EFFECTS OF SHADING AND MOISTURE STRESS ON YIELD AND OIL QUALITY OF HYDROPONICALLY GROWN ROSE GERANIUM

Rose geranium oil is used as a flavouring agent in many major food items and alcoholic and soft drinks. Relatively high radiation levels occur in South Africa during summer months and some hydroponically grown crops may need shading for optimum production. This study was conducted during spring and summer to evaluate the effects of shading and moisture stress on growth, oil yield and oil quality of rose geranium. A split plot experimental layout was assigned in randomized complete block design. Treatment with 0, 20, 40, 60 and 80% shading were allocated to the main plots. Subplots were exposed to two moisture stress levels of 0 and -0.15 MPa of osmotic pressure. The results show that rose geranium performs well when grown at a shade netting of 40%, where the number of branches, foliar fresh and dry mass, branch:height ratio as well as the oil yield peaked. Proline content was significantly higher at a low level of shading, where high levels of radiation were found and where moisture stress was applied. However, moisture stress did not affect any of the quality parameters measured for rose geranium oil. Most of the chemical substances produced at 40% shading level were of good oil quality. This study shows that 40% shade should be used to grow rose geranium in summer.