The effect of salinity on photosynthetic activity in potassium-deficient barley species

The interactive effects of salinity and potassium deficiency on the growth, mineral elements and photosynthetic performance were investigated in the wild barley (Hordeum maritimum L.) and the cultivated one (Hordeum vulgare L. var. Manel). At 28 days of growth plants were treated with 3 mM K and 0 mM NaCl (3-0); 3 mM K and 100 mM NaCl (3-100); 0 mM k and 0 mM NaCl (0-0), 0 mM K and 100 mM NaCl (0-100) for 14 days. In both species the biomass production decreased considerably when the two constraints were applied simultaneously. Salinity affected more shoots than roots, whereas for potassium deficiency the reverse occurred. Generally, potassium uptake was more affected in wild barley than in cultivated one and, independently of potassium availability, 100 mM NaCl increased Na+ content in both species, whereas K+ deprivation increased Na+ content only in Hordeum maritimum shoots (0-0). The potassium use efficiency (KUE) increased in all treated plants. Potassium deficiency increased the negative effects induced by salt in photosynthetic process of H. vulgare and this species seems to be not able to counteract the negative effects of salinity. H. maritimum showed limitation in CO2 photoassimilation but this species displays mechanisms that play a role in avoiding PSII photodamage aimed to dissipate the excess energy.