Post-stress restorative response of two quinoa genotypes differing in their salt resistance after salinity release

Soil salinity is one of the most important environmental factors that adversely affect plant growth and productivity. Quinoa emerges as a good food candidate due to its exceptional nutritive value, and its adaptability to various abiotic stresses. This high quinoa potential was investigated in the present study by evaluating the impact of salinity and post-stress restorative processes, in order to test how a pulse of saline water affects the growth and survival of two quinoa genotypes differing in salt resistance, Kcoito (salt sensitive) and UDEC-5 (salt resistant). Plants established in non-saline nutrient solution (hydroponic system) were exposed to a pulse of 0, 100 and 300 mM NaCl salinity for three weeks followed by four weeks in nutrient solution. Both genotypes survived exposure to salinity pulses. After stress removal, only the salt resistant variety UDEC-5 presented a significant stimulation of growth above the level of the non-pulsed treatment. Furthermore, the two varieties showed different responses in physiological, biochemical and antioxidant parameters. Again, the salinity release was highly controlled in pulsed UDEC-5 and more targeted as in Kcoito. In a win-win situation, the NaCl remaining in the tissues was used from UDEC-5 to optimize water uptake (osmotic force), to release vacuolar nutrients to enhance indirectly photosynthesis and to reduce ionic burden. This straightforward adjustment was accompanied by priming-effects such as a high proline accumulation and a balanced oxidative stress defense to scavenge remaining toxic reactive oxygen species (ROS), to stabilize enzymes and to be poised and to reduce lipid peroxidation and membrane damage. It can be concluded, that both species can tolerate short periods of exposure to saline conditions and this gives some flexibility of transient or permanent irrigation with saline water. However, taken together all of these markers indicate that only UDEC-5 quinoa can utilize salinity pulses in the applied range to enhance, growth, their antioxidant defense and water relations even above the level of non-pulsed plants.