Effects of planting date and salicylic acid on physiological traits of forage maize hybrids . Mehrnaz Zarei 1*, Jafar Masood Sinaki 2, Ali Rahbari 1, Hossin Abaspour2

Temperature changes occur in nature faster than other stressors. Plants due to inability to move and change their position, are exposed to extensive variations in daily or seasonal temperature, and therefore, should quickly and effectively adapt to temperature stress. In order to study the effects of heat stress on physiological traits of forage maize hybrids, a factorial split plot experiment was carried out in a completely randomized block design with three replications in 2011. Treatments consisted of two maize varieties Ks 704 and N 504, 2 concentrations of salicylic acid (0 mM and 1 mM) and 2 different planting dates (July 5th and 26th). The plant height, stem diameter, plant dry weight, dry matter production (DMP) and protein content (CP) were measured. Results showed that plant height was affected under the interaction of three factors of the study, i.e., planting date, hybrid and spraying salicylic acid. Plant height in the variety N 504, treated with 1 mM salicylic acid and the planting date of July 26th was 64.76% more than in the treatment including 0 mM salicylic acid and the planting date of July 5th. Maximum dry weight per plant was observed in the plants treated with 1 mM salicylic acid planted on July 26th. Dry matter production (DMP) in Ks 704 sprayed with 1 mM salicylic acid and the planting date of July 26th was 73.71%. On the other hand, the protein content (CP) in shoots with 0 mM salicylic acid was 15.68%.