Mohammad Pessarakli

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

Handbook of Plant and Crop Stress

Handbook of plant and crop stress , Handbook of plant and crop stress , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Handbook of plant and crop physiology

Plants/crops growth responses to environmental factors and climatic changes physiology of plant/crop growth and developmental stages cellular and molecular aspects of plant/crop physiology plant/crop physiology and physiological aspects of plant/crop production processes plant growth regulators - the natural hormones (growth promoters and inhibitors) and plant genes physiological responses of plants/crops under stressful (salt, drought, and other environmental stresses) conditions physiological responses of plants/crops to heavy metal concentration and agrichemicals physiological relationships between lower and higher plants physiology of lower-plants genetics and development using computer modelling in plant physiology plant/crop physiology under controlled conditions, in space, and on other planets.

Ammonium (15N) metabolism in cotton under salt stress

Abstract Plant growth and metabolism is impaired under stress conditions, resulting in decreased crop yields. The purpose of this investigation was to evaluate the NaCl stress effects on NH+ 4 metabolism in cotton plants at vegetative and reproductive stages of growth. Cotton (Gossypium hirsutum L.) plants grown in normal (control) and NaCl treated Hoagland solutions were analyzed for distribution of N15 in NH+ 4 plus amide‐N, free α‐amino‐N, total soluble‐N and protein‐N after the plants were provided 15NH4NO3 in nutrient solutions for 6, 12 and 24 h. The concentration of protein‐15N was enhanced under a low level of NaCl (‐0.4 MPa osmotic potential) at the vegetative growth stage. The difference between the protein‐15N concentration of the moderately salinized (‐0.8 MPa) plants and the controls was not significant. A high level of NaCl (‐1.2 MPa) significantly decreased protein‐N content of plants compared with the controls and any other level of salinity. The NaCl increased accumulation of NH4 + plus a...

Incorporation of recycled urea—N into ruminal bacteria flowing to the small intestine of dairy cows fed a high-grain or high-forage diet

Copyright (c) 1997 Elsevier Science B.V. All rights reserved. Dairy cows fitted with flexible T-type duodenal cannulas were fed either high-grain or high-forage diets in a switchover design. Urea labeled with 15 N was infused continuously into the jugular vein of each cow for 72 h, following 23 d of adjustment. Duodenal digesta, feces, and urine were sampled every 3 or 4 h, and milk and blood every 12 h during 5 d of collection. Also, urine was totally collected for the 5-d period. Enrichment of 15 N in digesta and bacteria entering the duodenum and in urine, feces, milk and blood all increased until cessation of infusion, but 15 N ratios of urinary N:bacterial N were constant between 40 and 72 h. Nonlinear regression was used to estimate enrichment values at the isotopic equilibrium applying the Marquardt method. Incorporation of endogenous urea into duodenal digesta and ruminal bacteria present in duodenal digesta also was calculated by isotopic equilibria. Endogenous urea contributed 19.1 and 37.5% of N in duodenal digesta and in duodenal bacteria for lactating cows fed the high-grain diet; whereas, values for the high forage diet were 7.4 and 12.7%, respectively. Flow of N from the rumen to the small intestine tended to be higher for cows fed the high-grain than high-forage diet (122 vs. 103% of N intake), a finding consistent with more recycled N on high-grain.

Physiological response of spring durum wheat genotypes to salinity.

Soil salinity is a serious threat in many parts of Iran, which negatively affects plant production. In order to investigate response of durum wheat to salinity, two genotypes, ‘Turkey 506’ (salt tolerant) and ‘Egypt 557’ (salt sensitive), were grown in hydroponic conditions, exposed to various salt levels (0, 50, 100, 150 and 200 mmol NaCl) in a split split plot based on randomized complete block design with three replications of each treatment. Salinity stress decreased relative water content (RWC), potassium content, potassium/sodium ratio, chlorophyll a (chla), chlorophyll b (chlb), and total chlorophyll contents, efficiency of photosystem II (Fv/Fm) and membrane stability index (MSI), and increased sodium, proline and soluble sugars concentrations and ratio of chla/chlb in both genotypes. The decrease in RWC, chla, chlb, Fv/Fm, and MSI were significantly higher in ‘Egypt 557’ than ‘Turkey 506’. ‘Turkey 506’ showed higher content of potassium, potassium/sodium ratio, proline, and soluble sugar concentrations as well as lower sodium content as compared with ‘Egypt 557’. The salinity tolerance of ‘Turkey 506’ is associated with higher RWC, potassium content, osmolyte concentrations, chlorophyll contents, Fv/Fm ratio, and maybe more vacuole sequestration of sodium.

Growth Responses and Nitrogen-15 Absorption of Desert Saltgrass Under Salt Stress

Abstract Saltgrass [Distichlis spicata (L.) Greene var. stricta (Gray) Beetle], accession WA-12, collected from a salt playa in Wilcox, AZ, was studied in a greenhouse to evaluate its growth responses in terms of shoot and root lengths, shoot dry-matter yield, and nitrogen (N) (regular and 15N) absorption rates under control and salt (sodium chloride, NaCl) stress conditions. Plants were grown under a control (no salt) and three levels of salt stress (100, 200, and 400 mM NaCl, equivalent to 5850, 11700, and 23400 mg L− 1 sodium chloride, respectively), using Hoagland solution in a hydroponics system. Ammonium sulfate [(15NH4)2SO4], 53% 15N (atom percent 15N) was used to enrich the plants. Plant shoots were harvested weekly, oven-dried at 60°C, and the dry weights measured. At each harvest, both shoot and root lengths were also measured. During the last harvest, plant roots were also harvested and oven-dried, and dry weights were determined and recorded. All harvested plant materials were analyzed for total N and 15N. The results showed that shoot and root lengths decreased under increasing salinity levels. However, both shoot fresh and dry weights significantly increased at 200 mM NaCl salinity relative to the control or to the 400 mM NaCl level. Shoot succulence (fresh weight/dry weight) also increased from the control (no salt) to 200 mM NaCl, then declined. The root dry weights at both 200 mM and 400 mM NaCl salinity levels were significantly higher than under the control. Concentrations of both total-N and 15N in the shoots were higher in NaCl-treated plants relative to those under the control. Shoot total-N and 15N contents were highest in 200 mM NaCl-treated plants relative to those under the control and 400 mM salinity.

Reactive Oxygen Species (ROS) Generation and Detoxifying in Plants

Environmental stresses present major challenges in our quest to achieve sustainable food production. The reactions of plants to environmental stresses are complex and involve many kinds of physiological and biochemical responses. Stress causes multifarious adverse effects in plants. Production of a family of reactive oxygen species (ROS) is a common phenomenon. When plants are subjected to environmental stress, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in an oxidative damage. Plants with high levels of antioxidant enzyme activity are reported to have greater resistance to this oxidative damage. The activities of component enzymes or the antioxidant levels are usually only double in response to many stress situations. This rather moderate response might be understood if we consider that the system is geared to self-destruction when it comes under threat. Understanding the mechanisms by which plants perceive environmental signals and transmit the signals to cellular machinery to activate adaptive responses is of fundamental importance to biology. The present review is focusing on ROS generation and plant defenses to them.

Response of Wheat Plants to Zinc, Iron, and Manganese Applications and Uptake and Concentration of Zinc, Iron, and Manganese in Wheat Grains

This experiment was conducted at Zahak Agricultural Research Station in the Sistan region in southeast Iran. A factorial design with three replications was used to determine the effects of zinc (Zn), iron (Fe), and manganese (Mn) applications on wheat yield, Zn, Fe, and Mn uptakes and concentrations in grains. Four levels of Zn [soil applications of 0, 40, and 80 kg ha−1 and foliar application of 0.5% zinc sulfate (ZnSO4) solution], two levels of iron sulfate (FeSO4; 0 and 1%) as foliar application, and two levels of Mn (0 and 0.5%) also as foliar application were used in this study. Results showed that the interactive effects of Zn and Mn were significant on the number of grains in each spike. The highest number of grains resulted from the application of 80 kg ZnSO4 ha−1 and foliar Mn. The interactive effects of Zn and Fe were significant on weight of 1000 grains. The highest weight of 1000 grains resulted from application of 80 kg Zn and foliar Fe. Application of 80 kg ZnSO4 ha−1 alone and 80 kg ZnSO4 ha−1 with foliar application of Mn significantly increased grain yield in 2003. The 2‐year results showed that foliar application of Zn increased Zn concentration and Fe concentration in grains 99% and 8%, respectively. Foliar application of Fe resulted in a 21% increase in Fe concentration and a 13% increase in Zn concentration in grains. The foliar application of Mn resulted in a 7% increased in Mn concentration in grains.

Salt Tolerance of Canola in Relation to Accumulation and Xylem Transportation of Cations

ABSTRACT This study was conducted in a greenhouse to evaluate the root and shoot response of canola (Brassica napus L.) to salt-stress conditions and the remobilization, deposition, and input rate of sodium (Na), potassium (K), and magnesium (Mg) at different salinity levels using two canola cultivars. A salt-tolerant (‘Kristina’) cultivar and a salt-sensitive (‘Hyola 308’) cultivar were grown in nutrient solutions with 0, 50, 100, 150, and 200 mol m−3 NaCl for 7 d. The plants were harvested after 6, 12, 18, and 24 h and 3 and 7 d after salt treatment. The results indicated that increasing salinity significantly decreased shoot and root weights 7 d after treatment. Also, K content and K-Na selectivity decreased in both cultivars, but the changes in ‘Hyola 308’ were greater than in ‘Kristina.’ Electrolyte leakage was increased significantly by salinity, and cell-membrane stability of ‘Hyola 308’ was damaged more than that of ‘Kristina’. Sodium import, transport, and deposition was increased by salinity concentration but remobilization was decreased. The K and Mg import, deposition, and remobilization were also decreased. From this experiment we can conclude that greater K and Mg remobilization in ‘Kristina’ could be a mechanism of salt tolerance in canola.