Stomatal conductance ( g s ) of all coexisting speciesregulates transpiration in arid and semiarid grasslands prone to droughts.However, the effect of drought stress on canopy conductance ( G s ) isdebated, and the interactive effects of abiotic and biotic constraints on G s remain poorly understood. Here, we used 18 O enrichment above thesource water ( Δ 18 O) of leaf organic matter as a proxy for G s in order toincrease the understanding of these effects. Three grassland transects wereestablished along aridity gradients on the Loess Plateau (LP), the Inner MongolianPlateau (MP), and the Tibetan Plateau (TP), which differ with respect to solar radiation andtemperature conditions. Results showed that G s consistently decreasedwith increasing aridity within transects. G s on the TP was lower than thaton the other two plateaus for a given level of aridity due to lowtemperature and high radiation. The primary determinant of drought stress on G s was soil moisture (SM) on the LP and MP, whereas it was the vapor pressure deficit(VPD) on the TP. Solar radiation exhibited a consistently negative effect on G s via drought stress within transects, while temperature had negativeeffects on G s on the TP but no effect on the LP or MP. Adding theinteraction of leaf area and abiotic factors increases the percentage ofexplained variability in G s by 17 % and 36 % on the LP and MP,respectively, although this is not the case on the TP, where the climate exerts an overwhelming effect.These results highlight the need to integrate multiple stressors and plantproperties to determine spatial variability in G s .

Background: Numbers of HIV latency reversal agents (LRAs) have been tested in clinical trials, but with limited effect. EK-16A is an ingenol derivative that isolated from Euphorbia kansui. Our prior studies have suggested that it could reactivate latent HIV and meanwhile inhibit HIV infection in vitro. Here, we further advanced the research in vivo.