Reduction In Photosynthetic Rate Research Articles

Integrative Analysis of Transcriptomic Profiles and Physiological Responses Provide New Insights into Drought Stress Tolerance in Oil Palm (Elaeis guineensis Jacq.).

Oil palm (Elaeis guineensis Jacq.) is a highly productive crop economically significant for food, cosmetics, and biofuels. Abiotic stresses such as low water availability, salt accumulation, and high temperatures severely impact oil palm growth, physiology, and yield by restricting water flux among soil, plants, and the environment. While drought stress's physiological and biochemical effects on oil palm have been extensively studied, the molecular mechanisms underlying drought stress tolerance remain unclear. Under water deficit conditions, this study investigates two commercial E. guineensis cultivars, IRHO 7001 and IRHO 2501. Water deficit adversely affected the physiology of both cultivars, with IRHO 2501 being more severely impacted. After several days of water deficit, there was a 40% reduction in photosynthetic rate (A) for IRHO 7001 and a 58% decrease in IRHO 2501. Further into the drought conditions, there was a 75% reduction in A for IRHO 7001 and a 91% drop in IRHO 2501. Both cultivars reacted to the drought stress conditions by closing stomata and reducing the transpiration rate. Despite these differences, no significant variations were observed between the cultivars in stomatal conductance, transpiration, or instantaneous leaf-level water use efficiency. This indicates that IRHO 7001 is more tolerant to drought stress than IRHO 2501. A differential gene expression and network analysis was conducted to elucidate the differential responses of the cultivars. The DESeq2 algorithm identified 502 differentially expressed genes (DEGs). The gene coexpression network for IRHO 7001 comprised 274 DEGs and 46 predicted HUB genes, whereas IRHO 2501's network included 249 DEGs and 3 HUB genes. RT-qPCR validation of 15 DEGs confirmed the RNA-Seq data. The transcriptomic profiles and gene coexpression network analysis revealed a set of DEGs and HUB genes associated with regulatory and transcriptional functions. Notably, the zinc finger protein ZAT11 and linoleate 13S-lipoxygenase 2-1 (LOX2.1) were overexpressed in IRHO 2501 but under-expressed in IRHO 7001. Additionally, phytohormone crosstalk was identified as a central component in the response and adaptation of oil palm to drought stress.

Photosynthetic performance of the red algae Gracilariopsis lemaneiformis under high seawater pH: Excess reactive oxygen production due to carbon limitation.

The red algae Gracilariopsis lemaneiformis is extensively cultivated at high densities, leading to significant increases in regional seawater pH due to its photosynthetic removal of inorganic carbon. We conducted a study on G. lemaneiformis cultured under various pH conditions (normal pH, pH 9.3, and pH 9.6) and light levels (dark and 100 μmol photons m-2 s-1) to investigate how high pH seawater environments affect the metabolic processes of G. lemaneiformis. The high pH did not directly damage the photosynthetic light reactions or the Calvin cycle. Instead, the observed reduction in photosynthetic rates was primarily due to CO2 limitation. However, under illuminated conditions, a high pH environment leads to a decrease in electron transport efficiency (ETo/RC) and reaction center density (RC/CSo), while simultaneously increasing the levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), and the activity of antioxidant enzymes. Under illuminated conditions, the limitation of inhibit the photosynthetic electron transport process, leading to energy imbalance and excessive production of reactive oxygen species, which in turn resulted in lipid peroxidation of the cell membrane. This might be one of the inducing factors responsible for the bleaching in sea-farmed G. lemaneiformis plants.

Cultivar-specific regulation of antioxidant enzyme activity and stomatal closure confer tolerance of wheat to elevated ozone: A two-year open-field study with five cultivars

Elevated concentrations of tropospheric ozone (O3) pose a significant threat to food production in many regions of the world. We conducted a two-year experiment with five winter wheat (Triticum aestivum L.) cultivars, Yangmai16 (Y16), Yangmai23 (Y23), Zhenmai12 (Z12), Yangmai29 (Y29), and Yangmai30 (Y30), to assess photosynthetic traits, lipid peroxidation, and antioxidant systems under ambient (A-O3) or elevated (E-O3; 1.5 times A-O3) O3 in a Free-Air O3Concentration Enrichment system (FACE). E-O3 accelerated leaf senescence, manifested by marked reductions in photosynthetic rate, stomatal conductance, total antioxidant capacity, and photosynthetic pigment content, accompanied by altered antioxidant enzyme activity and a significant increase in malondialdehyde content (an indicator of lipid peroxidation). Most parameters showed significant inter-cultivar differences, as well as interactions between O3 and cultivar. The response of the antioxidant system in wheat flag leaves was influenced by O3 exposure levels. The response of antioxidant enzymes at the grain filling stage and the timely closure of stomata conferred tolerance to O3. This tolerance was associated with higher antioxidant enzyme activity at the anthesis stage but was not related to the size of stomata. This study provides a crucial theoretical foundation for further breeding O3-tolerant cultivars.

Growth, ultrastructural and physiological characteristics of Abelmoschus cytotypes under elevated ozone stress: a study on ploidy-specific responses.

Tropospheric ozone (O3 ) is a significant abiotic stressor whose rising concentration negatively influences plant growth. Studies related to the differential response of Abelmoschus cytotypes to elevated O3 treatment are scarce and need further exploration to recognise the role of polyploidisation in stress tolerance. In this study, we analysed the changes in growth pattern, ultrastructure, physiology and foliar protein profile occurring under O3 stress in Abelmoschus moschatus (monoploid), Abelmoschus esculentus (diploid) and Abelmoschus caillei (triploid). Our findings showed that higher stomatal conductance in A. moschatus triggered higher O3 intake, causing damage to stomatal cells and photosynthetic pigments. Additionally, it caused a reduction in photosynthetic rates, leading to reduced plant growth, total biomass and economic yield. This O3 -induced toxicity was less in diploid and triploid cytotypes of Abelmoschus . Protein profiling by sodium dodecyl sulpate-polyacrylamide gel electrophoresis showed a significant decrease in the commonly found RuBisCO larger and smaller subunits. The decrease was more prominent in monoploid compared to diploid and triploid. This study provides crucial data for research that aim to enhance plant ability to withstand O3 induced oxidative stress. Our findings may help in developing a tolerant variety through plant breeding techniques, which will be economically more advantageous in reaching the objective of sustainable production at the high O3 levels projected under a climate change scenario.

Comparison of Different Temperature Control Systems in Tropical-Adapted Greenhouses for Green Romaine Lettuce Production

The cultivation of lettuce in greenhouses is negatively impacted by high temperatures, especially in hot climates. Therefore, developing an efficient method to regulate the internal temperature of greenhouses is essential to sustain crop productivity throughout the year. This study intends to investigate differential temperature control systems for green romaine lettuce production in the greenhouse. The experiment was conducted in a completely randomized design (CRD) with five replications. The four treatments consisted of (1) control, (2) Fogging + ventilation fan, (3) Fogging + shading, and (4) Fogging + ventilation fan + shading. The different temperature control systems influenced the growth and yield parameters, in which shading operation appears to cause reductions in photosynthetic rate, leading to declines of marketable fresh weight. However, the operation of the fogging and ventilation fan was considered the appropriate method for improving indoor air temperature since this resulted in higher growth and yield and a greater sensory evaluation. Maintaining VPD values between 1.62 and 1.76 kPa and controlling light intensity within the 530–700 mol m−2 s−1 range were recommended to ensure a consistent lettuce yield of 65–82 g plant−1 throughout the year.

Photosynthesis, chlorophyll content and water potential of a mistletoe-host pair in a semi-arid savanna

Mistletoes can have detrimental effects on host trees. Mistletoe-infected trees may suffer from reduced growth and loss of vigor thereby contributing to low productivity of host trees. However, hosts may tolerate low levels of infection. This study aimed to determine photosynthetic rate, chlorophyll content and transpiration rate of a mistletoe-host pair (Viscum rotundifolium-Boscia albitrunca) and the water potential of two mistletoe host pairs (V. rotundifolium-B. albitrunca and Tapinanthus oleifolius-Senegalia mellifera) in a semi-arid savanna at Windhoek, Namibia. Photosynthetic rates were measured using a LI-6400XT photosynthesis system, while photosynthetic pigments were extracted in acetone and quantified spectrophotometrically. Plant water potential was measured using a Scholander pressure chamber. Results revealed greater photosynthetic rates and amounts of photosynthetic pigments in B. albitrunca than in V. rotundifolium while transpiration rates showed opposite trends to photosynthetic rates. Non-host B. albitrunca trees recorded significantly higher photosynthetic rates than the hosts, which suggests a parasite-induced reduction of photosynthetic rate in host plants. Water potential was greater in host trees than in mistletoes. These findings show negative effects of mistletoes on host trees, which may ultimately affect their reproduction and survival. Further research may be required to determine effects of parasite density on host trees.

MdSWEET23, a sucrose transporter from apple (Malus × domestica Borkh.), influences sugar metabolism and enhances cold tolerance in tomato.

Photosynthetic products in most fleshy fruits are unloaded via the apoplasmic pathway. Sugar transporters play an important role in the apoplasmic unloading pathway and are involved in sugar transport for fruit development. The MdSWEET23, cloned from ''Hanfu'' apple (Malus × domestica Borkh.) fruits, belongs to Clade III of the SWEET family. Subcellular localization revealed that MdSWEET23 is localized on the plasma membrane. β-glucuronidase activity assays showed that MdSWEET23 was primarily expressed in the sepal and carpel vascular bundle of apple fruits. Heterologous expression assays in yeast showed that MdSWEET23 functions in sucrose transport. The overexpression of MdSWEET23 in the ''Orin" calli increased the soluble sugar content. The silencing of MdSWEET23 significantly reduced the contents of sucrose and sorbitol in apple fruits. Ectopic overexpression of MdSWEET23 in tomato altered sugar metabolism and distribution in leaves and fruits, causing a reduction in photosynthetic rates and plant height, enhanced cold stress tolerance, and increased the content of sucrose, fructose, and glucose in breaking color fruits, but did not increase sugar sink potency of tomato fruits.

Drivers of chaparral photosynthetic rate reduction under modern drought conditions

Terrestrial vegetation communities are experiencing rapid and novel changes to photosynthetic rates under the changing climate. Chaparral, a semi-arid shrubland ecosystem of the Southwestern United States and Northern Mexico, is projected to experience substantial increases in aridity and stochastic precipitation. This study identifies the primary meteorological drivers of photosynthesis for three widespread chaparral shrub species—Adenostoma sparsifolium, Adenostoma fasciculatum, and Ceanothus perplexans—from 2019 to 2021. Monthly leaf-level carbon exchange rates, water potentials (WPs), and meteorological conditions were collected for each species. Average monthly primary productivity (n = 25) demonstrated vapor pressure deficit (VPD) as a significant limit to photosynthetic rates for A. sparsifolium and A. fasciculatum. VPD was also the most influential predictor of WP for all three species. These results suggest increasing atmospheric dryness as a key predictor for reduction in chaparral primary productivity, particularly for deeply-rooted, resprouting species. There are additional indications that VPD could exacerbate drought-related mortality for C. perplexans and A. sparsifolium by pushing WP to novel extremes. This study concludes that atmospheric dryness, across 3 years of differing soil water stress levels, was consistently a substantial physiological limitation for three common, chaparral species. Although this experiment occurred over a limited window and cannot assess climatic response trends, acute increases in air temperature and VPD within the region would exacerbate photosynthetic limitation for these species and may contribute to declining primary productivity in broader chaparral ecosystems.

Light-induced changes in the morphology and fluorescence of Arthrospira platensis

The cyanobacterium Arthrospira platensis is a well-known source of bioactive substances. Growth and the generation of bioactive ingredients of Arthrospira platensis depend mainly on the quantity of light in a controlled environment. Photoinhibition is a time, nutrient, and light intensity-dependent decrease in photosynthetic efficiency. However, too strong illumination can induce two harmful effects: (1) photoinhibition as a reduction in photosynthetic rate and (2) photooxidation which can have lethal effects on the cells, and which can lead to total loss of the culture. The results of this microscopical study demonstrate, that under the procedures described and very high photon flux den-sities, not only a decrease in the photosynthetic efficiency but beyond, also destruction of Arthrospira platensis can occur.

Independent and combined influence of drought stress and nitrogen deficiency on physiological and proteomic changes of barley leaves

Drought stress and nitrogen (N) deficiency often interact mutually during crop growth, yet the combinational effects of both stresses are still poorly understood. In the present study, physiological changes of barley were determined under drought stress, N deficiency and combined both stresses. Barley leaf proteomes were detected by label-free proteomic techniques under drought stress or/and N deficiency. The results showed that few proteins involved in photosynthesis were changed, and the main reason for the reduction in photosynthetic rate (An) was the decrease in stomatal conductance (gs) under drought stress. The increased photorespiration as well as decreased gs and chlorophyll reduced An under combined stresses. Compared to drought stress and N deficiency, the combined stresses led to the greater expression of proteins related to energy, carbohydrate and amino acid metabolism, causing the development of more extensive signaling pathways. Barley plants generated more energy by enhancing aerobic respiration to maintain growth under combined stresses. The synthesis of proteins in plant leaves was decreased under drought stress or/and N deficiency, while the degradation of proteins was enhanced to provide free amino acids under N deficiency and combined stresses. Our results provided further information for the mechanisms of crop response to combined drought stress and N deficiency, and helped to understand the response and adaptation of plants to adverse environmental conditions.

The Role of Reactive Oxygen Species in Plant Response to Radiation.

Radiation is widespread in nature, including ultraviolet radiation from the sun, cosmic radiation and radiation emitted by natural radionuclides. Over the years, the increasing industrialization of human beings has brought about more radiation, such as enhanced UV-B radiation due to ground ozone decay, and the emission and contamination of nuclear waste due to the increasing nuclear power plants and radioactive material industry. With additional radiation reaching plants, both negative effects including damage to cell membranes, reduction of photosynthetic rate and premature aging and benefits such as growth promotion and stress resistance enhancement have been observed. ROS (Reactive oxygen species) are reactive oxidants in plant cells, including hydrogen peroxide (H2O2), superoxide anions (O2•-) and hydroxide anion radicals (·OH), which may stimulate the antioxidant system of plants and act as signaling molecules to regulate downstream reactions. A number of studies have observed the change of ROS in plant cells under radiation, and new technology such as RNA-seq has molecularly revealed the regulation of radiative biological effects by ROS. This review summarized recent progress on the role of ROS in plant response to radiations including UV, ion beam and plasma, and may help to reveal the mechanisms of plant responses to radiation.

Uso de diodosemissores de luz (LEDs) no desenvolvimento e resposta a estresse hídrico em mudas de Eucalyptus benthamii (Myrtaceae)

ABSTRACT: Plants use light as a source of energy in the process of photosynthesis. Different levels of luminosity cause physiological and morphological changes in the plant, and its success depends on its adaptation to these different levels. Light emitting diodes (LED) have been proposed as a light source in controlled environments. The present research evaluated physiological and morphological aspects in Eucalyptus benthamii (Myrtaceae) seedlings kept under different colors of LED lamps and submitted to water stress. The experiment was carried out in a completely randomized design, in which the treatments were defined as: T1 (control, with white light); T2 (blue light); T3 (red light) and T4 (mixed blue and red light). Red light resulted in the best response to most morphological variables in plant growth. In response to water stress, blue light LEDs resulted in a better seedling response, with slower reduction of photosynthetic rate and other variables. This may indicate the possibility of reducing water deficit damage in seedlings acclimated to blue light prior to field planting.

Oxygen stress mitigation for microalgal biomass productivity improvement in outdoor raceway ponds

Dissolved oxygen (DO) concentrations at supersaturated levels are commonly observed in microalgae cultures due to photosynthesis. Unlike cultivation in closed photobioreactors, the impact of excessive oxygen and the mitigation methods in open systems such as raceway ponds have hardly been studied. In this study, photosynthetic rates of Monoraphidium minutum 26B-AM and Scenedesmus obliquus UTEX393, two of the top DISCOVR strains for outdoor raceway cultivation, were compared at different DO levels. Increasing DO from 0 to 30 mg L−1 caused a 36.6 % and 26.1 % reduction in photosynthetic rate for M. minutum 26B-AM and S. obliquus UTEX393, respectively. To improve the outdoor pond biomass productivity of each strain, three oxygen stress mitigation methods were tested. The first method raised the dissolved bicarbonate concentration by an order of magnitude to favor bicarbonate transport into the cell, increasing the CO2:O2 ratio near RuBisCO, thus reducing photorespiration. Although this method increased the observed photosynthesis rate of M. minutum 26B-AM by 26 % and S. obliquus UTEX393 by 13 % in laboratory testing, it failed to improve biomass productivity under outdoor pond conditions for both strains. The second method added sodium sulfite as an oxygen scavenger to chemically lower the DO concentration in the culture. Chemical reduction of dissolved molecular oxygen did not significantly improve the biomass productivity of M. minutum 26B-AM; however, a 10 % improvement in biomass productivity for S. obliquus UTEX393 was observed. The final method sparged cultures with air to strip oxygen out of the liquid medium. This did not improve the biomass productivity of M. minutum 26B-AM, likely due to unfavorable weather conditions during cold season cultivation; however, an improvement of 36 % in biomass productivity was achieved for S. obliquus UTEX393 during the warm season cultivation. Of the three tested methods, air-sparging was the most effective and practical for improving outdoor biomass production.

Changes in ultrastructure, photosynthetic abilities, and secondary metabolite due to individual and interactive effects of chromium and ultraviolet-B radiation in Adhatoda vasica

The study was executed to assess individual and interactive effects of elevated ultraviolet-B (eUV-B) radiation and chromium (Cr) on a medicinal plant Adhatoda vasica Nees. The experiment was conducted under field conditions involving control, Cr, eUV-B, and Cr+eUV-B treatments. The results showed that Cr content was the highest in roots as compared to other parts under Cr+eUV-B. Significant reductions in photosynthetic rate, intercellular CO2 concentration, and stomatal conductance were observed under all treatments with maximum under Cr+eUV-B. Chlorophyll (Chl) fluorescence parameters showed variable responses under Cr and Cr+eUV-B. Chl content showed reductions under all treatments whereas Chl a/b ratio and carotenoids showed increment under eUV-B and reductions under Cr and Cr+eUV-B. The ultrastructure of leaves showed changes in chloroplasts under treatments. Vasicine (medicinally important secondary metabolite) increased under treatments. Our study revealed that A. vasica showed variable responses towards individual and interactive stress of Cr and eUV-B.

Transcriptome profiling shows a rapid variety-specific response in two Andigenum potato varieties under drought stress.

Potato is a drought-sensitive crop whose global sustainable production is threatened by alterations in water availability. Whilst ancestral Solanum tuberosum Andigenum landraces retain wild drought tolerance mechanisms, their molecular bases remain poorly understood. In this study, an aeroponic growth system was established to investigate stress responses in leaf and root of two Andigenum varieties with contrasting drought tolerance. Comparative transcriptome analysis revealed widespread differences in the response of the two varieties at early and late time points of exposure to drought stress and in the recovery after rewatering. Major differences in the response of the two varieties occurred at the early time point, suggesting the speed of response is crucial. In the leaves and roots of the tolerant variety, we observed rapid upregulation of ABA-related genes, which did not occur until later in the susceptible variety and indicated not only more effective ABA synthesis and mobilization, but more effective feedback regulation to limit detrimental effects of too much ABA. Roots of both varieties showed differential expression of genes involved in cell wall reinforcement and remodeling to maintain cell wall strength, hydration and growth under drought stress, including genes involved in lignification and wall expansion, though the response was stronger in the tolerant variety. Such changes in leaf and root may help to limit water losses in the tolerant variety, while limiting the reduction in photosynthetic rate. These findings provide insights into molecular bases of drought tolerance mechanisms and pave the way for their reintroduction into modern cultivars with improved resistance to drought stress and yield stability under drought conditions.

Photosynthetic, Biochemical and Secondary Metabolite Changes in a Medicinal Plant Chlorophytum borivillianum (Safed musli) against Low and High Doses of UV-B Radiation.

Plants are inevitably grown in presence of sunlight, therefore bound to be exposed to natural UV-B radiation. Several studies have already been conducted with UV-B and medicinal plants and only few studies showed dose dependent variation. The present study aims to find out the variations and adaptation in Chlorophytum borivillianum under two different doses of UV-B radiation; ambient + low (3.2 kJm-2 d-1 ) and high (7.2 kJm-2 d-1 ) UV-B dose, denoted as LD and HD, respectively. Reduction in photosynthetic rate was higher at HD, while plants receiving LD displayed nonsignificant variation. During vegetative and reproductive stage, significant reduction (P ≤ 0.001) in stomatal conductance was obtained when exposed to HD-eUV-B. Fv /Fm showed more reductions in HD-eUV-B (12.6%) followed by LD-eUV-B (7.9%). Low and high doses of UV-B enhanced the anthocyanin content but the increase was significant in HD, indicates epidermal protection strategy by the plants. Under LD-eUV-B, the content of saponin, a major phytochemical constituent was enhanced by 26%. Phytochemical analysis of roots revealed reduction mostly in fatty acid components whereas the steroidal components (stigmasterol and sarsasapogenin) showed enhancement in response to LD. The study suggests the importance of LD-eUV-B in the stimulation of medicinal compounds in C. borivillianum.

The effect of riparian pool‐riffles on the hydrochemistry of hyporheic habitats: The River Esk, Yorkshire, UK

AbstractEuropean Union Water Framework Directive (WFD) (2000/60/EC) waterbody statuses are often derived from the assemblage of mixed‐taxon organisms found within bed sediments. Yet no routine water chemistry samples are taken from riverbed substrate, despite many interstitial species being dependant on specific physicochemical conditions. This paper examines water and nutrient exchanges between stream and substrate, the hyporheic zone, and the consequent alteration to the chemistry of interstitial and in‐stream waters, which in turn leads to small‐scale but significant changes in habitat. Bed topography, principally a pool‐riffle sequence, was surveyed and hydraulically sampled to examine the hyporheic flow pathways generated between the stream, substrate, and groundwater—creating an ecotone. Hyporheic zone, in‐stream and groundwater hydrochemistry, and hydraulic measures were assessed at a braided woodland river reach using a dense monitoring approach. The findings demonstrate that through a 23‐m pool‐riffle sequence, where water infiltrates at the riffle‐head and subsequently exfiltrates at the riffle‐tail, there is a 5% reduction in mean in‐stream nitrate‐N and a 73% reduction in hyporheic zone concentration. When calcium‐enriched riffle‐tail exfiltrate meets riffle‐runoff water that is turbulently oxygenated from riffle‐flow, an interstitial redoxcline is created. Dissolved oxygen nocturnally drops, with photosynthetic rate reduction, which causes hyporheic nitrate‐N to double its daytime concentration. The results are related to the Yorkshire River Esk freshwater pearl mussels, Margaritifera margaritifera Linnaeus (1758), a declining endangered species. At present, scant monitoring of interstitial hydrochemistry and diurnal change across stream and substrate occurs.

Interactive effect of elevated [CO2] and temperature on the photosynthetic process, anti‐oxidative properties, and grain yield of rice

AbstractThe simultaneous increase of carbon dioxide and temperature causes significant changes in rice physiology and production, but limited studies have been performed in the past to examine the interactive effect of these two key variables on lipid peroxidation, anti‐oxidative properties, gas exchange parameters, and grain yield of rice. Thus, an experiment was conducted by growing two rice genotypes (IR83376‐B‐B‐24–2 and IR64) inside field‐based open‐top chambers (OTCs) with two levels of [CO2] (ambient and elevated; (500±25 ppm) and temperature (ambient and ambient+2°C) in order to determine their simultaneous effect on lipid peroxidation (thio‐barbituric acid substances, TBARS), anti‐oxidant properties (catalase, CAT and superoxide dismutase, SOD), gas exchange parameters (PN rate, gs, E), WUE and grain yield during the kharif seasons. Our study showed that under simultaneous elevation (CO2 and temperature), the activity of CAT and SOD were improved. CAT showed significant alterations in activity which was detected for genotype IR83376‐B‐B‐24–2 (twelve‐fold increase) under elevated temperature compared to ambient temperature. SOD activity was decreased by 35.1 and 35.7% with elevated [CO2] while it increased under elevated temperature by 103.6 and 41.1% in IR83376‐B‐B‐24–2 and IR64, respectively. No significant difference in TBARS content was observed under combined elevation of both [CO2] and temperature, as compared to ambient conditions. However, elevation in temperature by 2°C led to a reduction in photosynthetic rate and WUE but increased the rate of transpiration, CAT and SOD activity. Grain yield was also improved under elevated [CO2] while elevated temperature has negative impact on grain yield. Thus, the findings suggest that there are differential biochemical (TBARS, CAT, and SOD) and physiological (PN rate, gs, E, and WUE) responses of rice towards predicted climatic conditions. This study represents the significant findings on the anti‐oxidant defence mechanism in rice under combined elevated [CO2] and temperature levels. Furthermore, the genotypic differences observed in terms of photosynthesis mechanism and ROS scavenging system imply that it is possible to breed varieties that will be more suited for future rice production scenarios.

Overexpression of a Bcl-2-associated athanogene SlBAG9 negatively regulates high-temperature response in tomato

The Bcl-2-associated athanogene (BAG) gene is a multi-functional family of co-chaperones regulator, modulating plant stress response. Our previous study revealed that the SlBAG9 of tomato (Solanum lycopersicum) had the higher expression level induced by high-temperature (HT) at the transcriptional and protein levels, but its biological function was still unclear. Here, we conducted an in-depth analysis of SlBAG9. SlBAG9 protein was not located in the mitochondria but in the cytoplasm and nucleus. Many cis-acting elements involved in plant stress and hormone responses were located in the promoter regions of SlBAG9 including heat-shock element (HSE1). The β-glucuronidase (GUS) histochemical analysis showed that SlBAG9 promoter could drive GUS gene expression in transiently transformed Nicotiana tabacum leaves under non-inducing condition and HSE1 is critical for HT-induced GUS activity under HT. The transcription of SlBAG9 was expressed in different organs and was regulated by HT, cold, drought, and salt stresses as well as exogenous abscisic acid (ABA) and H2O2. To further elucidate SlBAG9 function in response to HT, the transgenic tomato plants overexpressing SlBAG9 were developed. Compared to the wild-type plants, SlBAG9-overexpressing plants exhibited more sensitivity to HT stress, reflected by the burning symptoms, the degradation of chlorophyll, and the reduction of photosynthetic rates. Additionally, SlBAG9-overexpressing lines showed higher accumulation of lipid peroxidation production (MDA) and H2O2, but lower activities of superoxide dismutase, catalase, and peroxidase. Therefore, it is speculated that SlBAG9 plays a negative role in thermotolerance probably by inhibition of antioxidant enzyme system leading to the oxidative damage, consequently aggravating the HT-caused injury phenotype.

Effects of Foliar Phylloxera (Hemiptera: Phylloxeridae) Infestations on Wine Grape Photosynthesis, Yield, and Fruit Quality

Abstract Grape phylloxera, Daktulosphaira vitifoliae Fitch (Hemiptera: Phylloxeridae), is an important pest that forms galls on the foliage and roots of Vitis species. The effects of grape phylloxera on grape root have been studied extensively. This study investigated the effects of the foliar form of grape phylloxera, which is a persistent pest of North American native Vitis species and cold-hardy hybrid wine grapes between Vitis vinifera L. and Vitis riparia Michx. For a susceptible variety, ‘Frontenac’, in commercial Minnesota vineyards, there were reductions in cluster weight due to foliar phylloxera infestations in 2017 (one site; P = 0.05) and 2018 (three sites; nonsignificant). Reductions in cluster weight can be economically important to growers. For four grape varieties (susceptible and resistant) evaluated in the greenhouse, there were numerical reductions in photosynthetic rate and localized photosystem II efficiency in 1 of 2 yr. Resistant varieties had less of a reduction on conductance due to grape phylloxera infestation than susceptible varieties in 1 of 2 yr. The degree to which this occurs in resistant varieties may be related to the formation of fewer adaxial stomata; however, this hypothesis requires additional research. These results add important information to better understand how foliar phylloxera injury affects wine grape photosynthesis and yield. The results serve as a foundation for investigating variety-specific responses to foliar phylloxera through the use of advanced phenotyping technologies. This knowledge will lead to a better understanding of the effect of the pest on the diversity of cold-hardy grape varieties grown in the Midwestern United States.