Dionaea muscipula J. Ellis is a South and North Carolina carnivorous endemic plant with medicinal properties. Its natural habitat is characterized by low availability of nutrients and poor plant cover, resulting in Venus flytrap exposure to various stress factors, especially UV-A radiation.

To evaluate response of Dionaea muscipula photosynthetic apparatus to increased level of UV-A radiation, plants cultivated in controlled conditions (30-40 % air humidity, temperature 23 ± 1 °C, light intensity 290 μmol m^–2 s^–1, 16 h light/8 h dark) (Control) were treated additionally with 50 μmols m^–2 s^–1 UV-A radiation for 24 h (Treated). Measurements of gas exchange, chlorophyll fluorescence and photosynthetic pigment content were conducted immediately after the exposure, both in Control and Treated plants. Additionally, the same parameters were evaluated in next 24 hours (Recovery).

UV-A treatment (Treated) did not change chlorophyll a + b content and chlorophyll a/b ratio. Furthermore, increased level of electron carriers (Area, Sm) and increased efficiency of electron transport between Q_A and PSI (ΦR₀, δR₀, ρR₀) was observed. Further, PSI and electron acceptors demonstrated increased ability to oxidize reduced plastoquinone pool (V_I decrease). As a consequence the rate of net photosynthesis increased significantly.

After 24h from the exposure (Recovery) the chlorophyll a + b content declined, but the ratio of chlorophyll a/b did not alter, what indicate decrease in the size of photosynthetic antennas and the number of active PSII centres. Additionally, inactivation of reaction centres (F₀ decrease, V_J and V_I increase) and decrease in amount of electron carriers, especially PQ poll (Sm) was observed. Moreover, decrease of electron flux and efficiency of electron transport between Q_A and PSI occurred (decrease of: ΦE₀, ψE₀, ET₀/RC, ET₀/CS₀, ΦR₀, ρR₀). Results may indicate the decrease of PSII photochemical efficiency. Simultaneously, PSI reactions remained unchanged and the rate of net photosynthesis increased significantly. This can be connected with activation of alternative pathways of electron transport. Activation of these pathways leads to limitation of NADPH synthesis and increase in ATP synthesis, what enable the plant effective acclimatization to stress conditions.