Interaction of Lead and Nitrate on Growth Characteristics of Ornamental Judas Tree (Cercis siliquastrum L.)

Lead is presently a significant heavy metal pollutant that is toxic for all types of life and is of worldwide concern. Various strategies may be applied to increase tolerance of plants to heavy metals, for example nitrogenous compounds have been shown to exert such effects. In the present study combinations of lead levels (0, 15, 30 mgL(-1)) and nitrate levels (0, 50, 100 mgL(-1)) applied through irrigation water, were evaluated for interactions affecting growth of ornamental Judas tree seedlings. The treatments were arranged in a randomized factorial design with four replications. The results showed that interactions between lead and nitrate levels on growth traits were not significant; however, the simple effects of lead and nitrate were significant on most morphological traits. The morphological traits of leaf SPAD (Soil and Plant Analysis Development) value, leaf area, new shoots growth and relative water content of leaf were reduced by application of lead (particularly at 30 mgL(-1)). Nevertheless, application of nitrate particularly at 100 mgL(-1) significantly offset the reduced plant growth traits induced by high levels of lead. The results indicate that presence of nitrate can significantly improve plant growth under high lead toxicity.