Morphological, physiological and biochemical responses of plants to nickel stress: A review

Abstract

The ability of plants to tolerate salts is determined by multiple biochemical pathways that facilitate retention and/or acquisition of water, protect chloroplast functions and maintain ion homeostasis. Essential pathways include those that lead to synthesis of osmotically active metabolites, specific proteins and certain free radical enzymes to control ion and water flux and support scavenging of oxygen radicals. No well-defined indicators are available to facilitate the improvement in salinity tolerance of agricultural crops through breeding. If the crop shows distinctive indicators of salt tolerance at the whole plant, tissue or cellular level, selection is the most convenient and practical method. There is therefore a need to determine the underlying biochemical mechanisms of salinity tolerance so as to provide plant breeders with appropriate indicators. In this review, the possibility of using these biochemical characteristics as selection criteria for salt tolerance is discussed.

Nickel bioaccumulation by the chosen plant species

“…Literature data indicate the necessity of this element for several microorganism, animal and plant species. In plant organisms, the element is a part of urease metalloenzyme participating in urea hydrolysis (Hussain et al 2013;Seregin and Kozhevnikova 2006). Nickel is taken up by plants mainly as ion (Ni 2? ), whereas it is much harder absorbed in a chelate form.…”

Growth of tropical grasses in Oxisol contaminated by nickel

“…On the other hand, the descending order of sensitivity or tolerance to Ni in the soil based on the CTD in shoot dry weight (Table 2) was 'Basilisk' > 'Xaraés' > 'Marandu' > 'Tanzania' > 'Aruana'; thus, tropical grasses are considered from sensitive to moderately tolerant to soil Ni (Yusuf et al, 2011;Hussain et al, 2013;Matraszek et al, 2016).…”

“…Levels below the CR indicate deficiency, while the plant exhibits toxicity above the CR. Most plants have a Ni CR between 0.05 and 10 mg kg -1 DM (Chen et al, 2009) with levels higher than 10 mg kg -1 being toxic for most plants (Yusuf et al, 2011;Hussain et al, 2013;Matraszek et al, 2016).…”

“…To determine the recommended dose (RD) and critical toxicity dose (CTD) of Ni for 90% maximum growth and 10% reduction in maximum growth of tropical grasses, a multivariate approach using the canonical variable joint analysis of variance of Ni doses was used for each tropical grass (Hair et al, 2009). With the canonical variable of greater self-worth, scores were obtained from the observation vector of each experimental unit of the studied grass growth variables, reducing them to a single value.…”

“…Although Ni is an essential element for plants (López and Magnitski, 2011;Fabiano et al, 2015), high levels of this metal in the environment can cause phytotoxicity (Kovácik et al, 2009) and even reach the animal and human food chain (Rodak et al, 2015). In general, critical toxicity levels are 10 mg kg -1 DM in sensitive species, 50 mg kg 1 DM in moderately tolerant species, 100 mg kg -1 DM in tolerant species (Yusuf et al, 2011;Hussain et al, 2013;Matraszek et al, 2016), and 1000 mg kg -1 DM in Ni hyperaccumulator plants, such as the Alyssum and Thlaspi species (Yusuf et al, 2011;Leitenmaier and Küpper, 2013;Matraszek et al, 2016).…”