Exogenous tannic acid relieves imidacloprid-induced oxidative stress in tea tree by activating antioxidant responses and the flavonoid biosynthetic pathway.

Pesticide stress on plants is receiving increased scrutiny due to its effect on plant secondary metabolism and nutritional quality. Tannic acid (TA) is a natural polyphenolic compound showing excellent antioxidant properties and is involved in alleviating stress. The present study thoroughly investigated the effects and mechanism of exogenous TA on relieving imidacloprid (IMI) stress in tea plants. Our research found that TA(10 mg/L) activated the antioxidant defense system, enhanced the antioxidant ability, reduced the accumulation of ROS and membrane peroxidation, and notably promoted tea plant tolerance to imidacloprid stress. Additionally, TA boosted photosynthetic capacity, strengthened the accumulation of nutrients. regulated detoxification metabolism, and accelerated the digestion and metabolism of imidacloprid in tea plants. Furthermore, TA induced significant changes in 90 important metabolites in tea, targeting 17 metabolic pathways through extensively targeted metabolomics. Specifically, TA activated the flavonoid biosynthetic pathway, resulting in a 1.3- to 3.1-fold increase in the levels of 17 compounds and a 1.5- to 63.8-fold increase in the transcript level of related genes, such as ANR, LAR and CHS in this pathway. As a potential tea health activator, TA alleviates the oxidative damage caused by imidacloprid and improves the yield and quality of tea under pesticide stress.

Response of the photosynthetic activity and biomass of the phytoplankton community to increasing nutrients during cyanobacterial blooms in Meiliang Bay, Lake Taihu.

Nutrient enrichment facilitates algal outbreaks in eutrophic shallow lakes. To further understand the influence of various inorganic nutrient forms on cyanobacterial blooms, a nitrate (NO3 ), ammonium (NH4 ), and orthophosphate (PO4 ) amendment experiment was conducted in a large shallow lake of China (Lake Taihu) during summer. The results showed that the photosynthetic performance of phytoplankton responded more positively to phosphorus (P) than nitrogen (N), and NH4 addition stimulated higher algal photosynthetic activities in P-enriched waters. Individual inorganic N or PO4 addition significantly activated cyanobacteria and green algae. Meanwhile, the N plus P amendment promoted higher biomass of the planktonic microbial community, and the dual addition of NH4  + PO4 yielded the highest chlorophyll a concentration. NH4 additions provisionally promoted higher green algae than cyanobacteria biomass in the beginning, while cyanobacteria dominated again with increasing NH4 :PO4 ratios. These results revealed that increasing ammonium would enhance the increase in phytoplankton biomass in advance and prolong the duration of algal blooms. Hence, based on the control of P loading, the reduction in external inorganic N focusing on ammonium sources (such as ammonia N fertilizer) at the watershed scale would help to alleviate eutrophication and cyanobacterial blooms over the long term in Lake Taihu. PRACTITIONER POINTS: Ammonium addition stimulated higher algal photosynthetic activities in P-enriched waters. Individual inorganic N or PO4 addition significantly activated cyanobacteria and green algae. The dual addition of NH4  + PO4 yielded the highest chlorophyll a concentration. Increasing NH4 would enhance the increase in phytoplankton biomass in advance and prolong the duration of cyanobacterial blooms.