Relative Changes in Growth and Recovery Responses of Rice to Fe-Toxicity at Different Growth Stages

Fe-toxicity is a critical and complicated constraint to rice growth that requires simple and quick screening methods for selection of tolerant rice to Fe-stress. This study revealed relative changes in the growth and recovery of rice responding to Fe-toxicity at germination and vegetative stages. Two rice cultivars were exposed to iron concentrations of 0, 50, 100, and 200 ppm at the germination stage and Fe–treatment of 50 – 100 and 100 – 200 ppm at the vegetative stage. Increasing Fe-toxicity reduced germination rates, seedling height, length and number of seedling roots. However, relative reduction to control in seedling height and root length at germination could be more dependable to check genotypes tolerant to Fe stress than other parameters. Growth characteristics measured at 6, 12, 18, and 24-day excess Fe indicated that plant height, number of tillers, and leaves were kept slightly relative increasing to control until 18-day and 12-day, respectively. In contrast, root length and root number decreased as soon as plants were exposed to Fe-stress. Relative decrease in growth to control increased with higher iron concentration and longer exposure time. Plants exhibited ability to recover after 24-day under stress with relative increase to the point before stress relieving from 3 – 12% for plant height, 1-11% for tiller number, and 7-19% for root number. There were significant differences between two cultivars for relative changes in growth and recovery parameters, suggesting a simple and efficient method, and suitable growth parameters for evaluating and selecting tolerant genotypes to Fe-stress at germination and vegetative stages.