Trehalose-6-phosphate synthase 8 increases photosynthesis and seed yield in Brassica napus.

Trehalose-6-phosphate (T6P) functions as a vital proxy for assessing carbohydrate status in plants. While class II T6P synthases (TPS) do not exhibit TPS activity, they are believed to play pivotal regulatory roles in trehalose metabolism. However, their precise functions in carbon metabolism and crop yield have remained largely unknown. Here, BnaC02.TPS8, a class II TPS gene, is shown to be specifically expressed in mature leaves and the developing pod walls of Brassica napus. Overexpression of BnaC02.TPS8 increased photosynthesis and the accumulation of sugars, starch, and biomass compared to wild type. Metabolomic analysis of BnaC02.TPS8 overexpressing lines and CRISPR/Cas9 mutants indicated that BnaC02.TPS8 enhanced the partitioning of photoassimilate into starch and sucrose, as opposed to glycolytic intermediates and organic acids, which might be associated with TPS activity. Furthermore, the overexpression of BnaC02.TPS8 not only increased seed yield but also enhanced seed oil accumulation and improved the oil fatty acid composition in B. napus under both high nitrogen (N) and low N conditions in the field. These results highlight the role of class II TPS in impacting photosynthesis and seed yield of B. napus, and BnaC02.TPS8 emerges as a promising target for improving B. napus seed yield.

A meta-analysis of photosynthetic efficiency and stress mitigation by melatonin in enhancing wheat tolerance.

BACKGROUND: Our meta-analysis examines the effects of melatonin on wheat under varying abiotic stress conditions, focusing on photosynthetic parameters, chlorophyll fluorescence, leaf water status, and photosynthetic pigments. We initially collected 177 publications addressing the impact of melatonin on wheat. After meticulous screening, 31 published studies were selected, encompassing 170 observations on photosynthetic parameters, 73 on chlorophyll fluorescence, 65 on leaf water status, 240 on photosynthetic pigments. RESULTS: The analysis revealed significant heterogeneity across studies (I² > 99.90%) for the aforementioned parameters and evidence of publication bias, emphasizing the complex interaction between melatonin application and plant physiological responses. Melatonin enhanced the overall response ratio (lnRR) for photosynthetic rates, stomatal conductance, transpiration rates, and fluorescence yields by 20.49, 22.39, 30.96, and 1.09%, respectively, compared to the control (no melatonin). The most notable effects were under controlled environmental conditions. Moreover, melatonin significantly improved leaf water content and reduced water potential, particularly under hydroponic conditions and varied abiotic stresses, highlighting its role in mitigating water stress. The analysis also revealed increases in chlorophyll pigments with soil drenching and foliar spray, and these were considered the effective application methods. Furthermore, melatonin influenced chlorophyll SPAD and intercellular CO2 concentrations, suggesting its capacity to optimize photosynthetic efficiency. CONCLUSIONS: This synthesis of meta-analysis confirms that melatonin significantly enhances wheat's resilience to abiotic stress by improving photosynthetic parameters, chlorophyll fluorescence, leaf water status, and photosynthetic pigments. Despite observed heterogeneity and publication bias, the consistent beneficial effects of melatonin, particularly under controlled conditions with specific application methods e.g. soil drenching and foliar spray, demonstrate its utility as a plant growth regulator for stress management. These findings encourage focused research and application strategies to maximize the benefits of melatonin in wheat farming, and thus contributing to sustainable agricultural practices.

Partial root-zone drying irrigation improves intrinsic water-use efficiency and maintains high photosynthesis by uncoupling stomatal and mesophyll conductance in cotton leaves.

Partial root-zone drying irrigation (PRD) can improve water-use efficiency (WUE) without reductions in photosynthesis; however, the mechanism by which this is attained is unclear. To amend that, PRD conditions were simulated by polyethylene glycol 6000 in a root-splitting system and the effects of PRD on cotton growth were studied. Results showed that PRD decreased stomatal conductance (gs) but increased mesophyll conductance (gm). Due to the contrasting effects on gs and gm, net photosynthetic rate (AN) remained unaffected, while the enhanced gm/gs ratio facilitated a larger intrinsic WUE. Further analyses indicated that PRD-induced reduction of gs was related to decreased stomatal size and stomatal pore area in adaxial and abaxial surface which was ascribed to lower pore length and width. PRD-induced variation of gm was ascribed to the reduced liquid-phase resistance, due to increases in chloroplast area facing to intercellular airspaces and the ratio of chloroplast surface area to total mesophyll cell area exposed to intercellular airspaces, as well as to decreases in the distance between cell wall and chloroplast, and between adjacent chloroplasts. The above results demonstrate that PRD, through alterations to stomatal and mesophyll structures, decoupled gs and gm responses, which ultimately increased intrinsic WUE and maintained AN.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology.

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.

Management of excessive soil H+ ion induced toxicities by application of organic seaweed amendment enhances photosynthesis and resource use efficiencies in rice (Oryza sativa).

Globally, soil acidification is a serious environmental issue that reduces commercial agricultural production. Rice is subjected to nutritional stress due to acidic soil, which is a major impediment to rice production. Since acid soil threatens rice plants with soil compaction, nutrient loss, and plant stress-induced oxidative cell damage that results in affecting the photosynthetic system, restricting the availability of water, and reducing overall plant growth and productivity. Since contemporary soil acidification management strategies provide mediocre results, the use of Sargassum wightii seaweed-based biostimulants (BS) and soil amendments is sought as an environmentally friendly alternative strategy, and therefore its potential isevaluated in this study. BS was able to mediate soil quality by improving soil pH and structure along with facilitating nitrogen phytoavailability. BS also increased the activity of the antioxidant enzyme system, superoxide dismutase ((48%), peroxidase (76.6%), and ascorbate peroxidase (63.5%), aggregating the monaldehyde-mediating accumulation of osmoprotective proline in roots, that was evident from rapid initiation of root hair growth in treated seedlings. BS was also able to physiologically modulate photosynthetic activities and chlorophyll production (24.31%) in leaves, maintaining the efficiency of plant water use by regulating the stomatal conductance (0.91 mol/m/s) and the transpiration rate (13.2 mM/m/s). The BS compounds were also successful in facilitating nitrogen uptake resulting in improved plant growth (59%), tiller-panicle number, and yield (52.57%), demonstrating a resourceful nitrogen use efficiency (71.96%) previously affected by stress induced by acid soil. Therefore, the study affirms the competent potential of S. wightii-based soil amendment to be applied not only to improve soil quality, but also to increase plant production and yield.

Effect of tropospheric ozone and its protectants on gas exchange parameters, antioxidant enzymes and quality of Garlic (Allium sativum. L).

An experimental study was conducted to assess the detrimental effect of ground-level ozone (O3) on garlic physiology and to find out appropriate control measures against ground-level O3, at TNAU-Horticultural Research farm, Udhagamandalam. Elevated ground ozone levels significantly decreased garlic leaf chlorophyll, photosynthetic rate, stomatal conductance, total soluble solids and pungency. The garlic chlorophyll content was highest in ambient ozone level and lowest in elevated ozone@200 ppb, highest stomatal conductance was recorded in ambient ozone with foliar spray of 3%Panchagavya, and the lowest was observed in elevated ozone@200 ppb. Since the elevated O3 had reduced in garlic photosynthetic rate significantly the lowest was observed in elevated O3@200 ppb and the highest photosynthetic rate was observed in ambient Ozone with foliar spray 3% of panchagavya after a week. The antioxidant enzymes of garlic were increased with increased concentration of tropospheric ozone. The highest catalase (60.97 µg of H2O2/g of leaf) and peroxidase (9.13 ΔA/min/g of leaf) concentration was observed at 200 ppb elevated ozone level. Garlic pungency content was highest in ambient ozone with foliar spray of 0.1% ascorbic acid and the lowest was observed under elevated O3@200 ppb. Highest total soluble solids were observed in ambient ozone with foliar spray of 3%Panchagavya and the lowest observed in elevated ozone@200 ppb. Thus, tropospheric ozone has a detrimental impact on the physiology of crops, which reduced crop growth and yield. Under elevated O3 levels, ascorbic acid performed well followed by panchagavya and neem oil. The antioxidant such as catalase and peroxidase had positive correlation among themselves and had negative correlation with chlorophyll content, stomatal conductance, photosynthetic rate, pungency and TSS. The photosynthetic rate has high positive correlation with chlorophyll content, pungency and TSS. Correlation analysis confirmed the negative effects of tropospheric ozone and garlic gas exchange parameters and clove quality. The ozone protectants will reduce stomatal opening by which the entry of O3 in to the cell will be restricted and other hand they also will alleviate ROS and allied stresses.

Aluminum uptake, translocation, physiological changes, and overall growth inhibition in rice genotypes (Oryza sativa) at vegetative stage.

Aluminum (Al) contamination in acidic soil is a major problem in paddy field, causing grain yield loss, especially in central plains of Thailand. The objective of this study was to assess Al content in the root tissues, its translocation to the leaves, and Al toxicity in three genotypes of rice, RD35 (local acidic-tolerant), Azucena (positive-check Al-tolerant), and IR64 (high yielding) under 0 (control) or 1 mM AlCl3 (Al toxicity) at pH 4.5. Al content in the root tissues of rice cv. RD35 under 1 mM AlCl3 was peaked at 4.18 mg g‒1 DW and significantly translocated to leaf tissues (0.35 mg g‒1 DW), leading to reduced leaf greenness (SPAD) (by 44.9% over the control) and declined net photosynthetic rate (Pn) (by 54.5% over the control). In contrast, Al level in cvs. Azucena and IR64 was restricted in the roots (2.12 mg g‒1 DW) with low amount of translocation in the leaf tissues (0.26 mg g‒1 DW), resulting in maintained values of SPAD and Pn. In cv. RD35, root and shoot traits including root length, root fresh weight, shoot height, shoot fresh weight, and shoot dry weight in 1 mM Al treatment were significantly dropped by > 35% over the control, whereas these parameters in cvs. Azucena and IR64 were retained. Based on the results, RD35 rice genotype was identified as Al sensitive as it demonstrated Al toxicity in both aboveground and belowground parts, whereas Azucena and IR64 were found tolerant to 1 mM Al as they demonstrated storage of Al in the root tissues to reduce toxicity in the leaf tissues. The study suggests that root traits, shoot attributes, chlorophyll degradation, and photosynthetic reduction can be successfully employed for the screening of Al-tolerant genotypes in rice breeding programs.

Iron (Fe) toxicity, uptake, translocation, and physio-morphological responses in Catharanthus roseus.

Iron (Fe) toxicity in plant species depends on the availability of Fe in the soil, uptake ability by the root system, and translocation rate to other parts of the plant. The aim of this study was to assess Fe uptake by root tissues of Catharanthus roseus, translocation rate to leaf tissues, and the impairment of plant physio-morphological characteristics. Fe uptake by the roots (~ 700 µg g-1 DW) of C. roseus was observed during the early exposure period (1 week), and translocation factor from root to shoot was fluctuated as an independent strategy. A high level of Fe content in the root tissues significantly inhibited root length and root dry weight. Under acidic pH condition, an enrichment of Fe in the shoots (~ 400 µg g-1 DW) led to increase in leaf temperature (> 2.5 °C compared to control) and crop stress index (> 0.6), resulting in stomatal closure, subsequently decreasing CO2 assimilation rate and H2O transpiration rate. An increment of CSI in Fe-stressed plants was negatively related to stomatal conductance, indicating stomatal closure with an increase in Fe in the leaf tissues. High Fe levels in the leaf tissues directly induced toxic symptoms including leaf bronzing, leaf spotting, leaf necrosis, leaf chlorosis, and leaf senescence in C. roseus plants. In summary, C. roseus was identified as a good candidate plant for Fe phytoextraction, depending on Fe bioaccumulation, therefore 50 mM Fe treatment was designated as an excess Fe to cause the growth inhibition, especially in the prolonged Fe incubation periods. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01379-5.

Can evolutionary history predict plant plastic responses to climate change?

Plant plastic responses are critical to the adaptation and survival of species under climate change, but whether they are constrained by evolutionary history (phylogeny) is largely unclear. Plant leaf traits are key in determining plants' performance in different environments, and if these traits and their variation are phylogenetically dependent, predictions could be made to identify species vulnerable to climate change. We compiled data on three leaf traits (photosynthetic rate, specific leaf area, and leaf nitrogen content) and their variation under four environmental change scenarios (warming, drought, elevated CO2 , or nitrogen addition) for 434 species, from 210 manipulation experiments. We found phylogenetic signal in the three traits but not in their variation under the four scenarios. This indicates that closely related species show similar traits but that their plastic responses could not be predicted from species relatedness under environmental change. Meanwhile, phylogeny weakened the slopes but did not change the directions of conventional pairwise trait relationships, suggesting that co-evolved leaf trait pairs have consistent responses under contrasting environmental conditions. Phylogeny can identify lineages rich in species showing similar traits and predict their relationships under climate change, but the degree of plant phenotypic variation does not vary consistently across evolutionary clades.

Alleviation of cadmium phytotoxicity through melatonin modulated physiological functions, antioxidants, and metabolites in tomato (Solanum lycopersicum L.).

The rising concentration of cadmium (Cd) builds a harmful effect on human and plant health associated with food chain contagion. Melatonin (MT) is an indole compound. Hence, the experiment was conducted to understand the physiological and biochemical mechanism of Cd detoxification by exogenous MT in tomato. Pots were filled with 30 ppm of Cd spiked soil and different concentration of exogenous MT was given to the plants through seed treatment (250 ppm), foliar spray viz., 25, 50, and 100 ppm, and both, whereas the foliar spray was given at 30 days after transplanting (DAT) and 46 DAT. When the plants are exposed to Cd stress, it reduces the gas exchange characters. The results revealed that foliar spray of 25 ppm of exogenous MT recorded the highest photosynthetic rate, stomatal conductance, and osmotic potential. MT had a direct interaction with reactive oxygen species scavenging by elevating endogenous antioxidant enzymes as well as the metabolites in plants. The contribution of MT foliar spray of 25 ppm at 30 and 46 DAT can mitigate Cd stress and it has potential implications for ensuring food safety and food security in marginal agriculture.

Transcriptome comparison of different ploidy reveals the mechanism of photosynthetic efficiency superiority of triploid poplar.

Triploid poplars have obvious growth advantages, especially in leaf development and photosynthetic characteristics, but the molecular mechanism has not been revealed yet. In order to better understand the regulation mechanisms of leaf and chlorophyll development in the triploid poplars, we combined the leaf phenotypic data with the transcriptomic data of the 5th, 10th, and 25th leaves from triploid and diploid poplars, using weighted gene co-expression network analysis (WGCNA), and revealed that PpnGRF5-1 had a strong correlation with leaf development and net photosynthetic rate (Pn). PpnGRF5-1 overexpression transgenic plants showed that the leaf area, Pn, and chlorophyll concentration were significantly increased. Transcriptomic data analysis of the third leaf from PpnGRF5-1 overexpression transgenic plants showed that PpnGRF5-1 could up-regulate the expression levels of chlorophyll synthesis genes and down-regulate the transcription of chlorophyll degradation enzymes. Overall, our studies have greatly expanded our understanding of the molecular mechanisms regulating triploid growth dominance.

Impact of exogenous nicotine on the morphological, physio-biochemical, and anatomical characteristics in Capsicum annuum.

Nicotine is an alkaloid which only highly exists in tobacco plants. It accounts for 95% of its total alkaloid content. Nicotine is synthesized in the roots and transported via the xylem to the shoot. This study aimed to investigate the morphological, physio-biochemical, structural, and ultrastructural impacts of different nicotine concentrations in bell pepper. Capsicum annuum seedlings were grown hydroponically in a growth chamber with different nicotine concentrations (0, 100, 400, 700, 1,000, 3,000, and 5,000 µM). Nicotine-treated leaves (3,000 and 5,000 µM) exhibited severe chlorosis and necrosis. Moreover, nicotine-treated seedlings (1,000, 3,000, and 5,000 µM) exhibited severe reduction in leaf area (p < 0.0001) and photosynthetic efficiency (p < 0.0001), which significantly reduce the photosynthetic rate (p < 0.0001). Also, the drop in the photosynthetic rate was associated with significant drop in stomatal conductance (p < 0.0001). The electron transmission micrographs revealed that nicotine-treated seedlings (3,000 and 5,000 µM) exhibited deformed chloroplasts with numerous plastoglobules reducing the photosynthetic rates.

This is one of few studies that deal with the impact of exogenous nicotine on plants. However, to the best of our knowledge, this is the first hydroponic study that used liquid pure nicotine implied to the plants. The morphological, physio-biochemical, and anatomical characteristics were investigated using Capsicum annuum as a model plant, a plant that synthesizes little endogenous nicotine. This study will shed more light about nicotine toxicity in plants.

Alleviation of adverse effects of nickel on growth and concentration of copper and manganese in wheat through foliar application of ascorbic acid.

We investigated the role of ascorbic acid (AsA) to alleviate nickel (Ni) induced adverse effects on growth and concentration of Ni, copper (Cu), and manganese (Mn) in hydroponically grown wheat varieties viz. Galaxy, Punjab-2011, and FSD-08. Plants were exposed to five levels of Ni viz. 0, 5, 10, 15, and 20 mg L-1. After 1 week, AsA (1 mM) was sprayed onto the Ni-stressed plants. FSD-08 produced the maximum SDW with and without AsA compared to other varieties. FSD-08, Galaxy, and Punjab-2011 witnessed 2.61-, 2.83-, and 7.5-fold increases in SDW with AsA, respectively. Wheat plants contained the maximum Ni in shoots and roots with a Ni level of 20 mg L-1 irrespective of varieties. Nickel in shoots decreased with AsA witnessing 13, 12, and 10% decrease in FSD-08, Punjab-2011, and Galaxy, respectively. Nickel in roots of FSD-08 decreased by 18% while increased by 3.34-fold and 3.50-fold in Galaxy and Punjab-2011, respectively with AsA. Nickel decreased Cu in shoot and Mn in shoot and root while Cu in roots of all wheat varieties increased. It was concluded that AsA improved the growth of Ni-stressed and FSD-08 performed better by maintaining good growth and less Ni in shoots compared to other varieties.

Exploiting plant internal mechanisms with foliar application of different organic substances have widely been investigated to decrease metal accumulation and their adverse effects on plants. However, the differential response of different varieties to metal accumulation in response to foliar application of ascorbic acid is not well documented. This study was conducted to investigate the effect of exogenous application of ascorbic acid on growth response, the concentration of Ni, Cu, and Mn in three wheat varieties.

Rice ß-Glucosidase 4 (Os1ßGlu4) Regulates the Hull Pigmentation via Accumulation of Salicylic Acid.

Salicylic acid (SA) is a stress hormone synthesized in phenylalanine ammonia-lyase (PAL) and the branching acid pathway. SA has two interconvertible forms in plants: SAG (SA O-ß-glucoside) and SA (free form). The molecular mechanism of conversion of SA to SAG had been reported previously. However, which genes regulate SAG to SA remained unknown. Here, we report a cytoplasmic ß-glucosidase (ß-Glu) which participates in the SA pathway and is involved in the brown hull pigmentation in rice grain. In the current study, an EMS-generated mutant brown hull 1 (bh1) displayed decreased contents of SA in hulls, a lower photosynthesis rate, and high-temperature sensitivity compared to the wild type (WT). A plaque-like phenotype (brown pigmentation) was present on the hulls of bh1, which causes a significant decrease in the seed setting rate. Genetic analysis revealed a mutation in LOC_Os01g67220, which encodes a cytoplasmic Os1ßGlu4. The knock-out lines displayed the phenotype of brown pigmentation on hulls and decreased seed setting rate comparable with bh1. Overexpression and complementation lines of Os1ßGlu4 restored the phenotype of hulls and normal seed setting rate comparable with WT. Subcellular localization revealed that the protein of Os1ßGlu4 was localized in the cytoplasm. In contrast to WT, bh1 could not hydrolyze SAG into SA in vivo. Together, our results revealed the novel role of Os1ßGlu4 in the accumulation of flavonoids in hulls by regulating the level of free SA in the cellular pool.

Controlled-release urea combined with fulvic acid enhanced carbon/nitrogen metabolic processes and maize growth.

BACKGROUND: Controlled-release urea (CRU) or fulvic acid (FA), when applied, have been shown to increase nitrogen (N) use efficiency (NUE) or to stimulate plant growth, yet their interactive effects are not well explored. The objective of this study was to investigate the synergistic mechanisms of CRU combined with FA (CRU + FA) on maize (Zea mays L.) growth. Through the experimental design with five treatments, the N metabolism through the transcriptomic analysis of maize leaf, endogenous hormones, photosynthesis enzymes in maize leaf and root, and maize yield and NUE were evaluated. RESULTS: Compared with CRU treatment, CRU + FA treatment significantly increased auxin, nitrate reductase, and glutamate dehydrogenase in leaf by 35.4%, 43.9%, 40.8% and 19.5%, respectively, as well as, the relative content of the leaf chlorophyll and photosynthetic rate by 14.8% and 45.6%, respectively, at 12-leaf collar stage; the carbon/nitrogen (C/N) metabolic process was significantly enriched in CRU + FA treatment by 312 and 418 genes, according to transcriptome profiles of C/N metabolic in leaves from various fertilizer treated maize; maize yield and NUE of CRU + FA treatment were increased by 6.3% and 38.4%, respectively. CONCLUSIONS: These results demonstrated that CRU + FA is a viable fertilization scheme that can enhance maize growth, yield and NUE through their synergies in improving N uptake, promoting photosynthesis, increasing C/N metabolic processes, and enhancing enzyme activities. © 2021 Society of Chemical Industry.

Deficit drip irrigation based on crop evapotranspiration and precipitation forecast improves water- use efficiency and grain yield of summer maize.

BACKGROUND: Limited and erratic precipitation with inefficient irrigation scheduling often leads to an unstable crop yield and low water-use efficiency (WUE) in semi-arid and semi-humid regions. A 2-year field experiment was conducted to evaluate the effect of three irrigation strategies (conventional irrigation (CK), full-drip irrigation (FI), based on crop evapotranspiration and precipitation forecast, and deficit drip irrigation (DI) (75% FI)) on photosynthetic characteristics, leaf-to-air temperature difference (∆T), grain yield, and the WUE of summer maize. RESULTS: The results showed that the daily average net photosynthetic rate (Pn) of DI and FI increased by 25.4% and 25.8% at jointing stage in 2018, and 26.3% and 26.5% at grain-filling stage in 2019 compared with CK, respectively. At jointing stage in 2018 and grain-filling stage in 2019, the transpiration rate (Tr) of DI was significantly lower than that of FI (P < 0.05) but there was insignificant difference in Pn value (P > 0.05). The ∆T between 12:00-14:00 of DI and FI was significantly lower than that of CK at jointing stage in 2018 and grain-filling stage in 2019 (P < 0.05). The 2-year average grain yields of DI and FI were 11.4 and 11.5 t ha-1 , which increased by 32.4% and 32.8% compared with CK, respectively. The WUE of DI was 2.82 kg m-3 , which was 17.9% and 33.8% higher than that of FI and CK, respectively. CONCLUSION: Deficit drip irrigation based on crop evapotranspiration and precipitation forecast improves crop WUE and maintains high grain yields in semi-arid and semi-humid regions. © 2021 Society of Chemical Industry.

Light availability in the cultivation environment and the action of glyphosate on Digitaria insularis: physiological aspects and herbicide root exudation.

The root exudation decreases the susceptibility of some species to herbicides, which is still little studied in Digitaria insularis, popularly known as sourgrass, one of the main weeds of annual crops in the world. Thus, we sought to identify whether there is an occurrence of root exudation of glyphosate in D. insularis and the influence of this herbicide on physiological and control parameters of this species when cultivated under different light conditions. The experimental design was 2 x 5, with the first factor represented by environments: full sun and artificial shading. The second factor was represented by doses 0, 370, 740, 1110, and 1480 g ha-1 of glyphosate. The plants grown in shading showed more significant injury in the initial phase. The increase in the glyphosate doses reduced the photochemical efficiency of the photosystem II (ФPSII), electron transport rate (ETR), photosynthetic rate, stomatal conductance, transpiration rate, and water use efficiency of D. insularis regardless of the cultivation environment. The light restriction increased the ФPSII in D. insularis at three days after applying the herbicide (DAH); at 6 DAH, the shaded plants showed a more pronounced reduction in ФPSII. D. insularis did not show root exudation of glyphosate, and shading did not influence this process.

[Attapulgite can improve yield and total ferulic acid content of Angelica sinensis by adjusting source-sink relationship].

Attapulgite(ATP), as a fertilizer slow-release agent and soil conditioner, has shown remarkable effect in improving the utilization rate of fertilizer and the yield and quality of agricultural products and Chinese medicinal materials. This study aims to explore the effect of ATP on the growth and root quality of Angelica sinensis. To be specific, Mingui 1 was used, and through the pot(soil culture) experiment in the Dao-di producing area, the effects of conventional chemical fertilizer added with ATP on the morphology, photosynthesis, soil respiration, and content of ferulic acid and volatile oil in roots of Mingui 1 were detected. The underlying mechanism was discussed from the perspective of source-sink relationship. The results showed that ATP, via the fertilizer slow-release effect, could meet the needs of A. sinensis for nutrients at the root expansion stage, improve the net photosynthetic rate of leaves and aboveground biomass of plants, and promote the transfer and accumulation of nutrients from the aboveground part(source) to the underground root(sink) in advance during the dry matter accumulation period of roots, so as to improve the root weight per plant. ATP can increase the content of total ferulic acid(the sum of free ferulic acid and coniferyl ferulate), the main effective component of Angelicae Sinensis Radix, by promoting the synthesis of ferulic acid in the roots and the transformation to coniferyl ferulate. However, it had little effect on the content of volatile oil. ATP had certain influence on soil respiration, which needs to be further explored from root activity, rhizosphere microorganisms, and soil microorganisms. This study can lay a basis for soil remediation and improvement and ecological cultivation of A. sinensis.

Effect of drought on photosynthesis, total antioxidant capacity, bioactive component accumulation, and the transcriptome of Atractylodes lancea.

BACKGROUND: Atractylodes lancea (Thunb.) DC, a medicinal herb belonging to the Asteraceae family, often faces severe drought stress during its growth. Until now, there has been no research on the effect of drought stress on the quality formation of A. lancea. Therefore, the present study aimed to study the effects of drought stress on A. lancea through physical and chemical analysis, and to reveal the related molecular mechanisms via transcriptome analysis. RESULTS: The photosynthesis was markedly inhibited under drought stress. There were alterations to photosynthetic parameters (Pn, Gs, Ci) and chlorophyll fluorescence (Fv/Fm, NPQ), and the chlorophyll content decreased. Twenty genes encoding important regulatory enzymes in light and dark reactions, including the Rubisco gene of the Calvin cycle, were significantly downregulated. After exposure to drought stress for more than 4 days, the activities of four antioxidative enzymes (SOD, POD CAT and APX) began to decrease and continued to decrease with longer stress exposure. Meanwhile, most of the genes encoding antioxidative enzymes were downregulated significantly. The downregulation of 21 genes related to the respiratory electron transport chain indicated that the blocked electron transfer accelerated excessive ROS. The MDA content was significantly elevated. The above data showed that 15 days of drought stress caused serious oxidative damage to A. lancea. Drought stress not only reduced the size and dry weight of A. lancea, but also lowered the amount of total volatile oil and the content of the main bioactive components. The total volatile oil and atractylodin content decreased slightly, whereas the content of atractylon and ß-eudesmol decreased significantly. Moreover, ten significantly downregulated genes encoding sesquiterpene synthase were mainly expressed in rhizomes. CONCLUSIONS: After exposed to drought stress, the process of assimilation was affected by the destruction of photosynthesis; stress tolerance was impaired because of the inhibition of the antioxidative enzyme system; and bioactive component biosynthesis was hindered by the downregulation of sesquiterpene synthase-related gene expression. All these had negative impacts on the quality formation of A. lancea under drought stress.

Enhanced photosynthetic nitrogen use efficiency and increased nitrogen allocation to photosynthetic machinery under cotton domestication.

Domestication involves dramatic phenotypic and physiological diversifications due to successive selection by breeders toward high yield and quality. Although photosynthetic nitrogen use efficiency (PNUE) is a major trait for understanding leaf nitrogen economy, it is unclear whether PNUE of cotton has been improved under domestication. Here, we investigated the effect of domestication on nitrogen allocation to photosynthetic machinery and PNUE in 25 wild and 37 domesticated cotton genotypes. The results showed that domesticated genotypes had higher nitrogen content per mass (Nm), net photosynthesis under saturated light (Asat), and PNUE but similar nitrogen content per area (Na) compared with wild genotypes. As expected, in both genotypes, PNUE was positively related to Asat but negatively correlated with Na. However, the relative contribution of Asat to PNUE was greater than the contribution from Na. Domesticated genotypes had higher nitrogen allocation to light-harvesting (NL, nitrogen in light-harvesting chlorophyll-protein complex), to bioenergetics (Nb, total nitrogen of cytochrome f, ferredoxin NADP reductase, and the coupling factor), and to Rubisco (Nr) than wild genotypes; however, the two genotype groups did not differ in PNUEp, the ratio of Asat to Np (itself the sum of NL, Nb, and Nr). Our results suggest that more nitrogen allocation to photosynthetic machinery has boosted Asat under cotton domestication. Improving the efficiency of nitrogen use in photosynthetic machinery might be future aim to enhance Asat of cotton.