Effect of Alkaline Salt Stress on Photosynthetic Activities of Potato Plants (Solanum tuberosum L.)

Land salinization severely limits the development of agriculture, and the growing global population poses a serious challenge to food security. As an abiotic stress factor limiting photosynthesis in potatoes (<i>Solanum tuberosum</i> L.), alkaline salt stress significantly impacts their photosynthetic activity. In this study, potted seedlings of the 'Atlantic' variety were planted in the pots. Sodium bicarbonate (NaHCO₃) was incorporated into the dry soil within the pots at four distinct concentration levels: 0 mmol/L, 20 mmol/L, 40 mmol/L, and 60 mmol/L. The findings indicated that at a concentration of 60 mmol/L, the initial fluorescence (<i>Fo</i>) exhibited its peak value. At this concentration, NaHCO₃ stress induced a significant decline in several parameters: variable fluorescence (<i>Fv</i>), the chlorophyll fluorescence ratio (<i>Fv</i>/<i>Fm</i>), dark-adapted maximum fluorescence (<i>Fm</i>), the <i>Fv</i>/<i>Fo</i> ratio, and overall plant performance. Compared to the control CK, the values of <i>Fv</i>, <i>Fv</i>/<i>Fm</i>, <i>Fm</i>, and <i>Fv</i>/<i>Fo</i> decreased by 42.36%, 20.44%, 54.1%, and 61.97%, respectively. At a stress concentration of 60 mmol/L, NaHCO₃ stress exhibited a more pronounced inhibition of chlorophyll synthesis. Under T3 treatment at this stress concentration, the contents of chlorophyll <b>a</b>, chlorophyll <b>b</b>, and total chlorophyll <b>a</b>/<b>b</b> were significantly lower than the control group (CK), decreasing by 46.29%, 54.3%, and 48.56%, respectively. The T2 treatment showed the next most pronounced reduction, with levels 33.26%, 45.75%, and 36.79% lower than CK, respectively. After a brief increase in the intercellular CO₂ concentration (Ci) in photosynthetic gas exchange, the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) decreased significantly with the gradual increase in concentration and prolongation of time. The expression levels of genes related to some subunits of photosystem II and photosystem I were down-regulated under stress, while the expressions of genes related to Fd and FNR were also down-regulated to varying degrees. In this study, photosynthetic activities such as fluorescence parameters, chlorophyll content, and photosynthetic gas exchange were measured, along with 16 key photosynthetic genes of potato plants. The aim was to explore the effects of alkaline salt stress on potato photosynthesis and its related mechanisms. The research outcomes contribute to a better understanding of potato's adaptive responses to alkaline stress, potentially informing future efforts in crop improvement and saline agriculture management.