Study of the effect of nickel heavy metals on some physiological parameters of <i>Catharanthus roseus</i>

Plants, in their life cycle, are usually exposed to various kinds of non-biological stresses including heavy metals. One of these heavy metals is nickel which affects many physiological processes of plants. Studies have shown that the changes in planting conditions can affect the qualitative and quantitative features of <i>Catharanthus roseus</i>; therefore, creating stressful conditions (e.g. NiCl₂) can be an effective way to investigate the changes. In this research, we investigated the effect of 0, 2.5, 5, 10, 25 and 50 mM concentrations of NiCl₂ on the degree of catalase enzyme activity, amount of proline aggregation and photosynthetic parameters on seeds of pink variety <i>of C. roseus</i>. The results indicated that the degree of catalase enzyme activity and the amount of proline aggregation increased in plants which were exposed to NiCl₂ treatments, especially in high concentrations, while the total protein decreased. The stress of Ni also affected photosynthetic parameters, and decreased the amount of pigments, as well as the efficiency of photosystem II.