Comparison of the Effects of Gradual and Acute Treatment with Mn on Physiological Responses of Rumex hydrolapathum Plants

Abstract

An understudied problem in plant heavy metal biology is the effects of acute versus gradual or chronic metal exposure. The aim of the present study was to compare the growth and physiological responses of Rumex hydrolapathum Huds. plants subjected to gradual or acute Mn stress treatment in controlled conditions. Heavy metal was applied to substrate either as one 1.00 g L−1 Mn dose (acute treatment) or the same dose in four steps of increasing amounts within 12 days (gradual treatment). Peroxidase activity in actively photosynthesizing leaves was used for monitoring induced biochemical changes resulting from Mn treatment. The number of leaves per plant significantly increased in the case of gradual treatment with Mn, but this effect was not statistically significant for acute treatment. Leaf fresh mass significantly decreased in both cases due to the decrease in leaf water content, but dry biomass of leaves was not affected, with no significant differences between the two types of treatments. A significantly lower chlorophyll fluorescence parameter Performance Index in large leaves of plants under the acute Mn treatment than in plants under the gradual treatment was evident. An increase in leaf peroxidase activity by Mn treatment was proportional to the metal dose received, but plants in the acute treatment with 1.00 g L−1 Mn had a significantly lower peroxidase response in comparison to the gradual treatment with 1.00 g L−1 Mn. In conclusion, under gradual treatment, biochemical changes related to the induction of tolerance to the heavy metal are expressed, as indicated by the continuous increase in leaf peroxidase activity after each treatment step.

Effects of Organic Amendments on the Morphology and Chemical Composition of Black Mustard (Sinapis nigra L.) Grown on Soil Contaminated with Copper

“…For example, wheat is highly sensitive to Cu deficiency or excess, while the sensitivity of corn, sugar beet, or cotton to Cu is relatively low [58]. Changes in the chloroplasts are the result of oxidative stress manifested by damage to cell membranes due to the accelerated production of reactive oxygen species (ROS) [59]. In the presented case, as a result of Cu toxicity, there was probably a "rescue" synthesis of chlorophyll, which, as inactive, accumulated in the leaf tissue.…”

“…Disturbances in metabolism caused by heavy metals described in the literature in relation to chlorophyll content [56][57][58][59] had a direct impact on plant morphology. Increasing Cu pollution caused a significant decrease in plant height and changes in their habit, manifested by a significant reduction in branching and the number of pods.…”