Effects of exogenous NO on antioxidant system of Taxus plants under simulated acid rain stress

Taxus is a famous medicinal and landscape tree species. The aim of this study was to explore the effect of exogenous nitric oxide (NO) on the resistance of Taxus plants to acid rain stress and to identify Taxus species with strong acid rain resistance by principal component analysis and comprehensive evaluation. In this study, sodium nitroprusside (SNP) was used as the exogenous NO donor. The effects of different SNP solution concentrations on the antioxidant systems of three Taxus species subjected to simulated acid rain stress (pH = 3.0) were compared. In order to achieve this goal, we determined the rate of O2- production, the ASA and GSH contents in leaves of three Taxus plants (Taxus mairei, Taxus chinensis, and Taxus yunnanensis). At the same time, the active leaves of some antioxidant enzymes (SOD, POD, CAT, APX and GR) were determined. For Taxus chinensis plants subjected to acid rain stress, treatment with an SNP concentration of 0.25 mmol·L-1 led to the most significant improvements in the antioxidant system. For Taxus mairei and Taxus yunnanensis, the treatment with the SNP concentration of 0.50 mmol·L-1 was best for improving their antioxidant systems under stress. Meanwhile, Taxus chinensis had the strongest resistance to simulated acid rain, followed by Taxus mairei and Taxus yunnanensis.

Earthworm and Arbuscular Mycorrhizal Fungi Improve Plant Hormones and Antioxidant Enzymes to Alleviate Simulated Acid Rain Stress

Aims Acid rain is considered one of the three most serious environmental disasters worldwide, disrupting the normal physiological metabolism of plants and inhibiting their growth. As important parts of soil biota community, both earthworms and arbuscular mycorrhizal fungi can promote the growth of plants under adverse conditions. However, whether them can improve the stress tolerance of plants under simulated acid rain stress remains to be explored.Methods Illumina high-throughput sequencing was used to conduct a relevant redundancy analysis (RDA) of soil microbial community structure and plant growth factors, and a structural equation model (SEM) was constructed for maize biomass and a biological index to study the mechanisms by which earthworms and mycorrhizal fungi affect maize stress resistance under simulated acid rain stress. Results Earthworms promoted the absorption of soil organic matter by maize; promoted the growth of the root system; and increased the hormone levels of GA3, ABA and IAA; ultimately improving the stress resistance of maize. Mycorrhizal fungi increased the relative abundance of plant growth-promoting rhizosphere bacteria, increased the levels of plant hormones and antioxidant enzymes, and improved the stress resistance of maize. Earthworms promoted infection by mycorrhizal fungi, and the interaction between earthworms and mycorrhizal fungi increased the root IAA content and the Shannon index of rhizosphere bacteria.Conclusions Both earthworms and mycorrhizal fungi can improve the stress resistance of maize through underground regulation. They interacted in increasing the root IAA content and the Shannon index of rhizosphere bacteria and alleviated the simulated acid rain stress of the aboveground part of the maize.

Physiological and Molecular Responses to Acid Rain Stress in Plants and the Impact of Melatonin, Glutathione and Silicon in the Amendment of Plant Acid Rain Stress

Air pollution has been a long-term problem, especially in urban areas, that eventually accelerates the formation of acid rain (AR), but recently it has emerged as a serious environmental issue worldwide owing to industrial and economic growth, and it is also considered a major abiotic stress to agriculture. Evidence showed that AR exerts harmful effects in plants, especially on growth, photosynthetic activities, antioxidant activities and molecular changes. Effectiveness of several bio-regulators has been tested so far to arbitrate various physiological, biochemical and molecular processes in plants under different diverse sorts of environmental stresses. In the current review, we showed that silicon (tetravalent metalloid and semi-conductor), glutathione (free thiol tripeptide) and melatonin (an indoleamine low molecular weight molecule) act as influential growth regulators, bio-stimulators and antioxidants, which improve plant growth potential, photosynthesis spontaneity, redox-balance and the antioxidant defense system through quenching of reactive oxygen species (ROS) directly and/or indirectly under AR stress conditions. However, earlier research findings, together with current progresses, would facilitate the future research advancements as well as the adoption of new approaches in attenuating the consequence of AR stress on crops, and might have prospective repercussions in escalating crop farming where AR is a restraining factor.

Physiological Responses of Earthworm Under Acid Rain Stress

Acid rain has become one of the major global environmental problems, and some researches reported that acid rain may have a certain inhibition on soil biodiversity. Besides this, it is well known that earthworm (Eisenia fetida) plays an important role in the functioning of soil ecosystems. For this point, we conducted a series of experiments to investigate whether acid rain would take effects on earthworms. In the present study, the earthworms were incubated on filter paper and in soil under acid rain stress. The mortality and behavior of earthworms were recorded, and epidermal damage and the activity of the CYP3A4 enzyme were measured for the tested earthworms. Our experimental results showed that the earthworms could not survive in the acid rain stress of pH below 2.5, and acid rain with weak acidity (i.e., 4.0 ≤ pH ≤ 5.5) promoted the activity of the CYP3A4 enzyme in the earthworms, while acid rain with strong acidity (i.e., 3.0 ≤ pH ≤ 3.5) inhibited it. Moreover, the degree of damage in sensitive parts of the earthworms increased with the decrease of pH value. This study suggests that acid rain can cause discomfort response and the direct epidermal damage of earthworms, and even kill them.