Growth and physiological alterations in Niger cultivars under drought stress

Aim of the present study was to determine differential responses in growth and physiology of tolerant (cv. IGPN 2004) and sensitive (cv. GA 10) cultivars of Niger (Guizotia abyssinica Cass.) using in vitro grown calli under water deficit conditions. The calli were subjected to drought stress using PEG-8000 (–0.16,–0.45,–0.87,–1.42 bar) for 15 d and relative growth rate (RGR), percent tissue water content (% TWC), osmolytes (proline–Pro, glycine betaine—GB, total soluble sugars—TSS) accumulation, malondialehyde (MDA) content as well as antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were analysed. Our findings showed that RGR and percent TWC was decreased significantly with the intensity of drought stress in both cultivars, but the RGR reduction was least (five folds) in cv. IGPN 2004 than in cv. GA 10 (6.2 folds). In osmolyte accumulation such as Pro and GB, cv. IGPN 2004 was found superior (5.5 and ten folds higher, respectively) to tolerate drought stress than GA 10; however, no change was observed in TSS accumulation. Further, it was noted that cv. IGPN 2004 caused least oxidative damage to the membranes. It also exhibited better SOD, CAT and APX activities and had higher α-tocopherol content. The least reduction in growth and MDA content and higher osmolytes and antioxidant activities in cv. IGPN 2004 revealed more drought stress tolerance at cellular level. It was suggested that increased drought tolerance of cv. IGPN 2004 was coupled with its better maintenance of RGR, percent TWC, reduced lipid peroxidation, more accumulation of osmolytes and higher antioxidant enzymes.     

Drought resistance in rice seedlings conferred by seed priming

Seed priming is a method by which seeds are subjected to different stress conditions to impart stress adaptation in seedlings germinating and growing under stressful situations. Drought stress is a major reason behind failure of crops. We studied the effects of hydropriming, dehydration priming (induced by PEG), and osmopriming (induced by NaCl and KH₂PO₄) on subsequent germination, growth and anti-oxidant defense mechanisms of 2-week-old rice seedlings under continuing dehydration stress. Unprimed seeds grown in PEG showed significantly lower germination and growth along with significantly higher reactive oxygen species (ROS) and lipid peroxidation levels. Among the priming methods, 5 % PEG priming was found to be the best in terms of germination and growth rate along with the lowest amount of ROS and lipid peroxidation (malondialdehyde [MDA]) values. MDA levels were reduced significantly by all of the priming methods. Hence, reduction of lipid peroxidation may be a key factor underlying the drought tolerance produced by the priming treatments. Glutathione peroxidase (GPX) activity seemed to bear an excellent correlation with oxidative stress resistance through seed priming. The PEG priming produced minimum peroxidative damage and superior germination and growth rate along with efficient GPX activity, overexpressed MnSOD and maintenance of HSP70 expression in normal as well as in drought condition. Therefore, in PEG-primed seeds the existence of robust protective mechanisms is definitely indicated.     

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5 mg L^?1), SWE (5% v/v), BAP + SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10 dS m^?1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K⁺) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na⁺) contents were decreased. Seed priming with SWE + BAP was the most effective in this regard. Under salt stress, the tissue Na⁺ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE + BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE + BAP > BAP > SWE > Hydropriming. In conclusion, seed priming with SWE + BAP may be opted to improve the tolerance against salt stress in wheat.     

Exogenously applied polyamines increase drought tolerance of rice by improving leaf water status,photosynthesis and membrane properties

Drought stress hampers rice performance principally by disrupting the plant–water relations and structure of biological membranes. This study appraised the role of polyamines (PAs) in improving drought tolerance in fine grain aromatic rice (Oryza sativa L.). Three PAs [putrescine (Put), spermidine (Spd) and spermine (Spm)] were used each at 10 μM as seed priming (by soaking seeds in solution) and foliar spray. Primed and non-primed seeds were sown in plastic pots with normal irrigation in a phytotron. At four-leaf stage, plants were subjected to drought stress by bringing the soil moisture down to 50% of field capacity by halting water supply. For foliar application, 10 μM solutions each of Put, Spd and Spm were sprayed at five-leaf stage. Results revealed that drought stress severely reduced the rice fresh and dry weights, while PAs application improved net photosynthesis, water use efficiency, leaf water status, production of free proline, anthocyanins and soluble phenolics and improved membrane properties. PAs improved drought tolerance in terms of dry matter yield and net photosynthesis was associated with the maintenance of leaf water status and improved water use efficiency. Among the antioxidants, catalase activity was negatively related to H₂O₂ and membrane permeability, which indicated alleviation of oxidative damage on cellular membranes by PAs application. Foliar application was more effective than the seed priming, and among the PAs, Spm was the most effective in improving drought tolerance.     

Recent methods of drought stress tolerance in plants

In the climate change scenario the drought has been diagnosed as major stress affecting crop productivity. This review demonstrates some recent findings on the amelioration of drought stress. Nanoparticles, synthetic growth regulators viz. Trinexapac-ethyl, and Biochar addition helps to economize the water budget of plants, enhances the bioavailability of water and nutrients as well as overcomes drought induced osmotic and oxidative stresses. Besides ABA, SA and JA are also involved in inducing tolerance to drought stress through modulation of physiological and biochemical processes in plants. Plant growth promoting rhizobacteria (PGPR) offer new opportunities in agricultural biotechnology. These beneficial microorganisms colonize the rhizosphere/endo-rhizosphere of plants and impart drought tolerance by improving root architechture, enhancing water use efficiency, producing exopolysaccharides, phytohormones viz, ABA, SA and IAA and volatile compounds. Further PGPR also play positive role in combating osmotic and oxidative stresses induced by drought stress through enhancing the accumulation of osmolytes, antioxidants and upregulation or down regulation of stress responsive genes. In transgenic plants stress inducible genes enhanced abiotic stress tolerance by encoding key enzymes regulating biosynthesis of compatible solutes. The role of genes/cDNAs encoding proteins involved in regulating other genes/proteins, signal transduction process and strategies to improve drought stress tolerance have also been discussed.     

Brassinosteroid seed priming with nitrogen supplementation improves salt tolerance in soybean

This study was conducted to evaluate the influence of brassinosteroid (24-epibrassinolide, EBL) seed priming and optimal nitrogen (N) supply in improving salt tolerance in soybean. The experimental treatments were (a) control (nutrient solution without N and without EBL priming), (b) nutrient solution without N and EBL seed priming, (c) N supplemented nutrient solution without EBL priming and (d) EBL seed priming + N supplemented nutrient solution under optimal (0 mM NaCl) and salt stress (0 mM NaCl) conditions. Salt stress caused significant reduction in growth and biomass accumulation of soybean. However, EBL seed priming and application of N improved the soybean performance under optimal and salt stress conditions. In this regard, treatments receiving both EBL and N were more effective. EBL priming and N, alone and in combination, triggered the accumulation of osmolytes including proline, glycine betaine and sugars resulting in better photo-protection through maintenance of tissue water content. Antioxidant activity and osmolyte accumulation significantly increased due to combined treatment of N and EBL under normal as well as salt stress conditions. In conclusion, salt stress caused reduction in growth and biomass soybean due to oxidative damage and osmotic stresses. However, soybean performance was improved by seed priming with EBL. Supplementation of N further improved the effectiveness of EBL treatment in improving salt tolerance in soybean.     

Sugar beet extract acts as a natural bio-stimulant for physio-biochemical attributes in water stressed wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The present study investigated the role of sugar beet extract (SBE) as a bio-stimulant to ameliorate the adverse effects of drought on seed germination and growth of wheat (Triticum aestivum L.). Different concentrations of SBE (0, 10, 20, 30, 40 and 50%) were used for priming the wheat seeds. The experiment was conducted in laboratory (PEG-8000 was used to create water stress) as well as under natural environmental conditions (using soil with 100 and 60% field capacity). Significant ameliorating effects of seed priming with SBE were recorded on different germination attributes, i.e., time to 50% emergence (E₅₀), germination index (GI), mean emergence time (MET), germination percentage (G%), coefficient of uniformity of emergence (CUE) and germination energy (GE) under water stress. Without priming, the plants exhibited symptoms of water stress like decreased biomass, reduction in photosynthetic pigments, e.g., chlorophyll, carotenoids. Seed pre-conditioning with SBE improved the plant growth, photosynthetic pigments, antioxidants’ activities and nutrient homeostasis of plants facing water deficit and grown under well-watered conditions. The maximum increase in biomass, content of chlorophyll, carotenoids and activities of superoxide dismutase (SOD) and peroxidase (POD) was 13.4, 8.5, 11.9, 7.6, 13.6, 42.0, 19.8%, respectively, with SBE seed priming under water stress. In conclusion, SBE seed priming effectively reduced the negativities of water stress on seed germination which resulted in better plant growth in terms of enhanced biomass, photosynthetic pigments, antioxidant defense mechanism and better nutrient homeostasis. Overall, the findings suggest that seed pre-conditioning with SBE as a bio-stimulant will be helpful for better crop stand establishment under low field capacity, especially in semi-arid and arid agricultural fields.     

Effects of drought stress and selenium supply on growth and physiological characteristics of wheat seedlings

The paper studied the effects of drought stress, selenium (Se) supply and their combination on growth and physiological characteristics of wheat (Triticum aestivum L. cv Shijiazhuang NO. 8) seedlings. The experimental design included two water treatments (well-watered, 75% of maximum field capacity; drought stress, 30% of maximum field capacity) and two Se levels (0; 0.5 mg/kg) to determine whether Se can modify the negative impacts of drought stress on seedling growth and physiological traits. Drought stress caused a marked decline in growth parameters and soluble protein content, whereas it induced an increase in root activity, proline content and the activities of peroxidase (POD) and catalase (CAT) of leaf tissue. On the other hand, Se supply induced an increase in biomass accumulation only under well-watered condition. Under drought stress, Se supply increased free proline content, root activity and the activities of POD and CAT in leaf tissue, but did not significantly affect on growth parameters. These results implied that drought stress brought harmful effects on wheat seedlings, and that Se supply was favorable for biomass accumulation of wheat seedlings under well-watered condition. However, it did not significantly affect on biomass accumulation under drought stress, although it increased root activity and activities of some antioxidant index in experimental periods.     

Tolerance of Mycorrhiza infected pistachio (Pistacia vera L.) seedling to drought stress under glasshouse conditions

The influence of Glomus etunicatum colonization on plant growth and drought tolerance of 3-month-old Pistacia vera seedlings in potted culture was studied in two different water treatments. The arbuscular mycorrhiza (AM) inoculation and plant growth (including plant shoot and root weight, leaf area, and total chlorophyll) were higher for well-watered than for water-stressed plants. The growth of AM-treated seedlings was higher than non-AM-treatment regardless of water status. P, K, Zn and Cu contents in AM-treated shoots were greater than those in non-AM shoots under well-watered conditions and drought stress. N and Ca content were higher under drought stress, while AM symbiosis did not affect the Mg content. The contents of soluble sugars, proteins, flavonoid and proline were higher in mycorrhizal than non-mycorrhizal-treated plants under the whole water regime. AM colonization increased the activities of peroxidase enzyme in treatments, but did not affect the catalase activity in shoots and roots under well-watered conditions and drought stress. We conclude that AM colonization improved the drought tolerance of P. vera seedlings by increasing the accumulation of osmotic adjustment compounds, nutritional and antioxidant enzyme activity. It appears that AM formation enhanced the drought tolerance of pistachio plants, which increased host biomass and plant growth.     

Selenium (Se) Seed Priming Induced Growth and Biochemical Changes in Wheat Under Water Deficit Conditions

Insufficient stand establishment at early growth stages in wheat (Triticum aestivum L.) due to drought stress is a major problem that limits overall efficiency and yield of crop. Priming of seed is an effective method for raising seed performance and improving tolerance of crops to abiotic stresses especially drought. The seeds of two local wheat cultivars (Kohistan-97 and Pasban-90) were soaked in distilled water or sodium selenate solutions of 25, 50, 75, and 100 μM for 1/2 or 1 h at 25 °C and later re-dried to their original moisture levels before sowing. One-hour priming significantly increased root length stress tolerance index, dry matter stress tolerance index, and total biomass of seedlings; however, no significant effect of changing duration of Se seed priming was observed on plant height stress tolerance index and shoot/root ratio. Among cultivars, Kohistan-97 was found to be more responsive to Se seed treatment as 1 h priming at 100 μM significantly increased its total biomass by 43 % as compared to control treatment. Although biomass of seedlings was not affected with Se seed priming under normal conditions, but it increased significantly with increase in rates of Se under drought stress conditions. One-hour priming at 75 μM increased the total sugar content and total free amino acids in both wheat cultivars. A more significant decrease in soluble proteins of seedlings was observed by 1 h priming than 1/2 h priming under drought stress conditions.     

Foliar application of zinc improves morpho-physiological and antioxidant defense mechanisms,and agronomic grain biofortification of wheat (Triticum aestivum L.) under water stress

Agronomic biofortification with zinc (Zn) may be engaged to improve the nutritious value of food crops along-with tolerance to water deficit conditions. The Zn may increase plant resistance to water stress by boosting physiological and enzymatic antioxidants defense mechanisms. Major objective of this study was to investigate the effect of foliar applied Zn on grain zin biofortification and drought tolerance in wheat. Treatments include application of Zinc at terminal growth phases (BBCH growth stage 49 and BBCH growth stage 65) with five levels: 0 (control-ck), water spray, 5, 10 and 15 mM under two levels of water regimes; well-watered (where 80% water holding capacity (WHC) was maintained in the soil) and water stress, (where 40% WHC was maintained in the soil). Results revealed that water stress significantly reduced relative water contents, gas exchange attributes, plant height, yield and yield related attributes of wheat. In contrast, hydrogen peroxide, free proline levels, activities of malondialdehyde, and concentration of soluble protein were markedly increased under water stress condition. Application of various levels of Zn significantly improved the CAT, SOD, POD and ASP activities at 40% WHC compared with control treatment. Foliarly applied 10 and 15 mM Zn predominantly reduced the damaging impact of water stress by improving the plant status in the form of plant height, RWC and gas exchange attributes. Likewise, wheat plant treated with 10 mM Zn under water stress condition increased the grain yield by improving number of grains per spike, 100 grain weight and biological yield compared with control. Moreover, increasing Zn levels also increased Zn concentration in grains and leaves. Overall, this study suggests that optimum level of Zn (10 mM) might be promising for alleviating the adverse impacts of water stress and enhance the grain biofortification in wheat.     

干旱胁迫与施氮对麻疯树幼苗渗透调节物质积累的影响

采用盆栽控水的方法,研究干旱胁迫(80％ FC、60％ FC、40％ FC和20％ FC)及施氮(N0 0 g·pot-1、N1 1.2 g·pot1、Nm3.6 g·pot-1和Nh6.0 g·pot-1)对麻疯树幼苗叶、茎和根部主要渗透调节物质积累的影响.结果表明:干旱胁迫条件下,麻疯树幼苗茎和根部的游离脯氨酸、可溶性蛋白和茎部可溶性糖大量积累,叶片中脯氨酸含量也随干旱胁迫程度的增加大幅度上升;Na+、Ca2+和Mg2+在麻疯树幼苗叶、茎和根中大量积累,而K+仅在茎中大量积累,叶片和根部K+含量略微上升.施氮对植株渗透调节物质的影响与干旱胁迫强度和施氮水平有关.在80％ FC和60％ FC水分条件下,增加N肥施用量能明显促进麻疯树幼苗各组分渗透调节物质的积累;在40％ FC水分条件下,Nh处理对渗透调节物质积累的促进作用减弱;而在20％ FC条件下,N1处理植株的渗透调节能力较高,Nm和Nh处理对植株渗透调节的促进作用不明显甚至转为抑制.     

Breeding implications of drought stress under future climate for upland rice in Brazil

Rice is the most important food crop in the developing world. For rice production systems to address the challenges of increasing demand and climate change, potential and on‐farm yield increases must be increased. Breeding is one of the main strategies toward such aim. Here, we hypothesize that climatic and atmospheric changes for the upland rice growing period in central Brazil are likely to alter environment groupings and drought stress patterns by 2050, leading to changing breeding targets during the 21st century. As a result of changes in drought stress frequency and intensity, we found reductions in productivity in the range of 200–600 kg/ha (up to 20%) and reductions in yield stability throughout virtually the entire upland rice growing area (except for the southeast). In the face of these changes, our crop simulation analysis suggests that the current strategy of the breeding program, which aims at achieving wide adaptation, should be adjusted. Based on the results for current and future climates, a weighted selection strategy for the three environmental groups that characterize the region is suggested. For the highly favorable environment (HFE, 36%–41% growing area, depending on RCP), selection should be done under both stress‐free and terminal stress conditions; for the favorable environment (FE, 27%–40%), selection should aim at testing under reproductive and terminal stress, and for the least favorable environment (LFE, 23%–27%), selection should be conducted for response to reproductive stress only and for the joint occurrence of reproductive and terminal stress. Even though there are differences in timing, it is noteworthy that stress levels are similar across environments, with 40%–60% of crop water demand unsatisfied. Efficient crop improvement targeted toward adaptive traits for drought tolerance will enhance upland rice crop system resilience under climate change.     

Elevated cytokinin content in ipt transgenic creeping bentgrass promotes drought tolerance through regulating metabolite accumulation

Increased endogenous plant cytokinin (CK) content through transformation with an adenine isopentyl transferase (ipt) gene has been associated with improved plant drought tolerance. The objective of this study is to determine metabolic changes associated with elevated CK production in ipt transgenic creeping bentgrass (Agrostis stolonifera L.) with improved drought tolerance. Null transformants (NTs) and plants transformed with ipt controlled by a stress- or senescence-activated promoter (SAG12-ipt) were exposed to well-watered conditions or drought stress by withholding irrigation in an environmental growth chamber. Physiological analysis confirmed that the SAG12-ipt line (S41) had improved drought tolerance compared with the NT plants. Specific metabolite changes over the course of drought stress and differential accumulation of metabolites in SAG12-ipt plants compared with NT plants at the same level of leaf relative water content (47% RWC) were identified using gas chromatography-mass spectroscopy. The metabolite profiling analysis detected 45 metabolites differentially accumulated in response to ipt expression or drought stress, which included amino acids, carbohydrates, organic acids, and organic alcohols. The enhanced drought tolerance of SAG12-ipt plants was associated with the maintenance of accumulation of several metabolites, particularly amino acids (proline, γ-aminobutyric acid, alanine, and glycine) carbohydrates (sucrose, fructose, maltose, and ribose), and organic acids that are mainly involved in the citric acid cycle. The accumulation of these metabolites could contribute to improved drought tolerance due to their roles in the stress response pathways such as stress signalling, osmotic adjustment, and respiration for energy production.     

Synergistic effect of colonization with arbuscular mycorrhizal fungi improves growth and drought tolerance of Plukenetia volubilis seedlings

The objective of this study was to investigate the effects of arbuscular mycorrhizal fungus (AMF) inoculation on plant growth and drought tolerance in seedlings of a promising oilseed crop, Sacha Inchi (Plukenetia volubilis L.), under well-watered or drought conditions. AMF inoculation was applied in four treatments: without AMF inoculation, Glomus versiforme, Paraglomus occultum, or combination of both microorganism inoculations. The results showed that AMF colonization significantly enhanced the growth of Sacha Inchi seedlings regardless of soil water conditions, and the greatest development was reached in plants dually inoculated under well-watered conditions. G. versiforme was more efficient than P. occultum. Plants inoculated with both symbionts had significantly greater specific leaf area, leaf area ratio and root volume when compared with the uninoculated control, G. versiforme, and P. occultum treatments alone, indicating a synergistic effect in the two AMF inoculation. Photosynthetic rate and water-use efficiency were stimulated by AMF, but not stomatal conductance. Inoculation with AM fungus increased antioxidant enzymes activities including guaiacol peroxidase and catalase, thus lowering hydrogen peroxide accumulation and oxidative damage, especially under drought stress conditions. However, proline content showed little change during drought stress and AMF colonization conditions, which suggested that proline accumulation might not serve as the main compound for osmotic adjustment of the studied species. These results indicate that AMF inoculation stimulated growth and enhanced drought tolerance of Sacha Inchi seedlings, through alterations in morphological, physiological and biochemical traits. This microbial symbiosis might be an effective cultivation practice in improving the performance and development for Sacha Inchi plants.     

Lipidomic reprogramming associated with drought stress priming‐enhanced heat tolerance in tall fescue (Festuca arundinacea)

Stress priming by exposing plants to a mild or moderate drought could enhance plant tolerance to subsequent heat stress. Lipids play vital roles in stress adaptation, but how lipidomic profiles change, affecting the cross‐stress tolerance, is largely unknown. The objectives of this study were to perform lipidomics, to analyse the content, composition, and saturation levels of lipids in leaves of tall fescue (Festuca arundinacea) following drought priming and subsequent heat stress, and to identify major lipids and molecular species associated with priming‐enhanced heat tolerance. Plants were initially exposed to drought for 8 days by withholding irrigation and subsequently subjected to 25 days of heat stress (38/33°C day/night) in growth chambers. Drought‐primed plants maintained significantly higher leaf relative water content, chlorophyll content, photochemical efficiency, and lower electrolyte leakage than nonprimed plants under heat stress. Drought priming enhanced the accumulation of phospholipids and glycolipids involved in membrane stabilization and stress signalling (phosphatidic acid, phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and digalactosyl diacylglycerol) during subsequent exposure to heat stress. The reprogramming of lipid metabolism for membrane stabilization and signalling in response to drought priming and subsequent exposure to heat stress could contribute to drought priming‐enhanced heat tolerance in cool‐season grass species.     

不同生育期水分胁迫对水稻根叶渗透调节物质变化的影响

 干旱是限制水稻(Oryza sativa)作物产量的主要生态因子之一,渗透调节是作物适应干旱逆境的生理机制之一。在人为控制水分的盆栽条件下, 对水稻生长的分蘖期、幼穗分化期、抽穗期、结实期分别进行水分胁迫,研究水稻根系及叶片渗透调节物质的变化规律。结果表明, 不同生育期 干旱胁迫后叶片水势均显著下降,根系和叶片的有机渗透调节物质如可溶性糖、游离氨基酸、脯氨酸和无机渗透调节物质包括K⁺、Mg²⁺等含量 均大幅度上升,而且幼穗分化期和抽穗期这两个对水分胁迫最敏感的时期上升幅度最大,其中又以有机渗透调节物质变化最显著。不同生育期渗 透调节大小的顺序为：抽穗期>幼穗分化期>结实期>分蘖期,反映了不同生育时期渗透调节能力的差异。同时幼穗分化期和抽穗期水分胁迫结束 后再复水后根系和叶片的有机渗透调节物质含量仍长期明显高于对照,而无机离子则变化规律比较复杂,有的升高有的则降低。叶片的渗透调 节能力大于根系,无论是叶片或根系都是K⁺对渗透调节的贡献最大;其次是Ca²⁺, 6 种渗透调节物质含量大小排列顺序为K⁺ > Ca²⁺ >可溶性糖 > Mg²⁺ > 游离氨基酸 > 脯氨酸。     

Seed biopriming with drought tolerant isolates of Trichoderma harzianum promote growth and drought tolerance in Triticum aestivum

Green house study was aimed to investigate the effect of seed biopriming with drought tolerant isolates of Trichoderma harzianum, viz. Th 56, 69, 75, 82 and 89 on growth of wheat under drought stress and to explore the mechanism underlying plant water stress resilience in response to Trichoderma inoculation. Measurements of relative water content, osmotic potential, osmotic adjustment, leaf gas exchange, chlorophyll fluorescence and membrane stability index were performed. In addition, analysis of the phenolics, proline, lipid peroxidation and measurements of phenylalanine ammonia‐lyase activity were carried out. Seed biopriming enhanced drought tolerance of wheat as drought induced changes like stomatal conductance, net photosynthesis and chlorophyll fluorescence were delayed. Drought stress from 4 to 13 days of withholding water induced an increase in the concentration of stress induced metabolites in leaves, while Trichoderma colonisation caused decrease in proline, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), and an increase in total phenolics. A common factor that negatively affects plants under drought stress conditions is accumulation of toxic reactive oxygen species (ROS), and we tested the hypothesis that seed biopriming reduced damages resulting from accumulation of ROS in stressed plants. The enhanced redox state of colonised plants could be explained by higher l ‐phenylalanine ammonia‐lyase (PAL) activity in leaves after 13 days of drought stress in Trichoderma treated plants. Similar activity was induced in untreated plants in response to drought stress but to a lower extent in comparison to treated plants. Our results support the hypothesis that seed biopriming in wheat with drought tolerant T. harzianum strains increased root vigour besides performing the process of osmoregulation. It ameliorates drought stress by inducing physiological protection in plants against oxidative damage, due to enhanced capacity to scavenge ROS and increased level of PAL, a mechanism that is expected to augment tolerance to abiotic stresses.