Leaf phosphorus spraying causes a fast and partial recovery of photosynthesis and improves biomass production of Phaseolus vulgaris L. plants facing phosphorus deficiency

Phosphorus (P) deficiency severely limits common bean (Phaseolus vulgaris L.) yield, especially during reproductive stages. This study aimed to evaluate the effect of leaf P spraying on photosynthetic performance, nutritional status, and growth in common bean plants facing P deficiency at the reproductive phase. The experiment was conducted in a greenhouse using hydroponics with three treatments: P-sufficient plants (P500), P-deficient plants (P20), and P-deficient plants receiving leaf P spraying (P20+P). We assessed leaf P and nitrogen concentrations, photosynthetic pigments (chlorophyll a and b), photochemistry (maximum and effective quantum efficiency of PSII), and leaf gas exchange (net CO2 assimilation rate, stomatal conductance, transpiration, intercellular CO2 partial pressure, intrinsic water use efficiency) at 4, 8, and 12 days after spraying. Additionally, mesophyll conductance, dark respiration rate, maximum carboxylation rate of RuBisCO and the maximum electron transport rate were measured for assessing how P deficiency impaired photosynthesis. Biomass production and pod development were evaluated at pod formation. P deficiency significantly decreased leaf P and nitrogen contents, chlorophyll content, photochemical efficiency, stomatal and mesophyll conductance, and the overall photosynthetic capacity, resulting in impaired growth and reduced pod production by 52%. Leaf P spraying significantly reduced these losses, reducing the pod dry mass gap to 16%, restoring pod weight to P-sufficient levels, and boosting overall biomass by 18%. Leaf P spraying led to a rapid, yet partial restoration of nutrient concentrations and photosynthetic traits within 4–8 days, enhancing biomass accumulation and pod yield. These positive effects diminished by 12 days post-application. Phosphorus deficiency during the reproductive phase impaired photochemistry and biochemistry of photosynthesis, growth and yield of common bean plants.Leaf P spraying restored leaf P and N concentrations and photosynthesis rapidly and partially.Increased shoot biomass and pod production were obtained in P-sprayed common bean plants.Leaf spraying is a promising management strategy to supply P in critical phenological phases. Phosphorus deficiency during the reproductive phase impaired photochemistry and biochemistry of photosynthesis, growth and yield of common bean plants. Leaf P spraying restored leaf P and N concentrations and photosynthesis rapidly and partially. Increased shoot biomass and pod production were obtained in P-sprayed common bean plants. Leaf spraying is a promising management strategy to supply P in critical phenological phases.