Characterization of the tolerance to excess manganese in four maize varieties

Abstract

Manganese (Mn) is an essential micronutrient in all organisms, but may become toxic when present in excess. Four maize (Zea mays L.) varieties, Kneja 605, Kneja 434, Kneja 509 and Kneja 537, were studied with respect to their responses to excess Mn in hydroponic solution. In the varieties Kneja 605, Kneja 509 and Kneja 537, increasing Mn concentrations in the nutrient solution negatively affected biomass accumulation, photosynthetic rate, transpiration, stomatal conductance and chlorophyll content. In addition, these varieties showed increased electrolyte leakage and lipid peroxidation (malondialdehyde [MDA] content). Increased Mn leaf concentrations, higher contents of chlorophyll a and chlorophyll b, higher photosynthetic rate and transpiration, lower concentrations of MDA and insignificant changes in the electrolyte leakage in the leaves were found in var. Kneja 434 compared with the other maize varieties studied. This variety appeared to possess a stronger ability to cope with Mn phytotoxicity, suggesting high potential for Mn detoxification and var. Kneja 434 could be a good candidate for improving maize productivity on acid soils under non-tropical conditions.

Breeding Maize for Tolerance to Acidic Soils: A Review

“…The first symptoms of Mn toxicity appear on the oldest leaves of plants as chlorosis, which later progresses to necrosis [62]. In addition, plants exposed to excess Mn exhibit a very strong inhibition of chloroplast structure and functions, reduced photosynthetic and transpiration rates, and inhibition of carbon dioxide (CO 2 ) fixation as a result of stomatal closure [63,64]. To date, there is a very limited number of published reports on manganese toxicity in plants.…”

“…The mechanisms of tolerance to Mn toxicity are not clearly established [64]. Different plant species and genotypes respond differently for tolerance to Mn toxicity [64,90].…”

“…Different plant species and genotypes respond differently for tolerance to Mn toxicity [64,90]. The tolerance of maize plants to Mn toxicity has been attributed to tolerance to high tissue concentrations of Mn [63].…”

“…The tolerance of maize plants to Mn toxicity has been attributed to tolerance to high tissue concentrations of Mn [63]. Stoyanova et al [64] evaluated four cultivars of maize under high and toxic concentrations and found that the most tolerant genotype, Kneja 434, expressed a stronger internal capacity of protection against the phytotoxicity of Mn and a higher potential of Mn detoxification. More research is needed to better understand the mechanisms of plant tolerance to Mn and Fe toxicities.…”

“…Some secondary traits are specific to certain mineral toxicities in the soil. For instance, chlorophyll content could be a useful secondary trait under Mn toxicity [64]. Table 2.…”