The effects of K+-deficiency on H<sub>2</sub>O<sub>2</sub> dynamics and sucrose in tomato

Abstract

Potassium (K+) deficiency inhibits the transport of photosynthetic products and causes severe crop yield losses. However, the underlying mechanisms are poorly understood. In this study, we used two tomato lines 081018 (K+-deficiency-sensitive) and 081034 (K+-deficiency-tolerant), showing tolerance to K+ deficiency to investigate the relationship between the H2O2 and sucrose in the tomato under K+-deficiency. The H<sub>2</sub>O<sub>2</sub> accumulation was increased by the low K+ condition (0.5 mM) after 8 h in 081018. The enzymes related to the metabolism of H<sub>2</sub>O<sub>2</sub> were decreased, and more malondialdehyde (MDA) was produced. After 24 h, the sucrose content had accumulated significantly in the leaves, however, it was deficient in the roots, and the expression level of the sucrose transporters (SUT1) was inhibited. In 081034, the activity of antioxidant enzymes was increased under K+-deficiency, and then the H2O2 subsequently returned to the control treatment (4 mM) levels and did not produce more MDA. The sucrose content was not significantly different from the control treatment after 24 h. The expression of SUT1 was not suppressed. These results suggested that the H2O2 dynamics played different roles in the two different strains. The transportation of sucrose was suppressed by the H<sub>2</sub>O<sub>2</sub> from the leaf (source) to the root (sink) in 081018, and unrestricted by the advantageous reactive oxygen species dynamics capacity in 081034.