Improvement of Cerium on Photosynthesis of Maize Seedlings Under a Combination of Potassium Deficiency and Salt Stress.

Added Ce can partly substitute for Ca or Mg and improve photosynthesis under the deficiency of these elements, but very few studies focused on photosynthetic improvement in maize seedlings caused by K deficiency, salt stress, especially a combination of K deficiency and salt stress. In the present study, the effects of Ce on the photosynthesis of maize seedlings under the three different stresses were investigated. The results showed that added Ce under various stresses increased the ratios of free water/bound water and of K/Na, the pigment contents, the values of Fv/Fm, Y(II), ETR(II), Y(NPQ), Qp, qL, NPQ, and qN of photosystem II (PSII), the values of Y(I) and ETR(I) of photosystem I (PSI) and the expression levels of LhcII cab1 and rbcL, and decreased the values of Y(NO) and Y(NA). This implied that added Ce depressed ion toxicity, photodamage of PSII, and acceptor side constraints of PSI, and enhanced adjustable energy dissipation, the responses of photochemistry, and carbon assimilation caused by K deficiency, salt stress, and the combination of K deficiency and salt stress. However, Ce mitigation of photosynthetic inhibition in maize seedlings caused by the combined stresses was greater than that of salt stress, and Ce mitigation under salt stress was greater than that under K deficiency. In addition, the results also showed that Ce cannot improve photosynthesis and growth of maize seedlings under K deficiency by substituting for K. [ABSTRACT FROM AUTHOR]