Effect of Herbicide Mesosulfuron-Methyl + Iodosulfuron-Methyl and Salicylic Acid Treatment on the Chlorophyll Fluorescence and Chlorophyll Content in Wheat (Triticum aestivum L.)

The use of herbicides is one of the important factors affecting crop production. High concentrations of herbicides can cause damage not only to weeds but also to the crops by altering physiological processes in plant cells. When plants are exposed to herbicidal stress, they may resist stress by activating antioxidant defense responses or where antioxidant defense is not sufficient, stress resistance can be improved by treatment with various signaling molecules such as salicylic acid (SA). In this study, the effects of salicylic acid in improving the damage caused by the use of herbicide mesosulfuron-methyl + iodosulfuron-methyl in wheat plants is investigated. One day after treatment (DAT) no significant effects were observed by the application of herbicide and salicylic acid on minimal fluorescence (Fo). In general, the value of Fo was increased over time and significant differences between the treatments tested in this work were observed. More specifically, the highest amount of Fo was recorded at herbicide dose of 72 g a.i. ha-1 without salicylic acid 7 DAT, which was 28.48% higher of that recorded in untreated wheat plants. The lowest amount of maximum fluorescence (Fm) and the ratio between variable fluorescence over Fm (Fv/Fm) were recorded at 72 g a.i. ha-1 of herbicidal dose without salicylic acid, 5 DAT. More specifically, 0.5 and 1 mM of SA caused an increase of 9.48 % and 10.12 % in Fm value and 3.40% and 5.58% in Fv/m value, respectively. The content of chlorophyll α, chlorophyll b and total chlorophyll decreased under 36 and 72 g a.i. ha-1 of herbicidal dose in all sampling occasions. The use of SA increased chlorophyll a, chlorophyll b and total chlorophyll in all concentrations and sampling occasions. Likewise, the content of carotenoids was also increased at all stages due to SA presence. The highest content of carotenoids was recorded when the plants exposed at 72 g a.i. ha-1 and had been pre-treated with 1 mM salicylic acid 7 DAT. On the contrary, the lowest amount was obtained under the treatment without herbicide and salicylic acid 3 DAT.