Effects of Nutrition on Wheat Photosynthetic Pigment Responses to Arsenic Stress

Abstract

Arsenic is a serious soil pollutant with toxic effects on biological systems. Elevated soil concentrations may negatively affect crop production and food safety. The impact of arsenic on plants depends on many factors, including nitrogen availability. Nitrogen (N) as an essential mineral affects overall energetics of plants, while its non-optimal doses have been shown to also impact plant performance and yield, as well as tolerance to environmental constraints. The combined effects of these two factors, however, have been rarely studied. Here we investigated the impact of sublethal doses of As 3+ (5 mM) on wheat plants grown in hydropony, applying a set of 8 different N concentrations spanning from starvation (0 mM N in the media) through optimum (7.5 mM N) to excessive amounts (up to 35 mM N). The results showed that the content of photosynthetic pigments varies depending on N concentration and As 3+ presence. The different energetic status of plants also affected the final As uptake. Establishing nutrition conditions might be important for limiting metal(loid) uptake from soil in contaminated areas.

Nitrogenous Nutrition Affects Uptake of Arsenic and Defense Enzyme Responses in Wheat

“…First, As 3+ reduces photosynthetic rate e.g. by decreasing chlorophyll content [21,22], inhibiting the enzymes responsible for their synthesis in plastids [43], replacing essential metallic ions such as Fe 2+ , Zn 2+ and Mg 2+ [17] and by hampering ATP and NADPH syntheses [44]. Better N nutrition can counteract these impacts; N is not only one of main constituents of chlorophyll and Rubisco [45], but also contributes to the protection of the photosynthetic apparatus providing key players of antioxidation and detoxification such as glutathione (GSH) and phytochelatins (PCs) [46,47].…”

“…Especially at the most excessive N concentrations, N toxicity likely additively contributes to detrimental effects of As 3+ , e.g. on the contents of some pigments and the growth [22]. Our data on overall activity of chitinases in wheat confirm this; while N deficiency alone might be responsible (at least partly) for relatively low activity values in roots under both normal and As stress conditions [61], excess of N apparently strengthened the impact of As toxicity on chitinases and caused suppression of overall activity (Fig.…”

“…The binding of As 3+ to thiols represents the key detoxification mechanism of both forms and results in the retention of a major part of As taken up by plants in roots [16]. Similar to many typical heavy metals like Cd or Pb, As impairs photosynthetic performance [21,22], but does not strongly affect genes related to carbon metabolism [15]. On the contrary, As causes dramatic changes in nitrogen transport and metabolism, altering the amino acid pools and energetic balance in cells [24].…”

Comparative Studies of Lead and Heavy Metals Concentrations in Pakistan Soil and Its Toxic Effects

“…It is crucial to establish the proper nutritional conditions to limit the metal uptake by plants from the soil of contaminated areas [47]. The heavy metal concentration can be decreased by avoiding irrigation with sewage water [33].…”

Variable accumulation of cadmium in flax (Linum usitatissimum L.)

“…3E). Though changes in pigment concentrations and their ratios are a good indicator of stress effects on plants (Maglovski et al 2019), their contents are affected by a number of internal factors as well, including genotype and leaf type (Dobroviczká et al 2013), age and type of leaf tissue (Hédiji et al 2010). The differences caused by cadmium are attributed to variability in the accumulation of glutathione and phytochelatins, which chelate and/or detoxify the metal (Gaudet et al 2011).…”