biostudies-literatureUnknown154(2)Pupillo PAlma Mater Studiorum - Università di BolognaAlthough many photosynthesis related processes are known to be controlled by the circadian system, consequent changes in photosynthetic activities are poorly understood. Photosynthesis was investigated during the daily cycle by chlorophyll fluorescence using a PAM fluorometer in Pulmonaria vallarsae subsp. apennina, an understory herb. A standard test consists of a light induction pretreatment followed by light response curve (LRC). Comparison of the major diagnostic parameters collected during day and night showed a nocturnal drop of photosynthetic responses, more evident in water-limited plants and consisting of: (i) strong reduction of flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (Jmax, ETR_EM) and effective PSII quantum yield (Φ<sub>PSII</subPhotosynthesis research143-153https://www.ebi.ac.uk/biostudies/studies/S-EPMC9630222biostudies-literatureThe circadian night depression of photosynthesis analyzed in a herb, Pulmonaria vallarsae. Day/night quantitative relationships.PMC9630222Sparla FTrost PPupillo PMelandri BAfalseThe circadian night depression of photosynthesis analyzed in a herb, Pulmonaria vallarsae. Day/night quantitative relationships.Although many photosynthesis related processes are known to be controlled by the circadian system, consequent changes in photosynthetic activities are poorly understood. Photosynthesis was investigated during the daily cycle by chlorophyll fluorescence using a PAM fluorometer in Pulmonaria vallarsae subsp. apennina, an understory herb. A standard test consists of a light induction pretreatment followed by light response curve (LRC). Comparison of the major diagnostic parameters collected during day and night showed a nocturnal drop of photosynthetic responses, more evident in water-limited plants and consisting of: (i) strong reduction of flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (Jmax, ETR_EM) and effective PSII quantum yield (Φ<sub>PSII</sub2022-01-01T00:00:00Z2022 Nov2025-04-18T19:21:06.052Z2025-04-07T07:04:04.138ZS-EPMC96302223608725010.1007/s11120-022-00956-1