Hypoxia induces stem and leaf nitric oxide (NO) emission from poplar seedlings

Abstract

Hypoxia leads to NO formation in poplar roots. Additionally, either NO or a NO derivative is transported from the roots to the shoot causing NO emission from aboveground plant organs. Nitric oxide (NO) is involved in the response of plants to various forms of stress including hypoxia. It also seems to play an important role in stomatal closure during stress exposure. In this study, we investigated the formation of NO in roots of intact poplar (Populus × canescens) plants in response to hypoxia, as well as its dependence on nitrate availability. We further addressed the question if root hypoxia triggers NO emission from aboveground plant parts, i.e., stems and leaves of young poplar trees. Our results indicate that NO is formed in poplar roots in response to hypoxia and that this production depends on the availability of nitrate and its conversion product nitrite. As long as nitrate was available in the nutrient solution, NO emission of roots occurred; in the range of the nitrate concentrations (10-100 µM) tested, NO emission was widely independent on nitrate concentration. However, the time period in which NO was emitted and the total amount of NO emitted strongly depended on the nitrate concentration of the solution. Hypoxia also led to increased NO emissions from the leaves and stems of the trees. There was a tight correlation between leaf and stem NO emission of hypoxia-treated plants. We propose that NO is produced by nitrate reductase in the roots and either NO itself, a metabolic NO precursor, or a NO derivative is transported in the xylem sap of the trees from the roots to the shoot thereby mediating NO emission from aboveground parts of the plant.

Molecular and physiological responses in roots of two full-sib poplars uncover mechanisms that contribute to differences in partial submergence tolerance

“…Thus, the increase in POPTR_0001s00700 expression might be a feedback regulation for Arg accumulation in LS2_FL1. Additionally, increased NOS activity might also lead to increased NO emission in LS2_FL, as reported in several flood-sensitive tree species 38 , 39 . Compared with that of LS2_FL, Phe was significantly accumulated in LS1_FL ( p < 0.01, Fig.…”

Drought-Enhanced Xylem Sap Sulfate Closes Stomata by Affecting ALMT12 and Guard Cell ABA Synthesis

“…Transpiration, stomatal conductance, and photosynthesis rates of poplar and Arabidopsis (wild-type and Atalmt12 mutant) plants were measured at the 10th attached poplar leaf of four to six plants or at a mature Arabidopsis leaf from 11 to 14 plants using a portable gas exchange system (GFS 3000; Walz; Liu et al, 2015). Attached poplar leaves were placed into a leaf enclosure with 8-cm 2 leaf areas and attached mature Arabidopsis leaves into a leaf enclosure with 3-cm 2 leaf area (Walz).…”

Physiological Responses and Expression Profile of NADPH Oxidase in Rice (Oryza Sativa) Seedlings under Different Levels of Submergence

“…Several studies have focused on the important role of ROS during hypoxia signaling under full submergence conditions (Baxter et al 2014 ; Fukao et al 2011 ; Liu et al 2015 ; Yang and Hong 2015 ). Plasma membrane NADPH oxidases in plants were discovered through their sequence similarity to mammalian respiratory burst NADPH oxidase subunit gp91 phox and have been named respiratory burst oxidase homologs (Rbohs) (Sagi and Fluhr 2006 ).…”