Vanadium Stressed Responses Of Chickpea Genotypes In Growth, Antioxidation And DNA Damage

Heavy metals are major environmental concern when they present in high concentration in soil. Heavy metals in agricultural land and products are of great attention throughout the world as they are toxic to both plants and human health. Among all non-essential metals, vanadium (V) is becoming a serious matter of discussion for the scientists who deals with heavy metals. Till now, the exact role of V in biological system is controversial due to lack of information. Previous studies considered that V plays role as essential trace element in plants while, in recent decades many reports are strongly disagreed for the essentiality of V and considered it toxic element for plants. Generally, the toxicity of V connected with V species like H2VO4, such kind of species chemically similar to essential plant nutrients. However till now, no definite criterion of V for the maximum permitted concentration in soils and crops grown in contaminated soils has been enacted.All the experiments for present work were conducted under hydroponic culture to evaluate the effect the V on chickpea genotypes. To understand the effects of V, the present work was designed to evaluate the V-stressed responses on growth, enzymatic activities, genes expression and its uptake and distribution in chickpea genotypes. Laboratory studies were preformed where seed germination, morphological parameters, antioxidant enzymes and non-enzymes, total soluble protein, ions leakage, photosynthetic pigments, DNA damage, genes expression, V uptake by shoots and roots and genes expression were measured as a response to exposure to V. The main objective of the present work was to screen chickpea genotypes into tolerant and sensitive against V-stress and to illustrate differential responses of vanadium stress between screened genotypes of chickpea.The first experiemnt was carried out to evaluate the effects of different concentrations of V on seed germination and seedling growth of six genotypes of chickpea (G-1, Z-1, Pb-2000, C-44, Balkasar and Noor-2009). The findings showed that the germination percentage, shoot and root length, shoot length vigor index (SLVI), shoot weight vigor index (SWVI), fresh biomass, germination index (GI), Protrusion percentage (PP) and mean daily germination (MDG) were reduced, while 50% germination of seeds (T50) increased in all observed genotypes by increasing the V concentrations moreover, V at the rate of 60 mg L-1 affected more than other treatments. Additionally, the genotypes Noor-2009 and C-44 were more resistant and G-1 and Balkasar were more sensitive to V stress at germination and seedling stage. Our results concluded that V significantly inhibited the seed germination and early growth of chickpea genotypes.One more study was conducted to elucidate the effects of V on growth, protein content, and its uptake and enzymes activity to sort out the V-tolerant and sensitive genotypes of chickpea under hydroponic conditions. The findings showed that V significantly increased the antioxidant enzymes (SOD, CAT and POD) and antioxidant non-enzymes (MDA and GSH) activities in all chickpea genotypes however, V significantly reduced the protein contents, and more accumulation of V was observed in roots than shoots in all genotypes. The plant biomass and lengths of roots and shoots were also significantly reduced by V. Moreover, NH4VO3 caused more toxicity than Na3VO4. The obtained data indicated that Noor-2009 and C-44 were proved tolerant and G-1 and Balkasar were proved sensitive genotypes of chickpea against V stress.A new experiment was done to elucidate the effects of V on photosynthetic pigments, membrane damage, antioxidant enzymes, protein and DNA integrity in screened chickpea genotypes. Changes in these parameters were strikingly dependent on levels of V:60 and 120 mg V L-1 induced DNA damage in Balkasar only, while photosynthetic pigments and protein were decreased from 15 to 120 mg V L-1 and membrane was also damaged. From 15-120 mg V L-1 showed declined in photosynthetic pigments and protein production and also damaged the membrane while DNA damage was not observed at any level of V stress in C-44. Moreover, the antioxidant enzymes (SOD, CAT and POD) activities were increased in both genotypes of chickpea against V stress however; more activities were observed in C-44 than Balkasar. Results also showed that roots accumulated more V than shoots while, C-44 accumulated more V contents than Balkasar. The results suggest that DNA damage in sensitive genotypes can be triggered due to exposure of vanadium.One more experiment was designed to determine the interactive effect of V and phosphorus (P), their uptake and genes expression at higher concentration of V with lower P and higher concentration of P with lower V in genotypes of chickpea. The results illustrate that the fresh biomass was decreased significantly at higher concentrations of V when P was fixed while the fresh biomass was increased with increasing P when V was fixed. The increasing trend in fresh biomass was more in C-44 than Balkasar. The accumulation of V was significantly declined in both genotypes with increasing P. On the other hand, both genotypes accumulated more V when solution contained lower P concentrations. The microscopic studies of treated leaves showed that at higher concentrations of V with fixed P, the cells were damaged badly and get smaller than fixed V with increasing P concentrations. The Hsp70 gene was only expressed in C-44 at elevated concentration of V (1180 μM) when P was fixed (500 μM) while Hsp90 was slightly activated in C-44 at elevated concentration of V (1180 μM) when P was fixed (500 μM) and the expression of GAPDH was same in all selected samples of both genotypes. In conclusion, higher concentrations of V reduced the uptake of P while higher concentrations of P inhibited the uptake of V by both chickpea genotypes.