Fitotoxicidad del mercurio durante la germinación de especies vegetales del bosque y matorral montano

Abstract

Abstract: Characterizing the response to heavy metal stress during early stages of the life cycle (germination and seedling quality) of some species of the Asteraceae and Malvaceae families may be a potential indicator of the success of their establishment in contaminated areas. Mercury (Hg) is one of the most toxic metals for living beings, and in low concentrations (between 1.0 and 1.5 mg L-1), it usually severely limits plant productivity. The objective of this work was to measure the percentage and germination rate of Bidens pilosa, Taraxacum officinale, Lactuca sativa (Asteraceae) and Heliocarpus americanus (Malvaceae) against different concentrations of mercury (0, 0.6, 2.0 and 4.0 mg L-1), as well as the length and diameter of the seedling radicle. The relative inhibitory effects on the germination percentage (from highest to lowest inhibition) were the following: T. officinale> B. pilosa> L. sativa> H. americanus. The T50 (Time to reach 50% of the germination) increased for L. sativa and B. pilosa as the concentration of Hg increased. In contrast, for H. americanus decreased significantly. The radicle length was the best indicator of phytotoxicity compared to the diameter. The effect of 4.0 mg L-1 of Hg on the radicle length was more pronounced in L. sativa (86%) compared to B. pilosa (55.3%) and H. americanus (31.5%). In a scenario of Hg contamination in the range evaluated in this study, such as soils affected by artisanal gold mining in southern Ecuador, B. pilosa and H. americanus could have a higher probability of establishment and survival.