Abstract
In order to study the effect of water deficit stress on some physiological characteristics including leaf water osmotic and turgor potentials and osmolytes including sugars, proline and invertase activity of Persian melon (Cucumis melo Group. cantaloupensis cv. samsoury), an experiment was conducted in complete randomized design. Treatments including three irrigation levels (start of irrigation at -50 (control), -65 (moderate stress) and -75 kPa (severe stress) of matric potentials. Severe decrease of osmotic potential even less than predicted value (about -23 bar) was happened in severe water deficit stress (start of irrigation at -75 kPa of matric potential). Results indicate that water deficit levels in this experiment were cause to changes in sugars content and invertase activity. Water deficit stress decreased invertase activity to 2.01 at 35th days after start of stress, while the activity of this enzyme at this stage was measured about 4.14, for control (start of irrigation at -75 kPa of matric potential). Severe level of water deficit (start of irrigation at -75 kPa of matric potential) increased fruit sucrose content (0.32 mg/g FW) and glucose content (0.08 mg/g FW), leaves proline content (0.35 µmol/ g FW) at 35th days after start of stress. Also, an osmotic regulation was happened in this plant by sucrose and proline aggregation under water deficit stress and according to the leaf osmotic potential has decresed even more than expected value.