Toxic effects of heavy metals Pb and Cd on mulberry (Morus alba L.) seedling leaves : Photosynthetic function and reactive oxygen species (ROS) metabolism responses

Copyright © 2020 Elsevier Inc. All rights reserved..

To explore the mechanism of how lead (Pb) and cadmium (Cd) stress affects photosynthesis of mulberry (Morus alba L.), we looked at the effects of different concentrations of Pb and Cd stress (at 100 and 200 μmol L-1), which are two heavy metal elements, on leaf chlorophyll (Chl), photosynthesis gas exchange, Chl fluorescence, and reactive oxygen species (ROS) metabolism in mulberry leaves. The results showed that higher concentrations of Pb and Cd reduced leaf Chl content, especially in Chl a where content was more sensitive than in Chl b. Under Pb and Cd stress, the photosynthetic carbon assimilation capacity of mulberry leaves was reduced, which was a consequence of combined limitations of stomatal and non-stomatal factors. The main non-stomatal factors were decreased photosystem II (PSII) and photosystem I (PSI) activity and carboxylation efficiency (CE). Damage to the donor side of the PSII reaction center was greater than the acceptor side. After being treated with 100 μmol L-1 of Pb and Cd, mulberry leaves continued to be able to dissipate excess excitation energy by starting non-photochemical quenching (NPQ), but when Pb and Cd concentrations were increased to 200 μmol L-1, the protection mechanism that depends on NPQ was impaired. Excessive excitation energy from chloroplasts promoted a great increase of ROS, such as superoxide anion (O2•-) and H2O2. Moreover, under high Pb and Cd stress, superoxide dismutase (SOD) and ascorbate peroxidase (APX) were also inhibited to some extent, and excessive ROS also resulted in a significantly higher degree of oxidative damage. Compared with Cd, the effect of Pb stress at the same concentration level displayed a significantly lower impact on Chl content, photosynthetic carbon assimilation, and stomatal conductance. Meanwhile, Pb stress mainly damaged activity of the oxygen-evolving complex (OEC) located on PSII donor side, but it reduced the electronic pressure on the PSII acceptor side and PSI. Furthermore, under Pb stress, the NPQ, SOD, and APX activity were all significantly higher than those under Cd stress. Thus under Pb stress, the degree of photoinhibition and oxidative damage of PSII and PSI in mulberry leaves were significantly lower than under Cd stress.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:195

Enthalten in:

Ecotoxicology and environmental safety - 195(2020) vom: 01. Juni, Seite 110469

Sprache:

Englisch

Beteiligte Personen:

Huihui, Zhang [VerfasserIn]
Xin, Li [VerfasserIn]
Zisong, Xu [VerfasserIn]
Yue, Wang [VerfasserIn]
Zhiyuan, Teng [VerfasserIn]
Meijun, An [VerfasserIn]
Yuehui, Zhang [VerfasserIn]
Wenxu, Zhu [VerfasserIn]
Nan, Xu [VerfasserIn]
Guangyu, Sun [VerfasserIn]

Links:

Volltext

Themen:

00BH33GNGH
1406-65-1
2P299V784P
Ascorbate Peroxidases
BBX060AN9V
Cadmium
Chlorophyll
EC 1.11.1.11
EC 1.15.1.1
Heavy metals
Hydrogen Peroxide
Journal Article
Lead
Mulberry
Pb and Cd stress
Photoinhibition
Photosynthesis
Photosystem I Protein Complex
Photosystem II Protein Complex
Reactive Oxygen Species
Reactive oxygen species
Superoxide Dismutase

Anmerkungen:

Date Completed 18.06.2020

Date Revised 18.06.2020

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1016/j.ecoenv.2020.110469

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM307659038