Endogenous hormonal and enzymatic responses of Catharanthus roseus with triadimefon application under water deficits

Absorption, translocation, and accumulation of the fungicide triadimefon in Pak choi (Brassica rapa var chinensis), pepper (Capsicum annuum), and cucumber (Cucumis sativus)

Triadimefon is a typical systemic fungicide that is widely used in the management of powdery mildew, rust disease, and southern blight. In this study, we measured fungicide residue to profile its absorption, translocation, and accumulation in three representative vegetable crops (Pak choi, cucumber, and pepper) after over-application. The fungicides were applied through entire-plant spraying (EPS), root-irrigation (RI), and middle-leaf-daubing (MLD). The half-life of triadimefon depends on the application method and plant species. In EPS, the half-life was 5.42 days (Pak choi), 6.86 days (cucumber), and 6.73 days (pepper), while in RI it was 4.39 days (Pak choi), 6.30 days (cucumber), and 5.98 days (pepper). In the EPS treatment, triadimefon is translocated both upward/outside and downward/inner-side from the daubed leaves in all the three vegetable crops. The transfer amount to each organ reached a peak on the 2nd day after fungicide application. The mesophyll of Pak choi exhibited a higher fungicide deposition compared to the petiole. In cucumber and pepper, the leaves demonstrated the highest accumulation of triadimefon (approximately 0.3-0.5 mg·kg-1), followed by stems. Roots and fruits displayed the lowest levels of triadimefon accumulation. Furthermore, triadimefon was found to have an impact on chlorophyll content, root activity, as well as the activity of superoxide dismutase and catalase in Pak choi, indicating its potential as a plant growth regulator. These aforementioned studies provide novel insights for the safe and efficient application of triadimefon in the production of Pak choi, cucumber, and pepper.

Beneficial effects of triadimefon in overcoming drought stress in soybean at fluorescence stage

Soybean (Glycine max [L.] Merr.) at fluorescence stage frequently experiences drought stress. Although triadimefon has been observed to improve drought tolerance of plants, reports on its role in drought resistance on leaf photosynthesis and assimilate transport are limited. This study examined the effects of triadimefon on leaf photosynthesis and assimilate transport at fluorescence stage of soybean experiencing drought stress. Results showed that triadimefon application relieved the inhibitory effects of drought stress on photosynthesis and increased RuBPCase activity. Drought increased soluble sugar contents, yet reduced starch content in the leaves by heightening the activities of sucrose phosphate synthase (SPS), fructose-1,6-bisphosphatase (FBP), invertase (INV), and amylolytic enzyme, impeding the translocation of carbon assimilates to roots and reducing plant biomass. Nevertheless, triadimefon elevated starch content and minimized sucrose degradation by augmenting sucrose synthase (SS) activity and restraining the activities of SPS, FBP, INV, and amylolytic enzyme compared with drought alone, regulating the carbohydrate balance of drought-stressed plants. Therefore, triadimefon application could reduce the photosynthesis inhibition and regulate the carbohydrate balance of drought-stressed soybean plants to lessen the impacts of drought on soybean biomass.

Roles of enzymatic and nonenzymatic antioxidants in plants during abiotic stress

Reactive oxygen species (ROS) are produced in plants as byproducts during many metabolic reactions, such as photosynthesis and respiration. Oxidative stress occurs when there is a serious imbalance between the production of ROS and antioxidant defense. Generation of ROS causes rapid cell damage by triggering a chain reaction. Cells have evolved an elaborate system of enzymatic and nonenzymatic antioxidants which help to scavenge these indigenously generated ROS. Various enzymes involved in ROS-scavenging have been manipulated, over expressed or downregulated to add to the present knowledge and understanding the role of the antioxidant systems. The present article reviews the manipulation of enzymatic and nonenzymatic antioxidants in plants to enhance the environmental stress tolerance and also throws light on ROS and redox signaling, calcium signaling, and ABA signaling.