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CO2-exchange and chlorophyll fluorescence responses of forage grasses during salt stress and recovery in Qinghai-Tibetan plateau (QTP)

Grassland degradation has become a core issue in research and policy due to recognition of the magnitude of anthropogenic and environmental threats in Qinghai-Tibetan Pleatu (QTP). The problem of soil salinity could worsen in recent scenario of global change. Therefore, an urgent need exists to select salt efficient forage species for sustaining ecosystem services in changing environment. The aim of this study was to investigate different level of salinity treatments and, recovery situations in three forage species (Avena sativa L., Elymus sibiricus L., and Phalaris arundinacea L.). The results showed that increase in salinity level was associated with more symptoms of damage while recovery benefited with the effects being different among three species. Gas exchange (Pn rates and iWUE) and chlorophyll fluorescence (qP, NPQ, Fv/Fm and ΦPSII) parameters revealed that performance of Elymus sibiricus was better during progressive salt stress followed by Phalaris arundinacea. However, Phalaris arundinacea performed better than Elymus sibiricus during recovery situation. Similar trend was observed through relative water content (RWC) and electrolyte leakage (EL) results. Taken together, these results demonstrated that Elymus sibiricus was relatively more salt-tolerant species, while Phalaris arundinacea exhibited better ability to recover in QTP environment. On the other hand, Avena sativa was screened as the most salt sensitive among these three species.