Effect of drought stress on some morphological characteristics of two sunflower (Helianthus annuus) hybrids at different planting densities

Effect of drought stress on some morphological characteristics of two sunflower (Helianthus annuus) hybrids at different planting densities was investigated. The experiment was conducted as split factorial based on randomized complete block design whit three replicates at research farm of Islamic Azad university of Tabriz in 006. Treatments was Record and Azarhghol sunflower hybrids, three levels of the drought stress including 75%, 50%, 5% available moisture, and three levels of planting density including 80, 90 and 00 thousand plants ha-. Between row spacing was 60 cm with in row spacing of 6, 8 and 0 cm, respectively for the three planting densities. The results indicated that exertion of the drought stress lead to a significant decline in plant height and diameter, sunflower head diameter and dry weight, and biomass weight per plant and per hectare (p<0.0). In addition, effect of the drought stress was thoroughly overlapped by density in the above characteristics. However, the 00% available moisture (control) in 80 thousand and 5% available moisture in 90 thousand plants ha- had the most and least dry weight of biomass, respectively. Azarghol hybrid had the highest plant and sunflower head diameter, while Record showed the most plant height at different drought stress levels. Height and diameter of plant and the sunflower head, dry weight of head and biomass showed significant and positive correlation with oil and seed yield per plant and hectare.