Search Results (10)

High temperature has an adverse effect on apple production worldwide. Photosynthesis is a process especially vulnerable to heat stress, which can reduce photosynthetic efficiency, plant growth, development, and ultimately yield. Although the effects of heat stress on apples have been partially examined, the photochemical reactions and heat tolerance of specific rootstocks have still not been sufficiently investigated. Identification of rootstocks with better photosynthetic performance and adaptation to heat stress enables the selection of rootstocks, which could contribute to stable yields and good fruit quality even at elevated temperatures. In this study, chlorophyll a fluorescence (ChlF) induction kinetics was used to investigate the heat tolerance between two apple rootstocks (M.9 and G.210). In addition, we employed lipid peroxidation measurements, hydrogen peroxide quantification, proline content, and total phenolic and flavonoid assessments. Analysis of chlorophyll fluorescence parameters and OJIP curves (different steps of the polyphasic fluorescence transient; O–J–I–P phases) revealed significant differences in their responses, with higher values of the PI_ABS parameter indicating better PS II stability and overall photosynthetic efficiency in M.9 rootstock. The higher contents of chlorophyll, carotenoids, proline, and significant increase in the accumulation of phenolics, and flavonoids in this rootstock also contributed to its better adaptation to heat stress. Oxidative stress was more pronounced in G.210 through higher H₂O₂ and MDA levels, which could point to its lower capacity to adjust to heat stress conditions. This research can provide a scientific basis for further breeding programs and growing plans due to climate change and the occurrence of extremely high temperatures. Full article

Rhododendron L., a renowned ornamental species and one of the ten famous flowers in China, is highly regarded for its aesthetic value and extensive applications in landscaping. However, its growth and quality are significantly compromised by drought stress, particularly in regions with dry conditions. To elucidate the drought response mechanisms of Rhododendron, two cultivars, ‘SaKeSiZhiXing’ (SKSZX) and ‘TuRuiMeiGui’ (TRMG), were subjected to natural drought stress, and changes in chlorophyll fluorescence and transcriptomic profiles were examined at 0 days (d), 4 d, and 8 d of drought exposure. An OJIP fluorescence transient (O-J-I-P) analysis revealed a progressive decline in the F_P parameter and an increase in the F_J parameter as drought stress intensified. Additionally, a delayed fluorescence (DF) analysis showed a gradual reduction in the I₁ and I₂ values within the induction and decay curves under prolonged drought conditions. The 820 nm curve indicated the deactivation of a transient phase characterized by a rapid decline, followed by a slow recovery in the modulated reflection (MR) signal. A transcriptomic analysis of leaves identified 24,352, 18,688, and 32,261 differentially expressed genes (DEGs) in SKSZX at 0 d, 4 d, and 8 d of drought treatment, respectively. In contrast, TRMG exhibited more pronounced and earlier drought-induced alterations. These DEGs were primarily enriched in pathways related to phenylpropanoid biosynthesis, plant hormone signaling, photosynthesis, and photosynthesis-antenna proteins. Additionally, 565 transcription factors (TFs) were identified, including bHLH, WRKY, bZIP, MYB-related, MYB, C2H2, and HSF families. The drought-induced changes in TRMG were more substantial and occurred earlier compared to SKSZX, with a greater impairment in the electron transfer capacity at both the donor and acceptor sides of photosystem II (PSII). This study provides valuable insights into the molecular mechanisms underlying drought tolerance in Rhododendron and offers a foundation for molecular breeding strategies aimed at enhancing drought resistance in future cultivars. Full article

The growing interest in Cannabis sativa as a highly used crop is present worldwide. There are limited data about the effect of potassium (K) fertilizer on industrial hemp yield for dual purposes (seed and stem production). The current study aimed to investigate the influence of adding two different K fertilizers, KCl and K₂SO₄, at two growth stages (flowering and ripening) on the productivity and chlorophyll a fluorescence (ChlF) of Cannabis sativa, variety Finola. Before sowing, different K treatments were applied: K₁—100 kg ha⁻¹ KCl (60% K) and K₂—100 kg ha⁻¹ K₂SO₄ (52% K, S 17%). The OJIP (O stands for “origin” (minimal fluorescence), P for “peak” (maximum fluorescence), and J and I for inflection points between the O and P levels) data were recorded and used for ChlF transients and individual ChlF parameters during vegetation. At harvest, the stem morphology parameters and yield (plant height, stem weight and diameter, and stem and seed yield), tensile strength, and the modulus of elasticity were determined. The results show the sensitivity of minimal (F₀) and maximal fluorescence (F_m), electron transport from Q_A to intersystem electron acceptors (ET₀/(TR₀ − ET₀)), and electron transport flux until PSI acceptors (RE₀/RC) to K fertilization. The parameters that described electron transport (ET₀/RC, ψE_0, and φE₀), performance index on absorption basis (PI_ABS, TR₀/DI₀, and φP₀), dissipation (DI₀/RC), and electron transport to photosystem I (φR₀ and δR₀/(1 − δR₀)) had a reaction only at the growth stage, indicating a change in their activity during the aging of the Cannabis sativa plants. The average stem height was 67.5 cm, and the stem diameter was 0.41 cm. The different K sources did not significantly influence the stem height and diameter, nor the dry stem (on average 12.2 t ha⁻¹) and seed yield (on average 1.85 t ha⁻¹). The tensile strength of individual hemp stems was the highest with K₂SO₄ (53.32 MPa) and the lowest with KCl (49.25 MPa). The stem stiffness by modulus of elasticity was about 5 GPa on average for all the treatments. In general, the photosynthetic parameters in this study varied more between the growth stages than between the different K fertilizer formulations. Moreover, based on the results of this study, it can be recommended to use both fertilizers, KCl and K₂SO₄, in dual-purpose industrial hemp production since no significant effect was found for the stem morphometric and biomechanical parameters as well as for the agronomic parameters. Full article

Leaf color mutants serve as valuable models for studying the regulation of plant photosynthesis, alternations in chloroplast structure and function, and the analysis of associated gene functions. A yellow leaf mutant, ylm, was separated from the wild tomato M82, with its yellowing intensity influenced by low temperature. To assess the low-temperature sensitivity of this mutant, the photosynthetic and chlorophyll fluorescence responses of ylm and M82 were examined under different temperature conditions. In this study, the ylm mutant and its wild type, M82, were exposed to three temperature levels, 16, 25, and 30 °C, for 48 h. The impact of these temperature treatments on leaf color change, chlorophyll content, photosynthetic performance, and chlorophyll fluorescence characteristics of mutant ylm was investigated. The results revealed the following: (1) After exposure to 16 °C, the ylm mutant exhibited significant yellowing, a marked reduction in chlorophyll content, and a notable increase in carotenoid content. At 25 °C, the differences were less pronounced, and at 30 °C, the differences between ylm and M82 were minimal. (2) The photosynthetic rate of the ylm mutant was lower than that of M82 at 16 °C, with the gap narrowing as temperature increased, eventually converging at higher temperatures. (3) The fluorescence transient curve (OJIP) of the ylm mutant differed significantly from that of M82 at 16 °C, with higher fluorescence intensity at the O point and lower intensity at the J, I, and P points. This difference was decreased at 25 °C and nearly disappeared at 30 °C. Additionally, the Fv/Fm, Fv/Fo, PIabs, PItotal, ABS/CSm, TRo/CSm, and ETo/CSm values of ylm were lower than those of M82 at 16 °C, while the ABS/RC and DIo/RC values were higher, with no significant differences observed at 30 °C. These findings suggest that the ylm mutant is highly sensitive to low temperature, with pronounced yellowing, reduced light energy absorption and capture efficiency, and impaired electron transport at lower temperature. Full article

Photosystem II (PSII) is the unique pigment–protein complex that is capable of evolving molecular oxygen using solar energy. The activity of PSII determines the overall productivity of all oxygenic photosynthetic organisms. It is well known that the absence of HCO₃⁻ induces a drop in the activity of PSII. However, it is not yet clear what type of photochemical reaction, single turn-over or multiple turn-over, HCO₃⁻ is involved in. Kinetic parameters of this (these) involvement(s) are almost unexplored now. This work addresses these issues. Using the JIP test, being the perspective noninvasive method for measuring PSII activity in plants, this paper describes how HCO₃⁻ deficiency affects the electron transfer on the oxidizing as well as the reducing sides of PSII in thylakoids and in PSII preparations from the leaves of pea plants. HCO₃⁻ was found to be simultaneously involved both in single turn-over and in multiple turn-over events (“dynamical processes”). Moreover, the involvement of HCO₃⁻ in dynamical photochemical processes was revealed to be associated with both sides of PSII, being the rate limiting on the reducing side, which follows from obtained kinetic parameters. The involvement of HCO₃⁻ in dynamical processes as the constant exchangeable ligand is discussed for both the electron donor and acceptor sides of PSII. Full article

In protected cultivation, increasing the light level via supplementary lighting (SL) is critical to improve external quality, especially in periods with low light availability. Despite wide applications, the effect of light quality remains understated. In this study, the effect of SL quality and nutrient solution electrical conductivity (EC) on growth and flowering of three bromeliad species was investigated. Treatments included solar light, and this supplemented with R90B10 [90% red (R) and 10% blue (B)], R80B20 (80% R and 20% B), and R70B30 (70% R and 30% B). These were combined with an EC of 1 and 2 dS m^-l. Irrespective of the light treatment, the higher EC promoted growth, inflorescence emergence, and development in Aechmea fasciata (Lindl.) Baker, whereas adverse effects were noted in Guzmania and Vriesea. The higher EC-induced negative effect in Guzmania and Vriesea was slightly alleviated by SL. With few notable exceptions, SL exerted limited effects on photosynthetic functionality. Depending on the species, SL improved external quality traits. In all species, SL increased root and inflorescence weight and stimulated biomass allocation to generative organs. It also accelerated inflorescence emergence and promoted inflorescence development. In this way, the time to commercial development stage was considerably shortened. These effects were more prominent at R80B20 and R70B30. Under those conditions, for instance, inflorescence emergence occurred 3–5 weeks earlier than in the control, depending on the species. In conclusion, SL with increased B proportion leads to shorter production period owing to faster emergence and improved development of the inflorescence and is recommended for commercial use. Full article

In type 1 diabetes (T1D) development, proinflammatory cytokines (PIC) released by immune cells lead to increased reactive oxygen species (ROS) production in β-cells. Nonetheless, the temporality of the events triggered and the role of different ROS sources remain unclear. Isolated islets from C57BL/6J wild-type (WT), NOX1 KO and NOX2 KO mice were exposed to a PIC combination. We show that cytokines increase O₂^•− production after 2 h in WT and NOX1 KO but not in NOX2 KO islets. Using transgenic mice constitutively expressing a genetically encoded compartment specific H₂O₂ sensor, we show, for the first time, a transient increase of cytosolic/nuclear H₂O₂ in islet cells between 4 and 5 h during cytokine exposure. The H₂O₂ increase coincides with the intracellular NAD(P)H decrease and is absent in NOX2 KO islets. NOX2 KO confers better glucose tolerance and protects against cytokine-induced islet secretory dysfunction and death. However, NOX2 absence does not counteract the cytokine effects in ER Ca²⁺ depletion, Store-Operated Calcium Entry (SOCE) increase and ER stress. Instead, the activation of ER stress precedes H₂O₂ production. As early NOX2-driven ROS production impacts β-cells’ function and survival during insulitis, NOX2 might be a potential target for designing therapies against early β-cell dysfunction in the context of T1D onset. Full article

Saffron is a valuable plant and one of the most expensive spices worldwide. Nowadays, there is a tendency to produce this crop in indoor plant production systems. However, the production of saffron is restricted by the need for the reproduction of high-quality corms. In this study, we investigated the effect of different ratios of red (R) and blue (B) light spectra (including 100% B (monochromatic B), 75%, 50%, 40%, 25% B, and 0% B (monochromatic R) on the photosynthetic performance and biomass partitioning as well as morphological and biochemical characteristics of saffron. The growth of flower, root, and corm was improved by increasing the proportion of B to R light. B-grown plants were characterized by the highest photosynthetic functionality with efficient electron transport and lower energy dissipation when compared to R-grown plants. B light directed biomass toward the corms and floral organs, while R light directed it toward the leaves. In saffron, the weight of a daughter corm is of great importance since it determines the yield of the next year. As the ratio of B to R light increased, the daughter corms also became heavier, at the cost of reducing their number, though increasing the proportion of B-enhanced antioxidant capacity as well as the activity of ascorbate peroxidase and catalase while superoxide dismutase activity was enhanced in R-grown plants. In conclusion, B light increased the production of high-quality daughter corms and altered biomass partitioning towards harvestable organs (corms and flowers) in saffron plants. Full article

To investigate the importance of light on healing and acclimatization, in the present study, grafted watermelon seedlings were exposed to darkness (D) or light, provided by blue (B), red (R), a mixture of R (68%) and B (RB), or white (W; 35% B, 49% intermediate spectra, 16% R) LEDs for 12 days. Survival ratio, root and shoot growth, soluble carbohydrate content, photosynthetic pigments content, and photosynthetic performance were evaluated. Seedling survival was not only strongly limited in D but the survived seedlings had an inferior shoot and root development, reduced chlorophyll content, and attenuated photosynthetic efficiency. RB-exposed seedlings had a less-developed root system. R-exposed seedlings showed leaf epinasty, and had the smallest leaf area, reduced chlorophyll content, and suppressed photosynthetic apparatus performance. The R-exposed seedlings contained the highest amount of soluble carbohydrate and together with D-exposed seedlings the lowest amount of chlorophyll in their scions. B-exposed seedlings showed the highest chlorophyll content and improved overall PSII photosynthetic functioning. W-exposed seedling had the largest leaf area, and closely resembled the photosynthetic properties of RB-exposed seedlings. We assume that, during healing of grafted seedlings monochromatic R light should be avoided. Instead, W and monochromatic B light may be willingly adopted due to their promoting effect on shoot, pigments content, and photosynthetic efficiency. Full article

Cuprous oxide (Cu₂O) homojunction thin films on Ti substrates were fabricated by an electrochemical deposition in which a p-Cu₂O layer was deposited on an n-Cu₂O layer by carefully controlled bath conditions. It was found that the open-circuit voltage of the homojunction solar cell was significantly influenced by the pH of the lactate bath. The variation of the pH was used to achieve the best possible crystal orientation for homojunctions. The crystallinity and morphology of the products were characterized by X-ray diffraction (XRD), high-energy x-ray diffraction (HEXRD), and scanning electron microscopy (SEM). The current density voltage (J-V) analysis showed that the sulfur treatment and annealing enhanced the photocurrent by ten-fold compared to the untreated and unannealed homojunction solar cell. X-ray photoelectron spectroscopy (XPS) studies confirmed that the sulfur treatment eliminated the surface CuO and formed a thin layer of CuS, which was very useful to make the front Ohmic contact. Transient measurements confirmed that the p-type Cu₂O layer, which was subjected to sulfur treatment, significantly reduced the recombination, thus enhancing the efficiency of the solar cell. The best sulfur treated annealed Ti/n-Cu₂O/p-Cu₂O/Au solar cell produced an energy conversion efficiency of 2.64% with an open-circuit voltage of 490 mV and a short circuit current density of 12.8 mA cm⁻² under AM 1.5 illumination. Full article