Background: Developing algal industries in saline-alkali areas is necessary. However, suitable strains and optimal production conditions must be studied before widespread commercial use. Objectives: The effects of light, temperature, KNO₃, and CO(NH₂)₂ on beta-carotene and biomass accumulation were compared and evaluated in order to provide scientific guidance for commercial algal production in northeastern Thailand. Materials and Methods: An orthogonal design was used for evaluating optimal conditions for the algal production of three candidate Dunaliella salina strains (KU XI, KU 10 and KU 31) which were isolated from saline soils and cultured in the column photobioreactor. Results: The optimal light and temperature for algae growth were 135.3 μmol m^-2 s^-1 and 22°C, while the conditions of 245.6 μmol m^-2 s^-1 and 22°C induced the highest level of beta-carotene production (117.99 mg L^-1). The optimal concentrations of KNO₃, CO(NH₂)₂, and NaHCO₃ for algae growth were 0.5 g L^-1, 0.36 g L^-1, and 1.5 g L^-1, respectively, while 0, 0.12 g L^-1 and 1.5 g L^-1 were best suited for beta-carotene accumulation. The highest beta-carotene rate per cell appeared with the highest light intensity (12.21 pg) and lowest temperature (12.47 pg), and the lowest total beta-carotene content appeared at the lowest temperature (15°C). There was not a significant difference in biomass accumulation among the three Dunaliella strains; however, the beta-carotene accumulation of KU XI was higher than that of the other two strains. Conclusions: Light and temperature were both relevant factors that contributed to the growth and beta-carotene accumulation of the three D. salina strains, and NaHCO₃ had significantly positive effects on growth. The degree of impact of the different factors on cell growth was temperature > NaHCO₃ > light intensity > KNO₃ > CO (NH₂)₂ > strains; the impact on beta-carotene accumulation was temperature > light intensity > KNO₃ > CO (NH₂)₂ > strains > NaHCO₃ Keywords: Beta-carotene; Biomass; Chlorophyll; Dunaliella salina

Salt leaching of heavy coastal saline silty soil by controlling the soil matric potential | Xiuping Wang, Zhizhong Xue, Xuelin Lu, Yahui Liu, Guangming Liu, Zhe Wu | Agricultural Journals

An isolated Dunaliella salina (D. salina) KU XI from saline soils in northeastern Thailand was cultured in f/2 medium in column photobioreactor. The variations of the growth, chlorophyll and beta-carotene content and the maximum quantum yield of PS II photochemistry (F_v/F_m) under different NaH₂PO₄ concentrations were studied. Based on the results, the growth kinetics of D. salina KU XI was established, which could simulate the algae growth rate under different phosphate concentrations and temperatures. The phosphorus could significantly affect the growth and pigments accumulations of this isolated strain. Increasing NaH₂PO₄ concentration improved the biomass, the total chlorophyll and beta-carotene content, retarded the decrease of F_v/F_m value. The optimal phosphate concentration for the growth of D. salina KU XI was above 72.6 μM. The maximum biomass and beta-carotene were 0.24 g L^-1 and 17.4 mg L^-1 respectively when NaH₂PO₄ was 290.4 μM. The algae growth was restrained by phosphate or nitrate when NaH₂PO₄ below 12.1 μM or above 72.6 μM. It indicated that properly supplementing nitrate in the late growth stage with high phosphate concentration was favored for enhancing the growth and biomass production.

Introduction: Soil moisture, temperature, and salinity critically constrain cotton production in saline soils. Understanding how cotton photosynthetic characteristics and yield respond to seasonal water-heat-salt dynamics is essential for improving management practices in these challenging environments.Methods: A two-year field study (2015–2016) was conducted comparing cotton growth, photosynthetic characteristics, and yield in mildly, moderately, and severely salinized fields. Seasonal soil water-salt dynamics in the 0–200 cm layer were monitored.Results: seasonal rainfall and temperature fluctuations significantly influenced soil water-salt dynamics in the 0-140 cm layer. During spring (April-May), drought maintained soil salinity above 3 g/kg, while low temperatures delayed cotton germination by over a day. In rainy season (July-August), rainfall leached salts from topsoil (0-40 cm), reducing salinity to below 5 g/kg and alleviating salt stress. Mildly saline fields exhibited superior photosynthetic performance, with leaf area index, chlorophyll content, and canopy photosynthetic rate being 1.2–1.5 times higher than in moderate/severe fields. These fields also showed extended "source-sink" organ development periods (16–28 days for "source," 4–24 days for "sink") and 13.8%–18.8% greater boll weight, ultimately achieving a seed cotton yield of 3,303 kg/ha—34.3%–120.7% higher than yields from moderate/severe fields.Discussion: Our results indicate that excessive soil salinity primarily impairs photosynthetic capacity and disrupts photosynthate allocation to bolls. Strategic interventions like drip irrigation could mitigate salt stress while improving photosynthetic efficiency and yield, providing practical solutions for cotton cultivation in saline fields.

Utilizing salt-tolerant plants is a cost-effective strategy for agricultural production on salinized land. However, little is known about the mechanism of dandelion (Taraxacum mongolicum Hand.-Mazz.) in response to saline stress and caffeic acid biosynthesis. We investigated the morphological and physiological variations of two dandelions, namely, “BINPU2” (dandelion A) and “TANGHAI” (dandelion B) under gradient NaCl concentrations (0, 0.3%, 0.5%, 0.7%, and 0.9%), and analyzed potential mechanisms through a comparison analysis of transcriptomes in the two dandelions. Dandelion A had a high leaf weight; high ρ-coumaric acid, caffeic acid, ferulic acid, and caffeoyl shikimic acid contents; and high activities of POD and Pro. The maximum content of four kinds of phenolic acids mostly occurred in the 0.7% NaCl treatment. In this saline treatment, 2468 and 3238 differentially expressed genes (DEGs) in dandelion A and B were found, of which 1456 and 1369 DEGs in the two dandelions, respectively, showed up-regulation, indicating that more up-regulated DEGs in dandelion A may cause its high salt tolerance. Further, Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that dandelion salt response and caffeic acid metabolism were mainly enriched in the phenylpropanoid biosynthesis pathway (ko00940) and response to ethylene (GO: 0009723). The caffeic acid biosynthesis pathway was reconstructed based on DEGs which were annotated to PAL, C4H, 4CL, HCT, C3′H, and CSE. Most of these genes showed a down-regulated mode, except for parts of DEGs of 4CL (TbA05G077650 and TbA07G073600), HCT (TbA03G009110, TbA03G009080, and novel.16880), and COMT (novel.13839). In addition, more up-regulated transcription factors (TFs) of ethylene TFs in dandelion A were found, but the TFs of ERF104, CEJ1, and ERF3 in the two dandelions under saline stress showed an opposite expression pattern. These up-regulated genes could enhance dandelion salt tolerance, and down-regulated DEGs in the caffeic acid biosynthesis pathway, especially CSE (TbA08G014310) and COMT (TbA04G07330), could be important candidate genes in the synthesis of caffeic acid under saline stress. The above findings revealed the potential mechanisms of salt response and caffeic acid metabolism in dandelion under saline stress, and provide references for salt-tolerant plant breeding and cultivation on saline–alkali land in the future.