Effects of drought in biomass production and allocation in three varieties of Trichloris crinita P. (Poaceae) a forage grass from the arid Monte region of Argentina

Abstract

Trichloris crinita, a perennial forage grass nativeto the west arid Monte region of Argentina, has shown great variability inforage production among populations originated in different environments. In aprevious study under irrigated conditions we concluded that higher productivityof some varieties was associated with larger total plant biomass and higher drymatter partitioning to aboveground organs. The goal of the present study was toinvestigate the ecophysiological basis of differential productivity in threevarieties of T. crinita under water stress conditions.Varieties PICHI, ARROYITO and ENCON of high, medium and low productivity wereevaluated under high and low water availability. Two cycles of water stress,maintained until leaves folded, were applied to each variety. Leaf foldingoccurred at different leaf water potential (Ψ_L) for eachvariety.At the end of the first stress cycle Ψ_L were: PICHI −4.27MPa, ARROYITO −3.26 MPa and ENCON −1.82MPa. Each variety finished the stress cycle at a different time.Shoot/root ratio and DM partitioning to different organs were not modified bythe water stress treatment for the three varieties thus, the relativedifferences among them were maintained. Shoot/root ratio of PICHI (3.2) wasmorethan double of the least productive variety (ENCON). The higher productivity ofPICHI is associated to a larger shoot/root ratio, faster production of leafareaand higher leaf, sheath, culm and panicle DM production. Root DM was notdifferent among varieties. ENCON, coming from an area with lower rainfall andhigher temperature, was the last to fold their leaves and had a higher leafwater potential at the end of the drought cycle, probably linked to its smallerleaf area and relatively larger root system.