Daily UV-supplementation during the plant fruiting stage of tomato (Solanum lycopersicum L.) growing indoors may produce fruits with higher nutraceutical value and better acceptance by consumers. However, it is important to ensure that the plant’s performance during this stage is not compromised by the UV supplement. We studied the impact of UV-A (1 and 4 h) and UV-B (2 and 5 min) on the photosynthesis of greenhouse-grown tomato plants during the fruiting/ripening stage. After 30 d of daily irradiation, UV-B and UV-A differently interfered with the photosynthesis. UV-B induced few leaf-necrotic spots, and effects are more evidenced in the stimulation of photosynthetic/protective pigments, meaning a structural effect at the Light-Harvesting Complex. UV-A stimulated flowering/fruiting, paralleled with no visible leaf damages, and the impact on photosynthesis was mostly related to functional changes, in a dose-dependent manner. Both UV-A doses decreased the maximum quantum efficiency of photosystem II (Fv/Fm), the effective efficiency of photosystem II (ΦPSII), and gas exchange processes, including net carbon assimilation (P_N). Transcripts related to Photosystem II (PSII) and RuBisCO were highly stimulated by UV supplementation (mostly UV-A), but the maintenance of the RuBisCO protein levels indicates that some protein is also degraded. Our data suggest that plants supplemented with UV-A activate adaptative mechanisms (including increased transcription of PSII peptides and RuBisCO), and any negative impacts on photosynthesis do not compromise the final carbohydrate balances and plant yield, thus becoming a profitable tool to improve precision agriculture.

Light composition modulates plant growth and defenses, thus influencing plant–pathogen interactions. We investigated the effects of different light-emitting diode (LED) red (R) (665 nm) and blue (B) (470 nm) light combinations on Actinidia chinensis performance by evaluating biometric parameters, chlorophyll a fluorescence, gas exchange and photosynthesis-related gene expression. Moreover, the influence of light on the infection by Pseudomonas syringae pv. actinidiae (Psa), the etiological agent of bacterial canker of kiwifruit, was investigated. Our study shows that 50%R–50%B (50R) and 25%R–75%B (25R) lead to the highest PSII efficiency and photosynthetic rate, but are the least effective in controlling the endophytic colonization of the host by Psa. Monochromatic red light severely reduced ΦPSII, ETR, Pn, TSS and photosynthesis-related genes expression, and both monochromatic lights lead to a reduction of DW and pigments content. Monochromatic blue light was the only treatment significantly reducing disease symptoms but did not reduce bacterial endophytic population. Our results suggest that monochromatic blue light reduces infection primarily by modulating Psa virulence more than host plant defenses.

Industrial applications of titanium dioxide nanoparticles (TiO₂ NPs) are wide, and their use in nano-fertilizing technology has been proposed in the last few years. Bioactivity evaluation of different TiO₂ NPs formulations is therefore crucial, not only to select the most appropriate formulation but also to validate potential agro-applications. In the current work, we compared the bioactivity of the two most used TiO₂ NPs formulations (anatase and rutile–anatase) on the photosynthesis of Lactuca sativa. Seeds were exposed to concentrations of 0, 10, and 50 mg L⁻¹ of anatase (A) or rutile–anatase (RA). Germination rate was not affected by NPs, but root growth was stimulated mainly by RA50. Compared with control, RA showed positive effects on photophosphorylation-related parameters. A50 was more efficient in promoting the gas exchange phase (PN, Ci, gs, and E) and in stimulating the absorption of some nutrients. Expanding on the biochemical and physiological data, we show that RA50 stimulated several genes coding for proteins involved in the electron transport in thylakoids (psbA, petB, petA, psaA, psaC, ndhA, ndhD) and ATP synthesis (atpA, atpB). The transcript coding for the large subunit of RuBisCO (rbcL), was stimulated by lower concentration (RA10). This suggests that RuBisCO is highly sensitive to these NPs even at low doses. RA at low doses has been demonstrated to be the most promising NP. These discriminative effects of TiO₂ NPs, based on their formulation and dose, may present advantages for their use in the precision nanoagroindustry.