Abstract
The lack of water is the most important problem in extensive landscape especially turfgrass in arid and semi arid regions. The root responses in native and commercial grasses under drought stress were investigated. This experiment was in a factorial experiment based on unbalanced completely random design on the year 2006. The specious that we used in this experiment included (i) commercial tall fescue (Festuca arundinacea) (ii) commercial perennial ryegrass (Lolium perenne) (iii) native tall fescue population (Festuca arundinacea). The drought stress levels included (i) 50%FC (ii) 25% FC (iii) recovery from drought stress and 3 groups of pots that was always in the field capacity condition. The replicates for control pots and drought/recovery treatments were 3 and 4 respectively. The results showed that root dry weigh of commercial and native tall fescue increased 40%, 11.9% respectively compared with control under severe drought stress. Whereas it decrease 33.6% in lolium perenne compared with control at same condition. Another root traits such as volume, total area and root total length in the native tall fescue increase 60.1%, 34.6%, 70.1% respectively compared with control under severe drought stress. This traits in plus 54% decrease in root diameter caused increased in rank of absorption and depletion of water from dry soil. That it caused better yield of this grass under drought stress. Ability of recovery in most morphological root characters increase in commercial grass after rewatering in compare with severe drought stress condition.

Keywords: Avoidance, Native population, Drought stress, Re-growth, Root