High-Resolution Analysis of Growth and Transpiration of Quinoa Under Saline Conditions

Abstract

The Plantarray 3.0 phenotyping platform® was used to monitor the growth and water use of the quinoa varieties Pasto and selRiobamba under salinity (0–300 mM NaCl). Salinity reduced the cumulative transpiration of both varieties by 60% at 200 mM NaCl and by 75 and 82% at 300 mM NaCl for selRiobamba and Pasto, respectively. Stomatal conductance was reduced by salinity, but at 200 mM NaCl Pasto showed a lower reduction (15%) than selRiobamba (35%), along with decreased specific leaf area. Diurnal changes in water use parameters indicate that under salt stress, daily transpiration in quinoa is less responsive to changes in light irradiance, and stomatal conductance is modulated to maximize CO2 uptake and minimize water loss following the changes in VPD (vapor pressure deficit). These changes might contribute to the enhanced water use efficiency of both varieties under salt stress. The mechanistic crop model LINTUL was used to integrate physiological responses into the radiation use efficiency of the plants (RUE), which was more reduced in Pasto than selRiobamba under salinity. By the end of the experiment (eleven weeks after sowing, six weeks after stress), the growth of Pasto was significantly lower than selRiobamba, fresh biomass was 50 and 35% reduced at 200 mM and 70 and 50% reduced at 300 mM NaCl for Pasto and selRiobamba, respectively. We argue that contrasting water management strategies can at least partly explain the differences in salt tolerance between Pasto and selRiobamba. Pasto adopted a “conservative-growth” strategy, saving water at the expense of growth, while selRiobamba used an “acquisitive-growth” strategy, maximizing growth in spite of the stress. The implementation of high-resolution phenotyping could help to dissect these complex growth traits that might be novel breeding targets for abiotic stress tolerance.

Photosynthesis is not the unique useful trait for discriminating salt tolerance capacity between sensitive and tolerant quinoa varieties

“…Under soil salinity conditions, plants suffer from water deficit and ion toxicity. Due to the limitation of water availability and consequent water uptake, growth is affected by the reduction of CO 2 availability resulting from stomatal closure and down regulation of photosynthetic metabolism (Jaramillo Roman et al 2021 ). Under these conditions, plants may be also affected by the ionic component of salinity suffering ion toxicity (Munns and Tester 2008 ).…”

“…Salinity tolerance comprises complex physiological responses to salt stress (Jaramillo Roman et al 2021 ). In light of this, plant phenotyping helps on the dissection of such complex responses, analysing traits that contribute to overall salinity tolerance, which are more genetically tractable (Morton et al 2019 ).…”

“…However, still few studies analysed the salinity tolerance of this species by this approach. Besides, these studies analysed specific stages, such as the germination stage (Mizuno et al 2020 ); specific measurements as yield components, ion concentrations and pigments (Rezzouk et al 2020 ); or a few varieties (Jaramillo Roman et al 2021 ). Considering this, phenotyping for salinity tolerance in quinoa taking into account different physiological processes and different varieties should be carried out.…”

“…On the other hand, although in the aforementioned studies a positive correlation between photosynthetic rates and biomass accumulation was detected, the studies should analyse more cultivars, since those studies were done only in one or two cultivars in the same study. Besides, the assessment of photosynthesis and the relation with growth and other physiological processes such as ion homeostasis, water relations and antioxidant metabolism provides a mechanistic account of the salinity effects at a whole plant level (Jaramillo Roman et al 2021 ).…”

Production Efficiency and Total Protein Yield in Quinoa Grown under Water Stress

“…Nevertheless, current water changes are expected to impact agriculture, making necessary to focus on efforts that increase overall water use efficiency to reduce the sector's impact on freshwater resources [33,34]. Therefore, optimization of agronomic management and selection of water stress-resistant genotypes with high seed yield and quality are becoming key issues for sustainable agricultural production [18,35,36].…”