Stomatal and non-stomatal limitations of bell pepper (Capsicum annuum L.) plants under water stress and re-watering: Delayed restoration of photosynthesis during recovery

• The plants were water stressed and re-watered to study photosynthetic behavior.
• Diffusive limitations were the main factor for photosynthesis depression.
• Water stress limited electron flow from the plastoquinone pool to the PSI end acceptors.
• Re-watering caused gradual recovery of linear electron flow and CO2 assimilation.
• JIP test parameters linked to events around PSI were efficient monitoring plant status.

Low soil water availability is the major environmental factor limiting plant growth and yield. The objective of this study was to elucidate the mechanisms underlying photosynthesis inhibition during water stress and recovery in Capsicum annuum L. cv. Cannon by evaluating soil and plant water relations, gas exchange and the prompt fluorescence rise OJIP. The soil (ΨS) and leaf (ΨL) water potential decreased from −0.16 and −0.53 to −1.1 and −1.7 MPa, respectively, and recovered after re-watering. The stomatal conductance (gs) decreased to 114 and 13 mmol m−2 s−1 under moderate and severe water stress, respectively. Similarly, the CO2 assimilation (A) and transpiration (Tr) rates decreased during water stress but recovered after re-watering. During severe water stress, photosynthesis decreased due to stomatal closure and to both slower maximum carboxylation rate (Vcmax) and ribulose 1,5-bisphosphate (RuBP) regeneration capacity mediated by maximum electron transport rate (Jmax). In fact, the fluorescence parameters reflecting the electron flow from the intersystem carriers to final reduction of photosystem I (PSI) end electron acceptors declined throughout water deficit development. In conclusion, water stress mainly damaged the electron transfer from the plastoquinone (PQ) pool to the PSI terminal acceptors; this, along with constraints to both stomatal and non-stomatal components of photosynthesis, limited carbon assimilation. Photosynthesis recovery after re-watering was mainly restricted by both stomatal conductance and the gradual recovery of the electron transport chain. Finally, JIP-test parameters that quantifying electron transfer from the PQ pool to the PSI end acceptors are effectives for monitoring water stress in crop plants.