Chlorophyll Fluorescence as an Indicator of Cellular Damage by Glyphosate Herbicide in <i>Raphanus sativus</i> L. Plants

Abstract

The fodder radish is an important alternative late summer crop in central-western Brazil. The fodder radish has a short growing cycle, is highly productive and possesses qualities that enhance its cultivation potential as an alternative in Brazil’s Biodiesel Program. However, drift of herbicides, such as glyphosate, may hinder the development of fodder radishes. Studies of chlorophyll fluorescence can provide measurements that help assess the effect of herbicide, being good indicator of the damage to photosynthetic apparatus promoted by herbicide. This study was carried out to analyze the effects of glyphosate by measuring chlorophyll a fluorescence, cellular membrane stability and chloroplast pigment contents in fodder radish plants. This experiment used a randomized block design in which the treatments consisted of the following 6 different doses: control, 0, 150, 300, 450, 600, 750 and 900 g i.a. ha - 1 of the recommended 480 g &middot L - 1 dose of glyphosate acid equivalent. The plants were sprayed 30 days after emergence and were assessed every 48 hours. The characteristics evaluated, including chlorophyll a fluorescence, chloroplast pigments and the rate of electrolyte leakage , indicated that radish plants are sensitive to glyphosate because the treatments resulted in reduced levels of photosynthetic efficiency and increased damage to cellular membranes, which led to a reduction in the chloroplast pigment content.