Javed Akhter

Differential changes in antioxidants, proteases, and lipid peroxidation in flag leaves of wheat genotypes under different levels of water deficit conditions

Changes in enzymatic antioxidants and oxidative injury were evaluated in flag leaves of seven wheat genotypes under well watered (WW), medium watered (MW), low watered (LW) and soil stored moisture (SSM) conditions maintained in lysimeters through neutron moisture prob. Genotypes behaved differentially in terms of antioxidant response and stress induced injury under above indicated water deficit levels. In general, antioxidant enzymes were rarely enhanced under MW condition, often increased under LW condition while remained unchanged, elevated or diminished under SSM condition (severe stress). Higher CAT and POD activities were observed in NR-234 and in Pfau followed by FD-83 respectively under LW conditions. Under SSM condition, APX and POD increased significantly in Nesser and Pfau and CAT in NR-234, Nesser and Pfau, while remained at control level or decreased in other genotypes. In NR-234, SOD activity enhanced only under LW condition. However, SOD rose in Nesser, FD-83 and Sarsabz while remained unaffected in NR-241, Sitta and Pfau under all water deficit conditions. Lipid peroxidation increased significantly in FD-83 only under MW condition along with raised protease activity and protein contents. However, peroxidation of lipids was significantly enhanced in all genotypes under LW and SSM conditions. It was concluded that response of genotypes vary under different levels of water deficit. Hydrogen peroxide scavenging system was more actively involved in detoxification of oxidative stress induced by water deficit. Raised antioxidants (CAT, POD) resulting in comparatively lower lipid peroxidation in Pfau under SSM condition and in Sitta under LW condition confer stress tolerance in these genotypes.

Influence of Salinity on Nitrogen Transformations in Soil

Laboratory experiments were carried out to study the influence of various salinity levels [1 (control), 9 (medium), 17 (high), and 27 dS m–1(strong)] on nitrogen (N) transformations in soil fertilized with urea and ammonium sulfate. Generally, soil salinization affected the normal pathway of N transformations. The results showed that salinity (medium to high) inhibited the second step of nitrification, causing nitrite (NO2 −) accumulation in soil. The inhibition was more severe in cases of high level of salinity. The greatest salinity level caused inhibition of even the first step of nitrification, leaving more ammonium (NH4)-N accumulation in soil. Severity in nitrification inhibition was observed with increase in salinity and rate of N application, which declined with time. Ammonium accumulation with increased salinity caused N losses in the form of ammonia (NH3) volatilization. After 14 days, the NH3 losses were 1.4-, 2-, and 5-fold greater at 9, 17, and 27 dS m–1 than that of the control (1 dS m–1). After 42 days, the losses reached up to 6-fold more than the control at the greatest salinity level. Initially (up to 14 days), NH3 losses were more from urea than from ammonium sulfate, whereas at the later stages (42 days), the losses were almost equal from both the fertilizers. The overall results revealed significant adverse effects of salinity on N transformations in soil.

Phytoremediation of Saline Soils for Sustainable Agricultural Productivity

Salinization of soils is one of the major factors which severely affect the agricultural productivity worldwide. Due to salinity, more than half a billion hectares of land are not being properly used for crop production. Thus, there is a need to search means to improve saline soils so that such soils could support highly productive and meaningful land-use systems to meet the current challenges of global food security. Although permanent solution of soil salinity problem necessitates a sound drainage system to manage the rising water table, this option, being energy- and cost-intensive cannot be employed on a large scale on vast areas. Phytoremediation or biological approach, i.e., plant-based strategies for improvement of deteriorated soils is an appropriate option. Phytoremediation of saline soils can be done by cultivating suitable plant species as well as by Exploiting the ability of plant roots to improve the dissolution and enhance levels of Ca in soil solution to efficiently remove Na from the soil cation exchange complex and leach it from the root zone. During the amelioration process, soil-aggregates stability, root proliferation, soil hydraulic properties and availability of nutrients to plants are also improved. Such improvement in soil properties facilitates cultivation of less tolerant plants, improves the environment in general, and the climatic conditions by enhancing carbon sequestration.

MODULATION OF PHYSIOLOGICAL AND BIOCHEMICAL METABOLITES IN SALT STRESSED RICE BY FOLIAR APPLICATION OF ZINC

An experiment was conducted to evaluate the effect of zinc (Zn) application on five rice cultivars grown under salt stress conditions. Two salinity levels of 0 and 10 dS m−1 were created with sodium chloride (NaCl) and foliar spray of Zn (0.05%; Chelated-Zn) was applied. A decrease in growth and yield related parameters were observed under salt stress, which was ameliorated in plants that received Zn foliar spray. Similar effects of salinity and Zn foliar spray were noted on photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, and water relations of plants. Salt induced increase in sodium (Na) content and decrease in other macro- and micronutrients contents were also reversed by Zn. Other salt tolerance indicating parameters likSe total free amino acids and total soluble sugars increased under Zn spray, clearing its role in improving salt tolerance.

MODULATION IN YIELD AND JUICE QUALITY CHARACTERISTICS OF CITRUS FRUIT FROM TREES SUPPLIED WITH ZINC AND POTASSIUM FOLIARLY

Citrus, especially K innow (Citrus deliciosa × Citrus nobilis), fruit yield and quality in Pakistan is not competitive with that of other countries which could be mainly attributed to the lack of good nutrient management for citrus orchards. The yield losses in this fruit crop occur mainly due to heavy fruit dropping. Experiments to overcome these problems were conducted at four different sites one each in Faisalabad, Toba Tek Singh, Jhang and Sargodha districts of Punjab, Pakistan. The soil and leaf chemical analysis showed severe deficiency of Zn and our pervious results have shown that soil amendment with potassium (K) at 75 K2O kg ha−1 improved the citrus fruit yield and quality at all selected sites. In the present experiments, effect of foliar application of Zn and K alone or in combination was studied on nutrient uptake, fruit yield, fruit dropping and juice quality. The fruit trees were pretreated with a selected K level of sulfate of potash (SOP) or muriate of potash (MOP), i.e., 75 kg K2O ha−1 along with recommended nitrogen (N) and phosphorus (P) doses. Zinc [Zn, 1% zinc sulfate (ZnSO4) solution], K [1% potassium sulfate (K2SO4) solution] and Zn + K (solution containing 0.5% each of ZnSO4 and K2SO4) were sprayed at the onset of spring and flush of leaves or flowers, fruit formation and at color initiation on fruit. Overall, application of Zn, K or Zn + K was effective in improving the nutrient uptake, yield and quality parameters of citrus fruit at all sites. Fruit dropping was also reduced by the foliar spray of Zn, K or Zn + K but the most promising results were recorded with foliar spray containing both Zn and K.

INFLUENCE OF DIFFERENT RATES OF PHOSPHORUS ON GROWTH, YIELD AND PHOSPHORUS USE EFFICIENCY IN TWO WHEAT CULTIVARS

To study the influence of different rates of phosphorus (P) on growth and yield of wheat, experiments were conducted at NIAB, Faisalabad, Pakistan under natural conditions. Results indicated that the P requirement of wheat at early growth was higher and adequate available P in the growth medium helped to attain relatively higher growth rate and resulted in higher grain yield. The two wheat cultivars when subjected to different rates of P application showed that the cultivar ‘MH-97’ was more responsive than ‘Pasban-90’ that attributed to its higher P translocation efficiency from roots to tops. The two cultivars also showed differential yield response when grown under field condition. At optimum nitrogen (N): P ratio of 1.5:1, the cultivar ‘MH-97’ gave 31.5% while cultivar ‘Pasban-90’ gave a maximum response of 25.9% over their respective N alone application. Contrarily, at the wider NP ratio of 3:1, yield response of cultivar ‘MH-97’ was 26.5% while that of cultivar ‘Pasban-90’ was only to the extent of 2.2%, thereby indicating a much wider difference in their yield response pattern. Thus, choosing an appropriate cultivar for a particular rate of fertilizer application would be more rewarding in terms of yield and profitability.

Optimal Supply of Micronutrients Improves Drought Tolerance in Legumes

Legumes are of considerable importance for providing food and feed world over. In comparison to cereal grains, legume seeds are rich in protein and thus provide highly nutritive food. Legumes are grown on a wide range of soils varying in texture and fertility. Most of the soils of arid and semi-arid regions, being low in soil moisture content, are also low in fertility. So to maximize plant productivity, proper supply of macro- and micro-nutrients to crops is essential. As a general practice, optimal supply of macronutrients to crops is usually ensured but that of micronutrients is ignored. In view of a plethora of literature, it is now well established that application of micronutrients is effective in alleviating the adverse effects of abiotic stresses such as salinity and drought. The involvement of micronutrients in different physiological and biochemical activities of the legume plants is well documented because correlations between micronutrient supply and crop growth and productivity have been often observed. Use of micronutrients like zinc (Zn), iron (Fe), boron (B), manganese (Mn), molybdenum (Mo), copper (Cu), cobalt (Co) and nickel (Ni) has now become a common practice to increase crop yield especially under adverse environmental conditions. Plants deficient in micronutrients may become susceptible to diseases and abiotic stresses. Rapid leaching of acids in sandy soils tends to produce a deficiency of tightly held nutrients such as Zn, Fe, Cu or B. Therefore, problem soils such as acid, alkaline or sandy soils are often deficient in one or more micronutrient elements. Micronutrient application not only improves the stress tolerance potential indirectly (because micronutrients deficient plants exhibit an impaired defense response) but also results in improving a number of metabolic phenomena. Thus, application of micronutrients as foliar or soil amendment is recommended to achieve optimum crop productivity from the soils having inherent micronutrient deficiency and low moisture contents. In this chapter, the role of micronutrient management in improving the drought tolerance potential and productivity of legumes is reviewed and critically discussed.

Crop Productivity and Water Use Efficiency: The Role of Carbon Isotope Discrimination Technique

At a time when global population continues to increase, global agriculture now accounts for 70% of the amount of water used on earth and crop losses due to water loss are much higher than crop losses due to any other causes. Reliable selection of crop varieties or genotypes with increased grain yield is essential both under irrigated and rain-fed conditions, due to water shortage commonly experienced in many environments. This can be obtained by increasing crop water use efficiency (WUE) either by breeding, or by soil, water and crop management. WUE can be enhanced by reducing water losses (runoff, drainage, evaporation), thus increasing the proportion of the water used by the crop. There is, indeed, a clear relationship between the amount of water transpired and yield across a diverse range of crop species. The carbon isotope discrimination technique has been proposed by several authors as a mean of selecting cultivars with improved WUE. Carbon isotope discrimination (Δ) of plant tissues (leaf or grain) has been shown to correlate negatively with transpiration efficiency and positively with grain yield in a wide range of crops. In the present chapter, recent progress in improving crops for yield and water-use efficiency using the carbon isotope discrimination technique are reviewed and some possible avenues for making further advances are discussed. The review describes the basis of carbon discrimination in C3 and C4 crops with a special emphasis on cereals, dominant food crops grown in irrigated and rain-fed areas.

Rapid and Inexpensive Steam Distillation Method for Routine Analysis of Inorganic Nitrogen in Alkaline Calcareous Soils

Determination of inorganic nitrogen (N) in soil is important in making N fertilizer recommendations for crops. To find a rapid, reliable, and economical method for the estimation of inorganic N in alkaline calcareous soils of Pakistan, three steam distillation methods were compared using soils varying in ammonium (NH4) and nitrate (NO3) N contents and other physicochemical properties. In the standard method, the soil sample is shaken with 2 N potassium chloride (KCl) for 1 h, and the extract is then analyzed by steam distillation. In the other two methods, the soil sample is distilled directly with either 2 N KCl or distilled/deionized water. Based on the results of the present work, a method that involves steam distillation with only distilled/deionized water and that requires half the quantity of magnesium oxide (MgO) of the standard method has been proposed, as all the three methods yielded identical results for NH4- and NO3-N contents. Being economical, the proposed method for inorganic N estimation by direct distillation of soil with distilled/deionized water deserves consideration for adoption by soil-testing laboratories.

Field determination of soil hydraulic properties for simulation of the optimum watertable regime

A field experiment to evaluate accurate cost and time efficient methodologies for determining soil hydraulic properties was done at the NIAB Research Station at Faisalabad, Pakistan. The experiment was performed on a freely draining loamy soil. This soil type is representative of 75% of the topsoil in a tile drainage area known as the Fourth Drainage Project. Redistribution of water was monitored at five locations, for seven depths, following a steady state infiltration for prolonged time. The data were analyzed with Darcian flow analysis, three simplified methods, and two parameter optimization programs to calculate unsaturated hydraulic conductivity. The Darcian flow analysis was used as a reference against which the simplified methods were compared. Two simplified methods produced satisfactory results with less effort. The drawback is that the simplified methods alone do not provide enough information for use in simulation models. The advantage of the two optimization programs — SFIT and RETC — is that they are based on a continuous function which describes complete h(ϑ) and K(ϑ) curves. This is a requirement for computer simulation of salt and water movement in the unsaturated soil. The results of the optimizations were evaluated by their correspondence to field measurements and to laboratory measurements and by their ability to simulate soil water flow. Both programs fit the observed field data well, but only the SFIT optimized parameters were suitable for soil water flow simulations.