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.

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.

Pigment cell composition, pigment content, tyrosinase content and activity analysis were investigated on three kinds of loaches Misgurnus anguillicaudatus; blackspot loaches (BBL), small blackspot loaches (SBL), and non-blackspot loaches (NBL), from Poyang Lake. Results showed that there were three types of skin pigment cells, namely, melanophores, xanthophores and iridophores. Melanophores in dorsum were more than in abdomen. Melanophore cytosomes in BBL were larger than those in SBL and NBL, and melanosomes were the largest in stage four. The melanophores in dorsal skin of SBL or NBL were small cell bodies, spindle-like, and in chain distribution. There was an extremely significant difference in melanin content in BBL between the dorsum and abdomen (P<0.01). There were no significant differences in melanin abdominal content, lutein and carotenoid contents among three kinds of loaches (P>0.05). In dorsal skin, tyrosinase content was the highest in BBL, and it was significantly lower in NBL than in BBL and SBL (P<0.01). This study reveals differences in pigment and tyrosinase content in three kinds of loaches and provides a theoretical basis for further study of the mechanism of black spot formation. This article is protected by copyright. All rights reserved.

Acid rain is considered one of the most serious plant abiotic stresses. Photosynthesis is the basis of crop growth and development. The effect of acid rain on barley photosynthesis remains unclear. A glasshouse experiment was conducted, and the photosynthetic rate, chlorophyll (Chl) fluorescence, and pigment content of barley were measured in simulated acid rain (SAR) under pH 6.5, 5.5, 4.5, and 3.5. The results showed that net photosynthetic rate, maximal photosynthetic rate, and light saturation point decreased and the light compensation point, and dark respiration rate increased with increasing acidity. The results suggested that photosynthesis in barley plants was inhibited by SAR stress. The Chl content and stomatal conductance declined in parallel with the reduced net photosynthetic rate when barley plants were under SAR stress conditions. This indicated that non-stomatal factors may contribute to reduced photosynthesis under acid rain stress. Acid rain had greater effects on the photosynthesis of the acid rain-sensitive plant Zhepi 33 than on non-sensitive Kunlun 12. A significant difference in parameters such as the maximal fluorescence, variable fluorescence, and active PSII reaction centers was found among the SAR treatments and may be used to evaluate the sensitivity of plants to acid rain stress. The visualization model showed that the photosynthetic reaction centers were inactivated in acid rain stressed barley plants. These findings are valuable for the evaluation of the plant sensitivity to acid rain stress and may be used for the detection and monitoring of acid rain effects on plants in the future.

Ornamental kale is popular because of its colorful leaves and few studies have investigated the mechanism of color changes. In this study, an ornamental kale line (S2309) with three leaf colors was developed. Analysis of the anthocyanin, chlorophyll, and carotenoid contents and RNA-seq were performed on the three leaf color types. There was less chlorophyll in the white leaves and purple leaves than in the green leaves, and the anthocyanin content was greatest in the purple leaves. All the downregulated DEGs related to chlorophyll metabolism were detected only in the S2309_G vs. S2309_W comparison, which indicated that the decrease in chlorophyll content was caused mainly by the inhibition of chlorophyll biosynthesis during the leaf color change from green to white. Moreover, the expression of 19 DEGs involved in the anthocyanin biosynthesis pathway was upregulated. These results provide new insight into the mechanisms underlying the three-color formation.

The multiple-contamination of heavy metals and nutrients worsens increasingly and Ulva sp. green tide occurs almost simultaneously. To reveal the biological mechanism for outbreak of the green tide, Ulva pertusa was exposed to seven-day-multiple-contamination. The relation between pH variation (VpH), Chl a content, ratio of (Chl a content)/(Chl b content) (Rchla/chlb), SOD activity of U. pertusa (ASOD) and contamination concentration is [Formula: see text] (p<0.05), Cchla=0.88±0.09-0.01±0.00×CCd (p<0.05), [Formula: see text] (p<0.05), and [Formula: see text] (p<0.05), respectively. Cammonia, CCd and CZn is concentration of ammonia, Cd2+ and Zn2+, respectively. Comparing the contamination concentrations of seawaters where Ulva sp. green tide occurred and the contamination concentrations set in the present work, U. pertusa can adapt to multiple-contaminations in these waters. Thus, the adaption to multiple-contamination may be one biological mechanism for the outbreak of Ulva sp. green tide.

Chlorophyll content, one of the most important physiological parameters related to plant photosynthesis, is usually used to predict yield potential. To map the quantitative trait loci (QTLs) underlying the chlorophyll content of rice leaves, a double haploid (DH) population was developed from an indica/japonica (Zhenshan 97/Wuyujing 2) crossing and two backcross populations were established subsequently by backcrossing DH lines with each of their parents. The contents of chlorophyll a and chlorophyll b were determined by using a spectrophotometer to directly measure the leaf chlorophyll extracts. To determine the leaf chlorophyll retention along with maturation, all measurements were performed on the day of heading and were repeated 30 days later. A total of 60 QTLs were resolved for all the traits using these three populations. These QTLs were distributed on 10 rice chromosomes, except chromosomes 5 and 10; the closer the traits, the more clustering of the QTLs residing on common rice chromosomal regions. In general, the majority of QTLs that specify chlorophyll a content also play a role in determining chlorophyll b content. Strangely, chlorophyll content in this study was found mostly to be lacking or to have a negative correlation with yield. In both backcross F1 populations, overdominant (or underdominant) loci were more important than complete or partially dominant loci for main-effect QTLs and epistatic QTLs, thereby supporting previous findings that overdominant effects are the primary genetic basis for depression in inbreeding and heterosis in rice.