Impairment of maize seedling photosynthesis caused by a combination of potassium deficiency and salt stress

The accumulation of intracellular sodium ions changes the ratio of K+:Na+ under salt stress, which seems to affect the bioenergetic processes of photosynthesis. However, very little work has been done to evaluate the photosynthetic damage to maize resulting from a combination of salt stress and K+ deficiency. Thus, our study investigated the effects of a combination of salt stress and K+ deficiency on chlorophyll (Chl) fluorescence in maize seedlings by a dual-wavelength pulse-amplitude modulated fluorescence monitoring system. The results showed that the reductions in plant growth, Chl, carotenoids, K+, Mg2+, maximum quantum efficiency (Fv/Fm), quantum yield (Y(II)), non-photochemical quenching (such as NPQ and qN) and photochemical quenching (such as qP and qL) of photosystem II (PSII), photochemical efficiency (Y(I)) of photosystem I (PSI) and non-photochemical quantum yield of PSI accepted side (Y(NA)), and electron transport rates of two photosystems of maize seedlings caused by a combination of salt stress and K+ deficiency were greater than those of each individual stress. Moreover, significant increases in Na+, Cl− and the parameters of quantum yield of energy dissipation of two photosystems, including Y(NPQ), Y(NO), and Y(ND), of maize leaves subjected to the combined stresses were observed. This implied that a combination of salt stress and K+ deficiency impaired the light reaction pathways of PSI and II in maize seedlings.