Two facets of world arsenic problem solution: crop poisoning restriction and enforcement of phytoremediation

Abstract

This review provides insights into As toxicity in plants with focus on photosynthesis and sugar metabolism as important arsenic targets and simultaneously defence tools against accompanying oxidative stress. Heavy metal contamination is a great problem all over the world. Arsenic, a metalloid occurring naturally in the Earth's crust, also massively spreads out in the environment by human activities. Its accumulation in crops poses a severe health risk to humans and animals. Besides the restriction of human-caused contamination, there are two basic ways how to cope with the problem: first, to limit arsenic accumulation in harvestable parts of the crops; second, to make use of some arsenic hyperaccumulating plants for phytoremediation of contaminated soils and waters. Progress in the use of both strategies depends strongly on the level of our knowledge on the physiological and morphological processes resulting from arsenic exposure. Arsenic uptake is mediated preferentially by P and Si transporters and its accumulation substantially impairs plant metabolism at numerous levels including damages through oxidative stress. Rice is a predominantly studied crop where substantial progress has been made in understanding of the mechanisms of arsenic uptake, distribution, and detoxification, though many questions still remain. Full exploitation of plant potential for soil and water phytoremediations also requires deep understanding of the plant response to this toxic metalloid. The aim of this review is to summarize data regarding the effect of arsenic on plant physiology with a focus on mechanisms providing increased arsenic tolerance and/or hyperaccumulation. The emphasis is placed on the topic unjustifiably neglected in the previous reviews - i.e., carbohydrate metabolism, tightly connected to photosynthesis, and beside others involved in plant ability to cope with arsenic-induced oxidative and nitrosative stresses.

Arsenic Toxicity-Induced Physiological and Metabolic Changes in the Shoots of Pteris cretica and Spinacia oleracea

“…Furthermore, the effect of As toxicity on photosynthesis was observed on both plant species due to changes in leaf gas-exchange parameters and chlorophyll fluorescence ( Table 4 , Figure 3 ). The reduction of photosynthesis by As stress was reported among different plant species [ 24 , 38 , 59 , 62 ]. In our study, P N , which directly reflects photosynthetic capacity [ 63 ], decreased with As treatment in P. cretica and S. oleracea shoots.…”

Multi-Component Antioxidative System and Robust Carbohydrate Status, the Essence of Plant Arsenic Tolerance

“…The latest studies published mention the negative photosynthesis response upon arsenic, e.g., in tobacco-related potato [18] or tomato [16], but also unrelated Artemisia annua [14,15] or Ricinus [19]. These results, although often accompanied by data showing growth retardation or even plant death, are only rarely combined with carbohydrate status determination as also reviewed by Abbas et al [20] and Kofroňová et al [21]. However, different environmental stresses adversely affect carbohydrate metabolism, thus having a far-reaching impact on plants [22,23].…”

“…A specific advantage of carbohydrates, versus other antioxidant molecules, lies in their ubiquity. Plant antioxidative defense under As stress, including the notion of carbohydrate participation, has recently been reviewed by Kofroňová et al [21]. Carbohydrates, besides their ROS quenching capacity, act in stress defense indirectly via the provision of energy and carbon sources for defense molecule syntheses, including antioxidant enzymes [29].…”

Remodeling of Root Growth Under Combined Arsenic and Hypoxia Stress Is Linked to Nutrient Deprivation

“…Numerous agricultural fields and groundwater reservoirs in South East Asia, Europe or North America are highly contaminated with As (Medunić et al, 2020). Remediation of contaminated sites using hyperaccumulator plants and generation of As-tolerant but non-accumulating crops, particularly in edible parts, is the need of hour (Kofroňová et al, 2018). However, co-occurring environmental factors aggravate As toxicity, tolerance and accumulation in crop plants and impede growth potential of As-hyperaccumulators.…”