Effect of cycocel on photosynthetic activity and essential oil of fennel (Foeniculum vulgare Mill.) under drought stress

Drought stress is one of the most important and most common environmental stresses that limit plant growth. Photosynthesis is the main determinant of plant growth and its retention ability under environmental stress condition is important for preservation of growth stability. To study the effect of spraying CCC on photosynthesis activity and essential oil content on ''Foeniculum vulgare''، an experiment was done in split plot design based on complete block with four replications in research field of University of Zanjan in 2011. Levels of drought stress included، control، soft stress (when 30% of available water was out of soil)، severe stress (when 90% of available water was out of soil)، and three concentration of CCC 0، 1500 and 3000 mg/L. The results showed that between rates foliar application on physiologic characteristics as photosynthesis rate، transpiration severity، RWC and TΔ intercellular (Ci)، stomata conductivity، mesophyll conductivity and essential oil content was significant. By spraying 3000 mg/L CCC، balanced the plant position against drought stress and could reduce negative effect. Foliar application of CCC caused significant increase in photosynthesis rate، mesophyll conductivity and significant decrease stomata conductivity، transpiration severity under drought stress and could increase essential oil content under soft stress. In this study، foliar application of CCC to content 3000 mg/L had the highest effect on this characters.