Effects of ozone (O3) and ethylenediurea (EDU) on the ecological stoichiometry of a willow grown in a free-air exposure system

Abstract

Ground-level ozone (O) concentrations have been elevating in the last century. While there has been a notable progress in understanding O effects on vegetation, O effects on ecological stoichiometry remain unclear, especially early in the oxidative stress. Ethyelenediurea (EDU) is a chemical compound widely applied in research projects as protectant of plants against O injury, however its mode of action remains unclear. To investigate O and EDU effects early in the stress, we sprayed willow (Salix sachalinensis) plants with 0, 200 or 400 mg EDU L, and exposed them to either low ambient O (AOZ) or elevated O (EOZ) levels during the daytime, for about one month, in a free air O controlled exposure (FACE); EDU treatment was repeated every nine days. We collected samples for analyses from basal, top, and shed leaves, before leaves develop visible O symptoms. We found that O altered the ecological stoichiometry, including impacts in nutrient resorption efficiency, early in the stress. The relation between P content and Fe content seemed to have a critical role in maintaining homeostasis in an effort to prevent O-induced damage. Photosynthetic pigments and P content appeared to play an important role in EDU mode of action. This study provides novel insights on the stress biology which are of ecological and toxicological importance.

Ethylenediurea (EDU) spray effects on willows (Salix sachalinensis F. Schmid) grown in ambient or ozone-enriched air: implications for renewable biomass production

“…Salix sachalinensis F. Schmid is a major, fast-growing willow species in willow-occurring environments, such as across the floodplain of Hokkaido's Ishikari River where it is a broad niche species (Niiyama 1987). That S. sachalinensis grows in highly humid environments suggests a high potential for increased O 3 uptake due to relatively more open stomata, and S. sachalinensis saplings grown in pots were found susceptible to elevated O 3 (Agathokleous et al 2016b(Agathokleous et al , 2018. To this end, we became interested in revealing whether S. sachalinensis trees grown in communities and with no root limitation due to pot effect (planted directly on the ground) would be adversely affected by elevated O 3 .…”

“…This research consisted of three parts (Table 1). Ozone effect on nutrients other than C and N remains poorly understood in open field-grown shrubs/trees, especially for different types of leaves (Shi et al 2017;Agathokleous et al 2018;Shang et al 2018). Hence, in the first part, we carried out an assessment of elevated O 3 effect on S. sachalinensis in the first growing season to evaluate chemical status (Mg, K, Ca, Mn, Fe, Ni, Al, Cr, P) in top and fallen leaves and identify mechanisms of elemental regulation that can potentially explain O 3 effects on plant physiology.…”

Salt Stress Reduced the Seedling Growth of Two Larch Species Under Elevated Ozone

“…This may be attributed to non-significant changes of the total dry mass in DL treated with single O 3 and the combined effect. It was reported that the stable P and iron (Fe) contents in leaves implied homeostatic readjustment, contributing to preventing physiological inhibition of eO 3 (Agathokleous et al, 2018). It is possible that the combined effect, and even single O 3 effect, were not detected due to the physiological status of seedlings, which were shown in F v /F m (Figure 1).…”

“…It was reported that a K fertilization compensated the O 3 effects on potted Norway spruce (Picea abies) seedlings although there were genetic-specific responses (Keller and Matyssek, 1990; Barnes et al, 1995), suggesting that the species with relatively higher K content may show insights for the O 3 tolerance. Furthermore, several studies have investigated the mineral homeostasis under eO 3 (Alcántara et al, 2006;Agathokleous et al, 2018). These studies suggest that the homeostatic adjustment in leaf element content can mitigate physiological inhibitions of eO 3 although they focused on the homeostasis of other mineral element such as iron and P.…”

Ozone will remain a threat for plants independently of nitrogen load

“…Two possible reasons for the O 3 ‐induced increase in N content were discussed: a smaller size of plants relative to N availability or retranslocation of N from leaves shed prematurely due to O 3 stress (Wittig et al, ). However, a series of experiments with tree species do not support the latter assumption either early in the stress or after several months (or multiple years) of exposure (Agathokleous et al, ; Shi et al, ; Shi, Watanabe, & Koike, ; Wallin et al, ). In fact, elevated O 3 can increase the whole‐tree N loss via shed leaves with decreased N resorption efficiency (Uddling, Karlsson, Glorvigen, & Selldén, ).…”