EXOGENOUS APPLICATION OF POTASSIUM DIHYDROGEN PHOSPHATE CAN ALLEVIATE THE ADVERSE EFFECTS OF SALT STRESS ON SUNFLOWER

A greenhouse experiment was conducted to examine whether foliarly applied potassium + phosphorus (K + P) in the form of monopotassium phosphate (KH₂PO₄) could mitigate the adverse effects of salt stress on sunflower plants. There were two levels of root-applied salt [0 and 150 mM of sodium chloride (NaCl)], and varying levels of KH₂PO₄ [(NS (no spray), WS (spray of water), 5 + 4, 10 + 8, 15 + 12, and 20 + 16 mg g^?1 K + P, pH 6.5] applied foliarly to 18-day old non-stressed and salt stressed sunflower plants. Salt stress adversely affected the growth, yield, photosynthetic capacity, and accumulation of mineral nutrients in the sunflower plants. However, varying levels of foliar applied KH₂PO₄ proved to be effective in improving growth and yield of sunflower under salt stress. The KH₂PO₄ induced growth in sunflower was found to be associated with enhanced photosynthetic capacity, water use efficiency and relative water contents.     

Responses of a salt‐tolerant and a salt‐sensitive line of sunflower to varying sodium/calcium ratios in saline sand culture

The effects on two‐week‐old plants of a salt‐tolerant line (Euroflor) and a salt‐sensitive (SMH‐24) line of sunflower, of varying sodium/calcium (Na/ Ca) ratios in a saline growth medium were assessed after three weeks growth in sand culture under greenhouse conditions. The different Na/Ca ratios of the salt treatment were 36.5, 74.0, and 149, at a constant concentration of 150 mol m^‐3 NaCl. Euroflor was superior to SMH‐24 in fresh and dry matters of shoots and roots at varying external Na/Ca ratios. The leaf Na⁺ concentration in SMH‐24 increased consistently with increase in external Na/Ca ratio, whereas that in Euroflor remained almost unaffected. Although leaf chlorine (Cl^‐) was significantly greater in SMH‐24 than Euroflor, there was no effect of decreasing Ca²⁺ concentration of the saline growth medium on the leaf Cl^‐ concentrations of both lines. The lines did not differ in K⁺, Ca²⁺ or Mg²⁺ concentrations of both shoots and roots. The leaf K/Na and Ca/ Na ratios, K versus Na selectivity were considerably higher in Euroflor than in SMH‐24. The lines also did not differ in leaf water potential and gas exchange and these variables were not affected due to decreasing Ca²⁺ concentration of the saline growth medium. Stomatal conductance and transpiration remained unchanged in Euroflor, whereas those in SMH‐24 decreased significantly at the highest external Na/Ca ratio. Euroflor had significantly greater stomatal conductance and transpiration than those of SMH‐24 at almost all external Na/Ca ratios, whereas the reverse was true for water use efficiency. It was established that Euroflor was tolerant to low Ca²⁺ concentrations of the saline growth medium as compared with SMH‐24. This was mainly attributable to accumulation of relatively low Na⁺ and Cl^‐ in the leaves, and maintenance of high leaf K/Na and Ca/Na ratios and K versus Na selectivity in Euroflor.     

Intra‐specific variation for salt tolerance in a potential oil‐seed crop,brown mustard (Brassica juncea (l.) Czern. and Coss.)

Thirty eight accessions of brown mustard (Brassica juncea (L.) Czern. and Coss.) were screened after two weeks growth in solution culture containing 120 mol m‐³ NaCl. Considerable variation for salt tolerance was observed in this set of germplasm, since some accessions showed relatively vigorous growth in saline medium.

In order to determine the consistency of degree of salt tolerance at different growth stages of crop life cycle two salt tolerant accessions, P‐15 and KS‐51 and two salt sensitive 85362 and 85605 were tested at the adult stage in 0(control), 100 and 200 mol m^‐3 NaCl. Both the tolerant accessions produced significantly greater fresh and dry biomass and had considerably higher seed yield than those of the salt sensitive accessions. Analysis of different ions in the leaves showed that salt tolerant accessions contained greater amounts of Na⁺, K⁺ and Ca²⁺ than the salt sensitive accessions, although they did not differ significantly for leaf Cl^‐. Only one salt tolerant accession P‐15 had greater leaf K/Na ratio and K⁺ versus Na⁺ selectivity compared with the tolerant KS‐51 and the two salt sensitive accessions.

From this study it was established that there is a considerable variation for salt tolerance in B.juncea which can be exploited by selection and breeding for improvement of its salt tolerance. Since the degree of salt tolerance in B.juncea does not change at different growth stages of the crop life cycle, selection for salt tolerance at the initial growth stages could provide individuals that would be tolerant at all other growth stages. Accumulation of Na⁺, K⁺ and Ca²⁺ in the leaves are important components of salt tolerance in B.juncea.     

Enhanced Sequential Flushing Process for Removal of Mixed Contaminants from Soils

The feasibility of a sequentially enhanced process for the remediation of soils contaminated by mixed contaminants, specifically multiple polycyclic aromatic hydrocarbons (PAHs) and heavy metals, was investigated. This process consists of sequential flushing using two chemical agents: a surfactant and a chelate. A series of laboratory column experiments was conducted with three different sequential schemes, designated as SEQ1, SEQ2, and SEQ3, in two distinct flushing stages, to remove PAHs and heavy metals from a field-contaminated soil. The SEQ1 scheme involved flushing 0.2 M ethylenediaminetetraacetic acid (EDTA) followed by flushing 5 % Igepal. The SEQ2 scheme involved flushing 5 % Igepal followed by flushing 0.2 M EDTA. SEQ1 was investigated under a constant hydraulic gradient of 1.2, while the SEQ2 scheme was investigated under hydraulic gradients that increased from 1.2 to 4.0. The SEQ3 scheme consisted of sequential flushing of 5 % Igepal (first stage) and 0.2 M EDTA (second stage) under a constant low hydraulic gradient of 0.2. The selected sequential schemes allowed an assessment of the efficacy of sequencing the surfactant and chelating flushing for the removal of multiple heavy metals and PAHs under various hydraulic gradients. The hydraulic conductivity (or flow) was found to vary depending on the flushing agent and the sequence scheme. Under the high hydraulic gradient, the hydraulic conductivity was lower during chelant flushing stage as compared with surfactant flushing stage in both SEQ1 and SEQ2. However, under a low gradient condition (SEQ3), the hydraulic conductivity was approximately the same during both chelant and surfactant flushing stages. The contaminant removal was also significantly affected by the flushing agent and sequence and the applied hydraulic gradient. Heavy metals were removed during chelant flushing, while PAHs were removed during surfactant flushing. The total removal efficiencies of Pb, Zn, and Cu were 76 %, 63 %, and 11 % in SEQ1 and 42 %, 40 %, and 7 % in SEQ2, respectively, while the total removal efficiencies of phenanthrene, anthracene, benz(a)anthracene, and pyrene were 51 %, 35 %, 58 %, and 39 % in SEQ1 and 69 %, 50 %, 65 %, and 69 % in SEQ2, respectively. Overall, the total mass removal of heavy metals and PAHs was higher in SEQ1 as compared with SEQ2, demonstrating that SEQ1 is the effective sequence scheme. Comparison of the results of high and low gradient conditions (SEQ2 and SEQ3) reveals that the removal of contaminants, especially heavy metals, is rate-limited. Overall, this study showed that the removal of co-existing heavy metals and PAHs from soils is possible through the careful selection of the sequence under which the flushing of chelant and surfactant occurs and depends on the site-specific soil and contaminant conditions. Additional research is needed to establish the most optimal flushing scheme (sequence duration and flow velocity) to remove the mixed contaminants effectively and efficiently.     

Influence of microflora and composition of root bathing solution on root exudation of maize plants

Root exudation of carbon (C) plays a major role in processes occurring in the plant rhizosphere. Environmental factors affecting root exudation have been identified but their effects are rarely quantified. The purpose of this work was to evaluate the impact of both the microflora and the chemical composition of the growth medium on root exudation, taking into account soluble exudates and mucilage fraction. Maize plants (Zea mays L.) were grown for 12 days in hydroponic conditions and then transferred in three root bathing solutions (demineralized water, KCl or nutrient solution) during 24 hours. In each case, presence of microflora was tested with a comparison between plants inoculated with maize rhizospheric strain and axenic plants. Exudation was measured in terms of C and biomass production. A strong interaction was noticed between microflora and chemical composition of the root bathing solution. In fact, the presence of rhizospheric microflora induces a stimulation of soluble exudates only in KCl and Nutrient solutions. In demineralized water, a different response was observed with a higher C release for axenic plants, probably due to the osmotic shock induced to the roots. Concerning mucilage fractions, small quantities were recovered on all treatments. This work demonstrates that the chemical composition of the root bathing solution and presence of microorganisms significantly modify the amount of soluble exudates. Attention must therefore be paid to the cultural conditions when exudation is studied because of the sensitivity of this process to root environment.     

Nitrate Reduction and Nutrient Accumulation in Wheat Grown in Soil Salinized with Four Different Salts

ABSTRACT

The effect of salinization of soil with Na₂SO₄, CaCl₂, MgCl₂, and NaCl (70:35:10:23) on the biochemical characteristics of three wheat (Triticum aestivum L.) cultivars (‘LU-26S,’ ‘Sarsabaz’ and ‘Pasban-90’) was investigated under natural environmental conditions. Twenty-day-old seedlings of all three cultivars were subjected to three salinity treatments: 1.3 (control), 5.0, and 10 dSm^?1 for the entire life period of plants. After 120 d of seed sowing, plant biomass production decreased by 49% and 65%, respectively, in response to 5 and 10 dSm^?1 salinity levels. Addition of salts to growth medium also had a significant adverse effect on plant height. Increasing salinity treatments caused a great reduction in nitrate reductase activity (NRA) of the leaf. The inhibitory effect of salinity on nitrate reduction rate was more pronounced at the reproductive stage than at the vegetative stage of plant growth. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ showed less reduction in NRA due to salinity compared with ‘Pasban-90.’ Ascending salinity levels significantly reduced potassium (K⁺) and calcium (Ca²⁺) accumulation in shoots, while the concentration of sodium (Na⁺) was increased. Salts of growth medium increased the shoot nitrogen (N) concentration, whereas phosphorous (P) concentration of shoots was significantly reduced due to salinity. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ proved to be the salt-tolerant ones, producing greater biomass, showing less reduction in NRA, maintaining low sodium (Na⁺), and accumulating more K⁺ and Ca²⁺ in response to salinity. These two cultivars also showed less reduction in shoot K⁺/Na⁺ and Ca⁺/Na⁺ ratios than in ‘Pasban-90,’ particularly at the 10 dSm^?1 salinity level.     

Protecting potato plants against PVX and PVY viral infections by the application of native and chemically modified legume proteins

Journal of Plant Diseases and Protection - Methylated soy and chickpea proteins (MSP and MCP, respectively), and 11S globulin (a soy protein fraction), are characterized by net positive charges and...     

Crop breeding for salt tolerance in the era of molecular markers and marker‐assisted selection

Crop salt tolerance (ST) is a complex trait affected by numerous genetic and non‐genetic factors, and its improvement via conventional breeding has been slow. Recent advancements in biotechnology have led to the development of more efficient selection tools to substitute phenotype‐based selection systems. Molecular markers associated with genes or quantitative trait loci (QTLs) affecting important traits are identified, which could be used as indirect selection criteria to improve breeding efficiency via marker‐assisted selection (MAS). While the use of MAS for manipulating simple traits has been streamlined in many plant breeding programmes, MAS for improving complex traits seems to be at infancy stage. Numerous QTLs have been reported for ST in different crop species; however, few commercial cultivars or breeding lines with improved ST have been developed via MAS. We review genes and QTLs identified with positive effects on ST in different plant species and discuss the prospects for developing crop ST via MAS. With the current advances in marker technology and a better handling of genotype by environment interaction effects, the utility of MAS for breeding for ST will gain momentum.     

Prospects of raising Sahiwal cow calves for veal production under tropical environment

The objective of present study was to evaluate the growth potential of Sahiwal calves for veal production on whole milk or whole milk and milk replacer combined in a ratio of 50:50 (MMR). For this purpose, 48 Sahiwal calves (both male and female) were assigned to four dietary treatments having 12 animals/treatment. Calves in the treatments A and B were offered whole milk at 15 or 20 % of their body weight (BW), respectively, up to day 84 adjusted on weekly basis. The calves in treatments C and D received the same amount of milk as in treatments A and B until day 21, respectively, after which 50 % of the milk offered was replaced with a blend of chickpea (Cicer arietinum) flour and vegetable (corn) oil mixed in water (MR) until day 84. The constituted MR had 3.1, 2.8, and 14.3 %, CP, EE, and DM, respectively. The growth and intake data were analyzed using repeated measures analysis, with MIXED Procedures of SAS in a 2?×?2 factorial design. The two factors were feeding level and feeding source. Calves offered whole milk grew faster (P?<?0.05) and had greater weaning weights (P?<?0.05) than those offered MMR (606.4?±?18.1 vs 331.3?±?18.1 g/day and 70.4?±?1.5 vs 47.8?±?1.5 kg, respectively). Greatest daily BW gain (656?±?26 g/day) and weaning weight (74.6?±?2.1 kg) were observed in calves given treatment B while the lowest production cost/kg of BW gain (≈US$3.6?±?0.2) was observed in calves given treatment A. The daily BW gain of calves fed milk ad libitum was 716?±?40 and 836?±?40 g/day, during 5–8 and 9–12 weeks, respectively. The number of days calves exhibited scours was higher in calves offered MMR than those offered whole milk. Replacement of 50 % milk with a blend of chickpea flour and vegetable oil, as an alternative to milk replacer, did not support growth equivalent to whole milk and was not effective in reducing feeding cost during the weaning period. Sahiwal calves may have promise for being raised for veal production under tropical environments.     

Alleviation of salt stress in Triticum aestivum by biopriming with Phanerochaete chrysosporium

Journal of Crop Science and Biotechnology - Wheat is one of the most important cereals, vital basic crop in Egypt, covering approximately 32.6% of the total winter land. However, sensitivity to...