Effect of arsenic tri- oxide on germination and seedlings growth in alfalfa (Medicago sativa)

Environmental pollution by arsenic is a global problem that is related to agriculture and organsims health. According to the previous studies, arsenic is toxic to the most plants and causes physiological and biochemical changes in them. Furthermore, its entrance to the food chains, can threat human health. The aim of this study was to investigate, effect of different concentrations (۰, ۵, ۱۰, ۱۵ and ۲۰ mg l-۱) of arsenic tri-oxide (As۳+), on germination percentage, germination rate, seedling vigor index and seedling length of alfalfa, during ۱۰ days in the laboratory. In this way, the experiment was conducted as a completely randomized design in three replications for each concentration of As۳+, and was performed in petri dishes containing wet filter paper and healthy, homogeneous sterilized alfalfa seeds. Data analysis was done by Tukey test. The results of experiments showed, with increasing concentration of the treatment, the percentage and the rate germination decreased significantly (P≤۰.۰۵) .The highest decrease related to these parameters (۹۸.۲۸% and ۹۷.۷۵%, respectively), was recorded in the highest level of the treatment. At levels over ۵ mg l-۱, Seedlings growth stopped and the seedling vigor index became zero. Based on the results, it can be concluded that arsenic, especially at high concentrations, inhibits alfalfa seedlings growth by interfering with metabolic processes. It seems, Arsenic has reacted with tissue enzymes and proteins and possibly has disrupted enzymatic activity and energy synthesis that eventually led to seed tissue death and inhibition of germination. As well as, the lack of adequate defense mechanisms at germination stage, can be a reason for the alfalfa greater sensitivity to arsenic toxicity at this stage. In order to have a comprehensive understanding of the arsenic effect on seed viability, it should be considered ROS, RNS and seed hormones interactions with arsenic. Field studies are also recommended.

کلیدواژه ها:

Crop plants ، seed development ، metalloid ، stress