Effect of different waterlogging periods on biochemistry, growth, and chlorophyll a fluorescence of Arachis hypogaea L

Ecotoxicological assessment of cigarette butts on morphology and photosynthetic potential of Azolla pinnata

Cigarette butts (CBs) have become the most ubiquitous form of anthropogenic litter globally. CBs contain various hazardous chemicals that persist in the environment for longer period. These substances are susceptible to leaching into the environment through waterways. The recent study was aimed to evaluate the effects of disposed CBs on the growth and development of Azolla pinnata, an aquatic plant. It was found that after a span of 6 days, the root length, surface area, number of fronds, and photosynthetic efficacy of plant were considerably diminished on the exposure of CBs (concentrations 0 to 40). The exposure of CBs led to a decrease in the FM, FV/F0, and φP0, in contrast, the φD0 increased in response to CBs concentration. Moreover, ABS/CSm, TR0/CSm, and ET0/CSm displayed a negative correlation with CB-induced chemical stress. The performance indices were also decreased (p-value ≤ 0.05) at the highest concentration of CBs. LD50 and LD90 represent the lethal dose, obtained value for LD50 is 20.30 CBs and LD90 is 35.26 CBs through probit analysis. Our results demonstrate that the CBs cause irreversible damage of photosynthetic machinery in plants and also reflect the efficacy of chlorophyll a fluorescence analysis and JIP test for assessing the toxicity of CBs in plants.

Sunlight-induced repair of photosystem II in moss Semibarbula orientalis under submergence stress

Lower plants such as bryophytes often encounter submergence stress, even in low precipitation conditions. Our study aimed to understand the mechanism of submergence tolerance to withstand this frequent stress in moss (Semibarbula orientalis ) during the day and at night. These findings emphasise that light plays a crucial role in photoreactivation of PSII in S. orientalis , which indicates that light not only fuels photosynthesis but also aids in repairing the photosynthetic machinery in plants. Submergence negatively affects photosynthesis parameters such as specific and phenomenological fluxes, density of functional PSII reaction centres (RC/CS), photochemical and non-photochemical quenching (Kp and Kn), quantum yields (ϕP0 , ϕE0 , ϕD0 ), primary and secondary photochemistry, performance indices (PIcs and PIabs), etc. Excessive antenna size caused photoinhibition at the PSII acceptor side, reducing the plastoquinone pool through the formation of PSII triplets and reactive oxygen species (ROS). This ROS-induced protein and PSII damage triggered the initiation of the repair cycle in presence of sunlight, eventually leading to the resumption of PSII activity. However, ROS production was regulated by antioxidants like superoxide dismutase (SOD) and catalase (CAT) activity. The rapid recovery of RS/CS observed specifically under sunlight conditions emphasises the vital role of light in enabling the assembly of essential units, such as the D1 protein of PSII, during stress in S. orientalis . Overall, light is instrumental in restoring the photosynthetic potential in S. orientalis growing under submergence stress. Additionally, it was observed that plants subjected to submergence stress during daylight hours rapidly recover their photosynthetic performance. However, submergence stress during the night requires a comparatively longer period for the restoration of photosynthesis in the moss S. orientalis .

Physiological and Transcriptome Analyses of Photosynthesis in Three Mulberry Cultivars within Two Propagation Methods (Cutting and Grafting) under Waterlogging Stress

Mulberry is a valuable woody plant with significant economic importance. It can be propagated through two main methods: cutting and grafting. Waterlogging can have a major impact on mulberry growth and can significantly reduce production. In this study, we examined gene expression patterns and photosynthetic responses in three waterlogged mulberry cultivars propagated through cutting and grafting. Compared to the control group, waterlogging treatments reduced levels of chlorophyll, soluble protein, soluble sugars, proline, and malondialdehyde (MDA). Additionally, the treatments significantly decreased the activities of ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT) in all three cultivars, except for superoxide dismutase (SOD). Waterlogging treatments also affected the rate of photosynthesis (Pn), stomatal conductance (Gs), and transpiration rate (Tr) in all three cultivars. However, no significant difference in physiological response was observed between the cutting and grafting groups. Gene expression patterns in the mulberry changed dramatically after waterlogging stress and varied between the two propagation methods. A total of 10,394 genes showed significant changes in expression levels, with the number of differentially expressed genes (DEGs) varying between comparison groups. GO and KEGG analysis revealed important DEGs, including photosynthesis-related genes that were significantly downregulated after waterlogging treatment. Notably, these genes were upregulated at day 10 in the cutting group compared to the grafting group. In particular, genes involved in carbon fixation were significantly upregulated in the cutting group. Finally, cutting propagation methods displayed better recovery capacity from waterlogging stress than grafting. This study provides valuable information for improving mulberry genetics in breeding programs.

Role of tillage measures in mitigating waterlogging damage in rapeseed

BACKGROUND

Tillage measures have been effectively adopted for mitigating waterlogging damage in field crops, yet little is known about the role of tillage measures in crop responses to waterlogging. A field experiment was performed to investigate the effect of conventional planting (CK), small ridge planting (SR), big ridge planting (BR) and film side planting (FS) on soil available nutrients and enzymatic activity, chlorophyll contents, leaf nutrients, soluble protein, soluble sugar, nitrate reductase, antioxidant enzyme activity, lipid peroxidation, agronomic traits and yield of rapeseed under waterlogging stress conditions.

RESULTS

Tillage measures remarkably improved rapeseed growth and yield parameters under waterlogging stress conditions. Under waterlogging conditions, rapeseed yield was significantly increased by 33.09 and 22.70% in the SR and BR groups, respectively, compared with CK. Correlation analysis showed that NO₃^--N, NH₄⁺-N, and urease in soils and malonaldehyde (MDA), superoxide dismutase (SOD), and nitrate reductase in roots were the key factors affecting rapeseed yield. The SR and BR groups had significantly increased NO₃^--N by 180.30 and 139.77%, NH₄⁺-N by 115.78 and 66.59%, urease by 41.27 and 26.45%, SOD by 6.64 and 4.66%, nitrate reductase by 71.67 and 26.67%, and significantly decreased MDA content by 14.81 and 13.35% under waterlogging stress, respectively, compared with CK. In addition, chlorophyll and N content in leaves, soluble sugar and POD in roots, and most agronomic traits were also significantly enhanced in response to SR and BR under waterlogging conditions.

CONCLUSION

Overall, SR and BR mitigated the waterlogging damage in rapeseed mainly by reducing the loss of soil available nitrogen, decreasing the MDA content in roots, and promoting urease in soils and SOD and nitrate reductase in roots. Finally, thorough assessment of rapeseed parameters indicated that SR treatment was most effective followed by BR treatment, to alleviate the adverse effects of waterlogging stress.