Abstract
The aim of this study was to assess the impact of the microalgae Chlorella vulgaris on the rice seedlings at physiological conditions and under cadmium (Cd) stress. We examined the effects of C. vulgaris in the nutrient solution on rice seedlings grown hydroponically in the presence and the absence of 150 μM CdCl2, using the low (77 K) temperature and pulse amplitude modulated (PAM) chlorophyll fluorescence, P700 photooxidation measurements, photochemical activities of both photosystems, kinetic parameters of oxygen evolution, oxidative stress markers (MDA, H2O2 and proline), pigment content, growth parameters and Cd accumulation. Data revealed that the application C. vulgaris not only stimulates growth and improves the functions of photosynthetic apparatus under physiological conditions, but also reduces the toxic effect of Cd on rice seedlings. Furthermore, the presence of the green microalgae in the nutrient solution of the rice seedlings during Cd exposure, significantly improved the growth, photochemical activities of both photosystems, the kinetic parameters of the oxygen-evolving reactions, pigment content and decreased lipid peroxidation, H2O2 and proline content. Data showed that the alleviation of Cd-induced effects in rice seedlings is a result of the Cd sorption by microalgae, as well as the reduced Cd accumulation in the roots and its translocation from the roots to the shoots.
Highlights
Cadmium (Cd) is one of the most toxic heavy metals and even at trace amounts has harmful effects on the plant’s development
The current study shows the effects of C. vulgaris on rice seedlings under physiological conditions as well as under Cd stress
Stimulation of the growth parameters and an increase in the chlorophyll content have been found in plants grown in the presence of C. vulgaris in the nutrient solution, which is probably due to the bioactive growth compounds contained in this microalga [20,52,53]
Summary
Cadmium (Cd) is one of the most toxic heavy metals and even at trace amounts has harmful effects on the plant’s development. It has been found that Cd stress leads to an increase in the production of reactive oxygen species (ROS) in crop plants [1–3], which causes oxidative damage and inhibits the growth and the photosynthetic activity of plants [4–8]. It is well known that the harmful effects of Cd on the function of photosynthetic apparatus are a result of an influence on the chlorophyll metabolism, chloroplast ultrastructure, and on the activity of both photosystems [4,6,9,10]. 2022, vol., no.7 membranes, which leads to the reduced quantum efficiency of photosystem I (PSI) and photosystem II (PSII) as well as the net photosynthetic rate [11]. Cadmium-induced changes on both the donor and the acceptor sides of PSII complex lead to an increase in the amount of inactive PSII centers [6,12]. The inhibitory effects on PSI activity were smaller in comparison to PSII [13]
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