Effect of salicylic and Jasmonic acid on yield and yield components of Milk thistle (Silybum marianum L.) under heat stress conditions

The experiment carried out as a factorial in a completely randomized block design with three replications. Factors included hormone salicylic acid in five levels (0, 10, 25, 50 and 100 ppm) and Jasmonic acid at three levels (0, 1 and 2 ppm). Results revealed that there is a significant interaction between the two hormones on the all traits except plant height, number of lateral branches and flower diameter. The number of seeds per flower rose dramatically compared to other treatments when the concentration of acetylsalicylic acid increased to 50 milligrams per liter. In contrast the number of seeds per flower declined when the concentration of Jasmonic acid increased. Therefore, the maximum number of seeds per flower was obtained in second level of both acetylsalicylic and Jasmonic acid. Moreover, the lowest number of seeds per flower was gained in the highest concentration of acid Jasmonic and the zero level of acetylsalicylic acid. The highest yield was obtained in the second level of both hormones. Increase in the concentration of both hormones simultaneously resulted in significant decline in grain yield and, therefore, the lowest seed yield was obtained in third level of both hormones. Regarding to grain weight, it increased with growth in concentration of both hormones except third level of hormones and maximum amount of grain weight was obtained in second level of acetylsalicylic acid and third level of Jasmonic acid. Furthermore, the lowest grain weight was gained in the second level of both hormones.