Abstract:
This study aimed to evaluate the impact of chromium (Cr) toxicity on physiological and
biochemical parameters, as well as the growth performance of tomato plants. The experiment
involved a pot experiment with different organic amendments, including biochar (BC). iron-
enriched biochar (Fe-BC), farmyard manure (FYM) and vermicompost (VC). The organic
amendments were fine-sieved and characterized using scanning electronic microscopy (SEM),
energy dispersive x-ray (EDX), fourier transform infrared spectroscopy (FTIR), and
thermogravimetric analysis (TGA). Tomato plants were harvested after 75 days of growth in
Cr contaminated soil, and their growth, physiological and biochemical parameters were
analyzed. Results showed that shoot growth, biomass, relative water contents, membrane
stability index, and chlorophyll contents decreased with increasing Cr concentration, however,
plants were unable to survive at 100 ppm Cr. Compared to control, significant decreases in
shoot length (SL) (40 & 61%), fresh weight (FW) (28 & 65%), membrane stability (MSI) (22
& 52%), and relative water content (RWC) (13 & 31%) were observed at 25 & 50 ppm Cr,
respectively. The toxic effect of Cr was attributed to Cr-induced oxidative damage by 1.9 and
2.7 folds under 25 and 50 ppm Cr, respectively, as compared to non-stressed plants. Application
of four amendments was effective in reducing Cr stress in tomato plants and among them, VC
significantly reduced Cr stress as compared to other amendments and showed the highest
growth. Interestingly, the addition of organic amendments helped the plants to withstand the
toxic level of 100 ppm Cr. The positive impact was majorly attributed to reduced uptake of Cr,
increased antioxidative enzyme activities (SOD=3.11 folds, CAT=1.14 folds, POD=2.95, and
APX=1.76 folds), and ultimately reduced damage caused by oxidative stress. Overall, the
results of the present study indicate the potential use of different organic amendments for
mitigating abiotic stresses in plants, but VC had better performance than other amendments
e.g., Cr toxicity, however, field tests are recommended to ascertain the response under natural
conditions.
