Reducing the Halotolerance Gap between Sensitive and Resistant Tomato by Spraying Melatonin

Salt stress is one of the primary abiotic stresses that negatively affects agricultural production. Melatonin, as a useful hormone in plants, has been shown to play positive roles in crop improvement to abiotic stress conditions. However, it remains unclear whether spraying melatonin could reduce the halotolerance gap between tomato genotypes with different salt sensitivities. Here, plant growth, H2O2 content, electrolyte leakage, antioxidant system, gas exchange, pigment content, and chloroplast ultrastructure of salt sensitive genotype (SG) and resistant genotype (RG) at CK (control), M (spraying melatonin), S (salt), and SM (spraying melatonin under salt stress) were investigated. The results showed that the weight, height, and stem diameter of the plant at SM from both genotypes significantly increased compared with S. The plant undergoing SM from both genotypes showed significantly decreased H2O2 but increased activity of SOD, APX, GR, and GSH, as well as net photosynthetic rate and Fv/Fm, as compared with S. The ratio between SM and S (SM/S) of SG was significantly higher than that of RG in terms of plant height and stem diameter, whereas antioxidant parameters, H2O2 content, and electrolyte leakage showed no difference between RG and SG in SM/S. The SM/S of SG in terms of photosynthetic parameters and pigment content were significantly higher than that of RG. Chloroplast ultrastructure showed remarkable changes under salt stress, whereas spraying melatonin reduced the destruction of chloroplasts, especially for SG. We concluded that spraying melatonin reduces the halotolerance gap between SG and RG by photosynthesis regulation instead of the antioxidant mechanism. This indicated that the positive roles of melatonin on tomato plants at salt stress depend on the genotype sensitivity.

The Effects of Environmental Contaminants on Freshwater Cyanobacteria

<p>Cyanobacteria are photosynthetic prokaryotes with a cosmopolitan distribution and are key contributors to Earth’s primary production. In favourable conditions, some taxa have the ability to form dense algal blooms. When blooms are created by toxin-producing strains they can become a public health threat and may lead to deaths of wild and domestic animals. Different species and strains respond differently to environmental conditions and contaminants, and this thesis investigates the impacts of natural (microcystin, a hepatotoxic cyanotoxin) and anthropogenic (glyphosate) contaminants on cyanobacteria. Some non-microcystin-producing cyanobacteria have the ability to sequester microcystin, one of them being the strain Cuspidothrix issatschenkoi CAWBG02, and the reason for this ability is unknown. This strain was supplemented with microcystin in a range of environmental conditions (temperature/light intensity combinations) to determine any impacts on fitness by measuring photosynthetic performance, growth, and pigment content (chlorophyll-a and phycocyanin). Microcystin supplementation at a concentration of 25 μg L-1 did not have an effect on growth or pigment content in C. issatschenkoi, and photosynthetic performance was also largely unaffected. Based on the results from this thesis, C. issatschenkoi does not acquire competitive advantages from microcystin sequestration due to the lack of effects on growth and photosynthetic functioning. Previous research has suggested that microcystin is used to suppress competitors, and a 33% decrease in maximum quantum yield was detected in one environmental condition (low temperature, intermediate light), however, there was no significant difference in all of the other conditions used. Therefore, the results from this study do not support the idea that microcystin is used to suppress competitors. Microcystin sequestration may be more beneficial to non-producing-strains within the same species as the toxin-producer (e.g. non-toxic M. aeruginosa). Glyphosate and MCPA are two of the most commonly used herbicides in New Zealand and globally. These herbicides enter waterways through leaching and come into contact with non- target species. To determine whether these herbicides have an effect on freshwater cyanobacteria in New Zealand, a screening assay was carried out on fourteen strains. Further, the impacts on pigment content (chlorophyll-a and phycocyanin), growth, and photosynthetic performance in two toxic (Nodularia spumigena, Microcystis aeruginosa) and two non-toxic (Dolichospermum lemmermannii, Microcystis wesenbergii) strains were quantified. Growth rates were not impacted by MCPA in any of the fourteen cyanobacterial strains. Glyphosate impacted growth in seven of the fourteen strains, and response differed between strains even within a single species. In general, strains employing a colonial growth strategy were more tolerant to glyphosate in the screening assay. N. spumigena and M. wesenbergii were unaffected by glyphosate at the concentrations used in the functional analysis, and D. lemmermannii had decreased photosynthetic performance from glyphosate. Intermediate concentrations of glyphosate resulted in promotion of PSII functioning in M. aeruginosa, and high concentrations inhibited maximum quantum yield. The lack of significant impacts on M.wesenbergii and N. spumigena, as well as negative effects of PSII functioning in D. lemmermannii, suggest that glyphosate contamination in freshwaters may benefit toxic M. aeruginosa more than competing toxic and non-toxic species or strains.</p>

The Effects of Environmental Contaminants on Freshwater Cyanobacteria

<p>Cyanobacteria are photosynthetic prokaryotes with a cosmopolitan distribution and are key contributors to Earth’s primary production. In favourable conditions, some taxa have the ability to form dense algal blooms. When blooms are created by toxin-producing strains they can become a public health threat and may lead to deaths of wild and domestic animals. Different species and strains respond differently to environmental conditions and contaminants, and this thesis investigates the impacts of natural (microcystin, a hepatotoxic cyanotoxin) and anthropogenic (glyphosate) contaminants on cyanobacteria. Some non-microcystin-producing cyanobacteria have the ability to sequester microcystin, one of them being the strain Cuspidothrix issatschenkoi CAWBG02, and the reason for this ability is unknown. This strain was supplemented with microcystin in a range of environmental conditions (temperature/light intensity combinations) to determine any impacts on fitness by measuring photosynthetic performance, growth, and pigment content (chlorophyll-a and phycocyanin). Microcystin supplementation at a concentration of 25 μg L-1 did not have an effect on growth or pigment content in C. issatschenkoi, and photosynthetic performance was also largely unaffected. Based on the results from this thesis, C. issatschenkoi does not acquire competitive advantages from microcystin sequestration due to the lack of effects on growth and photosynthetic functioning. Previous research has suggested that microcystin is used to suppress competitors, and a 33% decrease in maximum quantum yield was detected in one environmental condition (low temperature, intermediate light), however, there was no significant difference in all of the other conditions used. Therefore, the results from this study do not support the idea that microcystin is used to suppress competitors. Microcystin sequestration may be more beneficial to non-producing-strains within the same species as the toxin-producer (e.g. non-toxic M. aeruginosa). Glyphosate and MCPA are two of the most commonly used herbicides in New Zealand and globally. These herbicides enter waterways through leaching and come into contact with non- target species. To determine whether these herbicides have an effect on freshwater cyanobacteria in New Zealand, a screening assay was carried out on fourteen strains. Further, the impacts on pigment content (chlorophyll-a and phycocyanin), growth, and photosynthetic performance in two toxic (Nodularia spumigena, Microcystis aeruginosa) and two non-toxic (Dolichospermum lemmermannii, Microcystis wesenbergii) strains were quantified. Growth rates were not impacted by MCPA in any of the fourteen cyanobacterial strains. Glyphosate impacted growth in seven of the fourteen strains, and response differed between strains even within a single species. In general, strains employing a colonial growth strategy were more tolerant to glyphosate in the screening assay. N. spumigena and M. wesenbergii were unaffected by glyphosate at the concentrations used in the functional analysis, and D. lemmermannii had decreased photosynthetic performance from glyphosate. Intermediate concentrations of glyphosate resulted in promotion of PSII functioning in M. aeruginosa, and high concentrations inhibited maximum quantum yield. The lack of significant impacts on M.wesenbergii and N. spumigena, as well as negative effects of PSII functioning in D. lemmermannii, suggest that glyphosate contamination in freshwaters may benefit toxic M. aeruginosa more than competing toxic and non-toxic species or strains.</p>

Effects of Iron-Oxide Nanoparticles (Fe3O4) Released From Synthesized Iron-based Thiourea Catalyst on the Growth, Cell Density, and Pigment Content of Chlorella Vulgaris

This study investigated the effects of Fe3O4 nanoparticles released from synthesized Thiourea catalyst to Chlorella vulgaris as an essential primary producer in aquatic systems. A range of Fe3O4 concentrations (0, 10, 100, 250, 500, 750, and 1000 mg L-1) was applied for the exposure test. Biological parameters of C. vulgaris, including cell density, cell viability, and pigment content were assessed. Bioconcentration factor and bioaccumulation were evaluated for contaminated microalgae. Non-carcinogenic risks were then assessed using target hazard quotient (THQ) for potential human consumptions. Findings showed that C. vulgaris cell numbers increased from 0 to 500 mg L-1 of Fe3O4. Chlorophyll a represented a time-dependent response, and greatest values were detected in 250 and 500 mg L-1 Fe3O4 at 4.2 and 4 mg/g, respectively. Chlorophyll b content showed a time-related manner in exposure to Fe3O4 with the highest values recorded at 250 mg L-1 after 96 h. Moreover, bioaccumulation displayed a dose-dependent response as bioaccumulated iron was in the largest amount at 15000 µg/g dw in 1000 mg L-1, whereas the lowest one was in the control group at 1700 µg/g dw. The bioconcentration factor showed a concentration-relevant decrease in all iron treatments and 10 mg L-1 of Fe3O4 represented the greatest BCF at 327.3611. Non-carcinogenic risks illustrated negligible hazard (THQ < 1) in a dose-response pattern and the largest EDI and THQ were calculated in 1000 mg L-1 at 7.4332E-07 (mg kg-1 day-1) and 1.06189E-09, respectively. In essence, iron is an essential trace element for biological aspects in aquatic systems, but in exceeding concentrations could impose toxicity effects in C. vulgaris populations.

Enhancing Microalgae Cultivation using Biowastes as Growth Media for High Added-Value Co-Products Generation

This paper aims to study a new growth media using cheese whey and drainage water from agriculture for indigenous microalgae cultivation for value-added product generation. In this context, four combinations are studied beside the BG11 as reference, where BG11/Cheese whey (60/40, %v/v), drainage water 100%, drainage water/Cheese whey (60/40, % v/v), and Cheese whey 100 % have been used. Moreover, investigated parameters are biomass dry weight, pH variation, total chlorophyll and carotenoid content. Results showed that used growth media have a significant impact on microaglae culture, particularly in terms of cells growth, pigment content and pH variation. Moreover, the mixture BG11/Cheese whey (60/40, %v/v) shows the best impact for total chlorophylls and carotenoids content. Likewise, the mixture cheese whey/drainage water (60/40, %v/v) presents a positive effect on pigments content. The use of cheese whey and drainage water lead to enhance the biomass and pigment production. This study showed that using agro-industrial C-rich wastes and drainage water enhanced microalgae biomass and pigment content, thus contributing to pollution abatement. This will contribute to both reducing the cost of production and resources recycling.

​Standardization of Cold Solvent Extraction Parameters for Natural Red Pigments

Background: Selecting an appropriate extraction technique and optimization of extraction conditions must be done to improve the efficiency and productivity of natural colorant. Methods: Flesh and peels of four different raw materials viz., beetroot, carrot, pomegranate and grape were extracted independently using 100% ethyl alcohol using cold solvent extraction method adopting 1: 1 and 1: 2 w/v solid to solvent ratio for 24 and 48 hrs, forming 8 treatments replicated thrice in three factorial CRD. The collected extracts were evaporated at 60oC; per cent yield and pigment content were calculated. Result: Extract yield and pigment content were significantly influenced by raw material, solid to solvent ratio and duration of extraction. Extract yield was higher in flesh of carrot and beetroot as well as in peels of grape and pomegranate. Anthocyanin content in grape and pomegranate and betalain content in beetroot were high in peel where as β-carotene content was higher in carrot flesh extract. Per cent yield and pigment content increased with increased duration of extraction and solid to solvent ratio. Requirement of more solvent and longer extraction time are the drawback of conventional extraction methods and there is a growing demand for non-conventional techniques to enhance yield and maintain pigment stability.

Leaf Color Changes and Photosynthetic Characteristics of Five Superior Late-deciduous Ginkgo biloba Cultivars

Ginkgo biloba, a relict plant, has been popularized and planted in most areas of China for its leaves, timber, and fruits. In the present study, the dynamic changes in leaf color, leaf pigment content during the color change period, and photosynthetic characteristics in different growth periods were studied to explore the coloring mechanism and adaptability of five late-deciduous superior Beijing G. biloba cultivars (LD1–LD5). The results showed that the leaf color change of each superior cultivar was relatively stable, and the discoloration period of LD3 and LD5 was later than that of others. From September to November, the chlorophyll a, chlorophyll b, and total chlorophyll content in all superior cultivars showed a downward trend, except in LD3, in which the pigment content was slightly higher in October than in September. Except in LD3 and LD4, the ratio of carotene content to total chlorophyll content in other cultivars slightly decreased in October. In May, the photosynthetic capacity of LD5 was stronger than that of other cultivars. The photosynthetic capacity of LD3 was strong in July and October. Our results imply that LD3 and LD5 are suitable for mixed planting with common G. biloba to increase the overall leaf color viewing period. Ginkgo biloba leaves turn yellow in autumn because of both a decrease in the chlorophyll content after leaf senescence and an increase in the Car content during leaf senescence. Although LD5 presented rapid seedling emergence, LD3 grew faster during the vigorous and late growth stages and is thus suitable for agricultural production.

Physiological Responses of Pocillopora acuta and Porites lutea Under Plastic and Fishing Net Stress

Marine debris has become a global problem affecting coral health around the globe. However, the photophysiological responses of corals to marine debris stress remain unclear. Therefore, this study firstly investigated transparent and opaque plastic bag shading and fishing nets directly contacting the coral. Photosynthetic performance, pigment content, symbiont density, and calcification rate of a branching coral Pocillopora acuta and a massive coral Porites lutea were investigated after 4 weeks of exposure to marine debris. The results show that the maximum quantum yield of PSII significantly decreased in P. lutea with all treatments, while P. acuta showed no effect on the maximum quantum yield of PSII from any treatments. Transparent plastic bag shading does not affect P. acuta, but significantly affected the maximum photochemical efficiency of P. lutea. Photoacclimation of cellular pigment content was also observed under opaque plastic bag shading for both species at week 2. Fishing nets had the strongest effect and resulted in P. acuta bleaching and P. lutea partial mortality as well as a decline in zooxanthellae density. Calcification rate of P. acuta significantly decreased with treatments using opaque plastic bag and fishing net, but for P. lutea only the treatment with fishing net gave any observable effects. This study suggests that the sensitivities of corals to marine debris differ strongly by species and morphology of the coral.