Effects of cadmium on growth characteristics, photosynthetic pigments and some biochemical parameters of safflower (Carthamus tinctorius L.)

Cadmium is regarded as one of the most toxic elements for living organisms that plays no positive biological role. In order to study the effect of cadmium heavy metal on growth factors of Carthamus tinctorius, an experiment was conducted in a completely randomized design with three replications in open-air conditions. Different levels of cadmium sulphate applied to the pots in the experiment were 150, 300, 450, 600, 750, 900, and 1000 µM solutions. Based on the results of the present study, the dry weights of roots and shoots significantly decreased in response to varying levels of cadmium but shoot lengths and relative growth rates were not significantly different compared to control. The results of the analysis of variance showed that the amount of chlorophyll a,b and total chlorophyll significantly decreased compared with the control while the decrease in carotenoid compounds content and relative water content in Carthamus tinctorius with increasing cadmium concentration was not significantly different comparing with the control. The amount of soluble sugars in the roots and shoots of Carthamus tinctorius plants treated with cadmium increased, but the amount of insoluble sugars in the aforementioned organs decreased. The results of the analysis of variance also revealed that with increasing the concentration of cadmium, the cadmium levels of shoots increased. Findings also showed that with the increase in cadmium concentration at some levels (300, 750, 900, and 1000 µM) the activity of guaiacol peroxidase enzyme showed no significant difference compared to control. In addition, the amount of polyphenol oxidase enzyme increased which was significant at all levels comparing to control and only at 150 µM level no significant difference was observed compared to control. The results of this research showed that safflower is able to absorb cadmium in its tissues and it can be used for phytoremediation of cadmium heavy metal.