High doses of ethylenediurea (EDU) as soil drenches did not increase leaf N content or cause phytotoxicity in willow grown in fertile soil

Abstract

Ground-level ozone (O) levels are nowadays elevated in wide regions of the Earth, causing significant effects on plants that finally lead to suppressed productivity and yield losses. Ethylenediurea (EDU) is a chemical compound which is widely used in research projects as phytoprotectant against O injury. The EDU mode of action remains still unclear, while there are indications that EDU may contribute to plants with nitrogen (N) when the soil is poor in N and the plants have relatively small leaf area. To reveal whether the N content of EDU acts as a fertilizer to plants when the soil is not poor in N and the plants have relatively large total plant leaf area, willow plants (Salix sachalinensis Fr. Schm) were exposed to low ambient O levels and treated ten times (9-day interval) with 200mL soil drench containing 0, 800 or 1600mg EDU L. Fertilizer was added to a nutrient-poor soil, and the plants had an average plant leaf area of 9.1m at the beginning of EDU treatments. Indications for EDU-induced hormesis in maximum electron transport rate (J) and ratio of intercellular to ambient CO concentration (C:C) were observed at the end of the experiment. No other EDU-induced effects on leaf greenness and N content, maximum quantum yield of photosystem II (F/F), gas exchange, growth and matter production suggest that EDU did not act as N fertilizer and did not cause toxicity under these experimental conditions.

Ethylenediurea (EDU) mitigates the negative effects of ozone in rice: Insights into its mode of action

“…EDU has also been criticized earlier because it might act as a foliar fertilizer, as it contains 22% nitrogen (Godzik & Manning, ; Manning et al, ). However, EDU spraying did not affect leaf nitrogen content in our study (Figure c), indicating that EDU was not a significant source of nitrogen, which was also confirmed in willow plants (Agathokleous et al, ). In contrast, a previous study suggested that high concentrations of EDU (above 800 ppm) can increase leaf nitrogen content in willow plants grown in low nitrogen and organic matter free soil but did not show any toxicity effects (Agathokleous et al, ).…”

Effect of Long-Term vs. Short-Term Ambient Ozone Exposure on Radial Stem Growth, Sap Flux and Xylem Morphology of O3-Sensitive Poplar Trees

“…To overcome this issue, treatments with the chemical ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N0-phenylurea, abbreviated as EDU) are recommended [16,17]. Repeated applications of EDU at concentrations of up to 400 ppm are recognized to sufficiently protect against O 3 phytotoxicity [18,19]. In previous papers we showed that the long term exposure of the O 3 -sensitive hybrid poplar 'Oxford' clone decreased stem growth and leaf total area [20] with an early leaf shedding [21] and reduced above- [15] and below-ground biomass [22] relative to trees protected by EDU.…”

Out of sight, Out of mind — but not Out of scope: the need to consider ozone (O3) in restoration science, policy, and practice

“…Indeed, traits can provide unifying explanations as to when species are expected to be ozone‐sensitive or ozone‐tolerant (Zhang et al 2012; Feng et al 2018). Screening can also use techniques “borrowed” from agriculture, such as ethylenediurea (EDU) application, as soil drench or on leaves, to quickly assess O 3 tolerance (Manning et al 2011; Agathokleous et al 2015) or to protect trees from O 3 damage (Paoletti et al 2011) (noting the potential for unanticipated side effects; Agathokleous et al 2018).…”