LEPIDIUM SATIVUM L. HORMESIS INDUCED BY HEAVY METAL STRESS FOR SEED GERMINATION AND SEEDLING GROWTH

Abstract

The effect of numerous heavy metals such as Co (as CoCl 2 ), Cu (as CuSO 4 ), Zn (as ZnSO 4 ) and As (as Na 2 HAsO 4 ) concentrations on garden cress (L. sativum L.) was tested. During this experiment, the measurement of several parameters such as root length (RL), plumule length (PL), germination percentage (GP), germination index (GI), germination rate index (GRI), vigor index (VI), coefficient of velocity of germination (CVG) and mean germination time (MGT) were done. The results confirmed that various treatments of heavy metals possessed statistically significant impacts on the GRI, GI, MGT, CVG and VI. However, at different metal concentrations indicated that GP did not differ significantly for Co, Cu and Zn and differ significantly for As denoting an inverted threshold dose-response model. The results showed that the trend of GI, VI, CVG of As, RL and PL of As and Cu reduced with increasing metal doses indicating an inverted threshold model. The GRI decreased with mounting metal concentrations implying an inverted U-shaped germination curve of L. sativum L. seeds in the experiment, and the same for PL of Co and Zn. However, the results of MGT and CVG (of Co, Cu and Zn) denote no hermetic effect. In addition, the results indicated that root length was decreased more than shoot length and was expressed as the sensitivity index. Generally, it concluded that the toxicity of the examined metals diminishes by the following succession: As > Cu > Co > Zn.