Introduction:

The tree Prosopis nigra is native to the Western Chaco phytogeographic region, affected by the application of glyphosate in the surrounding crops.

Objective:

To determine the impact of simulated glyphosate drift on growth, photosynthesis and oxidative stress in P. nigra seedlings.

Methods:

We simulated drift in seedlings at doses of 0, 200, 400 and 800 g a.e. ha-1 of glyphosate. We also measured gas exchange and modulated fluorescence emission of chlorophyll a.

Results:

Glyphosate reduced biomass, photosynthetic rate, and stomatal conductance. Doses of 400 and 800 g a.e. ha-1 glyphosate produced photoinhibition. The electron transport rate was sensitive to glyphosate, and it decreased at all doses of the herbicide. Glyphosate generated oxidative stress, and produced damage to membranes, because of the accumulation of H2O2 and O2..

Conclusions:

Glyphosate reduces growth and photosynthesis in these seedlings. The inhibition of photosynthesis is due to stomatal closure, and alterations in the photochemical stage, associated with oxidative stress.