Response of radicle cells of fungicide treated and untreated maize seed subjected to stress conditions

Abstract

Ultrastructural changes within cells are influenced by stress such as increased temperature due to improper storage, lack of oxygen and blockage in pathways responsible for water uptake. The objective of this study was to assess the effect, if any, of fungicide treatments on the ultrastructure of radicle cells of maize (Zea mays) after seeds had been subjected to stress conditions. Maize seeds were treated with Celest® XL (fludioxonil + mefenoxam) and Apron® XL (metalaxyl-M). The control consisted of untreated seeds. Following treatment, seeds were subjected to 2 d accelerated aging and 48 h rapid imbibition and thereafter prepared for transmission electron microscopy. Initial percentage germination (81%) of the seed lot was reduced after 2 d accelerated aging, with the untreated control having the lowest percentage germination (61%) followed by Apron® XL (65%) and Celest® XL (69%). The most obvious ultrastructural difference between the untreated control and the two fungicide treatments was the position of the lipid bodies. These formed a layer in close association with the cell wall in fungicide treated seeds, but in the untreated control they appeared more concentrated in the cytoplasm. Treated and untreated seeds may use different mechanisms, namely numerous vauoles and/or the movement of lipid bodies from the cell wall, to tolerate the stress conditions during rehydration of the seed after accelerated ageing and rapid imbibition.