Effect of arsenic and phosphate Biofertilizer on physiological and Biochemical properties of green mint (Mentha spicata L.)

Soil contamination by heavy metals is one of the main environmental stress in agricultural and horticultural ecosystems Green mint as a vegetable and medicinal plant are directly and indirectly in the food basket of the Iranian community. Therefore, cultivation of this plant in heavy metals polluted fields or fields irrigated with unusual waters, wastewater, effluent from factories and industrial units, increases the accumulation of heavy metals, especially arsenic in the plant. In addition to its effect on the growth characteristics of plants, it poses a serious threat to the health of consumers. Therefore, the present study was conducted to evaluate the effect of phosphate bio fertilizer on the reduction of arsenic heavy metal toxicity on physiological and biochemical properties of green mint.

In this study, the effect of phosphate bio fertilizer on increasing arsenic tolerance of green mint was evaluated on a factorial experiment in completely randomized design under greenhouse condition at University of Guilan during 2016. Treatments consisted of different levels of arsenic (0, 50, 100 mg/kg soil) and phosphate bio fertilizer (0 and 0.5 mg/kg soil). Plants were taken about two months after planting. Morphological characteristics of the plants (number of leaves, number of stems, plant height, shoot and root dry weight, shoot dry weight and leaf area) were measured using ADC modeling apparatus. Biochemical properties including leaf chlorophyll and carotenoids content, carbohydrate, antioxidant enzymes and proline activity were also measured.

The results showed that with increasing arsenic concentration from 0 to 100, root dry weight (2.65 g), plant fresh weight (2.8 g), leaf number (4.88) and caratenoids content (2.05 mg) were decreased. Phosphate bio fertilizer application also increased relative moisture content, plant fresh weight and carotenoid. The comparison of mean interaction of fertilizer × arsenic showed that the lowest plant height (11.28 cm), plant dry weight (8.28 g), and leaf area (12.052 cm2) were decreased under treatment of 100 mg/kg arsenic without phosphate bio fertilizer.

Application of phosphate bio fertilizer in different arsenic treatments increased proline content, polyphenol oxidase, peroxidase, carbohydrate, total chlorophyll, chlorophyll a, b with decreasing of arsenic concentration in roots and shoots. The results showed that phosphate bio fertilizer could partially improve the plant growth and its tolerance to arsenic stress. Keywords: Antioxidant Enzymes, Chlorophyll , Heavy metals,Bio fertilizer.