Glyphosate effects on stomatal conductance of Lolium spp. biotypes with differential herbicide-sensitivity.

YANNICCARI, MARCOS EZEQUIEL; TAMBUSSI, EDUARDO; ISTILART, MARÍA CAROLINA; CASTRO, ANA MARÍA

Córdoba

Workshop; International Workshop on “Glyphosate Weed Resistance: European Status and Solutions”; 2012

Centro Andaluz de Agricultura Sostenible (Universidad de Córdoba)

Ryegrass (Lolium sp.) is a common weed in wheat and barley crops in the South region of Buenos Aires province (Argentina). Glyphosate is frequently used to control weeds on field prior to crop sowing or emergence. In the last years several Lolium spp. populations were characterized as glyphosate-resistant weeds. The aim of this work was to assess the glyphosate effects on the stomatal conductance (gs) of Lolium perenne L. biotypes with differential herbicide-sensitivity. Twenty four plants were propagated vegetatively trough tiller separation in order to obtain, at least, four propagules per each plant. When the propagules produced 3 tillers, each clone was treated with 0, 500, 1000, or 2000 g ae ha-1 of glyphosate. The last fully expanded leaf was used to determine the gs of adaxial side with a leaf porometer at 3, 6, 24, 48 and 72 hours post-application (HPA). Plants controlled by glyphosate were recorded at 10 days post-application. At 24 HPA stomatal conductance of controlled plants was significantly inhibited by the herbicide, around 45% less than their controls. Afterwards, gs decreased over time and reached a 65% lower value at 72 HPA. In survivor plants, gs decreased 15% compared to their controls at 24 HPA and subsequently the inhibition of gs was up to 35% at 72 HPA. Glyphosate-induced stomatal closure, assessed in the controlled plants, could be an important factor related to depressed CO2 assimilation. The current results suggest the gs as a parameter to assess the sensitivity to glyphosate, in an early lapse before the visual phytotoxic symptoms become evident.