Response of Leaf Gas Exchange Parameters to Mulching Materials in Wheat Field was Mediated by Stomatal Morphology and ABA Content.

Field mulching and deficit irrigation are applied more frequently in the North China Plain for higher water use efficiency. In order to explore the physiological response of winter wheat to mulching materials under different irrigation amounts, a field experiment with three mulching (no mulching, NM; transparent film mulching, TFM; and straw mulching, SM) and two drip irrigation (full and deficit irrigation, FI and DI) treatments were set up. Soil water content, leaf gas exchange parameters, leaf abscisic acid content, and stomatal morphological parameters were measured. The results showed that the soil water content of TFM and SM treatments were higher than that of NM treatment by 12.4%–29.8% and 6.1%–7.1% under FI, respectively. Because of the lower value and larger differences among treatments of soil water content at the filling stage treatment effects on gas exchange parameters were significant. Comparing to NM treatment under FI, the stomatal conductance of TFM and SM treatments under FI increased by 95.9% and 97.9%, respectively; however, the gas exchange parameters of TFM and SM treatments under DI had significantly different responses. In a manner that the net photosynthetic rate and stomatal conductance of TFM treatment increased by 21.7% and 71.7%, while that of SM treatment decreased by 27.2% and 36.1%. Those changes of the gas exchange parameters were accompanied with the change of stomatal morphological parameters and ABA. Line correlations were found between stomatal conductance and leaf abscisic acid content, net photosynthetic rate, and the stomatal perimeter. To sum up, the changes in leaf abscisic acid content and stomatal morphological characteristics mediated the responses of leaf gas exchange parameters to different treatments. The results also suggested that if one needs to reduce the irrigation amounts, transparent plastic film mulching instead of straw mulching should be applied to compensate for the drawback of the lower soil water content. [ABSTRACT FROM AUTHOR]