Ultrastructural changes caused by metazachlor on maize seedling leaves and root cells

Abstract

Maize (Zea mays L.) genotypes exhibit differential tolerance to metazachlor (2-chloro-N-(pyrazol-1-ylmethyl)acet-2'-6'-xylidide) in the greenhouse and in the field. However, since little is known on the effect of metazachlor on the ultrastructure of maize seedlings, laboratory experiments were conducted to determine this effect.Metazachlor caused ultrastructural changes in both root and leaf cell organelles of maize seedlings of susceptible genotypes. In susceptible genotypes root cell nucleoli were found to be abnormally large, empty and more abundant than those in untreated control plants. In susceptible plants the chromatids appeared disorganized in cell nucleoli, and both the nuclear and plasma membranes showed signs of disintegrating. There were more and larger vacuoles in the susceptible plants. Leaf cells from susceptible plants had more empty vacuoles and more chloroplasts with generally disorganized content. The bundle sheath chloroplast membranes were dilated in susceptible plants, and the orientation of the grana was disrupted. In the herbicide-tolerant plants, the ultrastructure was not affected. These findings show that metazachlor causes changes on the ultrastructure of susceptible maize genotypes.