Response of the eco-physiological characteristics to simulated photosynthetic radiation intensity in Stipa bungeana

A rtemisia sacrorum

Stipa grandis

A neurolepidium dasystachys leaves was investigated.Results showed that with increasing irradiation

Photosynthetic rate( Pn) was increased in lower density irradiation

but was reduced in higher density irradiation.transpiration rate( Tr) rate was enhanced with increasing irradiation.WUE for Stipa bungeana rose with increasing irradiation at first and then declined despite the intensified irradiation.WUE for Stipa grandis

A rtemisia sacrorum

and A neurolepidium dasystachys were enhanced with irradiation gradually.With growth midseason

Pn and WUE of the four species reached a maximum in July and a minimum in September

while Tr reached a maximum in August.The species ranked in the descendant order of A rtemisia sacrorum

Stipa grandis

A neurolepidium dasystachys

and Stipa bungeana in terms of the max Pn ; in the descendant order of Stipa bungeana

A neurolepidium dasystachys

Stipa grandis

and A rtemisia sacrorum in terms of Tr ; and in the descendant order of A rtemisia sacrorum

A neurolepidium dasystachys

Stipa grandis

and Stipa bungeana in terms of WUE.The chlorophyll fluorescence parameter indicated that the conversion efficiency of primary light energy under light ( Fv’/Fm’) of PSII

actual PSII efficiency (PhiPSII)

and PhiCO2 declined in line with the CO2 concentration

but the nonphotochemical quenching coefficient (NPQ) ascended.