Effect of salicylic acid on pigment, protein content and peroxidase activity in excised sunflower cotyledons

Abstract

Enviromental stress gives rise to the activation of adaptation and defence responses in plants. It is known that the role of salicylic acid (SA) is quite important in this mechanism. In this study its effect was investigated on excised cotyledons of sunflower (Helianthus annuus L.) seedlings. The sunflower seedlings were grown in dark conditions for 9 days and then their etiolated cotyledons were harvested. Then, they were transferred into Petri dishes containing 0.001 mu M, 0.1 mu M, 10 mu M, 1000 mu M SA. Cotyledons were incubated for 14 hours in the dark at room temperature, then they were incubated in light period for 3 hours. Chlorophyll, carotenoid content, protein amount and peroxidase (POD) activity in the cotyledons was examined. SA 1000 mu M solution showed the toxic effect in growth considering the results of total chlorophyll, carotenoid content and protein amount. An increasing 2 fold of chlorophyll content in 10 mu M SA and 3.5 fold of carotenoid content in 0.1 mu M SA treated cotyledons comparing to the control were observed. Protein amount increased in all concentrations except 1000 mu M SA. POD activity was also stimulated in all concentration of SA solutions. However, the clear difference in 0.001 mu M SA was not seen. As a result, chlorophyll, carotenoid, protein contents and POD activity increased in exogenic SA applications