Effects of Auxin at Different Concentrations on the Growth, Root Morphology and Cadmium Uptake of Maize (Zea mays L.)

Abstract

Indoleacetic acid (IAA) is an important regulator that plays a crucial role in plant growth and responses to abiotic stresses. In the present study, a sand cultivation experiment was carried out to investigate the effects of IAA at different concentrations (0, 0.01, 0.1, 0.5, 1, and 2.5 mmol/L) on maize growth, root morphology, mineral elements (Ca, Mg) and Cd uptake under 20 mg/kg Cd stress. The results showed that 0.01 mmol/L is the optimal IAA concentration for enhancing the Cd tolerance of maize. Compared with the control treatment, 0.01 mmol/L IAA promoted maize growth, with significant increases in the height, shoot and root biomass by 34.6%, 25.0% and 16.3%; altered the root morphology, with increases in root length, root tip number, and root tip density by 8.9%, 31.4% and 20.7%, respectively; and enhanced the mineral element uptake of maize, resulting in signifi- cant increases in the Ca content in shoots and roots by 640.6% and 1036.4% and in the Mg content in shoots by 205.8%, respectively. In addition, 0.01 mmol/L IAA decreased the Cd content and uptake in the shoots by 51.9% and 39.6%, respectively. Furthermore, the Cd content and uptake exhibited a significant negative correlation with Ca content in roots and a significantly positive correlation with root morphology, and the Cd content in shoots was significantly and negatively correlated with root tip number. Thus, 0.01 mmol/L IAA was effective in enhancing the Cd tolerance and plant growth of maize.