 0.0186, and 0.0327 µmol CO2 µmol−1 PAR for the upper, middle, and lower canopy, respectively. The initial slope of the photosynthetic response curve to CO2 was highest in the upper canopy and lowest in the lower canopy. The seasonal variation in photosynthetic rates exhibited a two-peaked pattern at all canopy positions, with the two peaks occurring in June and September. The stand biomass and biomass carbon storage were 144.7 t ha−1 and 71.6 t C ha−1 in the examined forests, respectively. The study provides a scientific reference for future research on accessing carbon sequestration and designing forest management practices, specifically in regulating canopy structure in subtropical regions.

Physiological adaptation to irradiance in duckweeds is species and accession specific and depends on light habitat niche.

Duckweeds span 36 species of free-floating aquatic organisms with body sizes ranging from 2 mm to 10 mm, where each plant body plan is reduced to a largely leaf-like structure. As an emerging crop, their fast growth rates offer potential for cultivation in closed systems. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats, profiled for growth, photosynthesis, and photoprotection (non-photochemical quenching, NPQ) responses. Twenty-three accessions of three Lemna species and one Spirodela polyrhiza were grown under relatively low light (LL: 100 μmol m-2 s-1) and high light (HL: 350 μmol m-2 s-1) intensities. We observed broad within- and between-species level variation in photosynthesis acclimation. Duckweeds grown under HL exhibited a lower growth rate, biomass, chlorophyll, and quantum yield of photosynthesis. In HL compared with LL, carotenoid de-epoxidation state and NPQ were higher, whilst PSII efficiency (φPSII) and Chl a:b ratios were unchanged. The dLL plants showed relatively stronger acclimation to HL compared with dHL plants, especially Lemna japonica accessions. These achieved faster growth in HL with concurrent higher carotenoid levels and NPQ, and less degradation of chlorophyll. We conclude that these data support local adaptation to the light environment in duckweed affecting acclimation in controlled conditions.

Contrasting leaf-scale photosynthetic low-light response and its temperature dependency are key to differences in crop-scale radiation use efficiency.

Radiation use efficiency (RUE) is a key crop adaptation trait that quantifies the potential amount of aboveground biomass produced by the crop per unit of solar energy intercepted. But it is unclear why elite maize and grain sorghum hybrids differ in their RUE at the crop level. Here, we used a non-traditional top-down approach via canopy photosynthesis modelling to identify leaf-level photosynthetic traits that are key to differences in crop-level RUE. A novel photosynthetic response measurement was developed and coupled with use of a Bayesian model fitting procedure, incorporating a C4 leaf photosynthesis model, to infer cohesive sets of photosynthetic parameters by simultaneously fitting responses to CO2 , light, and temperature. Statistically significant differences between leaf photosynthetic parameters of elite maize and grain sorghum hybrids were found across a range of leaf temperatures, in particular for effects on the quantum yield of photosynthesis, but also for the maximum enzymatic activity of Rubisco and PEPc. Simulation of diurnal canopy photosynthesis predicted that the leaf-level photosynthetic low-light response and its temperature dependency are key drivers of the performance of crop-level RUE, generating testable hypotheses for further physiological analysis and bioengineering applications.

The effect of increasing the proportion of the far red region in full-spectrum LED irradiation on the growth and development of sugar beet plants (<i>Beta vulgaris</i> L. ssp. <i>vulgaris var. saccharifera</i> Alef.) in closed agrobiotechnological systems

Relevance and methodology. In order to determine the effect of increasing the proportion of far red light (different ratio of red and far red light) in the total spectrum of polychrome irradiation on the growth rates of sugar beet plants of the Smena hybrid, they were grown for 82 days under LED lighting under controlled climate conditions in a Synergotron digital device of the ISR 2.01 model with a twofold increase in the proportion of far red light compared to control.Results. An increase in the proportion of far red light led to an increase in the specific weight of leaves with a smaller area of leaves in the initial period of plant growth, higher values of the quantum yield of photosynthesis, the rate of electron transport, and a decrease in energy losses mainly to heat. The biometric indicators of plants changed depending on the period of ontogeny. In the initial period, the biomass of the aerial part prevailed, in the subsequent period, the biomass of root crops. In the experimental variant, the accumulation of biomass in the aerial parts of plants in the initial period of the experiment turned out to be less than in the control, and only at the end of the experiment was an excess of the total biomass in the experimental variant by 12.2%. There was an increase in the accumulation of root biomass compared to the control by 38.7%. The predominant part of the aboveground biomass of sugar beet was made up of leaf blades, the proportion of petioles was much less and practically did not depend on the composition of the light. At the end of the growing period, the dry matter content in root crops increased by 2.44% compared to the control, sugar content – by 0.65%. The data obtained can be used in the development of technology for artificial lighting of sugar beets when grown in closed agrobiotechnosystems in order to increase the yield and sugar content of root crops.

РЕАКЦИЯ СОРТА CENTENNIAL SEEDLESS НА НАГРУЗКУ КУСТОВ ПОБЕГАМИ И ГРОЗДЯМИ В УСЛОВИЯХ ЦЕНТРАЛЬНОЙ АГРОЭКОЛОГИЧЕСКОЙ ЗОНЫ ВИ-НОГРАДАРСТВА ПО ФИЗИОЛОГИЧЕСКИМ КРИТЕРИЯМ

The article considers the issue of the influence of the different loads of bushes with shoots and bunches on the physiological state of the leaves of Centennial Seedless grape variety in the agroecological conditions of the Central viticul-ture zone of the Krasnodar region. The Centen-nial Seedless variety is cultivated in a covering and grafted culture on a SO4 rootstock, drip irrigation. Climate is moderately continental, the soils are low-humus, leached powerful cherno-zems. The assessment of the physiological state of Centennial Seedless grape plants was carried out according to the variants of differentiated load by shoots and bunches (high, medium and low) according to the following parameters: quantum yield of photosynthesis, chlorophyll a and b content, carotenoids, relative water con-tent in leaves, water content in leaves and elec-trolyte leakage. In the studied summer months, the average air temperature was +24.3 °C, which is 0.4 °C above the climatic norm, the maximum temperatures rose to +35 °C. The total precipita-tion was 132 mm higher than normal due to heavy rains in some decades. The physiological and biochemical parameters of the leaves of the Centennial Seedless grape variety during the summer period were within the normal range – the quantum yield was above 0.7, the relative water content in the leaves was above 85 %, the water content was above 70 % except in Au-gust, the amount of chlorophylls a and b was above 1 except for the variant with the average load in July, the electrolyte leakage varied from 7.3 % to 17.3 %. In August, during the period of the greatest temperature stress for the leaves, the variant with a high load of bushes with shoots and bunches proved to be the best.

Effects of maize and peanut co-ridge intercropping on crop photosynthetic characteristics and intercropping advantages

To clarify the photosynthetic mechanism contributing to the enhancement of intercropping advantages through co-ridge intercropping of maize and peanut, we conducted a field randomized block experiment under two phosphorus levels of 0(P0) and 180 kg P2O5·hm-2(P180) with flat intercropping of maize and peanut (FIC) as the control. We analyzed the effects of co-ridge intercropping of maize and peanut (RIC) and groove-ridge intercropping of maize and peanut (GIC) on crop leaf area index (LAI), SPAD values, CO2 carboxylation ability, photosystems coordination (ΦPSⅠ/PSⅡ), and intercropping advantage of yield. The results showed that RIC significantly increased SPAD value at the silking stage of intercropping maize, and significantly improved the apparent quantum yield of photosynthesis (AQY), maximum electron transfer rate (Jmax), maximum rate of Rubisco carboxylation (Vc,max), net photosynthetic rate at the CO2 saturation (Amax) and ΦPSⅠ/PSⅡ of intercropping maize compared with those of FIC and GIC at silking stage and milking stage, but reduced the ratio of variable fluorescence Fk to amplitude Fj-Fo(Wk) and the ratio of variable fluorescence Fj to amplitude Fp-Fo(Vj) of the functional leaf photosystem Ⅱ (PSⅡ) at the milking stage of maize. There were no significant differences in these parameters between FIC and GIC. Compared with FIC, both RIC and GIC increased LAI of intercropping peanut at late growth stage and SPAD value at pod setting stage, significantly improved Vc,max, Amax, and ΦPSⅠ/PSⅡ, and reduced Wk and Vj values of intercropping peanut functional leaves at pod expanding stage. The difference in these parameters between RIC and GIC were not significant. The land equivalent ratio and intercropping advantages of RIC were higher than those of FIC and GIC. Phosphorus application could further promote Vc,max, Jmax, Amax and ΦPSⅠ/PSⅡ of intercropping maize and peanut, and significantly improve yield advantages of intercropping. The findings indicated that co-ridge intercropping could enhance CO2 carboxylation and fixation by improving photosynthetic electron transport and pho-tosystems coordination, improve the photosynthetic rate of functional leaves of maize and peanut, thus increase crop yield and intercropping advantages.

Influence of photons of the near-ultraviolet radiation on the growth and development of sugar beet (<i>Beta vulgaris</i> L. ssp. <i>vulgaris var. saccharifera</i> Alef.) in a closed agrobiotechnosystem

Relevance and methodology. In order to determine the effect of near-ultraviolet radiation with a wavelength of 380 nm on the growth and development of a sugar beet hybrid plant, Smena was grown for 82 days under LED lighting with phytolamps and under conditions of increased UV-A intensity of the light range (an increase in the UV/PPFD ratio (0.027) compared with the control (0.0075) while maintaining the ratio of the remaining sites spectrum). The study was carried out on the basis of the digital software package "Synergotron" with a controlled internal environment.Results. An increase in the share of UV-A in the illumination spectrum leads to a significant change in the biometric indicators of plants – the aboveground biomass increases by 2.2 times compared to the control, and the mass of the underground part (root crops), on the contrary, decreases by 86.9%. At the same time, the share of root crops in the total biomass of plants decreases from 60% in the control to 30%. The morphological structure of the leaf apparatus changes: the proportion of petioles increases significantly compared to leaf blades (64.8% of petioles in aboveground biomass, whereas in the control 30%). Probably, an increase in the share of UV-A in the spectrum can favorably affect the cultivation of leaf forms of beets and other root crops. UV-A radiation leads to a change in the chemical composition of root crops, in particular, a decrease in the accumulation of dry substances (by 1.58%) and a decrease in sugar content (by 1.8%). An increase in the proportion of UV-A in the irradiation spectrum changes the parameters of chlorophyll fluorescence and contributes to an increase in the maximum quantum yield of Fv/Fm, non-photosynthetic quenching of NPQ fluorescence and a decrease in the real quantum yield of photosynthesis Y(II), as well as the electron transport rate (ETR).

Interrelations between Canopy Architecture and Growth Yield Attribute on Selected Growth Habit Peanut Genotypes

Background: Crop architecture plays a major role in the growth and development of semi determinate crops like peanut.The orientation of branches and leaves in the plant canopy plays a major role in the radiation penetration, which influences the canopy photosynthetic rate and hence the crop productivity. Light penetration and radiation use efficiency effect the drymatter production of many crops. However, links between canopy orientation, growth attributes and yield potentiality of peanut are poorly understood. Hence the aim of the present study was to determine interrelationships among various growth habit peanut genotypes for canopy architecture, canopy photosynthesis, growth parameters and yield attributes. Methods: The experiment was laid out in a randomized block design with ten treatments and replicated thrice. Ten spanish bunch peanut genotypes varying in growth habits viz., decumbent-2, decumbent-3 and erect growth habit.Five plants were selected randomly in each plot by avoiding border rows and recorded canopy traits. Canopy photosynthetic parameters viz., light interception (Lux meter) and photosynthetic rate (IRGA) were recorded at the grand growth period (45 and 60 DAS). Result: Plant height had a significant negative correlation with peg to pod ratio. Among the various canopy architecture traits, wider angle between primary branch and main stem and number of secondary branches per plant established significantly positive correlation with rate of photosynthesis, radiation use efficiency, growth attributes, pod yield, shelling percentage and test weight. Spreading architecture exhibit a higher maximum quantum yield of photosynthesis.

Using an optimised neural architecture search for predicting the quantum yield of photosynthesis of winter wheat

The quantum yield (QY) values of crops are important for assessing photosynthetic efficiency. Our hypothesis is that high-throughput prediction models of QY values can be established based on vegetation indices (VIs). The objectives of this research were to predict QY values based on VIs with high correlations and to compare the performances of classical machine learning with that of B-NAS methods. Compared with support vector regression (SVR) and other traditional prediction methods, in this study, a novel prediction model based on an optimised neural architecture search (B-NAS) was proposed, and achieved comparatively better results. In addition, an improved architecture was obtained and compared for ten different search architectures on the experimental dataset. The experimental results showed that the neural network model constructed based on the B-NAS method predicted QY values outperformed the models obtained using SVR and Adaboost methods in terms of all considered performance metrics (R2, RMSE, RPD, Bias). Meanwhile, the proposed model meets the criteria for a class A model. The final B-NAS model was tested on an independent validation set, obtaining similar performance metrics and an accuracy of 92% for post-prediction classification into three equal interval QY classes. An analysis of the neural architecture obtained by B-NAS showed that a four-layer network architecture had certain advantages. As well, the importance of the preprocessing and dropout layers is discussed.

Photosynthesis in rice is increased by CRISPR/Cas9-mediated transformation of two truncated light-harvesting antenna.

Plants compete for light partly by over-producing chlorophyll in leaves. The resulting high light absorption is an effective strategy for out competing neighbors in mixed communities, but it prevents light transmission to lower leaves and limits photosynthesis in dense agricultural canopies. We used a CRISPR/Cas9-mediated approach to engineer rice plants with truncated light-harvesting antenna (TLA) via knockout mutations to individual antenna assembly component genes CpSRP43, CpSRP54a, and its paralog, CpSRP54b. We compared the photosynthetic contributions of these components in rice by studying the growth rates of whole plants, quantum yield of photosynthesis, chlorophyll density and distribution, and phenotypic abnormalities. Additionally, we investigated a Poales-specific duplication of CpSRP54. The Poales are an important family that includes staple crops such as rice, wheat, corn, millet, and sorghum. Mutations in any of these three genes involved in antenna assembly decreased chlorophyll content and light absorption and increased photosynthesis per photon absorbed (quantum yield). These results have significant implications for the improvement of high leaf-area-index crop monocultures.

Effective Microorganisms and Olive Mill Wastewater Used as Biostimulants to Improve the Performance of Tanacetum balsamita L., a Medicinal Plant

The use of biostimulants and/or biofertilizers has acquired considerable importance and can contribute to the sustainable management agriculture, reducing the use of chemical fertilizers, pesticides, and water. This study aims to assess the effects of Effective Microorganisms (EM) and Olive Mill Wastewater (OMW) on the growth, photosynthetic performance and polyphenols content of the medicinal plant Tanacetum balsamita. The EM and OMW were used at two dilution rates. The EM was added to 5% v/v and 10% v/v, while OMW was added to 2.5% v/v and 5% v/v in plants at the early growth stage. After 75 days of treatment, all the treated plants had a leaf number and leaf area almost 2-fold higher than in the Control plants. Moreover, the treatments, at all the concentrations applied had a positive effect on the photosynthetic activity, with an improvement both in terms of the quantum yield of photosynthesis and electrons transport efficiency. The best photosynthetic and growth performances in the treated plants coincided with the higher production of phenolic compounds; indeed, after 75 days, the content of chlorogenic acid, caffeic acid, and isochlorogenic acid was even 2-fold of the Control plants. Also, rutin content was 1.28–1.50-fold respect to the Control extracts. The highest phenolic compound content was reflected by the highest antiradical activity, found in the extracts of the treated plants. The effectiveness of EM to increase the growth and quality of plants and in particular, the potential use of OMW on the cultivated crop was confirmed to this study.

Changes in the photosynthetic performance, the activity of enzymes of nitrogen metabolism, and proline content in the leaves of wheat plants after exposure to low CO<sub>2</sub> concentration

The changes in photosynthetic activity, as well as the activity of nitrogen-metabolism enzymes, the intensity of lipid peroxidation, and proline content were studied in <i>Triticum aestivum</i> L. plants after their incubation at a low CO₂ concentration in a sealed chamber for 10 d. CO₂ deficiency (-CO₂) compared to normal CO₂ concentration (control) led to a decrease in the rate of O₂ gas exchange at the plateau of the light curve and quantum yield of photosynthesis. The maximum and effective quantum photochemical yields also decreased. CO₂ deficiency reduced the activity of nitrate reductase, but increased the activities of nitrite reductase, glutamine synthetase, and glutamate dehydrogenase, and promoted proline accumulation. It is assumed that with a lack of CO₂, an excess of nitrogen-containing compounds occurs, which must be removed from metabolic processes. Also, we suggest the partial storage of nitrogen in the form of nitrogen-containing compounds such as proline.

Leaf pigments and photosystems stoichiometry underpin photosynthetic efficiency of related C3 , C-C4 and C4 grasses under shade.

The quantum yield of photosynthesis (QY, CO2 fixed per light absorbed) depends on the efficiency of light absorption, the coupling between light absorption and electron transport, and the coupling between electron transport and carbon metabolism. QY is generally lower in C3 relative to C4 plants at warm temperatures and differs among the C4 subtypes. We investigated the acclimation to shade of light absorption and electron transport in six representative grasses with C3 , C3 -C4 and C4 photosynthesis. Plants were grown under full (control) or 25% (shade) sunlight. We measured the in vivo activity and stoichiometry of PSI and PSII, leaf spectral properties and pigment contents, and photosynthetic enzyme activities. Under control growth-light conditions, C4 species had higher CO2 assimilation rates, which declined to a greater extent relative to the C3 species. Whole leaf PSII/PSI ratios were highest in the C3 species, while QY and cyclic electron flow (CEF) were highest in the C4 , NADP-ME species. Shade significantly reduced leaf PSII/PSI, linear electron flow (LEF) and CEF of most species. Overall, shade reduced leaf absorptance, especially in the green region, as well as carotenoid and chlorophyll contents in C4 more than non-C4 species. The NAD-ME species underwent the greatest reduction in leaf absorptance and pigments under shade. In conclusion, shade compromised QY the least in the C3 and the most in the C4 -NAD-ME species. Different sensitivity to shade was associated with the ability to maintain leaf absorptance and pigments. This is important for maximising light absorption and minimising photoprotection under low light.