Alleviation of Zinc Toxicity Consequences on Trigonella foenum-graecum Seedlings using Ammonium Sulphate

Although zinc (Zn) is an essential element required for normal growth, excessive amounts may be toxic for plants. This study highlighted the negative impact of Zn toxicity on the growth of Trigonella foenum-graecum and the role of ammonium sulphate (AMS) to ameliorate the induced oxidative stress. Growth parameters of seedlings as well as mitotic behaviour of root tip cells were monitored. Under Zn stress, a remarkable growth suppression of seedlings including low rate of germination, reduced root lengths, decreased fresh and dry matters were recorded. At the same time, high protein contents, high malondialdehyde (MDA), H₂O₂ levels and induced peroxidase (POD) and catalase (CAT) activities were recorded in Zn-stressed seedlings. Meanwhile, the seedlings treated with AMS and Zn/AMS were more or less similar to the control treatment. On the other side, the mitotic index (MI) of Zn-treated root tip cells showed significantly lowered values. The microscopic studies of Zn-stressed root tip cells showed several kinds of aberrations including sticky and lagging, fragmentation, multipolarity and formation of single and multi-chromatid bridges, which affected negatively on mitotic behaviour of root tip cells and overall growth of roots. These mitotic abnormalities were not detected in root tip cells treated with AMS and Zn/AMS. This study indicated that growth retardation and mitotic abnormalities of fenugreek resulted from Zn stress can be ameliorated by the application of AMS. AMS could work against Zn toxicity through supplying the plants with ammonium required for protein synthesis working in Zn detoxification.