Engineered nanoparticles (NPs) are considered potential agents for agriculture as fertilizers and growth enhancers. However, their action spectrum differs strongly, depending on the type of NP, its concentrations, and plant species per se, ranging from growth stimulation to toxicity. This work aimed to investigate effects of iron oxide (Fe₃O₄) NPs on growth, photosynthesis, respiration, antioxidant activity, and leaf mineral content of wheat plants. Wheat seeds were treated with NP for 3 h and plants were grown in the soil at two light intensities, 120 and 300 μmol (photons) m⁻²·s⁻¹, followed by physiological assessment at several time points. High NP treatment (200 and 500 mg·L⁻¹) enhanced plant growth, photosynthesis and respiration, as well as increasing the content of photosynthetic pigments in leaves. This effect depended on both the light intensity during plant growth and the age of the plants. Regardless of concentration and light intensity, an effect of NPs on the primary photochemical processes was not observed. Seed treatment with NP also led to increased activity of ascorbate peroxidase and reduced malondialdehyde (MDA) content in roots and leaves. Treatment with Fe₃O₄ also led to noticeable increases in the leaf Fe, P, and K content. It is concluded that iron oxide (Fe₃O₄)-based NP could enhance plant growth by improving photosynthetic performance and the availability of Fe and P.

The optimization of plant-specific LED lighting protocols for indoor plant growing systems needs both basic and applied research. Experiments with lettuce, Lactuca sativa L., plants using artificial lighting based on narrow-band LEDs were carried out in a controlled environment. We investigated plant responses to the exclusion of certain spectral ranges of light in the region of photosynthetically active radiation (PAR); in comparison, the responses to quasimonochromatic radiation in the red and blue regions were studied separately. The data on plant phenotyping, photosynthetic activity determination, and PAM fluorometry, indicating plant functional activity and stress responses to anomalous light environments, are presented. The study on carbon isotopic composition of photoassimilates in the diel cycle made it possible to characterize the balance of carboxylation and photorespiration processes in the leaves, using a previously developed oscillatory model of photosynthesis. Thus, the share of plant photorespiration (related to plant biomass enrichment with ¹³C) increased in response to red-light action, while blue light accelerated carboxylation (related to ¹²C enrichment). Blue light also reduced water use efficiency. These data are supported by the observations from the light environments missing distinct PAR spectrum regions. The fact that light of different wavelengths affects the isotopic composition of total carbon allowed us to elucidate the nature of its action on the organization of plant metabolism.

Varying the spectral composition of light is one of the ways to accelerate the growth of conifers under artificial conditions for the development of technologies and to obtain sustainable seedlings required to preserve the existing areas of forests. We studied the influence of light of different quality on the growth, gas exchange, fluorescence indices of Chl a, and expression of key light-dependent genes of Pinus sylvestris L. seedlings. It was shown that in plants growing under red light (RL), the biomass of needles and root system increased by more than two and three times, respectively, compared with those of the white fluorescent light (WFL) control. At the same time, the rates of photosynthesis and respiration in RL and blue light (BL) plants were lower than those of blue red light (BRL) plants, and the difference between the rates of photosynthesis and respiration, which characterizes the carbon balance, was maximum under RL. RL influenced the number of xylem cells, activated the expression of genes involved in the transduction of cytokinin (Histidine-containing phosphotransfer 1, HPT1, Type-A Response Regulators, RR-A) and auxin (Auxin-induced protein 1, Aux/IAA) signals, and reduced the expression of the gene encoding the transcription factor phytochrome-interacting factor 3 (PIF3). It was suggested that RL-induced activation of key genes of cytokinin and auxin signaling might indicate a phytochrome-dependent change in cytokinins and auxins activity.

Effect of UV-A radiation (10 W/m², 2 h) and modifying effect of brief exposure to red light (RL) (1.8 W/m², 20 min) on photochemical activity of photosystem II (PSII) (F_v/F_m), as well as on activity of ascorbate peroxidase (AsP) and phenylalanine ammonia-lyase (PAL), were investigated in the leaves of 26–28-day-old Аrabidopsis thaliana (L.) Heynh. plants of wild type (WT) and mutants: hy3 deficient in phytochrome B (phyB) and hy2 defective in phytochromobilin synthesis. UV-A reduced photochemical activity of PSII and activities of AsP and PAL. Exposure to RL increased PAL activity in only WT plants and in mutant hy3. Elevation of expression of genes APX1, sAPX, tAPX, and PAL encoding enzymes AsP and PAL was detected upon the exposure to RL and UV-A. For instance, expression of gene APX1 in WT plants and in mutant hy3 rose upon exposure to RL and UV-A; in mutant hy2, it increased only upon UV-A treatment. Expression of gene tAPX in WT plants rose only under the effect of RL, whereas expression of gene sAPX did not rise in any type of treatment. In mutant hy2, expression of the above-named genes decreased upon the effect of RL. Upon joint action of RL and UV-A (RL followed by UV), the negative effect of UV-A on the activity of the total pool of AsP was nullified by RL in only WT plants and in mutant hy3. Partial removal of the negative effect of UV-A on activity of PSII as a result of pretreatment of plants with RL is probably related to a rise in the activity of antioxidant enzymes. This is evident in WT plants whose PSII is more sensitive to RL radiation than in mutants deficient in phytochromes. We believe that PSII resistance to UV-A radiation depends on the potential of the plant antioxidant system, which rises when the share of the active form of phytochrome in its total pool increases as a result of plants’ pretreatment with RL and is partially realized by way of induction of transcriptional activity of antioxidant genes.