Circadian rhythm response and its effect on photosynthetic characteristics of the Lhcb family genes in tea plant.

BACKGROUND: The circadian clock, also known as the circadian rhythm, is responsible for predicting daily and seasonal changes in the environment, and adjusting various physiological and developmental processes to the appropriate times during plant growth and development. The circadian clock controls the expression of the Lhcb gene, which encodes the chlorophyll a/b binding protein. However, the roles of the Lhcb gene in tea plant remain unclear. RESULTS: In this study, a total of 16 CsLhcb genes were identified based on the tea plant genome, which were distributed on 8 chromosomes of the tea plant. The promoter regions of CsLhcb genes have a variety of cis-acting elements including hormonal, abiotic stress responses and light response elements. The CsLhcb family genes are involved in the light response process in tea plant. The photosynthetic parameter of tea leaves showed rhythmic changes during the two photoperiod periods (48 h). Stomata are basically open during the day and closed at night. Real-time quantitative PCR results showed that most of the CsLhcb family genes were highly expressed during the day, but were less expressed at night. CONCLUSIONS: Results indicated that CsLhcb genes were involved in the circadian clock process of tea plant, it also provided potential references for further understanding of the function of CsLhcb gene family in tea plant.

Heterologous expression of ACC deaminase gene in Pelargonium graveolens showed elevated tolerance to chromium stress.

An essential aromatic plant, Pelargonium graveolens, does not grow well in areas where chromium contamination is a problem. Because of oxidative stress and the collapse of the photosynthetic system, crops frequently sustain severe damage. The production of excess ethylene, known as stress ethylene, which is detrimental to plant growth, the formation of roots, and early senescence, is also increased by heavy metal exposure. The effectiveness of the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene in transgenic Pelargonium graveolens under the control of CaMV 35S promoter was investigated to lessen the stress ethylene during chromium stress. Chromium was administered as potassium dichromate (K2Cr2O7) at four distinct concentrations (100 µM, 200 µM, 300 µM, and 500 µM) to transgenic and wild-type P. graveolens and stress-induced physiological changes were monitored. Transgenic P. graveolens demonstrated greater tolerance to chromium stress than wild-type P. graveolens, as evidenced by higher leaf-relative water content, chlorophyll content, CO2 absorption, transpiration rate, stomatal conductance, proline buildup, and antioxidant activity. The L1, L5, and L7, ACC deaminase-expressing transgenic lines also show a drop in ACC content during chromium stress, which subsequently lowered ethylene synthesis. Therefore, the reported transgenic P. graveolens lines having the ACC deaminase gene could be useful resources for growing in chromium-prone regions.

Biochar and saline soil: mitigation strategy by incapacitating the ecological threats to agricultural land.

Soil salinity caused a widespread detrimental issue that hinders productivity in agriculture and ecological sustainability, while waste-derived soil amendments like biochar have drawn attention for their capacity to act as a mitigating agent, by enhancing the physical and chemical features of soil, and contributing to the recovery of agricultural waste resources. However, the information concerning biochar and salinity which affect the physicochemical characteristics of soils, crop physiology, and growth is limited. To investigate whether biochar mitigates the salinity stress on wheat crop seedlings, we grow them with salinity stress (120 mM), and biochar (20 tons ha-1), and its interactive effects. The soil properties of soil organic carbon (SOC), soil organic matter (SOM), dissolved organic carbon (DOC), and soil available phosphorus (SAP) decreased in the saline soil by 36.71%, 46.97%, 26.31%, and 15.00%, while biochar treatment increased SOC, DOC, and SAP contents by 7.42%, 31.57%, and 15.00%, respectively. On the other hand, dissolved organic nitrogen (DON) contents decreased in all the treatments compared to the control. The root growth traits, SPAD values, leaf nitrogen, photosynthetic parameters, antioxidant enzymes, and reactive oxygen species decreased in the saline treatment while increasing in the biochar and interactive treatment. Thus, these activities resulted in higher leaves and root biomass in the biochar treatment alone and interactive treatment of salinity and biochar. According to principal component analysis, redundancy analysis, and the mantel test, using biochar in conjunction with salinity treatment was found to be more effective than salinity treatment alone. The results of this study suggest that biochar can be used as a sustainable agricultural technique and a means of mitigation agent by lowering soil salinity while increasing the biomass of crops.

Biochar improves the physical and nutritional quality of soil and plant function.Salinity stress declined the physiological activities and biomass of the crop.Biochar mitigates the salinity stress in soil and enhances the plant functioning.Exposure to both treatments enhances the antioxidant enzyme activity and biomass.

Effects of foliar spraying different sizes of zinc fertilizer on the growth and cadmium accumulation in rice.

BACKGROUND: Nanotechnology has been widely applied in agricultural science. During the process of reducing metal toxicity and accumulation in rice, nanomaterials exhibit size effects. However, there is limited knowledge regarding these size effects. We aim to explore the impact of fertilizer with various sizes of ZnO nanoparticles (ZnO-NPs) on rice growth and cadmium (Cd) accumulation and to elucidate the potential mechanism of Cd reduction in rice. Foliar applications of different concentrations (0.5 and 2 mmol L-1) and different sizes (30 and 300 nm ZnO-NPs) of zinc (Zn) fertilizer (Zn(NO3)2) were performed to investigate the effects on rice growth, Cd accumulation and subcellular distribution, and the expression of Zn-Cd transport genes. RESULTS: The results suggested that all the foliar sprayings can significantly reduce the Cd concentrations in rice grains by 41-61% with the highest reduction in the application of ZnO-NPs with large size and low concentration. This is related to the enhancement of Cd fixation in leaf cell walls and downregulation of Cd transport genes (OsZIP7, OsHMA2, OsHMA3) in stem nodes. Foliar ZnO-NPs applications can increase the Zn concentration in grains by 9-21%. Foliar applications of Zn(NO3)2 and small-sized ZnO-NPs promoted plant growth and rice yield, while the application of large-sized ZnO-NPs significantly reduced rice growth and yield. CONCLUSION: The study suggests that the rice yield and Cd reduction are dependent on the size and concentration of foliar spraying and the use of large-sized ZnO-NPs is the most effective strategy when considering both yield and Cd reduction comprehensively. © 2024 Society of Chemical Industry.

Physiological responses of coriander (Coriandrum sativum L.) to exogenous 2,4-epibrassinolide at different concentrations.

BACKGROUND: Brassinolide, known as the seventh plant hormone, can improve the photosynthetic capacity of plants, promote plant growth and development, promote the formation of horticultural crop yield, improve the quality of horticultural crops, and also improve the ability of plants to resist biological and abiotic stresses. RESULTS: The effects of different concentrations of exogenously sprayed 2,4-epibrassinolide (EBR) on growth, physiological and photosynthetic characteristics of 'All-round large leaf coriander' were studied in substrate culture. The results showed that 0.05, 0.1, and 0.5 mg.L- 1 EBR promoted the growth of coriander and increased the aboveground fresh and dry weights, with 0.5 mg.L- 1 EBR having the most significant effect. Spraying 0.1 mg.L- 1 EBR increased the content of soluble sugars and protein of coriander leaves. Spraying 0.1 and 0.5 mg.L- 1 EBR significantly increased the chlorophyll content and photosynthetic parameters of coriander leaves, and 0.5 mg.L- 1 EBR also significantly increased the chlorophyll fluorescence parameters of coriander leaves. Spraying 0.5 mg.L- 1 EBR upregulated the expression of CsRbcS, CsFBPase, and CsAld. Correlation analysis showed that aboveground fresh weight under exogenous EBR treatment was significantly positively correlated with aboveground dry weight, plant height, Pn, Gs, Ci, and CsAld (P < 0.05), and soluble sugar content was significantly positively correlated with the number of leaves, Y(II), qP, and CsRbcS. The results of the principal component analysis (PCA) showed that there was a significant separation between the treatment and the control groups. Spraying 0.5 mg.L- 1 EBR can promote the growth of coriander, improve the quality of coriander leaves, and strengthen coriander leaf photosynthetic capacity. This study provides new insights into the promotion of coriander growth and development following the application of exogenous EBR. CONCLUSION: Exogenous EBR treatment increased coriander plant height, leaf growth and aboveground dry weight, and enhanced photosynthesis. Exogenous spraying of 0.5 mg.L- 1 EBR had the most significant effect.

Photosynthetic performance under adaxial and abaxial illumination in three Mediterranean Quercus species differing in branch architecture and individual leaf area.

Light availability effects on canopy-level carbon balance constitute an especially difficult issue to address, owing to the strong spatial and temporal changes of the light environment within the canopy. One of the least explored aspects in relation to light environment is the interaction between leaf angle and leaf anatomy. The inclination of the leaf may affect the distribution of light between the adaxial and abaxial surface. The purpose of this study is determining the proportions of the leaf area receiving light from the abaxial side in branches of isolated trees in three Mediterranean oaks, as well as the photosynthetic responses to light under adaxial and abaxial illumination. The proportions of the leaf area illuminated from below were low for sun incidence angles near 0° with respect to the main axis of the branch. However, for sun incidence angles about 45°, the proportion of leaves receiving abaxial illumination was considerable. PPFD levels on the sunlit part of the abaxial surface were always lower than those in the upper leaf side, as a consequence of the lower projection efficiency for the leaves facing the sun by the lower side. Light absorptance was also lower on the abaxial side. The differences between both sides of the leaf tended to be stronger for thicker, longer-living leaves. We conclude that mean C assimilation of the canopy is significantly decreased by the presence of leaves facing the sun by the lower side and that this decrease is stronger in evergreen species with thicker leaves.

Effect of enhanced UV-B radiation on growth and photosynthetic physiology of Iris tectorum maxim.

Iris tectorum Maxim. is an important plant that plays a very crucial role in the ecological welfare of wetlands. In this study, the effects of different intensities of UV-B radiation on the growth, photosynthetic pigment content, chlorophyll fluorescence characteristics, chloroplast ultrastructure, and gas exchange parameters of Iris tectorum Maxim. were studied. The results showed that enhanced UV-B radiation had a significant influence on the above-mentioned parameters of iris. Compared with the control, enhanced UV-B radiation caused certain damage to the leaf appearance. With the increasing intensity of radiation, the apparent damage degree became more serious. Enhanced UV-B radiation significantly decreased leaf chlorophyll contents, and the effect accumulated with the exposure time. Enhanced UV-B radiation increased Fo, significantly increased the non-photochemical quenching coefficient NPQ, reduced PSII and Qp, and significantly decreased the Fm, Fv/Fm, and Fv/Fo in leaves. The effect of UV-B radiation on PSII destruction of Iris tectorum Maxim. increased as the radiation intensity increased and the exposure time prolonged. The chloroplast structure was damaged under the enhanced UV-B radiation. More specifically, thylakoid lamellae were distorted, swelling and even blurred, and a large number of starch granules appeared. The effect of the high intensity of radiation on chloroplast ultrastructure was greater than that of lower intensity. Enhanced UV-B radiation reduced significantly the net photosynthetic rate, stomatal conductance, and transpiration rate, and the degree of degradation increased with the increasing irradiation intensity. However, the intercellular CO2 content increased, which suggests that the main reason for the decrease of photosynthetic rate was the non-stomatal factors.

Photosynthesis and pigment production: elucidation of the interactive effects of nutrients and light on Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii produces a variety of compounds that can be beneficial to human and animal health. Among these compounds, application of photosynthetic pigments, such as chlorophylls and carotenoids, has gained considerable interest in numerous industries. A better understanding on the interactive effects of essential nutrients and light on microalgal physiology and pigment production would be beneficial in improving cultivation strategies. Therefore, this study evaluated biomass, carotenoid and chlorophyll yield and the following fluorescence parameters: quantum yield in PS II [Y(II)] and electron transport rate (ETR) using response surface methodology (RSM). The Fv/Fm, Y(NO) and Y(NPQ) were also monitored; however, no significant relationship was observed. From the investigation it was apparent that nitrogen and carbon; as well as the interactive effects of (nitrogen and carbon) and (carbon and light irradiance) were significant factors. The model predicted the optimum conditions for maximum carotenoids (8.15 ± 0.389 mg g-1) were 08.7 mol l-1 of nitrogen, 0.2 mol l-1 and 50 µmol photon m-2 s-1 of light irradiance. While maximum chlorophyll (33.6 ± 0.854 mg g-1) required a higher nitrogen (11.21 mol l-1). The photosynthetic parameters [Y(II), ETR] was correlated with the primary pigments and biomass production. Increased photosynthetic activity was associated with high carbon and light. The Y(II)and ETR of PSII under these conditions were 0.2 and ~ 14, respectively. This approach was accurate in developing the model, optimizing factors and analysing interaction effects. This study served to provide a better understanding on the interactions between factors influencing pigment biosynthesis and photosynthetic performance of Chlamydomonas reinhardtii.

Using multiple endpoints to assess the toxicity of cadmium and cobalt for chlorophycean Raphidocelis subcapitata.

Metals may cause damage to the biota of contaminated environments. Moreover, using multiple endpoints in ecotoxicological studies is useful to better elucidate the mechanisms of toxicity of these compounds. Therefore, this study aimed to evaluate the effects of cadmium (Cd) and cobalt (Co) on growth, biochemical and photosynthetic parameters of the microalgae Raphidocelis subcapitata, through quantification of lipid classes composition, chlorophyll a (Chl a) content, maximum (ΦM) and effective (Φ'M) quantum yields and efficiency of the oxygen-evolving complex (OEC). Both metals affected the algal population growth, with an IC50-96h of 0.67 and 1.53 µM of Cd and Co, respectively. Moreover, the metals led to an increase in the total lipid content and reduced efficiency of OEC and ΦM. Cell density was the most sensitive endpoint to detect Cd toxicity after 96 h of treatment. Regarding Co, the photosynthetic parameters were the most affected and the total lipid content was the most sensitive endpoint as it was altered by the exposure to this metal in all concentrations. Cd led to increased contents of the lipid class wax esters (0.89 µM) and phospholipids (PL - at 0.89 and 1.11 µM) and decreased values of triglycerides (at 0.22 µM) and acetone-mobile polar lipids (AMPL - at 0.44 and 1.11 µM). The percentage of free fatty acids (FFA) and PL of microalgae exposed to Co increased, whereas AMPL decreased in all concentrations tested. We were able to detect differences between the toxicity mechanisms of each metal, especially how Co interferes in the microalgae at a biochemical level. Furthermore, to the best of our knowledge, this is the first study reporting Co effects in lipid classes of a freshwater Chlorophyceae. The damage caused by Cd and Co may reach higher trophic levels, causing potential damage to the aquatic communities as microalgae are primary producers and the base of the food chain.

Biomass and pigment production for Arthrospira platensis via semi-continuous cultivation in photobioreactors: Temperature effects.

This study describes the response of Arthrospira platensis to a variety of temperature conditions as reflected in variations of photosynthetic parameters, pigmentation, and biomass productivity in indoor photobioreactor (PBR) cultivations. These experiments are designed to better understand the impact of temperature, seasonal variations, and acclimation effects on outdoor biomass production. The irradiance level and temperature range (20-39°C) are chosen to enable modeling of semi-continuous operation of large-scale outdoor PBR deployments. Overall, the cultivations are quite stable with some pigment-related instabilities after prolonged high-temperature exposure. Changes in productivity with temperature, as reflected in measured photosynthetic parameters, are immediate and mainly attributable to the temperature dependence of the photosaturation parameter, a secondary factor being variation in pigment content on a longer time scale corresponding to turnover of the culture population. Though pigment changes are not accompanied by significant changes in productivity, prolonged exposure at 35°C and above yields a clear degradation in performance. Productivities in a semi-continuous operation are quantitatively reproduced with a productivity model incorporating photosynthetic parameters measured herein. This study confirms the importance of temperature for biomass and pigment production in Arthrospira cultivations and provides a basis for risk assessments related to temperature mitigation for large-scale outdoor cultivations.

Foliar application of selenium and zinc to alleviate wheat (Triticum aestivum L.) cadmium toxicity and uptake from cadmium-contaminated soil.

Due to the large area of agricultural soils contaminated by Cd worldwide, cost-effective and practical method for safety food production are necessary. The roles of micronutrient on reducing Cd accumulation in crops are recently introduced. In the current study, a pot-culture experiment in the greenhouse was conducted to study the foliar spraying of Se (Na2SeO4) and Zn (ZnSO4) on physiological and growth parameters, as well as Cd concentrations in wheat plants grown in Cd-contaminated soil. The foliar was sprayed with four concentration of Se and Zn (0, 10, 20, and 40 mg L-1) at different growth stage (tillering, elongating and heading) and whole wheat plants were collected after maturity. Both foliar spraying with Se and Zn significantly enhanced the photosynthesis, tissue biomass and antioxidant enzyme activity. Additionally, Se and Zn application can also increase Se and Zn concentrations in different plant tissues. Selenium and Zn decreased malondialdehyde (MDA) and Cd concentrations in wheat grains, hulks, leaves, stalks and root in a dose-additive manner. Overall, Se and Zn both efficiently enhanced the wheat growth and Se and Zn concentrations, and simultaneously decreased the Cd concentration in wheat plant. Compared with Zn, Se more efficiently improved wheat growth and reduced Cd concentration in the wheat in a Cd-contaminated soil. Present results suggest that use of foliar spraying, especially Se, could be a cost-effective strategy and could be recommended for remediation of light-or moderate-polluted soils contaminated by Cd.

Zinc effects on cadmium toxicity in two wheat varieties (Triticum aestivum L.) differing in grain cadmium accumulation.

Presence of cadmium (Cd) in food poses serious risks to human health. Understanding the effects of zinc (Zn) on Cd absorption by crops could help provide a theoretical basis for the treatment with Zn on contaminated soils. In this study, two wheat varieties, differing in grain-Cd accumulation ability (L979, a Cd low-accumulation variety, and H27, a high-accumulation variety) were selected to investigate the effect of Zn addition on Cd toxicity. Cd was applied to nutrient solutions at 0 and 10 µM, and added Zn were 0, 50 and 100 µM. Zn supplements alleviated decreases in biomass induced by Cd toxicity for both varieties, and both varieties had different reduced concentrations of Cd in their shoots. Application of 50 µM Zn to H27 resulted in a 17% decrease in Cd concentrations. When treated with 100 µM Zn, only L979 showed a reduction in Cd concentration. The higher proportion of Cd in the soluble fraction was found in L979. In addition, ion-selective scanning at the root-surface indicated that Zn supplements reduced net root Cd2+ flux by 55% for L979, and 69% for H27. These mitigating effects of Zn in both varieties involved mechanisms related to photosynthesis, root growth, and antioxidant production. Additionally, both Zn available in the medium and absorbed in plant tissue causes antagonistic effects on Cd absorption for wheat. It seemed that vacuolar compartmentation could contribute Cd detoxification especially for low accumulation variety.

Selenium Improves Physiological Parameters and Alleviates Oxidative Stress in Strawberry Seedlings under Low-Temperature Stress.

Here, we investigated the effects of selenium (Se) applications on two strawberry varieties, Akihime and Benihoppe, under chilling stress and recovery conditions. Changes in photosynthetic parameters, antioxidant enzyme activities, ascorbate (AsA)-glutathione (GSH) cycle-related enzyme activities, and low-molecular-mass antioxidant contents were determined. Foliar spraying with Se alleviated the decline in the net photosynthetic rate and chlorophyll content and increased the malondialdehyde and hydrogen peroxide contents of strawberry seedlings’ leaves under chilling stress. As the time under chilling stress increased, the stomatal conductance decreased and intercellular CO2 concentration increased, suggesting that nonstomatal factors had major limiting effects on the net photosynthetic rate's decrease. Se applications significantly alleviated the adverse impacts of chilling stress on changes in stomatal conductance and intercellular CO2 concentration. Se, especially at lower concentrations, significantly increased superoxide dismutase, catalase, and peroxide enzyme activities during chilling stress. Approximately 5 mg·L−1 of sodium selenite solution had the greatest stress-alleviating effects. Among the AsA-GSH cycle-related enzymes, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase (MDHAR) treatments, coupled with an appropriate dose of Se, significantly enhanced ascorbate peroxidase and MDHAR activities, which suggested that Se applications played important roles in strawberry leaves by affecting AsA-GSH cycle-related defenses against the oxidative damage caused by chilling stress. Furthermore, MDHAR was the key enzyme required to maintain the balance between AsA consumption and regeneration that may assist in protecting strawberry seedlings in a low-temperature environment.

Comparative Proteomic Analysis during the Involvement of Nitric Oxide in Hydrogen Gas-Improved Postharvest Freshness in Cut Lilies.

Our previous studies suggested that both hydrogen gas (H2) and nitric oxide (NO) could enhance the postharvest freshness of cut flowers. However, the crosstalk of H2 and NO during that process is unknown. Here, cut lilies (Lilium "Manissa") were used to investigate the relationship between H2 and NO and to identify differentially accumulated proteins during postharvest freshness. The results revealed that 1% hydrogen-rich water (HRW) and 150 µM sodium nitroprusside (SNP) significantly extended the vase life and quality, while NO inhibitors suppressed the positive effects of HRW. Proteomics analysis found 50 differentially accumulated proteins in lilies leaves which were classified into seven functional categories. Among them, ATP synthase CF1 alpha subunit (chloroplast) (AtpA) was up-regulated by HRW and down-regulated by NO inhibitor. The expression level of LlatpA gene was consistent with the result of proteomics analysis. The positive effect of HRW and SNP on ATP synthase activity was inhibited by NO inhibitor. Meanwhile, the physiological-level analysis of chlorophyll fluorescence and photosynthetic parameters also agreed with the expression of AtpA regulated by HRW and SNP. Altogether, our results suggested that NO might be involved in H2-improved freshness of cut lilies, and AtpA protein may play important roles during that process.

Local plant responses to global problems: Dactylis glomerata responses to different traffic pollutants on roadsides.

The growing number of road vehicles is a major source of regional and global atmospheric pollution increasing concentrations of CO2 in the air, and levels of metals in air and soil. Nevertheless, the effects of these pollutants on plants growing at roadsides are poorly documented. We carried out an observational study of unmanipulated plants growing by the road, to identify the morpho-physiological responses in a perennial grass Dactylis glomerata. Firstly, we wanted to know the general effect of traffic intensity and ambient CO2 and its interactions on different plant traits. Accordingly, we analyzed the photosynthetic response by field A/Ci Response Curves, SLA, pigment pools, foliar nitrogen, carbohydrates and morphological traits in plants at three distances to the road. Secondly, we wanted to know if Dactylis glomerata plants can accumulate metals present on the roadside (Pb, Zn, Cu, and Sr) in their tissues and rhizosphere, and the effect of these metals on morphological traits. The MANCOVA whole model results shown: 1) a significant effect of road ambient CO2 concentration on morphological traits (not affected by traffic intensity, P interaction CO2 x traffic intensity>0.05), that was mainly driven by a significant negative relationship between the inflorescence number and ambient CO2; 2) a positive and significant relationship between ambient CO2 and the starch content in leaves (unaffected by traffic intensity); 3) a reduction in Jmax (electron transport rate) at high traffic intensity. These lines of evidences suggest a decreased photosynthetic capacity due to high traffic intensity and high levels of ambient CO2. In addition, Pb, Cu, Zn and Sr were detected in Dactylis glomerata tissues, and Cu accumulated in roots. Finally, we observed that Dactylis glomerata individuals growing at the roadside under high levels of CO2 and in the presence of metal pollutants, reduced their production of inflorescences.

A new method to estimate photosynthetic parameters through net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve and chlorophyll fluorescence measurements.

Gas exchange (GE) and chlorophyll fluorescence (CF) measurements are widely used to noninvasively study photosynthetic parameters, for example the rates of maximum Rubisco carboxylation (Vcmax ), electron transport rate (J), daytime respiration (Rd ) and mesophyll conductance (gm ). Existing methods for fitting GE data (net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve) are based on two assumptions: gm is unvaried with CO2 concentration in the intercellular space (Ci ); and light absorption (α) and the proportion of quanta absorbed by photosystem II (ß) are constant in the data set. These may result in significant bias in estimating photosynthetic parameters. To avoid the above-mentioned hypotheses, we present a new method for fitting A-Ci curves and CF data simultaneously. This method was applied to a data set obtained from cucumber (Cucumis sativus) leaves of various leaf ages and grown under eight different light conditions. The new method had significantly lower root mean square error and a lower rate of failures compared with previously published methods (6.72% versus 24.1%, respectively) and the effect of light conditions on Vcmax and J was better observed. Furthermore, the new method allows the estimation of a new parameter, the fraction of incoming irradiance harvested by photosystem II, and the dependence of gm on Ci .

Physiological responses of three soybean species (Glycine soja, G. gracilis, and G. max cv. Melrose) to salinity stress.

Understanding the mechanism for salt tolerance in wild soybean (Glycine soja) can help researchers improve that trait in cultivated soybean lines. We analyzed the effects of excess NaCl on the growth, physiology, and ion distribution in three soybean species: wild G. soja (W8), semi-wild G. gracilis (SW18), and the cultivated salt-sensitive G. max (cv. Melrose). These comparisons revealed that, under salt stress, shoot and root lengths and biomass (either shoot or root dry weights) were significantly higher for the W8 genotype than for the other two. Most of the morphological parameters for roots from the W8 plants were also increased, including total length, specific root length, and surface area. However, the average root diameter for W8 was significantly lower than that of either SW18 or 'Melrose' soybeans. In response to salinity, photosynthesis was suppressed to a greater extent in 'Melrose' than in W8. The relatively higher tolerance shown by W8 plants was also associated with lower levels of malondialdehyde, hydrogen peroxide, and relative electrical conductivity, but higher activities by superoxide dismutase and peroxidase, as well as more free proline and glycine betaine. In addition, the W8 plants contained less Na+ and Cl-, but more K+, and they had a higher K+/Na+ ratio in their leaves and roots when compared with either SW18 or 'Melrose' plants. Therefore, the W8 genotype performs better in terms of seedling growth, photosynthetic characteristics, and physiological indexes. These findings provide guidance for developing new soybean cultivars with improved tolerance to salt stress. Our data also contribute to the knowledge base for plant salt tolerance as a tool for increasing the yields of other crops in high-salinity soils.

[Effects of stereoscopic cultivation on photosynthetic characteristics and growth of Tulipa edulis].

The effect of stereoscopic cultivation on the growth, photosynthetic characteristics and yield of Tulipa edulis was studied to explore the feasibility of stereoscopic cultivation on efficient cultivation of T.edulis. Total leaf area and photosynthetic parameters of T.edulis under stereoscopic cultivation (the upper, middle and the lower layers ) and the control were measured using LI-3100 leaf area meter and LI-6400XT photosynthesis system in the growing peak period of T.edulis.Plant biomass and biomass allocation were also determined.In addition, the bulb regeneration and yield of T.edulis were measured in the harvesting time.The results indicated that in the middle layer of stereoscopic cultivation, leaf biomass proportion was the highest, but total bulb fresh and dry weight and output growth (fresh weight) were the lowest among the treatments.And total bulb fresh weight in the middle of stereoscopic cultivation reduced significantly, by 22.84%, compared with the control.Light intensity in the lower layer of stereoscopic cultivation was moderate, in which T.edulis net photosynthetic rate and water use efficiency were higher than those of the other layers of stereoscopic cultivation, and bulb biomass proportion was the highest in all the treatments.No significant difference was detected in the total bulb fresh weight, dry weight and output growth (fresh weight) between the middle layer of stereoscopic cultivation and the control.In general, there was no significant difference in the growth status of T.edulis between stereoscopic cultivation and the control.Stereoscopic cultivation increased the yield of T.edulis by 161.66% in fresh weight and 141.35% in dry weight compared with the control in the condition of the same land area, respectively.In conclusion, stereoscopic cultivation can improve space utilization, increase the production, and achieve the high density cultivation of T.edulis.

Cadmium negatively affects the growth and physiological status and the alleviation effects by exogenous selenium in silage maize (Zea mays L.).

Increasing soil cadmium (Cd) contamination is a serious threat to human food health and safety. In order to reduce Cd uptake and Cd toxicity in silage maize, hydroponic tests were conducted to investigate the effect of exogenous Cd on the toxicity of silage maize in this study. In the study, a combination of Cd (5, 20, 50, 80, and 10 µM) treatments was applied in a hydroponic system. With increasing Cd concentration, Cd significantly inhibited the total root length (RL), root surface area (SA), root volume (RV), root tip number (RT), and branching number (RF) of maize seedlings, which were reduced by 28.1 to 71.3%, 20.2 to 64.9%, 11.2 to 56.5%, 43.7 to 63.4%, and 38.2 to 72.6%, respectively. The excessive Cd accumulation inhibited biomass accumulation and reduced silage maize growth, photosynthesis, and chlorophyll content and activated the antioxidant systems, including increasing lipid peroxidation and stimulating catalase (CAT) and peroxidase (POD), but reduced the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in the root. Besides, selenium (Se) significantly decreased the Cd concentration of the shoot and root by 27.1% and 35.1% under Cd50, respectively. Our results reveal that exogenously applied Cd reduced silage maize growth and impaired photosynthesis. Whereas silage maize can tolerate Cd by increasing the concentration of ascorbate and glutathione and activating the antioxidant defense system, the application of exogenous selenium significantly reduced the content of Cd in silage maize.