Influence and interaction of iron and lead on seed germination in upland rice

Abstract

Lead is a hazardous heavy metal pollutant present in the environment, and iron is an essential micronutrient with numerous cellular functions in normal physiology. However few studies have focused on the influence and interaction of lead and iron changes during plant growth. So the present study investigated the mechanism how lead and iron affected in upland rice (Oryza sativa L.) in order to clarify the relationship between iron and lead. The seeds of upland rice were supplied with iron (Fe), lead (Pb), and Fe and Pb together, respectively. Then the seed germination, ion absorption, gibberellins (GAs) and abscisic acid (ABA) metabolism and sugar utilization were determined. Lead treatment delayed upland rice seed germination, deactivated GA, inhibited GA signal transduction and increased ABA synthesis in the seed. In addition, the soluble sugar concentration in seeds was reduced alongside reduction in the activity levels of α-amylase (EC 3.2.1.1) and β-amylase (EC 3.2.1.2) during the earlier stages, but these increased in a time-dependent manner, reaching a stable level in response to lead-induced stress at 72 h. In contrast, iron alleviated the lead-induced changes in seed germination stage. Notably, the interaction between iron and lead increased GA signal transduction and inhibited ABA synthesis, whilst increasing starch hydrolysis and sugar consumption to augment rice seed germination. The results suggest that iron (such as in iron fertilizers) may be promising additives for agricultural use, improving plant germination, whilst simultaneously reducing the toxicity of lead in widely contaminated soils.