Beyond the ionic and osmotic response to salinity in Chenopodium quinoa: functional elements of successful halophytism

Abstract

Chenopodium quinoa Willd. (quinoa) is a halophyte for which some parameters linked to salt tolerance have been investigated separately in different genotypes and under different growth conditions. In this study, several morphological and metabolic responses were analysed in parallel after exposure to salinity. In vitro seed germination was initially delayed by a 150 mM NaCl treatment but eventually reached the same level as the control (0 mM NaCl), whereas seedling root growth was enhanced; both parameters were moderately inhibited (~35-50%) by 300 mM NaCl. In pot grown plants, plant size was reduced by increasing salinity (0-750 mM NaCl). Transpiration and stomatal conductance were decreased at the highest salinity levels tested, consistent with reduced stomatal density and size. The density of epidermal bladder cells (EBCs) on the leaf surface remained unaffected up to 600 mM NaCl. Tissue contents of Na + and Cl -increased dramatically with salt treatment, but resulted in only a 50% increase in Na + from 150 to 750 mM NaCl. Internal K + was unaffected up to 450 mM NaCl but increased at the highest salinity levels tested. Excretion through sequestration into EBCs was limited (generally 20%) for all ions. A modest dose-dependent proline accumulation, and concomitant reduction in total polyamines and putrescine efflux occurred in NaCl-treated plants. Results confirm the importance of inorganic ions for osmotic adjustment, the plant's ability to maintain K + levels and the involvement of putrescine efflux in maintaining ionic balance under high salinity conditions. Conversely, ion excretion and proline appear to play a minor role. Taken together these results indicate which parameters could be used for future comparison among different genotypes.

Akaline, saline and mixed saline–alkaline stresses induce physiological and morpho‐anatomical changes in Lotus tenuis shoots

“…On other hand, our results from plants treated exclusively with NaHCO 3 showed no changes in g or E. This would advocate a possible compensation effect between an increase in stomatal opening and a reduction in the stomatal density in these plants. A similar salinity-induced reduction in stomatal density was recently reported for the halophyte Chenopodium quinoa (Orsini et al 2011;Shabala et al 2012), and was interpreted as a fundamental mechanism by which quinoa plants may improve water use efficiency under saline conditions. Since the waxy cuticle of leaves allows water and small amounts of CO 2 to pass through (Scott 1964(Scott , 1966Norris & Bukovac 1968;Leon & Bukovac 1978;Boyer et al 1997), one may also hypothesise that the increase in cuticle thickness observed in plants from this treatment could have contributed to the E balance.…”

Response of polyamine pools in marine phytoplankton to nutrient limitation and variation in temperature and salinity

“…They carry positive charges (2 in PUT; 4 in SPM) at physiological pH (7.4), and contribute to stabilizing membranes and nucleic acids by binding to negatively charged groups (Galston & Sawhney 1990, Incharoensakdi et al 2010, Orsini et al 2011. A correlation between RNA synthesis and SPD concentration indicates that PAs could regulate RNA synthesis or indirectly affect protein synthesis (Stevens 1970).…”

Exploring the Potential of Quinoa Accessions for Salt Tolerance in Soilless Culture

“…As for the K + content in leaves, it decreased with increasing salinity levels and at 300 mM, there was a significant improvement in its contents in genotype Q7. Orsini et al (2011) reported that K + concentrations declined at levels starting from 150 mM and increased at higher salinity levels. In the genotype Q9, K concentration increased up till 200 mM and then decreased at 300 mM.…”

“…Salinity caused a decrease in transpiration and thus gas exchange in quinoa (Sanchez et al, 2003). It has been reported that quinoa reduces stomatal density and cuticular pores under salinity (Razzaghi et al, 2011), which may adjust water use efficiency in these conditions (Orsini et al, 2011;Shabala et al, 2012).…”