Abstract
Excess of cadmium (Cd) in soil leads to a number of adverse effects which challenge agricultural production. Aims of this study were to investigate variations in Cd content in leaves (Zea mays L.) of different maize genotypes and to detect effects of Cd on photosynthesis through chlorophyll a fluorescence. Pot vegetation experiments with four maize genotypes and four different soil Cd levels were repeated for two years. Chlorophyll fluorescence, photosynthetic pigments and inductively coupled plasma (ICP) analysis for ear-leaf Cd and zinc (Zn) and soil Cd were carried out. Significant differences between genotypes were found for leaf Cd, where higher Cd soil concentrations resulted in higher Cd leaf concentrations. Cd uptake into maize leaves increased with increasing Cd levels in soil, which was genotype-dependent and higher and lower Cd accumulating groups were formed. Changes in chlorophyll fluorescence caused by elevated Cd levels in soil were mostly visible as changes in dissipation energy, yields of primary photosystem II photochemistry and electron transport. Decrease of reaction centers per antenna chlorophyll and increased variable fluorescence at J step (VJ) resulted in decrease of performance indexes in the highest Cd concentration. Decreases in chlorophyll fluorescence parameters suggest reduced functionality of reaction centers and problems in re-oxidation of primary quinone acceptor (QA).
Highlights
Toxic trace metals are a global problem in agriculture affecting crop plants but indirectly animals and humans
inductively coupled plasma (ICP) analysis of Cd in ear-leaves shown on Figure 1A revealed that Cd accumulation is different in four analyzed genotypes
Toxic trace metals impair the process of photosynthesis at several steps; it is reasonable to assume that plants under trace metal stress will be challenged by oxidative stress, which has been shown previously [9,61,62]
Summary
Toxic trace metals are a global problem in agriculture affecting crop plants but indirectly animals and humans. Due to human activities such as mining, smelting, application of commercial fertilizers and sewage sludge, metal pollution is becoming a risk to many ecosystems [1,2]. Cadmium (Cd) is a non-essential metal with no known physiological function. As a non-essential metal, causes many adverse effects in plant functionality. Plants vary in their ability for Cd uptake, as well as in thresholds for its toxicity, but generally, 5–10 μg Cd/g plant dry mass is expected to induce toxicity in most higher plants [9]. Metals tend to Agronomy 2020, 10, 986; doi:10.3390/agronomy10070986 www.mdpi.com/journal/agronomy
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