The distribution pattern of perennial native grasses in the dune systems of the Monte desert might be determined by the ability of plant roots to acquire water under drought conditions in different topographical positions and soil substrates. This study examined differences in root traits of two species growing in sand dunes, Aristida mendocina and Panicum urvilleanum, and two species growing in interdune valleys, Pappophorum caespitosum and Leptochloa crinita, under different water availability conditions in a sand substrate. Grasses were grown in rhizotrons and the factorial design included species, irrigation treatments, days from sowing, and depth soil profile. Root length, total root length, number of root branches, length of root branches-to-number of root branches ratio (LB:NB), daily elongation rate (DER), root length density (RLD), root angles, aerial and root dry mass, and shoot-to-root ratio (S:R) were measured. The four species studied were affected by drought conditions causing a decrease in root growth and modifying root structure, partition of assimilates, root angles, and exploration of the soil profile. However, we found that species from sand dunes were less affected by drought and showed a deeper root exploration under drought conditions, mainly due to proliferation of longer and more lateral roots in the deepest soil layer. The different root traits and responses of the species under drought conditions would imply adaptations to the topographical position each species occupies and could explain their spatial distribution in desert dunes.

蒙特沙漠沙丘系统中多年生原生草的分布方式可能取决于植物根系在干旱条件下在不同地形位置和土壤基质下获得水分的能力。本研究在两个品种的根系性状差异沙丘，种植芒草门多萨和柳枝urvilleanum，以及两个物种在垄间的山谷增长，Pappophorum caespitosum和千金子crinita，在不同的水分供应条件下，在沙质基质中。草在根茎中生长，析因设计包括树种，灌溉处理，播种天数和土壤深度。根长，总根长，根枝数，根枝数与根枝数之比（LB：NB），日伸长率（DER），根长密度（RLD），根角，气生根和根测量干重和茎根比（S：R）。所研究的四个物种受到干旱条件的影响，导致根系生长减少，改变了根系结构，同化物的分配，根系角度以及土壤剖面的探测。但是，我们发现沙丘中的物种受干旱的影响较小，并且在干旱条件下显示出更深的根系探索，主要是由于在最深的土壤层中更长和更多的侧根繁殖。该物种在干旱条件下的不同根系性状和响应将暗示其对每种物种占据的地形位置的适应性，并可以解释其在沙漠沙丘中的空间分布。