Similarities and differences between the responses to osmotic and ionic stress in quinoa from a water use perspective

Faced with the consequences of climate change, such as increased drought and salinization of soils, the species Chenopodium quinoa may be a good alternative crop because of its high tolerance to these conditions and its high nutritional value. The objective of this work was to analyze the response of the quinoa plant in drought and salinity conditions. Under conditions of drought and severe saline stress (500 mM NaCl), highly similar reductions in growth and relative water content were observed. However, the strategies implemented by the plants in either stress condition and their relative importance were different. Under salt conditions, responses related to osmotic adjustment were more prominent than under drought conditions, where more dehydration was detected. In addition, despite a similar reduction in stomatal conductance in drought and saline conditions, a greater non-stomatal effect was observed in drought conditions, which was demonstrated by the fact that the intercellular CO2 concentration was increased. Moreover, the antioxidant metabolism also responded differently to the two stresses. Photoassimilate allocation was also different between treatments: the root/shoot ratio remained constant independent of salt concentration, whereas under drought conditions, this ratio increased. A similar trend between treatments was detected for water use efficiency, which was maintained under salt stress and increased under drought conditions, indicating that under reduced water conditions, quinoa can use lower amounts of water per unit of biomass production. These results suggest that C. quinoa could be irrigated with brackish or even higher salinity water without severely affecting the growth during its early growth stage, thereby making C. quinoa a promising alternative crop for arid and semi-arid regions.