Effect of Different Priming on Seed Germination Indices and Enzyme of Sorghum (Sorghum bicolor L.) SOR834 Genotype under Cadmium Chloride and Nitrate Toxicity

Background and Objectives The impact of toxicity of heavy metals such as cadmium in living organisms is a major global concern. Plant kingdom also is not exempted from the adverse effects to exposure of heavy metals. This study was conducted in order to investigate the effect of different priming on seed germination indices of sorghum under Cadmium chloride and nitrate stress condition in laboratory.
Materials and Methods The germination experiment was carried out as factorial based on a completely randomized design with four replications. The first factor was heavy metal treatments including 7 levels of cadmium chloride and nitrate, each in four levels (0, 200, 400 and 600 mM) and the second factor included 9 levels: gibberellic acid priming at concentrations of 400 and 800 mg/l, salicylic acid in two levels 0.3 and 0.6 mM, potassium nitrate with concentrations of 1 and 2% and concentrations of -3 and -6 bar of PEG and non-priming.
Results The results of the germination experiment showed that the highest and lowest seed germination rates and percentage were obtained in 200 mM of cadmium nitrate and 600 mM of cadmium nitrate and chloride treatment, respectively, while 0.3 and 0.6 mM of salicylic acid application increased the germination rate. The highest and lowest length and weight vigor index were observed in 0 mM cadmium and 600 mM of cadmium chloride respectively, that 800 mg/l of gibberellic acid application leads to increasing the vigor index. Catalase activity in seed sorghum was increased by increasing of cadmium concentrations but decreased by using different priming.
Discussion In relation to the slow germination under stress cadmium cell membrane, probably one of the important points is that the severely damaged cells leak out and vigor will be reduced. Priming with the reconstruction of damaged cells, reduces barriers to the growth of the fetus, increases the quality and quantity of protein synthesis, and increases tolerance to environmental stresses. Cadmium also reacts to sulfhydryl groups in the structure of enzymes and proteins. Plant water relations and gas exchange pores have a negative effect on processes of respiration and photosynthesis and increase production of reactive oxygen species in plant cells causes. Active oxygen species due to the desire for high electron affinity, and the basic biomolecules such as lipids, cells, proteins and nucleic acids can cause damage.