Full Strength Hoagland's Solution Research Articles

How Changes in Nitrogen Levels Impact Metabolites and Physiological Features of Hypericum androsaemum

Background: The manipulation of mineral nutrition may affect secondary metabolite production and thus determine the nutritional value of food/medicinal plants. Objectives: The present study investigated the impact of nitrogen supply on the production of secondary metabolites and physiological parameters of Hypericum androsaemum plants grown in sand culture. Methods: Four-week plants were irrigated by full-strength Hoagland solution (control), nitrate was reduced to 1/3, and no nitrate was provided for 14 days. Results: The growth of shoots was inhibited by nitrate limitation, but root growth was stimulated. Soluble proteins and water content were significantly affected by nitrate deficiency. Antioxidative enzyme activities (ascorbate peroxidase (APX) and superoxide dismutase (SOD)) were increased due to nitrate deficiency. Treatment of plants with NO3- deficiency caused an increase in total soluble phenols and phenylalanine ammonia-lyase (PAL) activity, while flavonoid content was mainly elevated by NO3- deficiency. At the level of specific metabolites, NO3- deficiency positively affected hypericin and pseudohypericin content but decreased hyperforin content. The expression of the putative gene for hypericin biosynthesis (hyp-1) was up-regulated in response to nitrate deficiency. Conclusions: The results demonstrated that the nitrogen deficiency in the H. androsaemum plant positively affected the antioxidant system, valuable phenols, and secondary metabolites.

Interactive Effects of Nitrogen and Sulfur Nutrition on Growth, Development, and Physiology of Brassica carinata A. Braun and Brassica napus L.

Brassica carinata (carinata) has emerged as a potential biofuel source due to its high erucic acid content, making it desirable for various industrial applications. Nitrogen (N) and sulfur (S) are required as primary sources of nutrition for growth and development in different oilseed crops and their utilization is interdependent. The purpose of the study was to analyze the interactive effect of N and S nutrition on the growth and other physiological activities of carinata and B. napus (napus). Four treatments, i.e., optimum NS (+N+S, 100% N and 100% S); N limited (−N+S, 0% N, 100% S); S limited (+N−S, 100% N, 0% S), and NS limited (−N−S, 0% N and 0% S) of N and S in full-strength Hoagland solution were imposed in the current study. Effect of different NS treatments was observed on vegetative traits such as number of primary and secondary branches, total leaf area, total biomass production and allocation, and physiological traits such as production of photosynthetic pigments, net photosynthesis, electron transport, and other aspects for both carinata and napus. The traits of stem elongation, number of nodes, node addition rate, internode length, number of primary and secondary branches were 60%, 36%, 50%, 35%, 56%, and 83% lower, respectively, in napus in comparison to carinata. Different NS treatments also positively influenced the production of photosynthetic pigments such as chlorophyll (Chl) a and b and carotenoids in carinata and napus. The concentration of Chla was 11% higher in napus in comparison to carinata. The rate of net photosynthesis, electron transport, and fluorescence was 12%, 8%, and 5% higher based on overall value, respectively, in napus compared to carinata. On the other hand, the overall value for stomatal conductance decreased by 5% in napus when compared to carinata. Different growth-related traits such as vegetative (plant height, node number, internode length, leaf area, number of primary and secondary branches), reproductive (pod number, pod length, seeds per pod), and photosynthetic capacity in oilseed brassicas are correlated with the final seed and oil yield and chemical composition which are of economic importance for the adoption of the crop. Thus, the analysis of these traits will help to determine the effect of NS interaction on crop productivity of carinata and napus.

Soybean Growth, Development and Productivity in Response to Flood Stress at Reproductive Stage

Abstract Objectives The objectives of this study were to investigate the impact of flooding on: Reproductive, growth, and development Nutrient concentration Soybean productivity and resilient in changing environment Methods An out-door pot-culture experiment was conducted to determine flooding effects on soybean growth and physiology during the reproductive period. Cultivar Asgrow AG5332 was seeded in 5.2 L pots filled with 3:1 by volume fine sand and topsoil and irrigated with full-strength Hoagland's nutrient solution. After 34 days of sowing, treatments were induced flooding at 2.5 cm above the soil surface for 16 additional days. Measurements were made on soil oxygen content and leaf gas exchange and pigment. Growth parameters and plant components biomass were also measured, 66 days after sowing. Results Soil oxygen levels declined rapidly to 0% in around 5-days of flood treatment, but the control remained 18%. The nutrient: N and Mg concentrations significantly decreased with flooding. All plant growth parameters and reproductive potential declined in the treatments at P = 0.001. Pod numbers and weights as a measure of reproductive potential declined in the plants under flood conditions. Conclusions This study confirmed that the soybean plant during the reproductive period is highly sensitive to flooding. Flood-resistant cultivar should be encouraged by farmers to improve crop productivity and food security. Funding Sources United State Soybean Production Board USAID.

Selenite antagonizes the phytotoxicity of Cd in the cattail Typha angustifolia.

The Phytotoxicity of and mechanism underlying selenite-mediated tolerance to Cd stress in Typha angustifolia were studied hydroponically with respect to metal uptake and translocation, photosynthesis-related parameters, contents of proline and O2•-, products of lipid peroxidation, cell viability, enzymatic and non-enzymatic antioxidants, glyoxalases and phytochelatins. T. angustifolia were exposed to 25, 50 and 100μM of Cd alone and in conjunction with 5mgL-1 of selenite in full-strength Hoagland's nutrient solution for 30 days. Results showed that Cd contents in T. angustifolia leaves and roots increased in a dose-dependent manner and were higher in roots, but those of BAC, BCF and TF changed in a contrary pattern. Addition of selenite to Cd-containing treatments further reduced Cd levels in T. angustifolia leaves and roots, as well as BAC, BCF and TF. A diphasic effect was found in T. angustifolia for the contents of total chlorophyll, GSH, PC and GSSG, as well as activities of CAT, POD, SOD and GR, in response to Cd stress alone and in conjunction with selenite supplementation, but the same effect was not observed for Pn, Cond, Tr, Ci, Fv/Fm and ϕPSII. In contrast, exogenous selenite supplementation enhanced the contents of total chlorophyll and the non-enzymatic antioxidants, as well as activities of enzymatic antioxidants, while the values of photosynthetic fluorescence parameters were rescued. Selenite addition decreased Cd-induced cell death. Proline contents and Gly I activities in T. angustifolia leaves kept increasing in a dose-dependent manner of Cd concentrations in the growth media and selenite addition further enhanced both parameters. Addition of selenite could quench Cd-mediated generation of MDA, O2•- and MG in T. angustifolia leaves and reduce Cd-induced Gly II activity. A U-shaped GSH/GSSG ratio in T. angustifolia leaves suggests a possible trade-off between PC synthesis and GR activity since both share the same substrate GSH. Therefore, confined BAC, BCF and TF were a mechanism that confers T. angustifolia tolerance to Cd stress, and that exogenous selenite supplementation could depress Cd-induced stress in T. angustifolia by rescuing the photosynthetic fluorescence, enhancing non-enzymatic and enzymatic antioxidants that scavenge O2•- and MG, and potentiating PC synthesis that chelates Cd.

Brassica carinata and Brassica napus Growth, Nitrogen Use, Seed, and Oil Productivity Constrained by Post‐Bolting Nitrogen Deficiency

ABSTRACTNitrogen limitation after bolting in oilseed brassicas limits reproductive performance as nutrients are sequentially translocated from leaves to developing reproductive structures. In addition to limiting crop growth and productivity, N deficiency may also modify the chemical composition and oil output of Brassica carinata A. Braun and B. napus L. A greenhouse study was conducted at the North Florida Research and Education Center in Quincy, FL, during 2014–2015 to determine the effects of N limitation on B. carinata (cultivar AAC A110) and B. napus (cultivar Canterra 1918) growth, seed and oil yields, N use, and fatty acid composition. Four N treatments (0, 33, 66, and 100% of N in full strength Hoagland solution) were imposed 78 d after planting (DAP) at bolting. At 154 DAP, carinata accumulated 19% greater biomass and nine times more reproductive branches than napus across all N levels. As a result, carinata produced 43% greater seed yield across all N levels than napus. This increased seed productivity resulted in greater agronomic efficiency (58%), apparent N recovery (59%), N utilization efficiency (41%), and partial factor productivity (29%) than napus, respectively. Restricting N availability (0 N) reduced carinata and napus oil yield by 35 and 50% respectively, relative to 100% N. Nitrogen availability during seed development and maturation had an effect on the synthesis of fatty acids and their quantities in the oils of mature carinata and napus seeds. This study demonstrated the plasticity of oilseed brassicas and the relationship of reduced growth to seed productivity as a function of N supply.

海藻提取物对甘蔗幼苗抗旱性的影响

本文研究海藻提取物对甘蔗苗期叶片抗氧化酶活性、株高、生物量及叶片SPAD值的影响，为明确海藻提取物缓解甘蔗苗期干旱胁迫提供依据。采用水培方式以粤糖94-128幼苗为研究对象，在10% PEG6000模拟干旱胁迫条件下分别用浓度为0%、0.5%和1% (V/V)的海藻提取物施用于营养液，处理3天后分别测定甘蔗苗期叶片过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性以及丙二醛(MDA)含量，处理10天后分别测定株高、生物量鲜重及叶片SPAD值。研究结果表明，在干旱胁迫下施用海藻提取物能提高叶片POD、SOD和CAT等抗氧化酶活性，降低叶片MDA含量，使叶片脱水速率得到显著降低，相对含水量得到显著提高，电导率显著下降，增加甘蔗株高和生物量，显著提高叶片SPAD值(p < 0.05)。因此，海藻提取物有望成为一种新的甘蔗抗旱调节剂。 A hydroponic experiment was conducted to explore the effects of various rates of seaweed extracts (prepared from brown alga) on sugarcane growth and physiological response under stimulated drought stress. Yuetang 94-128 was selected based on seedling growth under drought and were planted in pots containing 10 liter of Hoagland solution. The seedlings were subjected to drought levels using 0% or 10% PEG6000 mixed with Hoagland solution. Three seaweed extract treatments consisting of 0%, 0.5%, and 1% (V/V) of the seaweed extract level in full strength Hoagland solution were applied. The activity of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), the content of MDA and electric conductivity (EC) of leaves were measured after 3 days with treatments; the leaf dehydration rate (LDR), the relative water content (RWC), plant height and fresh weight were measured after 10 days with treatments. The results showed that the antioxidant enzymes activity in sugarcane leaves of POD, SOD and CAT were improved, the MDA content, the electric conductivity and the leaf dehydration rate were significantly decreased, while the relative water content, plant height, biomass, leaf SPAD value were greatly increased with the application of seaweed extract under drought stress (p < 0.05), which implied that seaweed extract has a potential for drought-resistant modulation.

Response of Alfalfa under Salt Stress to the Application of Potassium Sulfate Nanoparticles

A greenhouse study was conducted to explore the effect of various rates of potassium sulfate (K2SO4) nanoparticles on alfalfa (Medicago sativa L.) growth and physiological response under salt stress. One salt-tolerant genotype (Mesa-Sirsa) and one salt-sensitive genotype (Bulldog 505) were selected based on germination under salt and were planted in pots containing 2 kg of sand. The two genotypes were subjected to 0 and 6 dS·m-1 salt levels using CaCl2·2H2O: NaCl (2:1) mixed with Hoagland solution. Three K2SO4 nanoparticle treatments consisting of, 1/4, 1/8, and 1/10 of the potassium (K) level in full strength Hoagland solution (235 mg·L-1) were applied. Adding K2SO4 nanoparticles at the 1/8 level resulted in the highest shoot dry weight, relative yield, root length and root dry weight in both genotypes. The different rates of K2SO4 nanoparticles affected significantly Na/K ratio and the concentrations of Calcium (Ca), Phosphorus (P), Copper (Cu), Manganese (Mn), and Zinc (Zn) in plant tissue. The application of K2SO4 nanoparticles at the 1/8 rate enhanced the plant’s physiological response to salt stress by reducing electrolyte leakage, increasing catalase and proline content, and increasing antioxidant enzymes, activity. These results suggest that the application of K nanoparticles may have better efficiency than conventional K fertilizers in providing adequate plant nutrition and overcoming the negative effects of salt stress in alfalfa.

A practicable method for zinc enrichment in lettuce leaves by the endophyte fungus Piriformospora indica under increasing zinc supply

Zinc (Zn) deficiency is well-documented public health issue and a significant factor hampering to crop production. There is a close overlap between soil deficiency and human deficiency of Zn, indicating a need for increasing Zn content in crops and vegetables. In this study, the effects of endophytic fungus Piriformospora indica and Zn treatment on growth parameters, chlorophyll amounts, and Zn and some other micronutrient concentrations in Lactuca sativa cv. Siyahoo plants were investigated. The experiment was carried out including two treatments (P. indica inoculation and non-inoculation), each having four Zn concentrations (0, 2.5, 5 and 10mg/l Zn added to full-strength Hoagland solution) in a sand culture substrate. By increasing Zn concentration in sand substrate, growth parameters, chlorophyll content and leaf Zn concentration were significantly increased from 34.1 to 185.1μg/g DW, whereas leaf iron (Fe) concentration was decreased. Significant increase in various parameters including growth, chlorophyll content and leaf Zn concentrations (7.6 fold) were observed in plants inoculated with P. indica under supplemented concentration of 10mg/l Zn. Results from this study indicate that P. indica inoculation with Zn supplementation can help in Zn enrichment in lettuce plants.

Comparative response of Brassica carinata and B. napus vegetative growth, development and photosynthesis to nitrogen nutrition

Nitrogen availability is a major limiting factor controlling growth, CO2 assimilation and productivity of oilseed brassicas, however, little is known about the physiological and morphological responses of B. carinata to N. A greenhouse study was conducted at North Florida Research and Education Center, Quincy, Florida during 2014/2015 to determine the effects of N rate on carinata (B. carinata A. Braun) cv. AAC A110 and (B. napus L.) cv. Canterra 1918 growth, development and photosynthesis. Four N treatments (0, 33, 66 and 100% of N in full strength Hoagland solution) were imposed 30days after planting. Plant height, leaf area, node number, branches and total biomass and its components (leaf, stem and root dry weights) in both species decreased linearly with N reduction. Intra-specific total dry matter and photosynthetic capacity did not vary 55days after treatment (DAT). However, partitioning biomass to various plant components differed between the species and was modified by N availability. At all N rates, carinata apportioned >53% of total biomass to the stem component while in canola stems comprised 17–34% of total biomass. Roots contributed more to total dry weight in canola (33–46%) than in carinata (23–29%) except at the highest N level. In both species, root dry matter increased with decreasing N availability. At 55 DAT, total chlorophyll, Chla and Chlb concentrations, specific leaf area and photosynthetic capacity for both species decreased with N deficiency. Parameters of leaf photosynthetic responses to photosynthetically active radiation and internal CO2 concentration curves were also altered by N availability. During the vegetative stage, N deficiency restricted plant growth, biomass production and also modified resource allocation which may have implications for N use efficiency and recovery during reproductive development.

Changes in hydraulic conductance cause the difference in growth response to short-term salt stress between salt-tolerant and -sensitive black gram (Vigna mungo) varieties

Black gram (Vigna mungo) is an important crop in Asia, However, most black gram varieties are salt-sensitive. The causes of varietal differences in salt-induced growth reduction between two black gram varieties, ‘U-Taung-2’ (salt-tolerant; BT) and ‘Mut Pe Khaing To’ (salt-sensitive; BS), were examined the potential for the first step toward the genetic improvement of salt tolerance. Seedlings grown in vermiculite irrigated with full-strength Hoagland solution were treated with 0mM NaCl (control) or 225mM NaCl for up to 10 days. In the 225mM NaCl treatment, plant growth rate, net assimilation rate, mean leaf area, leaf water potential, and leaf photosynthesis were reduced more in BS than in BT plants. Leaf water potential was closely related to leaf photosynthesis, net assimilation rate, and increase in leaf area. In response to salinity stress, hydraulic conductance of the root, stem, and petiole decreased more strongly in BS than in BT plants. The reduction in stem and petiole hydraulic conductance was caused by cavitation, whereas the reduction in root hydraulic conductance in BS plants was caused by a reduction in root surface area and hydraulic conductivity. We conclude that the different reduction in hydraulic conductance is a cause of the differences in the growth response between the two black gram varieties under short-term salt stress.

Responses of Spinach to Salinity and Nutrient Deficiency in Growth, Physiology, and Nutritional Value

Salinity and nutrient-depleted soil are major constraints to crop production, especially for vegetable crops. The effects of salinity and nutrient deficiency on spinach (Spinacia oleracea L.) were evaluated in sand cultures under greenhouse conditions. Plants were watered every day with Hoagland nutrition solution, deprived of nitrogen (N), phosphorous (P), or potassium (K) for nutrient deficiency, either with or without 20/10 mm sodium chloride (NaCl)/calcium chloride (CaCl2) for salinity treatment. Salinity significantly decreased shoot fresh weight (FW) and dry weight (DW), leaf relative water content (RWC), and specific leaf area (SLA) relative to controls after 4 weeks of treatment and increased chlorophyll content, maximum photochemical efficiency (Fv/Fm), and photochemical yield [Y(II)]. Nitrogen deficiency greatly reduced shoot FW and DW, SLA, and chlorophyll content, regardless of salt treatment. Y(II) and Fv/Fm were reduced by N deficiency and salinity treatment. Phosphorous and K deficiencies, similarly, decreased shoot FW and DW irrespective of salinity treatment and increased chlorophyll content without salt stress. Phosphorous deficiency increased Y(II) under control and Fv/Fm under both control and salt treatment. Salinity and nutrient deficiency also affected the nutritional value of spinach. Salt stress increased carotenoid and flavonoid contents, and reducing power in full-strength Hoagland solution, and decreased leaf ferrous ion chelating ability (FICA). Nutrient deficiency increased reducing power regardless of salinity treatment. Nitrogen deficiency increased anthocyanin and total phenolic contents, decreased carotenoids and flavonoids regardless of salinity treatment, and increased antioxidant capacity under no-salt conditions. Phosphorous deficiency increased carotenoid and flavonoid contents under no-salt condition and enhanced total phenolic content and reduced FICA and amino acid content under salt stress. Potassium deficiency increased total phenolic, carotenoid, and flavonoid contents and antioxidant capacity under non-salt condition, but decreased FICA regardless of salinity treatment. These results suggest that spinach nutritional value could be improved with only moderately or slightly reduced yield through cultural practices that impose either low fertilizer levels or slight salt stress.

Abscisic acid increases leaf starch content of polyethylene glycol-treated wheat seedlings by temporally increasing transcripts of genes encoding starch synthesis enzymes

The molecular mechanism of starch synthesis regulated by abscisic acid (ABA) under water deficiency in plants was explored in this study. Starch content in leaves of wheat seedlings hydroponically grown in full-strength Hoagland solution increased quickly, however, 15 % polyethylene glycol (PEG)-induced water deficiency significantly inhibited starch content. ABA treatment markedly alleviated starch content inhibition in the leaf organ of wheat seedlings suffering from PEG-induced water deficiency. The expression levels of the starch biosynthesis enzyme genes were measured using quantitative real-time polymerase chain reaction analysis. Under PEG-induced water deficiency conditions, exogenous ABA significantly enhanced transcript levels of many starch biosynthesis enzyme genes at different time points, including TaAGPS2 at 1, 2, 3, and 4 days; TaAGPL2 at 1, 4, and 5 days; TaGBSSII at 2, 3, and 4 days; TaSSI at 1, 3, and 4 days; TaSSIIIb at 1 and 5 days; TaSSIV at 1, 2, and 3 days; TaBEIIa at 1 and 5 days; TaPHOL at 1, 3, and 4 days; and TaDPE2 at 3, 4, and 5 days. Our results indicate that exogenous ABA application increased starch content in the leaf organ of wheat seedlings under PEG-induced water deficiency, possibly by temporally regulating the expression levels of the starch synthesis enzyme genes.

Physiological, Ultrastructural and Proteomic Responses in the Leaf of Maize Seedlings to Polyethylene Glycol-Stimulated Severe Water Deficiency.

After maize seedlings grown in full-strength Hoagland solution for 20 days were exposed to 20% polyethylene glycol (PEG)-stimulated water deficiency for two days, plant height, shoot fresh and dry weights, and pigment contents significantly decreased, whereas malondialdehyde (MDA) content greatly increased. Using transmission electron microscopy, we observed that chloroplasts of mesophyll cells in PEG-treated maize seedlings were swollen, with a disintegrating envelope and disrupted grana thylakoid lamellae. Using two-dimensional gel electrophoresis (2-DE) method, we were able to identify 22 protein spots with significantly altered abundance in the leaves of treated seedlings in response to water deficiency, 16 of which were successfully identified. These protein species were functionally classified into signal transduction, stress defense, carbohydrate metabolism, protein metabolism, and unknown categories. The change in the abundance of the identified protein species may be closely related to the phenotypic and physiological changes due to PEG-stimulated water deficiency. Most of the identified protein species were putatively located in chloroplasts, indicating that chloroplasts may be prone to damage by PEG stimulated-water deficiency in maize seedlings. Our results help clarify the molecular mechanisms of the responses of higher plants to severe water deficiency.

Tolerance of Wheat Doubled Haploids to Elevated Levels of NaCl at Germination and Seedling Stages

Genetic variability in salt tolerance of bread wheat could be induced via crossing diverse parents and producing doubled haploid (DH) lines from such crosses. One hundred seventeen DH lines resulted via anther culture technique from the cross between Sakha-8 (salt tolerant old variety) and Line-25 (a high yielding promising line) along with the two parents and two check cultivars (Sakha93 and Sids-1), making a total number of 121 genotypes, were evaluated at different salinity levels under controlled greenhouse conditions at germination (in petri dishes) and seedling (in pots) stages. The aims were to identify the most tolerant DH lines to elevated levels of salinity and to determine the traits of strong association with salinity tolerance. A factorial experiment based on randomized complete blocks design in three replications was used. Full strength Hoagland solution was added to four saline solutions, namely zero (distilled water + Hoagland solution), 3000, 6000 and 9000 ppm NaCl. Increasing concentration of NaCl caused a gradual and significant decrease for most studied traits. On the contrary, increasing salt level caused a significant increase in mean germination time (MGT) (delay) at 6000 and 9000 ppm, shoot dry weight (SDW) at 3000 ppm and root:shoot ratio (RSR) at 9000 ppm NaCl level. At the highest salinity level (9000 ppm NaCl), the 121 genotypes under study were classified based on their salinity tolerance index (STI) into four Original Research Article Al-Naggar et al.; IJPSS, 5(5): 249-267, 2015; Article no.IJPSS.2015.079 250 categories, i.e., tolerant (T), moderately tolerant (MT), sensitive (S) and very sensitive (VS), with a number of 39, 36, 38 and 8 genotypes, respectively; 28 DH lines showed much higher salinity tolerance than the highest salt tolerant check cultivar in this study (Sakha-93). The relationship between NaCl levels and means of studied traits is of quadratic (curvilinear) nature for all categories ofgenotypes, expect for root dry weight (RDW) of all categories, root fresh weight (RFW) of the two groups S and VS and shoot length (SL) of the group VS, where the relationship was near linear regression. The quadratic regression was in the direction of decrease with increasing of NaCl levels for all studied traits, except for MGT of all wheat categories and RSR of S and VS groups of genotypes, which showed a curvilinear increase. Salinity tolerance trait index (STTI) of T group of genotypes increased by increasing NaCl levels, while STTI of MT, S and VS groups decreased for most studied traits. In general, increasing salinity level increased correlation coefficients among absolute means and each of STTI's and STI for all studied traits. Traits showing strong correlations with STI, high heritability estimates, high expected selection gain and wide phenotypic and genotypic variability were shoot fresh weight (SFW), SDW, RFW and shoot length (SL) at 9000 ppm and RDW and SL at 3000 and 6000 ppm; they were recommended as selection criteria for salinity tolerance.

Effect of different levels of nitrogen deficiency on switchgrass seedling growth

Switchgrass (Panicum virgatum L.) is a warm-season rhizomatous perennial grass that can tolerate diverse abiotic stresses while yielding relatively high biomass, and is considered a leading biofuel feedstock for marginal lands. Nitrogen (N) is crucial for the growth and development of switchgrass, and its tolerance to low N supply and high N use efficiency are very important for its production under poor conditions. The large-scale planting of switchgrass on marginal lands could be an effective approach to solving the problem of feedstock supply for biomass energy. This study used a hydroponic experiment to evaluate the effect of N deficiency on switchgrass seedlings. Three N treatments (0, 0.15, and 1.50mmolL−1 Hoagland's solution) and six cultivars were used, three of each ecotype (upland and lowland). The results showed that biomass, leaf area, root surface area, net photosynthesis, and total chlorophyll content significantly decreased under low N treatments compared with those in full strength Hoagland's nutrient solution. However, once established, all plants survived extreme N stress (0mmolL−1) and, to some extent, were productive. Cultivar Kanlow performed best of the six cultivars under stress. Significant interactions between stress treatment and cultivars showed that breeding for cultivars with high yield and superior performance under N deficiency is warranted. The lowland outperformed the upland ecotypes under stress, suggesting that lowland cultivars may survive and be productive under a wider range of stress conditions. However, given the better adaptability of lowland ecotypes to hydroponic cultivation, further study is needed.

Triacontanol-induced changes in growth, yield, leaf water relations, oxidative defense system, minerals, and some key osmoprotectants in Triticum aestivum under saline conditions

To investigate the effect of exogenous application of triacontanol (TRIA) on 2 wheat (Triticum aestivum L.) cultivars (S-24 and MH-97) under salt stress, an experiment was conducted in a greenhouse under natural climatic conditions. Both cultivars were grown in full strength Hoagland's nutrient solution under nonsaline (0 mM NaCl) or saline (150 mM NaCl) conditions in sand culture. Three optimized TRIA levels (0, 10, and 20 µM) were used as foliar spray at 3 growth stages, i.e. vegetative, boot, and vegetative + boot stages. Ninety-two-day-old plants were subjected to data analysis. Salinity stress adversely affected various growth, physiological, and biochemical attributes in both wheat cultivars at all growth stages. Under salt stress, activities of superoxide dismutase (SOD) and peroxidase (POD) decreased (cv. MH-97), while those of catalase (CAT) and POD (cv. S-24) increased. Contents of hydrogen peroxide (H_{2}O_{2}), malondialdehyde (MDA), Na^+, and Cl^- increased in both wheat cultivars at all growth stages. A foliar spray of 10 µM TRIA was more effective in reducing the adverse effects of salt stress on growth, yield, and leaf water relations of wheat plants when applied at the vegetative or vegetative + boot growth stages.

Triacontanol modulates photosynthesis and osmoprotectants in canola (Brassica napus L.) under saline stress

An experiment was conducted to assess the effect of pre-sowing seed treatment with triacontanol (TRIA) in canola (Brassica napus L.) cultivar (RBN-3060) under saline stress. Canola seeds were soaked in three levels of TRIA (0, 0.5, and 1 mg L−1) for 12 hours. Three levels of salt stress (0, 100, and 150 mM NaCl) in full strength Hoagland's nutrient solution were applied to 56-days-old plants. Salt stress caused a significant reduction in growth, gas exchange, photochemical quenching (qP), and shoot and root K+ contents, while increased leaf glycine betaine, free proline, and shoot Na+ contents. Pre-sowing seed treatment with TRIA increased shoot fresh weight, number of seeds per plant, photosynthetic rate, transpiration rate, ratio of chlorophyll a/b, qP, electron transport rate, shoot and root K+ contents, and free proline and glycine betaine contents of canola plants at various TRIA levels under nonsaline or saline conditions.

Assessment of variation in drought tolerance using some key physiological criteria in potential wheat (Triticum aestivum L.) cultivars of different geographic origins

The present experiment comprised seven wheat cultivars, two drought levels (0 and 17% PEG-8000) and four replicates. The seeds of six wheat cultivars (Al-lugaimi, Bonus, Kronos, Yecora-rojo, Irena and Sama) were supplied by the King Saud University, Riyaz, Saudi Arabia, whereas S-24 was obtained from the Department of Botany, University of Agriculture, Faisalabad. The seeds were allowed to germinate and grow for 20 days in medium having full-strength Hoagland's nutrient solution or Hoagland's solution with 17% PEG-8000. For the appraisal of drought tolerance, various physiological traits such as gas-exchange attributes (A, E, Ci, gs , and A/E), leaf water relations (ψw, ψs and ψp) and the activities of key antioxidant enzymes (SOD, POD and CAT) were determined. On the basis of biomass and gas-exchange attributes (A, E, and gs ), cultivars Al-lugaimi and Sama were found to be drought tolerant, cultivars Yecora-rojo and Irena moderately drought tolerant, and cultivars S-24, Bonus and Kronos drought sensitive. However, plant osmotic adjustment and the activities of potential antioxidant enzymes (SOD, POD and CAT) were not found to be associated with drought tolerance of the different wheat cultivars.

Exogenous application of mannitol and thiourea regulates plant growth and oxidative stress responses in salt-stressed maize (Zea mays L.)

The mechanism of growth amelioration in salt-stressed maize (Zea mays L. cv., DK 647 F1) by exogenously applied mannitol (M) and thiourea (T) was investigated. Maize seedlings were planted in pots containing perlite and subjected to 0 or 100 mM NaCl in full strength Hoagland's nutrient solution. Two levels of M (15 and 30 mM) or T (3.5 and 7.0 mM) were sprayed to the leaves of maize seedlings 10 days after germination. Salinity stress caused considerable reduction in plant dry biomass, chlorophyll content, and relative water content in the maize plants. However, it increased the activities of catalase (CAT; EC 1.11.1.6), superoxide dismutase (SOD; EC 1.15.1.1), and polyphenol oxidase (PPO; EC 1.10.3.1), and levels of hydrogen peroxide (H2O2) and electrolyte leakage, but it did not change peroxidase (POD; EC 1.11.1.7) activity. Foliar application of M or T was found to be effective in checking salt-induced shoot growth inhibition. Exogenously applied M or T reduced the activities of CAT, SOD, POD, and PPO in the salt-treated maize plants compared to those in the plants not fed with these organic compounds. Salinity increased Na+ contents but decreased those of K+, Ca2 +, and P in the leaves and roots of the maize plants. Foliar-applied M or T increased the contents of K+, Ca2 +, and P, but decreased that of Na+ in the salt-stressed maize plants with respect to those of the salt-stressed plants not supplied with mannitol or thiourea. Mannitol was found to be more effective than thiourea in improving salinity tolerance of maize plants in terms of growth and physiological attributes measured in the present study.

EFFECT OF CADMIUM ON PHYSIOLOGICAL RESPONSES OF WHEAT AND CORN TO IRON DEFICIENCY

This work evaluated the effect of cadmium (Cd) on the physiological responses of corn (Zea Mays L.) and wheat (Triticum aestivum L.) to iron (Fe) deficiency. For this purpose, seedlings of corn and wheat were cultivated under controlled conditions, plants were grown in different strength Hoagland's solutions for one month. In the fifth week, some seedlings were still in full strength Hoagland's solution (+Fe) and others were in full strength Hoagland's solutions without iron (−Fe). The plants were exposed to different cadmium (Cd) concentrations for four days. The plant chlorophyll content of young leaves, Fe and Cd content in shoots and roots, biomass production, and phytosiderophores (PS) release by roots were assessed. Results showed that Cd decreased the chlorophyll content of young leaves, accompanied by a significant shoot and root biomass reduction for Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments. However, chlorophyll content and shoot and root biomass of Fe-deficient wheat and corn were lower than Fe-sufficient plants at different Cd concentrations. Iron-deficiency induced Cd accumulation compared to Fe-sufficient in wheat and corn; however, a depressive effect of Cd on iron acquisition in shoots and roots of Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments was observed. Cadmium also inhibited PS release in Fe-deficient and Fe-sufficient wheat and corn. Iron-deficient PS release was higher than Fe-sufficient corn and wheat across all Cd treatments. These results suggested that Cd might reduce capacity of plants to acquire iron from solution by inhibiting PS release.