Metabolic And Biochemical Changes Associated With Root Growth Restriction Under Cd Stress During Maize Pre-Emergence

Abstract Cadmium (Cd) pollution of agricultural soils is a growing global problem. Plant growth restriction is the main visible symptom of Cd toxicity, and this metal may be particularly harmful to the preformed, seminal root during the pre-emergence stage. In the present study, we focused on Cd phytotoxicity on seminal root growth, nutrient composition, redox status, and hormone homeostasis during the pre-emergence stage, distinguishing between the root apex and the remaining root tissue. After 72 h of metal exposure (50 and 100 µM CdCl2), root length and biomass was diminished, as well as Ca, Fe, Mg, and Mn contents. A redox imbalance was evidenced by changes in peroxidase activities and decreased ascorbate-dehydroascorbate ratio in both root parts. There was less accumulation of carbonylated proteins in both root fractions upon exposition to 50 µM Cd, compared to 100 µM Cd, and this was related to increased 20S proteasome activities. Cd incremented ABA, IAA, and SA contents, but drastically reduced the biologically active gibberellin GA4 and the conjugate jasmonoyl isoleucine (JA-Ile). We demonstrated that the whole root tissue is involved in maize response to Cd stress, which entails redox and hormonal rearrangements, probably directed to widen plant defense lines at the expense of root growth.