Evaluate the effect of deficit irrigation on water relations, growth and physicochemical changes in Petunia (Petunia garandiflora) var. " Supercascade", " Tango Blue" and " Tango White"

Drought stress is one of the most important and most common environmental stress that is limited agricultural production. to evaluate the effect of different levels of deficit irrigation on some properties of three varieties of petunia, a factorial experiment in a completely randomized design with four replicationswas conducted in research greenhouse of Ferdowsi University of Mashhad. Examined factors including drought in four levels (100, 80, 60 and 40% of field capacity) and three varieties of petunia (Supercascade, Tango blue and Tango white). Traits were included fresh weight of plant components, total dry weight, stem diameter, spad, antioxidant activity, leaf weight ratio (LWR), leaf area ratio (LAR), Relative Water Loss (RWL), Water Saturation Defficient (WSD) and Leaf Water Content per unit leaf Area (LWCA). The results showed that with increasing drought from control to severe stress (40% FC) Spad increased from 35.4 to 42.6. percentage of antioxidant activity in Tango White and Tango Blue was more than Supercascade. the most leaf fresh weight was in Tango White and in control stress levels (6.08 g) and 80% of field capacity (5.9 g) and the maximum stems fresh weight (9.7g/plant) and flower fresh weight (15.1 g/plant) were seen in Tango White varity and control stress. total dry weight was observed in Tango White and 100% FC. LWR value in Supercascad, Tango Blue and Tango White were 0.283, 0.538 and 0.496 respectively. WSD (72) and RWL (65%) in Supercascade varity and under severe stress (40% FC) with a significant effect was higher than other treatments. Generally the results showed Tango White and Tango Blue varities, in control and also under water stress conditions had more fresh weight, dry weight and antioxidant activity and had WSD and RWL less than Supercascad and so are more resistant.