Photosynthetic function analysis under rhizosphere anaerobic conditions in early-stage cassava

To enhance land use efficiency and meet rising cassava demand, cultivation is expected to expand into unsuitable lowland areas. This trend highlights the need for waterlogging-tolerant cassava genotypes. However, research on cassava survival mechanisms under waterlogged conditions through photosynthetic functions remains limited. This study investigated the physiological responses of cassava to waterlogging stress. It focused on photosynthesis, stomatal conductance, soil plant analysis development (SPAD), and chlorophyll fluorescence (Fv/Fm) to determine chlorophyll degradation and its effect on photoreceptors. Cassava was subjected to waterlogging by maintaining water-filled buckets throughout the treatment. Variables were measured periodically at intervals of 0, 3, 6, 9, 12, and 15 days after treatment (DAT). Results showed a reduction of net photosynthetic rate (A) by 82.6%, resulting from a 96.7% reduction in stomatal conductance (gs) and 21% in transpiration rate (E). A, gs, and E in three-month-old cassava varied and declined with increasing waterlogging duration, while SPAD value showed no significant differences compared to the control across all measurement dates. Fv/Fm showed a significant decrease at 3DAT followed by recovery, likely due to light de-excitation rather than chlorophyll degradation, as SPAD value remained unchanged, indicating no chlorophyll breakdown or photoreceptor damage in three-month-old cassava under waterlogging conditions. The study concluded that cassava exhibits a functional stay-green type of SPAD, and photosynthetic nitrogen use efficiency, along with stomatal and nonstomatal limitations that regulate photosynthesis under waterlogged conditions. Study provides insights into how cassava cope with waterlogging and guide breeding or agronomic strategies to improve their resilience in waterlogged environments.