Effects of different soil moisture regimes on gas exchange in response to light, growth and biomass in naked oat (Avena nuda L.)

Naked oat is an important food and forage crop and principally distributed across arid and water scarce regions of China. The objective of this study was to determine the gas exchange to light, growth and biomass accumulation of naked oat (Avena nuda L.) under three soil humidity levels (high, moderate and low) using a new type of negative hydraulic pressure controlled auto irrigator. Net photosynthetic rate (A n ), transpiration rate (E), instantaneous water-use efficiency (WUE i ) and instantaneous light-use efficiency (LUE i ) were decreased as soil humidity was reduced. Under low soil humidity, maximum A n decreased by 43% and 44%, and light saturation point (LSP) was reduced by 40% and 41%, moreover, light compensation point (LCP) increased by 85% and 123%, than under moderate and high soil humidity. There was little effects on plant height, tiller number and stem diameter under moderate and high soil humidity but significantly decreased among parameters (exceeding 6%, 60% and 13%) under low soil humidity. The highest biomass accumulation was recorded under moderate soil humidity, which was significantly enhanced by 21.2% and 108.1% both high and low soil humidity, respectively. This study concluded that imposed drought in appropriate stages on naked oat has little effect on gas exchange and growth, on the contrary, could clearly improve biomass accumulation.