For establishment and growth of newly planted seedlings it is essential to overcome environmental stress at the planting site. Adding the amino acid arginine at planting is a novel treatment aiming at increased establishment success, so far tested in a limited number of applied studies. We examined the effects of adding arginine-phosphate (arGrow (R)), mechanical site preparation (MSP), and planting time on survival and growth of Norway spruce and Scots pine seedlings in two field experiments in boreal southeastern Norway. After three growing seasons, survival for spring planted seedlings of both species was significantly better following MSP, while addition of arginine-phosphate did not have any effect. Autumn planted pine seedlings with MSP and arginine had higher survival and also larger diameter than spring planted ones with MSP but without arginine. Spruce and pine seedlings with MSP were taller and had larger diameter than those without MSP. For spring planted seedlings of both species, dry weight of roots and shoots was positively affected by MSP, but not by arginine. To conclude, arginine-phosphate had neutral to modestly positive effects on survival and growth, while MSP had clear positive effects. The effect of planting time varied with species.

Drought (D) and chromium (Cr) stress co-occur in agricultural fields due to the accumulation of excessive Cr in soils from industrial pollution and increasing frequency of water scarcity. Carrageenan (Car), a compound extracted from red seaweed, is an emerging biostimulant with multifaceted roles in plants. This study investigated the role of exogenous Car in mediating tolerance to D-, Cr-, and DCr-stress in wheat seedlings, aiming to elucidate the potential of Car in mitigating toxicity and promoting plant resilience. Wheat seedlings exposed to DCr-stress exhibited reduced growth and biomass production, along with elevated levels of reactive oxygen, carbonyl, and nitrogen species. Moreover, D-stress exacerbated Cr-toxicity, as demonstrated by principal component analysis (PCA), which showed a strong positive correlation between DCr-stress and stress marker parameters. This suggests that DCr-stress resulted in higher Cr uptake and increased oxidative damage compared to individual D-or Cr-stress, making DCr-stress more detrimental than either stress applied alone. However, Car priming ameliorated the toxic effects of DCr-stress and promoted the growth performance of DCr-stressed wheat seedlings. In PCA, the positive correlation of D + Car, Cr + Car, and DCr + Car treatments with growth and plant defense-related parameters suggests that Car-mediated improvement in stress tolerance can be attributed to reduced accumulation of toxic Cr, increased levels of total free amino acids and soluble sugars, enhanced antioxidant enzyme activity, elevated non-enzymatic antioxidant levels, higher phenolic and flavonoid content, and improved metal chelation and detoxification. Our results indicated Car is a potential and cost-effective biostimulant for managing D-, Cr-, or DCr-stress in wheat.

Soil salinity, a critical environmental stressor, substantially impacts plant growth and productivity. It induces osmotic stress, disrupts ion homeostasis, and triggers the excessive production of reactive oxygen species (ROS), which can lead to oxidative damage within plant cells. To counteract these detrimental effects, plants have evolved sophisticated defense mechanisms, one of which involves the production of secondary metabolites (SMs). These SMs function as biostimulants that bolster antioxidative defenses and modulate signal transduction pathways, thus enhancing the plant's tolerance to salt stress. Recent evidence reveals SMs like sulforaphane (glucosinolate-derived) uniquely stabilize redox cofactors and reprogram stress-responsive miRNAs. Furthermore, they influence key signaling cascades, such as the mitogen-activated protein kinase (MAPK) pathway and various hormone-regulated pathways, which are instrumental in orchestrating adaptive responses to saline conditions. The regulation of SMs biosynthesis under salt stress is mediated by transcription factors like MYB, WRKY, and bHLH, which are essential for activating the genes involved in these metabolic pathways. Elucidating the intricate mechanisms by which SMs operate as biostimulants not only advances our understanding of plant stress responses but also paves the way for developing sustainable agricultural practices aimed at improving crop resilience in saline environments. This knowledge is instrumental for cultivating crops that can thrive under challenging soil conditions, ultimately contributing to global food security.

Climate change events significantly impact the food production chain by damaging crops in their most fragile phenological states. Furthermore, increasing human population and excess food waste present agricultural systems with the challenge of closing the yield gap and securing food demands in the future as well as protect the soil health and biodiversity. Biostimulants are a novel alternative in agriculture that can effectively use inputs, enhance crop resilience to abiotic stresses and improve food quality. Additionally, biostimulants offer a promising and eco-friendly solution for reducing the use of chemical fertilizers, as they have the potential to increase crop nutrient use efficiency and yield. Because of their effects on plant growth, a wide range of products can be marketed as biostimulants. Presented in this review is an overview of recent literature on the use of plant growth-promoting microbes and microalgae-derived extracts obtained from either waste streams or recycled substrates. Starting from their source material, extraction technologies and application modalities, a view of their factors shaping the composition and activity of biostimulants is provided to elucidate a mechanistic model of action which leads to increased stress resilience in crops. This work further sets out to understand if the biostimulants can be used to transform waste into a valuable product that can accelerate the transition to sustainable agriculture.This article is part of the theme issue 'Crops under stress: can we mitigate the impacts of climate change on agriculture and launch the 'Resilience Revolution'?'.

Environmental stresses, particularly drought and salinity, significantly impair plant growth and productivity. This study explores the novel synergistic interaction between biochar and arbuscular mycorrhizal fungi (AMF) in enhancing the resilience of sweet pepper plants subjected to the individual or combined stresses of drought and salinity. The impact of these biostimulants on growth parameters, photosynthetic efficiency, and biochemical traits was assessed. Sweet pepper plants were subjected to drought stress (35 and 75% of field capacity (FC)), salinity (0 and 150 mM NaCl), and their combined effects (150 mM NaCl +35% of FC), with treatments including biochar (2.5 g/kg soil), AMF, and their combination. Under drought stress, the dual application of biochar and AMF notably improved plant growth indicators such as shoot fresh weight, shoot height, and number of leaves by 50, 14, and 3%, respectively compared to the control plants. Under drought and salinity combined, this combination also enhanced photosynthetic pigments content by 144% for Chl a, 316% for Chl b, 212% for Chl T and 302% for carotenoids content respectively compared to the control plants. Additionally, AMF and Biochar combined reduced the oxidative effect of malondialdehyde (MDA) by 37% and hydrogen peroxide (H2O2) by 43%, indicating a reduction in oxidative damage. Furthermore, a significant increase in antioxidant enzyme activities was observed, with peroxidase activity (POX) rising by 33% and polyphenol oxidase activity (PPO) increasing by 212%, indicating enhanced stress tolerance. This study underscores the efficacy of using biochar and AMF together to bolster sweet pepper plant resilience, offering a viable strategy for improving plant performance under challenging environmental conditions.

The increasing soil pollution has accelerated the implementation of new agricultural regulations that significantly limit the use of synthetic nitrogen (N) fertilizers. Consequently, plants are likely to experience nutrient stress, leading to decreased productivity and potential threats to food security. To address these critical challenges, microbial-based biostimulant (BS) products, which utilize metabolites from microorganisms, offer a sustainable and eco-friendly solution to mitigate plant nutrient stress. This study evaluated the effects of the radicular application of a microbial-based BS containing L-alpha-amino acids on lettuce and pepper crops under two nitrogen regimes: optimal N availability and N stress (NS). Various parameters, including growth, production, soluble proteins, photosynthetic pigment content, and oxidative stress markers, were assessed. Under optimal N conditions, BS application enhanced commercial biomass in lettuce and vegetative biomass in pepper, indicating that BSs can reduce the need for nitrate uptake and endogenous amino acid synthesis, thereby conserving energy for other physiological processes. Despite BS application, NS conditions significantly reduced vegetative and reproductive growth in both species. However, BS treatment in pepper plants increased chloroplast pigments, improving light absorption and photosynthetic efficiency. The reduction in the carotenoid/chlorophyll ratio suggests efficient N allocation to growth and production. Thus, BS application proved effective in mitigating NS in pepper plants, enhancing pepper production, while under optimal conditions, it improved lettuce yield, particularly commercial biomass. These findings underscore the potential of symbiotic microbial-based BSs as a promising tool for sustainable agriculture under reduced N availability.

BackgroundGlobally, salinity poses a threat to crop productivity by hindering plant growth and development via osmotic stress and ionic cytotoxicity. Plant extracts have lately been employed as exogenous adjuvants to improve endogenous plant defense mechanisms when grown under various environmental stresses, such as salinity. This study investigated the potential of melatonin (Mt; 0, 50, and 100 mM) as an antioxidant and licorice root extract (LRE; 0.0 and 3%) as an organic biostimulant applied sequentially as a foliar spray on faba bean (Vicia faba L.) grown in cadmium (Cd)-contaminated saline soil conditions [Cd = 4.71 (mg kg- 1 soil) and ECe = 7.84 (dS m- 1)]. Plants not receive any treatment and sprayed with H2O were considered controls. The experimental treatments were laid out in strip plot in a randomized complete block design replicated thrice, where the LRE and Mt were considered as vertical and horizontal strips, respectively. Growth characteristics, photosynthetic pigments, nutrient uptake, physiology and metabolic responses, anatomical features, and yield were assessed.ResultsCadmium (Cd) and salinity-induced stress significantly altered leaf integrity, photosynthetic efficiency, total soluble sugars (TSS), free proline (FPro), total phenolic, DPPH, and total soluble proteins (TSP), non-enzymatic and enzymatic antioxidants, growth characteristics and yield-related traits. However, the application of LRE + Mt considerably improved these negative effects, with higher improvements were observed due to application of LRE + Mt100. Application of LRE + Mt significantly reduced hydrogen peroxide (H2O2) accumulation, lipid peroxidation and Cd content in leaves and seeds, all of which had increased due to Cd stress. Application of LRE + Mt significantly mitigated the Cd-induced oxidative damage by increasing the activity of reactive oxygen species (ROS) scavenging enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, in parallel with enhanced ascorbate and reducing glutathione content. Exogenous application of LRE + Mt significantly increased osmolyte content, including FPro, TSS, and total phenols and mitigated Cd-induced reduction to considerable levels.ConclusionsOur findings showed that LRE + Mt increased V. faba plants' morphological, physiological, and biochemical properties, reducing Cd stress toxicity, and promoting sustainable agricultural practices.Clinical trial numberNot applicable.

The land areas and crop species adversely impacted by salinity and heavy metals are growing rapidly. Current research indicates that plant growth-promoting microorganisms offer an environmentally friendly option for improving physiological and biochemical processes in plants growing under stress conditions. The aim of the present study was to investigate the potential mitigation of simultaneous salinity and cadmium (Cd) stress in rapeseed ( Brassica campestris cv. BARI Sarisha-17) by the application of Azospirillum sp. (Az), phosphate solubilizing bacteria (PSB), potassium mobilizing bacteria (KMB), and vesicular arbuscular mycorrhiza (VAM). Seeds were treated with PSB or KMB prior to sowing, whereas Az, PSB, KMB, or VAM were added as supplements during soil preparation. At 21 days after sowing, the plants were treated with a combination of salt (100 mM NaCl) and Cd (0.25 mM CdCl2), with several applications at 7-day intervals. The combination of salt and Cd stress decreased plant growth and biomass, relative water content, and photosynthetic pigment levels, while also increased electrolyte leakage, lipid peroxidation, and the generation of excess reactive oxygen species (ROS). Salt and Cd stress also impaired plant ion balances of sodium, potassium and nitrate, antioxidant defenses, and glyoxalase system activity. Application of Az, PSB, or KMB restored these parameters to unstressed levels by facilitating the scavenging of ROS, maintaining water status, restoring ion balances, enhancing plant antioxidant defenses, and increasing glyoxalase enzyme activity, while reducing methylglyoxal toxicity and improving photosynthetic activity. The application of KMB was the most effective; however, all microbe supplementations showed the ability to alleviate the damage caused by stress in rapeseed. These findings highlight the ability of soil microorganisms with plant growth-promoting properties to improve the physiological and biochemical functions of rapeseed under Cd and salt stress.

Global climate change has significantly reduced the yield of many crops due to various abiotic stressors. These stressors include water-related issues such as drought and flooding, thermal changes like extremely low and high temperatures, salinity, and adverse soil pH conditions including alkalinity and acidity. Biostimulants have emerged as promising and effective tools for mitigating the damage caused by these abiotic stressors in plants, ultimately enhancing both the quantity and quality of crops. Biostimulants are naturally derived substances that include humic acid, protein hydrolysates, nitrogenous compounds, seaweed extracts, beneficial bacteria, and molds. Even at low concentrations, biostimulants play a critical role in activating important plant enzymes, inducing antioxidant defenses, improving water relations and photosynthetic activity, stimulating hormone-like activities (particularly auxins, gibberellins, and cytokinins), and modulating root system development. This review discusses the physiological effects of microbial biostimulants on the quality and productivity of fruit crops, as well as their experimental applications.

Drought is a crucial abiotic stress having a devastating effect on crops, including tomatoes (Solanum lycopersicum L.). Exogenous application of plant biostimulants and essential/beneficial nutrients is an efficient method for increasing plant tolerance and maintaining productivity under drought stress. Individual soil application of the commercial Ascophyllum nodosum seaweed extract (ASE) and potassium (K) has been widely used in alleviating drought stress in many crops. However, little information has been gained regarding the role of the integrated application of ASE and K in mitigating detrimental effects of drought stress. This study examines the combined effect of ASE and K on tomato plants on growth, fruit yield and quality, and water productivity (fruit yield [kg] per volume of water input [m(3)] throughout the growing season) under drought stress conditions. The commercial formulation of ASE was incorporated in five doses (0 [control], 1.25, 2.5, 3.75, and 5 mL L-1) along with a uniform dose of K (100 kg K2O ha(-1)) under three different soil water contents (50%, 75%, and 100% field capacity [FC]). Control plants did not receive any application of ASE or K; K applied at the same dose (100 kg K2O ha(-1)) without ASE was also included as a treatment. Poor vegetative growth, fruit yield, and physiological responses were observed with decreasing soil water content irrespective of ASE doses. Leaf area, root dry matter, fruit yield, water productivity, and membrane stability index were reduced from 26-55%, 42-58%, 53-72%, 27-48%, and 37-57%, respectively, at the lowest soil water content (50% FC) compared with 100% FC across ASE doses. Reducing soil water content to 50% FC triggered up to a 50% increase in fruit firmness and 33-67% increase in electrolyte leakage than those at 100% FC across ASE doses. Application of ASE in combination with K was effective at all doses with the highest dose of 5 mL L-1 producing up to 266% increased fruit yield, up to178% higher water productivity, up to 60% higher leaf relative water content, and up to 125% higher membrane stability index across all three soil water contents. The same dose reduced electrolyte leakage of plants by up to 48% across three soil water contents. The sole application of K resulted in a significant improvement in growth, fruit yield, and physiological traits of tomato plants. Fruit yield of plants grown with ASE (5 mL L-1) and K (100 kg K2O ha(-1)) at 50% FC was statistically similar to fruit yield of the control plants at 100% FC. Water productivity was even higher for the same treatment combinations. The same was also largely true for other growth and physiological parameters, highlighting the benefits of the integrated application of ASE and K in mitigating drought stress effects on tomato plants. An integrated program comprising ASE (5 mL L-1) and K (100 kg K2O ha(-1)) may constitute a potential beneficial strategy for tomato cultivation in water-scarce areas due to their synergistic response against drought stress.