Abstract: Pteris vittata is the first reported arsenic (As) hyperaccumulator, which is an ideal plant for remediation of As contaminated soils. Flooding stress is an important factor affecting the growth and geographical distribution of P. vittata, limiting its application in environment with high humidity. Therefore, it is of great importance to understand the response of P. vittata to flooding stress and the underlying mechanisms. Calcium (Ca) and phosphorus (P) can promote the survival and growth of plants by improving their resistance to drought, cold, salt and alkali stresses. The effects of Ca and P on plant responses to flooding stress are less studied. We analyzed photosynthetic rate, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and biomass of P. vittata under saturation water retention (relative moisture content 35%) and flooding stress (relative moisture content 40%). The regulatory effects of Ca and P on P. vittata flooding stress resistance were studied with no Ca or P as a control (CK). Compared to the treatment with 35% moisture content, leaf photosynthetic rate decreased by 30.8%, SOD activity decreased by 71.7%, MDA content increased by 46.4%, and biomass decreased by 77.3% under 40% flooding stress, indicating that flooding stress reduced the resistance of P. vittata to antioxidant stress, resulting in significantly decreased leaf photosynthetic rate and biomass (P<0.05). Under flooding stress, 5-20 g·kg^-1 Ca or 0.1-0.2 g·kg^-1 P increased photosynthetic rate, SOD activity, and biomass by 0.15-1.65, 0.58-1.91, and 0.91-5.01 times, and decreased MDA content by 14%-36.1% compared to CK. This result indicated that Ca and P addition can alleviate the adverse effects of flooding stress on P. vittata, which was enhanced with increasing Ca and P application amounts. The correlation analysis confirmed that Ca and P application reduced the negative correlation between moisture content and leaf photosynthetic rate, SOD activity, biomass, and the positive correlation between moisture content and MDA, which was increased with increasing Ca and P application, indicating that Ca and P can improve the resistance ability of P. vittata to flooding stress. Therefore, Ca and P application can improve the tolerance of P. vittata to flooding stress via increasing antioxidant enzymes activity, increasing scavenging active oxygen species, and reducing membrane lipid peroxidation, thereby maintaining high photosynthetic activities.

Key words: Pteris vittata, flooding stress, calcium and phosphorus, photosynthetic rate, enzyme activity, biomass