Physiological and biochemical effects of Pb on Zea mays L. seedlings

In this research the effects of 0.25, 0.5, 1 and 2mM pb(NO3)2 adjusted to pH 6 were examined on the four day old seedlings of Zea mays L. in the controlled condition for 72h. At the end of treatment the roots and shoots of seedlings were harvested separately.The length, dry weigh and fresh weigh of the roots and shoots of plants were measured.The results showed that Pb toxicity inhibits significantly root elongation and biomass. Analysing of Pb content in the roots and shoots of different treatments by atomic absorption indicated that: a)Pb absorption goes up by increasing level of Pb in growth solution; b) Pb accumulates in the roots and its transport to the shoots is very low. Determination of the amount of soluble sugars and total proteins indicated that the soluble sugars increased in the roots but their changes in shoots were not significant, while the total proteins were decreased in both roots and shoots. The profile of proteins by SDS-PAGE showed some changes related to control plants such as increasing of 56, 60 and 74 KD proteins.This research indicated that the Zea mays is a tolerant plant to Pb and takes up high levels of Pb from growth medium at pH 6. So, it would be necessary to understand the mechanisms of tolerance in this plant.