The effect of potassium fertilizers on chlorophyll content of medicinal plant lavender (Lavendula officnalis L.) in a lead and cadmium contaminated soil

The aim of this study was to examine the effect of different sources of potassium in soils contaminated with lead and cadmium and their effect on photosynthesis by investigating changes in chlorophyll content in lavender (Lavandula officinalis L.). This study consisted of two independent factorial experiments in a completely randomized design with three replications. In the first experiment, two factors of potassium fertilizers (potassium chloride, potassium sulfate and potassium nitrate were applied at two levels of 55 and 110 mg kg-1 soil along with control) and cadmium chloride (0 and 15 mg kg-1 soil). In the second experiment, the factors included potassium fertilizers, similar to the first experiment, and lead nitrate (0 and 100 mg kg-1 soil). Analysis of variance of data showed that potassium fertilizers have a significant effect on the amount of chlorophyll a, b and total chlorophyll. The results showed that in soil contaminated with cadmium and lead, the chlorophyll content decreases significantly compared to uncontaminated soil. The results also indicated that in soils contaminated with cadmium, the greatest amount of total chlorophyll was obtained at the level of 110 mg kg-1 of potassium chloride, which showed a significant increase of 70% over the control level. The results of laboratory analyzes confirm that in lead contaminated soils, the greatest amount of chlorophyll a was obtained at the level of 110 mg kg-1 of potassium chloride, which showed a significant increase of 71% over control; Therefore, it seems that the use of potassium fertilizers may be effective in increasing the amount of chlorophyll, in which the effect of potassium chloride fertilizer is greater than that of the other two fertilizers.