Breeding for dwarf-type bermudagrass (Cynodon dactylon) with enhanced drought resistance is important for producing quality turf with reduced irrigation. A dwarf-type mutant (S-20–1) that exhibits slower vertical growth, and shorter internodes and leaf length was selected from the gamma-ray–irradiated seeds of a bermudagrass cultivar Sundevil II (S-CK). S-20–1 had slower turf coverage than S-CK. Compared with S-CK, the vertical growth of S-20–1 was more promoted by gibberellin (GA3) treatment. S-20–1 showed an enhanced drought resistance in greenhouse and field tests. Under drought stress, S-20–1 maintained higher relative water content and lower levels of ion leakage, malondialdehyde, and leaf firing than S-CK. Antioxidant enzyme activities and antioxidant content showed no difference between S-20–1 and S-CK under well-watered conditions, while higher enzyme activities were maintained in S-20–1 under drought stress. Free proline accumulated in response to drought stress and showed a positive correlation to the increased ion leakage, while S-20–1 had lower levels than S-CK. Our results indicated that the dwarfism in S-20–1 induced by gamma-ray irradiation might be the result of less GA3 or decrease of sensitivity to GA3 in the mutant. The improved drought resistance of the mutant is associated with maintenance of higher levels of antioxidant enzyme activities. More accumulation of proline in S-CK than S-20–1 reflected a physiological response to the drought-induced injury rather than an association with drought resistance of S-20–1.
Two challenges exist for modeling gas transport in shale. One is the existence of complex gas transport mechanisms, and the other is the impact of hydraulic fracture networks. In this study, a truly three dimensional semianalytical model was developed for shale gas reservoirs with hydraulic fractures of various shapes. Using the instantaneous point source solution, the pressure are solved for a bounded reservoir with fully 3D, partially penetrated hydraulic fractures of different strike angles and dip angles. The fractures could have various shapes such as rectangles, disks and ellipses. The shale gas diffusion equations considers complex transport mechanism such as gas slippage and gas diffusion. This semianalytical model is verified with a commercial software and an analytical method for single fully penetrated rectangle fracture, and the production results of shale gas are consistent. The impacts of fracture height and strike angles are investigated by five systematically constructed models. The comparison shows that the production increases proportionally with the fracture height, and decreases with the increase of strike angles. The method proposed in this study could also be applied in well testing to analyze the reservoir properties and used to forecast the production for tight oil and conventional resources.
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