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Drought stress in plants: effects and tolerance
Статья обзорная
Water is the catalyst of life and plays a profound role in plant physiological processes ranging from photosynthesis to intermolecular interactions through a hydrophobic bond. Because of the alterations due to changing environmental conditions, the plants are continuously exposed to a lack of optimum water availability, leading to impaired growth and disturbance in water transport and uptake. Drought is a prominent environmental factor that triggers various plant processes from morphological, physiological, biochemical, and molecular. Plants portray an array of drought tolerance mechanisms; these responses differ based on the type of plant species and may involve the functions of various stress genes. Reduction in plant growth and productivity due to stomatal closure affects photosynthetic efficiency, altering membrane integrity and several enzymes involved in adenosine triphosphate synthesis. Plants exhibit a range of drought tolerance mechanisms and undergo several phenological, morphological, physiological, biochemical, and molecular adaptations at the cellular, subcellular and whole plant levels. Also, drought stress induces the production of reactive oxygen species at the cellular level and is strongly protected by the increase in the enzymatic and non-enzymatic antioxidative system. This chapter/ review provides a glimpse of the effects and tolerance strategies adapted by the plant under drought stress.
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Drought tolerance induced by foliar application of abscisic acid and sulfonamide compounds in tomato
Статья научная
The effects of exogenous abscisic acid and two sulfonamide compounds: Sulfacetamide and Sulfasalazine were studied on tolerance of tomato ( Lycopersicon esculentum Mill. cv. Super chief) under drought stress and compared with abscisic acid effects. Eight-week old plants were treated with ABA (10 and 25 mg/L), Sulfacetamide (25, 50 and 100 mg/L) and Sulfasalazine (25, 50 and 100 mg/L). Solutions were sprayed daily and sampling was done at 0 h, 48 h, 96 h, 144 h and 48 h after re-watering (recovery phase or 192 h). Treated plants showed relatively greater drought tolerance. This indicates that, Sulfacetamide and Sulfasalazine may improve resistance in tomato, like ABA, increasing levels of proline, glycine betaine and malondialdehyde and the activity of ascorbate peroxidase. Daily application of Sulfasalazine and Sulfacetamide during drought stress period was effective in increasing tomato plants tolerance to drought as was ABA.
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Dynamics of Pinus sylvestris L. needles activity in Predbaikal’ye forests
Статья научная
The study was aimed to analyse changes in peroxidase activity of common pine needles throughout the year. The needles of the 1-st, 2-nd and 3-d years were collected. Total activity of guaiacol-dependent peroxidase was determined. Minimum peroxidase activity is observed in January and February. In March intense overall activation of peroxidase is observed in the needles of all ages, which might be related to spring enhancement of physiological processes and activation of metabolism. Autumn period is characterized by more or less high activities of guaiacol peroxidase from September till November, which is related to its participation in stress-adaptation to low temperatures in winter. Peroxidase activity changes depending on the season of the year. Needles of different age are characterized by their own peroxidase activity level in various time periods.
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Статья научная
Xerophytic cereal Stipa krylovii Roshev is interesting as a relic with extensive capabilities to adapt to severe climatic conditions of Eastern Zabaikal’ye, which allows it to occupy a vast areal. The species under study is characterized by distinctive ecological-biological peculiarities, which are underpinned by not only distribution, but historical establishment of the species. The primary goal of the research was to study ecological-biological peculiarities of adaptation of wild cereal Stipa krylovii to the habitat in Eastern Zabaikal’ye. According to the observations, Stipa krylovii is characterized by late development rate coinciding with the period of optimal heat and moisture availability. Seed embryos have a well-developed scutellum, distinct structures and well differentiated embryo axis. The studies identified no lateral or secondary roots in the cereal. In nature, seeds of S. krylovii are characterized by profound organic peace period, which persists in the course of sprouting under optimal conditions. Peace period of S. krylovii caryopses is likely to be due to the presence of sprouting inhibitors and is overcome in moist autumn period. Seed viability was determined under various soil moisture parameters up to its complete water capacity; the impact of moisture content on seed sprouting rate was studied. The results of the tests on caryopses sprouting with various moisture content demonstrated that at minimum moisture content (10%) S. krylovii forms epidermal hairs on coleorhiza; 30% of soil water content is enough for growth activation, viability and sprouting rate of this cereal, which is due to its xerophytic nature. This morphological peculiarity is likely to ensure in nature sprouting of these species in early spring, when soil contain minimum water. Intensity of the initial growth was determined by a number of parameters: rate of change in linear growth of trunk and root parts of the embryo, growth of dry substance of plantlets and roots (4-th and 6-th days of sprouting). Thus, characteristic morphological peculiarities in cereal structure play a certain role in adapting sprouting seeds to moisture deficit; so embryos of the species may be supposed to have their morphological mechanisms of regulating moisture absorption. Study of individual embryo parts demonstrates potential ecological-biological abilities of embryos to sprout with lack and excess of moisture.
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Статья научная
Background : Cascabela thevetia (L.) Lippold, a popular member of family Apocynaceae, (Yellow Oleander), contains pharmacologically active constituents include terpenoids, a-vonoid, steroids and glycosides in seeds. This plant is being the preferred tool for suicides in villages of India.
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Статья научная
Abiotic stresses, such as temperature, drought and salinity are serious threats to agriculture. Temperature stress is the primary cause of crop loss worldwide, reducing average yields for most major crop plants. In present study role of 24-epibrassinolide in three Brassica species ( B. carinata, B. juncea and B. napus ) on lipid peroxidation and proline under temperature stress was investigated. Seeds were given temperature treatments (4, 14, 24, 34 and 44°C) for 5 hours alone or in combination with EBR (10 -11, 10 -9 and 10 -7 M). Temperature stress whether low and high causes stress in terms of lipid peroxidation. High temperature causes more stress as compared with low temperature stress, as level of temperature stress rises increase in the membrane damage was observed. However the seeds treated with the EBR shows positive effect as there is decrease in the lipid peroxidation in terms of MDA content. Accumulation of proline was also observed in all temperature stress in all three Brassica species. Application of EBR at all concentrations causes significant increase in the proline content as compared with control and untreated.
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Статья научная
Legumes play very important role in agriculture as they form associations with bacteria that, fix nitrogen from the air. French bean is used in all over of the world as an edible vegetable crop. Seed ageing is the main problem of seed storage. Changes of bio-chemical and reduction of seedling growth are consequence of seed deterioration. An experiment was conducted to evaluate the effects of accelerated ageing on French bean seed germination and vigour indexes and hormone activity. Seeds of Phaseolus vulgaris L. were treated by accelerating treatments for 4, 6 and 8 days and the influence of ageing, GA3 (20, 30 & 40 ppm) and IBA (5, 10 & 20 ppm) under different concentrations in 8 days aged seeds of French bean were observed. Various parameters were taken for consideration such as germination percentage, along with the mean daily germination, speed of germination, dry weight of seedling and vigour index-I & II. Seeds of P. vulgaris showed 96.66% germination without any treatment (control condition) but during the exposure of specific temperature (42°C) with 100% relative humidity, seeds showed 30% reduction in germination just after 8 days of ageing treatments. While the treatment for 4 and 6 days did not show any remarkable changes in percent germination. So the seeds treated for ageing for 8 days were taken to enhance the germination by treatment of different hormones i.e. GA3 and IBA with different concentrations. Aged seeds treated with GA3 20 ppm showed high germination (82.99%) in comparison to GA3 40 ppm (66.32%).
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Статья обзорная
Copper (Cu) and manganese (Mn) are essential micronutrients for plants, but toxic at high concentrations. Responses of rice (Oryza sativa L.) and sunflower (Helianthus annuus L.) to toxic concentrations of Mn and Cu (up to 100 µM) were studied under three light intensities including low (LL, PPFD=100), intermediate (IL, PPFD=500) and high (HL, PPFD=800) light intensities in hydroponic medium. Rice plants showed higher susceptibility than sunflower to both heavy metals concerning dry matter of shoot and root. Growing under higher light intensity strengthened the effect of Cu toxicity while ameliorated that of Mn, the latter was attributed to the lower Mn accumulation of HL plants in both shoot and root. Chlorophyll content of leaves was influenced negatively only by Cu treatment and that at the highest concentration in the medium (100 µM). Similar with growth results, reduction of net assimilation rate (A) was higher in HL than LL plants treated by excess Cu, but in contrast to growth response, reduction was more prominent in sunflower than rice. Excess Mn-induced reduction of A was similar between LL and HL plants and was greater in sunflower than rice. Reduction of A was partly attributable to stomatal limitation, but non-stomatal mechanisms were also involved in this reduction. Copper and Mn treatment did not change the optimal quantum efficiency of PSII in dark-adapted chloroplasts (Fv/Fm ratio), but Fv/F0 was influenced particularly by Cu treatment, the reduction was higher in rice than sunflower and in HL compared to LL plants. Regarding excess Cu and Mn-mediated alterations in chlorophyll concentration, Fv/F0 and Tm values, it was suggested that, Cu and Mn toxicity depress the leaf photosynthetic capacity primarily by causing a significant alteration of the composition and functional competence of the photosynthetic units rather a reduction in the number of photosynthetic units (PSUs) per unit leaf area.
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Статья научная
Heavy metals are the elements that are present in the environment naturally, with the development of industries in the world, there is a drastic increase of heavy metals in the biosphere. Among the heavy metals, lead (Pb) is the most toxic metal that easily gets accumulated in the soil and sediments. Lead is not an important element for plant growth but it gets easily absorbed and accumulated in different parts of the plant. In this study, Setaria italica (foxtail millet - CO (Te) 7) is treated with different concentrations of lead to evaluate the changes in the morphological growth parameters such as rate of percentage of germination, Tolerance Index (TI) and phytotoxicity. The germination percentage is comparatively greater in the control plant and gradually decreases as the concentration of Pb increases. The length of root and shoot, the amount of fresh weight and dry weight also decrease with the increase in the concentration of heavy metals. The root length and shoot length in the control on the 45th day were 20.2±0.16 and 48.7±0.24 whereas in the maximum concentration of metal (250 mg/kg) it showed a minimum reading of 11.1±0.43 and 27.3±0.33 respectively. The percentage of phytotoxicity increases as the concentration of the metal increases. Tolerance indices decrease as the percentage of phytotoxicity increases.
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Статья научная
Increasing atmospheric CO2 concentration is generally expected to enhance plant growth, allocation and chemical composition of alkaloids in medicinal plants. The response to the elevated CO2 concentrations of various medicinal plants were studied with reference to growth and biochemical changes. Catharanthus roseus is an important medicinal plant which is being cultivated commercially in India for different purposes. It has gained interest from the pharmaceutical industry; the alkaloids vincristine and vinblastine from its sap have been shown to be an effective treatment for leukemia and lymphoma. It has a great importance in studying different parameters of C. roseus. The present study was carried out for growth and bio-chemical changes of C. roseus in different elevated CO2 levels. Open top chambers (OTCs, 3.0 m diameter, 3.0 m in height) were used to expose plants to ambient and elevated CO2 concentration (600 and 900 ppm).The experiment was conducted for five months. Carbon-dioxide enrichment studies in special open top chambers help us in understanding the changes at individual Biochemical changes and plant growth. The bio-chemical analysis revealed that the highest phenol, flavonoid, carbohydrate and tannin were recorded at 600 ppm+rh, and alkaloid was at 900 ppm. In ambient condition the highest protein was recorded in C. roseus. The plant growth revealed that the maximum fresh weight, shoot length and number of leaves were observed in 900 ppm. The maximum number of roots was observed in 600 ppm and the highest root length observed in 600+Rh. In the ambient condition, the above said characters were found to be in the lowest level.
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Effect of Exogenous Trehalose on Physiological Responses of Wheat Plants Under Drought Stress
Статья научная
Drought stress causes physiological changes in plant morphological growth and development. The protective role of trehalose (Tre) was investigated through exogenously applied to seedlings of wheat cv. Sakha 93 plants. Pots experiment were divided into four groups: control, Tre treatment, drought stress and drought stress with Tre treatment. Samples were collected in two stages after 7 and 14 days from drought stress to determine the fresh weight, dry weight, chlorophyll pigments, relative water content, electrolytic leakage, proline, malondialdehyde, antioxidant enzyme activities, and carbohydrates content. Drought stress reduced many growth and physiological characters. It significantly increased specific activities of guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) and significantly decreased the catalase (CAT) activity. It caused significantly increased in the Tre content while reduced sucrose and starch contents. Combination exogenous applied Tre (40 mM) with drought stress improved some growth parameters and photosynthetic pigments. Application of Tre markedly decreased proline and malondialdehyde contents, GPX; APX activities whereas increased CAT activity. Tre treatment appeared increased in the internal Tre content, on the other hand; exogenous Tre maintained the sucrose and starch contents in the seedlings of wheat plants under drought stress. The results concluded that applied Tre alleviated the adverse effect of drought stress on wheat plants by enhancing the antioxidant defense system and conservation of the membrane stability.
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Статья научная
The present investigation was conducted in the Norman E. Borlaug Crop Research Centre in G. B.Pant University of Agriculture and Technology, Pant nagar, Uttarakhand, with an objective to elucidate the role of MeSA on antioxidant activity which is significantly corelated with increase in allelopathic and yield potential of rice genotypes. For the study two allelopathic (UPR 2962-6-2-1 and Govind) and another non-allelopathic (UPR 2992-17-3-1) rice genotypes were undertaken and thereafter dealt with MeSA solution at diverse amount (1 mM, 2 mM, and 3 mM). Exogenous treatment of rice (Oryza sativa L.) with MeSA improved its allelopathic probability and led to buildup of additional phenolics, and an increase in gene transcription of enzymatic activities (SOD) Increasing phenolic content and enzymes activities without compromising the yield of the crop plants is necessary for increasing the competitiveness of the genotypes. Antioxidant activity was measured at different growth stages. In the present investigation superoxide dismutase (SOD) was found to be 10-50% enhanced in the rice plants with the application of MeSA .Treatment with MeSA has resulted in increase in antioxidant activity which can be suggested to improve the competitive ability of the genotypes and amongst all the treatments 0.2 mM dose of MeSA has responded best. From our study it is highlighted that the resilient capacity and plasticity of these contrasting genotypes is different in response to MeSA treatments which can further be evaluated and moreover antioxidant activity can be presuppose to be applied as suitable trait in rice weed interaction for sustainable agriculture.
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Статья научная
Heavy metals are elements that are naturally present in the environment. However anthropogenic activities such as the production of industrial wastes and domestic effluents, dumping of sewage waste, urban storm, water runoff, and atmospheric sources can give rise to the concentration of these metals relative to the normal background values. Any metal or metalloid with a density exceeding 5g /cm−3 is termed as “heavy metal”. These metallic ions are always associated with pollution and toxicity, although some of these elements are required by organisms at low concentrations. Some of the heavy metals such as zinc, iron and copper are essential for the physiological functioning of living organisms. The same essential elements become toxic when their concentration increases from their initial value. The present review article features the occurrence and toxicity of various heavy metals and compiles the sources, effects and the treatment of heavy metals with reference to cadmium, chromium and lead. This work also investigates the abilities of plants in terms of tolerance and degradation of these metals. It also reviews deeply about the heavy metal uptake mechanisms and several research studies associated with the topics. An evaluation of the present status of technology exploitation and the capability of some cultivated plants to reduce the contaminant is also reported and suggested for future work.
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Статья научная
Present report deals with the effect of increasing levels (0-300 mM) of MgCl2 salt on sorghum cultivars, Phule Vasudha and Phule Revati. Although MgCl2 stress did not show considerable adverse effects on germination, however, at higher (>200 mM) concentrations, the seedlings turned brown and did not showed any further growth, with comparably higher magnitude of negative effects on Phule Revati than Phule Vasudha. Overall, increasing MgCl2 stress reduced plant growth and biomass production significantly in both the cultivars, though with lesser extent in Phule Vsudha as compared to Phule Rvati. Contrasting behavior was evidenced in both the cultivars in terms of protein content under varying levels of MgCl2 concentration at vegetative growth level, where salinity induced reduction in protein content was higher in Phule Revati than Phule Vasudha. The genotype Phule Vasudha showed higher proline content under non-saline condition. MgCl2 stress-induced proline accumulation was observed in both the sorghum cultivars, however, interestingly, Phule Revati (439% of control plants) showed comparably higher proline content than Phule Vasudha (324% of control plants) at the highest (300 mM) level of stress. Even though, malondialdehyde (MDA: lipid peroxidation indicator) content was on higher side under non-saline conditions in cultivar Phule Vasudha as compared to cultivar Phule Revati, however the rate of increase in MDA with increasing salt stress was much higher in the latter cultivar, indicating the comparably higher level of lipid peroxidation under the influence of MgCl2 stress. The salt tolerance nature of Phule Vasudha was positively correlated with its better performance in terms of physiological and biochemical parameters.
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Статья научная
In this study we compare a few physiological parameters of a salt sensitive (Jaya) and salt resistant (Korgut) rice varieties to understand mechanism of salt tolerance. Jaya, high yielding salt-sensitive rice (Oryza sativa) variety, and Korgut, a 100% salt-tolerant rice variety, were grown for 15 days in vermiculite irrigated with NaCl solutions of 0 – 200 mmolL-1 prepared in Hoagland’s solution (pH 6.5). It was observed that initial fluorescence (F0) value increased, and the maximal fluorescence ratio (Fm) decreased in Jaya; however, the Korgut variety maintains the F0 and Fm value without much significant variation as NaCl increased. On the other hand, Actual efficiency (ΦPSII) significantly decreased in Jaya showed slightly decreased at 200 mmolL-1 NaCl treatment. The polypeptide composition of the thylakoid membrane decreases after NaCl treatment in the Jaya variety, but it's maintained in the Korgut variety. Photo-inactivation of PSII in Jaya includes the loss of the D1 and D2, (32-34 kDa) protein, probably from greater photosynthetic damage caused by salinity stress; Korgut is not showing alternation of the same protein, and it's maintained the greater photosynthetic. In Jaya, most prominently, the dramatic decline of the 47-kDa chlorophyll protein (CP), 17-kDa (F0), and (10kDa) OEC protein vice versa in Korgut. The decreased in 47-kDa, and 23kDa proteins in Jaya lead to the decreased energy transfer from the light-harvesting antenna to PSII due to the marked alterations in the composition of thylakoid membrane proteins. The most important of changes in Korgut indicate maintained chlorophyll fluoresces without altering the thylakoid membrane protein towards adaptation to salinity. These findings can be translated into efforts to develop more salt-tolerant cultivars and exhaust the possibilities of using saline soils.
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Effect of NaCl priming duration and concentration on germination behavior of Tunisian safflower
Статья научная
Priming is an effective technique that improves germination of several crop species. That's why; this study was carried in order to evaluate the effect of NaCl seed priming techniques on germination and early growth of safflower (Carthamus tinctorius L.). Safflower seeds were primed with four concentrations of NaCl as priming media (5, 10, 15 and 20 g/l) for 12, 24 and 36 hours. Results indicated that different priming concentrations and duration have significant on total germination percentage, mean germination time, germination index and coefficient of velocity of safflower seeds. It was also observed that 12 h priming duration had the most effect on studied traits as 5 g/l priming concentration treatment. In general, primed seeds showed better performance than control (non primed seeds) in all studied parameters.
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Статья научная
Salinity is one major problem of increasing production in crop growing areas throughout the world. The objective of this research was to evaluate the effect of NaCl priming on seed germination of Tunisian fenugreek ( Trigonella foenum-graecum L.) under salinity conditions. Seeds of fenugreek were primed with NaCl (4g/l) for 36 h in continuous 25°C. Experimental factors were included 2 priming treatments (NaCl and non-priming as control) and five salinity solution (4,6,8,10 and 12 gl -1). Results showed that seed priming increased final germination percentage, germination speed and radicle length over the non-primed treatment. At the lowest levels of salinity, there were no notable differences between primed and non-primed seeds, but with increasing salinity levels, primed seeds showed the better performance than non-primed seeds. These results indicated that NaCl priming significantly improved seed performance under salinity conditions.
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Effect of PEG-6000 imposed water deficit on chlorophyll metabolism in maize leaves
Статья научная
Drought stress is one of the major abiotic constraint limiting plant growth and productivity world wide. The current study was undertaken with the aim to investigate the effect of water deficit imposed by PEG-6000, on chlorophyll metabolism in maize leaves to work out the mechanistic details. Leaf segments prepared from primary leaves of etiolated maize seedlings were treated with varying concentrations of polyethylene glycol-6000 (PEG-6000; w/v- 5%, 10%, 20%, 30%) in continuous light of intensity 40 Wm -2 at 26±2 °C for 24 h in light chamber. The results demonstrate a concentration dependent decline in chlorophyll content with increasing concentration of polyethylene glycol-6000 (PEG-6000). Reduction in chlorophyll ‘a’ level was to a greater extent than the chlorophyll ‘b’. The RNA content decreased in a concentration dependent manner with PEG, however, proline content increased significantly. Relative water content decreased significantly with the supply of 30% PEG only. A substantial decrease in chlorophyll synthesis due to significant reduction in ALA content and ALAD activity, with no change in chlorophyllase activity with the supply of PEG suggests that water deficit affects chlorophyll formation rather than its degradation.
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Effect of Stress on Structural Behavior of Periplasmic Membrane In Pathogenic Organism
Статья научная
Microorganisms have an assortment of evolutionary adaptations and physiological advancement mechanism which permit them to survive and stay dynamic in face of environmental stress. The examination propose that all the more proficiently coordinating microbial ecology into biological system nature will require more complete integration of microbial physiological ecology, population biology and process ecology. Microorganisms also have genomic and metabolic plasticity to adapt the numerous stressful conditions they come across during their life. They give a remarkable illustration of adaptation to the most diverse environments. There is still plenty to learn on how pathogens react to host imposed stresses, how environmental microorganisms become acclimated to so viably to the continually changing environments, how metabolic changes at last shape their genome and how all the above can be exploited to our advantage, for example preventing food to spoil, improving food safety, performing industrial synthesis with nominal or no contamination. The revealing insight into fundamental parts of microbial reactions to stress can have commonsense consequences in irrelevant fields, for instance in the fix of human sicknesses. The aim is additionally to provide a strong interdisciplinary climate which will give a gathering to the flow of new various thoughts for better understanding microbial physiology under stress. There are a few stress to organisms include osmotic stress, oxidative stress, pH stress, thermal stress, periplasmic stress, and nutrient and starvation stresses. Environmental stresses are commonly active during the cycle of microbial fermentation and have critical impact on microbial physiology. Microorganisms have built up a progression of systems to oppose ecological anxieties. They keep up the honesty and smoothness of cell films by tweaking their configuration and composition, the penetrability and activities of carriers are changed in accordance with control nutrient transport and ion exchange.
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Статья научная
Rheum emodi is a rare medicinal herb in the Himalayan region due to its medicinal cum aromatic properties it is highly over-exploited from nature. Complete Randomized Design was executed and study aimed to understand the effect of different concentration of Lead and Cadmium in growth and biochemical parameters of Rheum emodi (Wall. Ex Meissn) as comparison to control. In plants, heavy metals Quantity were analyzed to show their effects on the animal and human beings who consume them as such or their derived products. In this study, encouraging results were obtained which favoured maximum (53.33%; p<0.05) mean germination in control and minimum in 1.5g concentration in both case of Lead and Cadmium treatment.
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