Four strains of green microalgae (Scenedesmus acutus, Scenedesmus vacuolatus, Chlorella sorokiniana, and Chlamydomonas reinhardtii) were compared to determine growth and pigment composition under photoautotrophic or heterotrophic conditions. Batch growth experiments were performed in multicultivators with online monitoring of optical density. For photoautotrophic growth, light-limited (CO2-sufficient) growth was analyzed under different light intensities during the exponential and deceleration growth phases. The specific growth rate, measured during the exponential phase, and the maximal biomass productivity, measured during the deceleration phase, were not related to each other when different light intensities and different species were considered. This indicates species-dependent photoacclimation effects during cultivation time, which was confirmed by light-dependent changes in pigment content and composition when exponential and deceleration phases were compared. Except for C. reinhardtii, which does not grow on glucose, heterotrophic growth was promoted to similar extents by acetate and by glucose; however, these two substrates led to different pigment compositions. Weak light increased the pigment content during heterotrophy in the four species but was efficient in promoting growth only in S. acutus. C. sorokiniana, and S. vacuolatus exhibited the best potential for heterotrophic biomass productivities, both on glucose and acetate, with carotenoid (lutein) content being the highest in the former.

Brassinosteroids (BRs) are a group of polyhydroxylated steroids for plant growth and development, regulating numerous physiological and biochemical processes and participating in multi-pathway signaling in plants. 24-Epibrassinolide (EBR) is the most commonly used BR for the investigation of the effects of exogenous steroidal phytohormones on plant physiology. Although SlSERK3B is considered a gene involved in the brassinosteroid (BR) signaling pathway, its specific role in plant growth and development has not been reported in detail. In this study, tomato (Solanum lycopersicum L.) seedlings treated with 0.05 μmol L-1 EBR showed a significant increase in plant height, stem diameter, and fresh weight, demonstrating that BR promotes the growth of tomato seedlings. EBR treatment increased the expression of the BR receptor gene SlBRI1, the co-receptor gene SlSERK3A and its homologs SlSERK3B, and SlBZR1. The SlSERK3B gene was silenced by TRV-mediated virus-induced gene silencing (VIGS) technology. The results showed that both brassinolide (BL) content and BR synthesis genes were significantly up-regulated in TRV-SlSERK3B-infected seedlings compared to the control seedlings. In contrast, plant height, stem diameter, fresh weight, leaf area and total root length were significantly reduced in silenced plants. These results suggest that silencing SlSERK3B may affect BR synthesis and signaling, thereby affecting the growth of tomato seedlings. Furthermore, the photosynthetic capacity of TRV-SlSERK3B-infected tomato seedlings was reduced, accompanied by decreased photosynthetic pigment content chlorophyll fluorescence, and photosynthesis parameters. The expression levels of chlorophyll-degrading genes were significantly up-regulated, and carotenoid-synthesising genes were significantly down-regulated in TRV-SlSERK3B-infected seedlings. In conclusion, silencing of SlSERK3B inhibited BR signaling and reduced photosynthesis in tomato seedlings, and this correlation suggests that SlSERK3B may be related to BR signaling and photosynthesis enhancement.

Environmental pollution is considered to lead to Ulva sp. green tides. Nevertheless, nutrients with high concentrations inhibit algae which may be damaged by antibiotics, such as OTC (oxytetracycline). Thus, Ulva sp. algae might pay a physiological cost under nutrient-OTC combined pressures. If this hypothesis is confirmed, Ulva sp. algae cannot easily form green tides, or green tides are difficult to maintain. To test this hypothesis, an uniform design experiment during which OTC, ammonia (NH4-N) and phosphate (PO4-P) were factors was set to simulate nutrient-OTC combined pressures, and Ulva lactuca was exposed to the pressures for 96 h. The TN (total nitrogen, CTN) or TP (total phosphorus, CTP) content in U. lactuca increased with increasing nutrient concentrations, as CTN = 21.206±1.000+ 1.227±0.418NH4-N × PO4-P (R2 = 0.282, p < 0.05) and CTP = 1.886±0.266+ 0.877±0.126PO4-P (R2 = 0.689, p < 0.05), respectively. The increase in dry weight of U. lactuca (Wdry) had a relationship with combined pressures, Wdry = 0.011±0.029 - 0.036±0.014PO4-P (R2 = 0.243, p < 0.05), i.e., the algal growth was inhibited by increasing PO4-P concentration. The SOD (Superoxide dismutase) activity (ASOD) was stimulated by OTC, as ASOD = 127.868±8.741+9.587±4.179 OTC (R2 = 0.193, p < 0.05). The contents of Chl a and b (Ca and Cb) were negatively affected by OTC or PO4-P with high concentration, as Ca = 0.566±0.042 - 0.024±0.022 OTC × PO4-P (R2 = 0.179, p < 0.05) and Cb = 0.512±0.043-0.044±0.020PO4-P (R2 = 0.180, p < 0.05). Thus, too high concentrations of PO4-P or OTC may hinder the formation and maintenance of Ulva sp. green tides.

The Bouguer-Lambert-Beer (BLB) law serves as the fundamental basis for the spectrophotometric determination of pigment content in microalgae. Although it has been observed that the applicability of the BLB law is compromised by the light scattering effect in microalgae suspensions, in-depth research concerning the relationship between the light scattering effect and the accuracy of spectrophotometric pigment determination remains scarce. We hypothesized that (1) the precision of spectrophotometric pigment content determination using the BLB law would diminish with increasing nonlinearity of absorbance, and (2) employing the modified version of the BLB (mBLB) law would yield superior performance. To assess our hypotheses, we cultivated Phaeodactylum tricornutum under varying illumination conditions and nitrogen supplies in controlled indoor experiments, resulting in suspensions with diverse pigment contents. Subsequently, P. tricornutum samples were diluted into subsamples, and spectral measurements were conducted using different combinations of biomass concentrations and path lengths. This was carried out to assess the applicability of the BLB law and the nonlinearity of absorbance. The chlorophyll a and fucoxanthin contents in the samples were analyzed via high-performance liquid chromatography (HPLC) and subsequently used in our modeling. Our findings confirm our hypotheses, showing that the modified BLB law outperforms the original BLB law in terms of the normalized root mean square error (NRMSE): 6.3% for chlorophyll a and 5.8% for fucoxanthin, compared to 8.5% and 7.9%, respectively.

The duration and intensity of freezing stress are the most critical factors determining injury in autumn chickpeas, limiting their production and development. To evaluate the effects of freezing temperature and duration on the survival rate (SU%), as well as the physiological and biochemical characteristics of autumn chickpea seedlings, a study was conducted using five different temperatures (0, -6, -8, -10, and -12°C) and five different durations (1 h, 2 h, 3 h, 4 h, and 5 h) of exposure to freezing stress. The SU% of chickpea seedlings decreased to zero after exposure to temperatures of -10°C and -12°C for 5 hours. As the temperature decreased from -8°C to -12°C and the duration of exposure to freezing stress increased from 1 to 5 hours, the leaf membrane stability index decreased by 33%, 48%, 46%, 57%, and 58%, respectively. The highest and lowest total pigment contents were observed after 1 hour at 0°C and 5 hours at -12°C, respectively. The maximum photochemical efficiency of photosystem II (Fv\'/Fm\') was not affected by temperatures as low as -8°C in any of the time treatments during the recovery period. However, this parameter\'s value decreased as the freezing stress duration increased. At -12°C, the activity of ascorbate peroxidase, catalase, and peroxidase increased by 44.6%, 38.3%, and 33.0%, respectively, as the duration of stress was increased from 1 hour to 5 hours. A positive and significant correlation was observed between plant dry weight, membrane stability index, photosynthetic pigment content, and Fv\'/Fm\' with SU% after exposure to freezing stress. The minimum temperature and the maximum duration of freezing stress tolerance in chickpea seedlings were observed at -12°C for two hours. Our findings confirm that prolonging the freezing duration disrupts the defense mechanisms of chickpea seedlings. Therefore, future studies on breeding chickpeas tolerant to freezing stress should concentrate on attributes strongly correlated with SU%.

Tomato (Solanum lycopersicum) seedlings were exposed by foliar or root applications to Zn in different nanoscale and non-nanoscale forms (40 mg Zn/L) under hydroponic conditions for 15 days. Under foliar exposure, ZnO QDs significantly promoted tomato growth, while ZnO NPs and BPs had lower impacts. ZnO QDs increased fresh weight and plant height by 42.02 % and 21.10 % relative to the untreated controls, respectively. The ionic control (ZnSO4·7H2O, 176.6 mg/L) decreased fresh weight by 39.31 %. ZnO QDs also significantly increased the Chla/Chlb ratio, as well as carotenoids and protein content by 7.70 %, 8.90 % and 26.33 %, respectively, over the untreated controls, suggesting improvement in seedling photosynthetic performance. Antioxidant enzyme (POD, PPO and PAL) activities in ZnO QDs treated shoots were significantly decreased by 31.1 %, 17.8 % and 48.3 %, respectively, indicating no overt oxidative damage from exposure. Importantly, the translocation factor of Zn (TFZn) in the foliar exposure of the ZnO QDs treatment was 73.2 %, 97.1 % and 276.9 % greater than the NPs, BPs, and ionic controls, respectively. Overall, these findings clearly demonstrate that foliar spray of nanoscale nutrients at the appropriate concentration and size can significantly increase crop growth and be a sustainable approach to nano-enabled agriculture.

With developments in industry, petroleum and heavy metal pollution are increasingly affecting soil, significantly harming the environment, biosecurity, and human health. Therefore, the remediation of contaminated soil is becoming increasingly important. In this study, ryegrass (Lolium perenne L.) was planted in petroleum-heavy metal co-contaminated soil with the application of nitrogen and phosphorus fertilizers. Three treatments were set up: uncontaminated soil + ryegrass (SH); petroleum-heavy metal co-contaminated soil + ryegrass (SPGH); and petroleum-heavy metal co-contaminated soil + ryegrass + nitrogen and phosphorus fertilizer (SPGH + NP). The results showed that the petroleum-heavy metal co-contamination promoted increases in the root length, surface area, volume, and diameter of ryegrass roots, increasing the below-ground biomass and decreasing the photosynthetic pigment content in the early stages of the experiment. The ratios of chlorophyll a/b and chlorophyll/carotenoid also increased. However, the application of fertilizer reduced the length, surface area, volume, and diameter of ryegrass roots in the co-contaminated soil, and the below-ground biomass decreased while the above-ground biomass increased. Furthermore, the photosynthetic pigment content was significantly higher than that in the unfertilized treatment and the chlorophyll a/b ratio decreased while the chlorophyll/carotenoid ratio increased. Therefore, fertilizers could alleviate the toxic effects of petroleum-heavy metal combined pollution on ryegrass roots and promote the synthesis of chlorophyll and other pigments, thus reducing the inhibitory effect of petroleum-heavy metal combined pollution on ryegrass growth and facilitating the remediation of the polluted soil.

The coloration of the apple fruit (Malus × domestica Borkh.) depends on pigment content. Light stimulus activates a broad range of photosynthesis-related genes, including carotenoids. The effect of light on two red commercial apple cultivars, \'Summer Prince\' and \'Arisoo\' at the juvenile stage were examined. Apple fruits were either bagged to reduce light irradiation or were exposed to direct, enhanced sunlight (reflected). The pigment content and the expression of carotenoid metabolism genes in the peel and flesh of apple fruits were significantly different between the shaded and the reflected parts. These parameters were also different in the two cultivars, highlighting the contribution of the genetic background. Further, a combination of light and transient overexpression of carotenogenic genes increased fruit coloration and pigment content in the variety \'RubyS\'. Western blot analysis showed the expression of small heat shock proteins (smHSP) in lysates extracted from the reflected part of the fruits but not in the bagged fruits, indicating the activation of smHSP in response to heat generated by the reflected light. Therefore, the synergy between the genes and the environment dictates the color of apple fruits.

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.

Chlorella ellipsoidea is a freshwater green microalga that has great prospect for the sustainable development of aquaculture industry. Microalgae require optimal lighting conditions for efficient photosynthesis. The key to cost-effective algal biomass production is to optimize algae growth conditions. This study aimed to investigate the effects of various wavelengths viz. white (380-750 nm), green (510 nm), blue (475 nm), and red (650 nm) light-emitting diodes (LEDs) on the growth, pigment content (chlorophyll-a, chlorophyll-b, and β-carotene), and proximate composition of C. ellipsoidea with a photoperiod of 12 h:12 h light: dark cycle under indoor environmental conditions. C. ellipsoidea was cultured in Bold\'s Basal Medium for 18 days. The cell density (125.36×105 cells ml-1), cell dry weight (58.9 ± 4.57 mg L-1), optical density (1.66 ± 0.08 g L-1), chlorophyll-a (7.31 ± 0.04 μg ml-1), chlorophyll-b (2.73 ± 0.13 μg ml-1), and β-carotene (0.39 ± 0.04 μg ml-1) content of C. ellipsoidea were significantly (P < 0.05) higher at 15th-day when cultured under blue LED light exposure. Significantly lower growth and nutritional values were obtained under red LED light exposure compared to the control and other LEDs spectra. In Pearson correlation analysis, the cell density and cell dry weight values showed a strong positive correlation with the values of pigment contents of C. ellipsoidea in all the treatments. The LEDs light spectra showed significant effects on proximate composition of C. ellipsoidea. Protein and lipid contents of C. ellipsoidea were significantly higher in blue LED growth conditions compared to white, green, and red LEDs. C. ellipsoidea cells were 3-7.04 μm in size and the maximum area of the cell was 38.94 μm2 in blue LED treatment. Results of this study demonstrated that blue LED light spectra was the most suitable condition to induce nutritionally rich biomass production of C. ellipsoidea, which can be used as a potential source of fish feed towards sustainable aquaculture.