Silicon Improves Ion Homeostasis and Growth of Liquorice (Glycyrrhiza Uralensis Fisch. and Glycyrrhiza Inflata Bat.) Under Salt Stress by Reducing Plant Na+ Uptake

Silicon effectively alleviates the damage caused by salt stress in plants and can improve plant salt tolerance. However, the details of the mechanism by which silicon improves salt tolerance of liquorice are limited, and the effects of foliar application of silicon on different liquorice species under salt stress are not known. Here, the effects of foliar spray of silicon on the growth, physiological and biochemical characteristics, and ion balance of Glycyrrhiza uralensis Fisch. and Glycyrrhiza inflata Bat. were investigated. High salt stress resulted in the accumulation of a large amount of Na+, decreased photosynthetic pigment content, perturbed ion homeostasis, and eventually inhibited the both liquorice species growth. These effects were more pronounced in G. uralensis, as G. inflata is more salt tolerant than G. uralensis. Foliar spraying of silicon effectively reduced the decomposition of photosynthetic pigments, improved gas exchange parameters, and promoted photosynthesis. It also effectively inhibited lipid peroxidation and electrolyte leakage and enhanced osmotic adjustment of plants. Further, silicon application increased the K+ concentration, reduced Na+ absorption, transport and accumulation in the plants. The protective effects of silicon were more pronounced in G. uralensis than those in G. inflata. In conclusion, silicon reduces Na+ absorption, improves ion balance, and alleviates the negative effects of salt stress in the two liquorice species studied, but the effect is liquorice species-dependent. These findings may inform novel strategies for protecting liquorice plants against salt stress and also provide a theoretical basis for the evaluation of salt tolerance and the scientific cultivation of liquorice.

Molecular Characterization of a Tolerant Saline-Alkali Chlorella Phosphatidate Phosphatase That Confers NaCl and Sorbitol Tolerance

The gene encoding a putative phosphatidate phosphatase (PAP) from tolerant saline-alkali (TSA) Chlorella, ChPAP, was identified from a yeast cDNA library constructed from TSA Chlorella after a NaCl treatment. ChPAP expressed in yeast enhanced its tolerance to NaCl and sorbitol. The ChPAP protein from a GFP-tagged construct localized to the plasma membrane and the lumen of vacuoles. The relative transcript levels of ChPAP in Chlorella cells were strongly induced by NaCl and sorbitol as assessed by northern blot analyses. Thus, ChPAP may play important roles in promoting Na-ion movement into the cell and maintaining the cytoplasmic ion balance. In addition, ChPAP may catalyze diacylglycerol pyrophosphate to phosphatidate in vacuoles.

Acclimation with humic acids enhances maize and tomato tolerance to salinity

Background Salinity is one of the major environmental threats to agriculture, limiting plant growth and reducing crop yield. The use of humic substances to alleviate salt stress in plants is well reported, but the mechanisms remain unclear. This work aimed to apply humic acids on seedlings to acclimate plants to tolerate further salt stress exposition as a pre-treatment. Materials and methods Two independent experiments with mono (maize) and dicot (tomato) seedlings were carried out. Maize was primed by humic acids (4 mM C) and further submitted to moderate salinity exposition (60 mM NaCl). The acclimation period of maize seedlings was characterized by ion balance and transcriptomic analysis of salt response genes. The tomato seedlings were also primed by humic acids (4 mM C) and exposed further to salinity (200 mM NaCl), and we measured only physiological aspect, including the activity of plasma membrane proton pumps and net photosynthesis rate. Results Seedlings primed by humic acids minimized the salinity stress by changing ion balance, promoting plasma membrane proton pumps activity and enhancing photosynthesis rate and plant growth. We showed for the first time that maize seedlings treated with humic acids had a high transcription level of salt responsive genes and transcription factors even before the salt exposition. Conclusion Humic acids previously activate cellular and molecular salt defence machinery, anticipating the response and reducing salinity stress. This is a key knowledge to manipulate manufactured biostimulants based on humic substances towards a maximized crop protection. Graphic abstract

Exogenous melatonin improves the salt tolerance of cotton by removing active oxygen and protecting photosynthetic organs

Background As damage to the ecological environment continues to increase amid unreasonable amounts of irrigation, soil salinization has become a major challenge to agricultural development. Melatonin (MT) is a pleiotropic signal molecule and indole hormone, which alleviates the damage of abiotic stress to plants. MT has been confirmed to eliminate reactive oxygen species (ROS) by improving the antioxidant system and reducing oxidative damage under adversity. However, the mechanism by which exogenous MT mediates salt tolerance by regulating the photosynthetic capacity and ion balance of cotton seedlings still remains unknown. In this study, the regulatory effects of MT on the photosynthetic system, osmotic modulators, chloroplast, and anatomical structure of cotton seedlings were determined under 0–500 μM MT treatments with salt stress induced by treatment with 150 mM NaCl. Results Salt stress reduces the chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, PSII photochemical efficiency, PSII actual photochemical quantum yield, the apparent electron transfer efficiency, stomata opening, and biomass. In addition, it increases non-photochemical quenching. All of these responses were effectively alleviated by exogenous treatment with MT. Exogenous MT reduces oxidative damage and lipid peroxidation by reducing salt-induced ROS and protects the plasma membrane from oxidative toxicity. MT also reduces the osmotic pressure by reducing the salt-induced accumulation of Na+ and increasing the contents of K+ and proline. Exogenous MT can facilitate stomatal opening and protect the integrity of cotton chloroplast grana lamella structure and mitochondria under salt stress, protect the photosynthetic system of plants, and improve their biomass. An anatomical analysis of leaves and stems showed that MT can improve xylem and phloem and other properties and aides in the transportation of water, inorganic salts, and organic substances. Therefore, the application of MT attenuates salt-induced stress damage to plants. Treatment with exogenous MT positively increased the salt tolerance of cotton seedlings by improving their photosynthetic capacity, stomatal characteristics, ion balance, osmotic substance biosynthetic pathways, and chloroplast and anatomical structures (xylem vessels and phloem vessels). Conclusions Our study attributes help to protect the structural stability of photosynthetic organs and increase the amount of material accumulation, thereby reducing salt-induced secondary stress. The mechanisms of MT-induced plant tolerance to salt stress provide a theoretical basis for the use of MT to alleviate salt stress caused by unreasonable irrigation, fertilization, and climate change.

Pengembangan LKPD Berbasis Model ARCS Pada Pokok Bahasan Kesetimbangan Ion dan pH Larutan Penyangga

This study aims to develop student worksheets based on the ARCS model on ionic equilibrium and pH of the buffer solution subject, determining the validity of student worksheets of the aspects of content, ARCS characteristics, language, presentation, graphics and find out user responses through student worksheets based on ARCS models on ionic equilibrium and pH buffer solution subject. This research is a Research and Development (R&D) with a 4-D development model. The object of this research is student worksheets based on the ARCS model. The data collection instruments were in the form of validation sheets given to three validators and user questionnaires given to teachers and students. After two revisions, the validity results obtained in the aspects of content, ARCS characteristics, language, presentation and graphics, respectively, namely 93.75%, 93.75%, 98.33%, 97.92% and 98%. the average score was 96.33% that comes to valid criteria. student worksheets which was valid by the validator tested one by one on 3 students who had studied the ion balance and pH of the buffer solution. Furthermore, asking for response to 3 chemistry teachers and 20 students resulted the teacher’s response and resultied a student response 91.07% and 79.73% that comes to very good criteria. Based on the results of the data analysis, it concluded that student worksheets based on the ARCS model was valid and can be used during high school chemistry lessons on the ion balance and pH of buffer solution subject.

PENGEMBANGAN E-LKPD BERBASIS DISCOVERY LEARNING MENGGUNAKAN APLIKASI ADOBE ACROBAT 11 PRO EXTENDED PADA MATERI KESETIMBANGAN ION DAN pH LARUTAN GARAM UNTUK KELAS XI SMA/MA SEDERAJAT

This study aims to develop E-LKPD based on Discovery Learning using the Adobe Acrobat 11 Pro Extended application on the ion balance and pH of salt solution for class XI SMA / MA, to determine the validity of E-LKPD based on aspects of content feasibility, characteristics of Discovery Learning, linguistic aspects, presentation aspects, graphic aspects, size, cover design, content design and knowing the user's response to the developed E-LKPD. This development research is a type of Research and Development (R&D) with the Plomp development model. The data collection instruments are in the form of validation sheets given to two material validators and two media validators, as well as user response questionnaires for teachers and students. After two revisions, the validity results obtained by the material validator on the content feasibility aspect were 94.44%, the characteristic aspects of Discovery Learning were 95.83%, the presentation aspects were 90%, the linguistic aspects were 90.62% and the graphic aspects were 93.5% which each of these aspects is included in the valid criteria. Furthermore, the results of data analysis obtained validity by the media validator on the graphic aspect which included the E-LKPD size of 100%, the cover design was 90.63%, and the content design was 94.32%, each of which was categorized as valid. E-LKPD which has been declared valid by the validator is tested one by one on 3 students who have studied the ion balance and pH of the salt solution. Then ask for a response questionnaire to 3 chemistry teachers and 20 students. The results of the teacher's response were 95.55% including very high and practical criteria, the results of students' responses were 90.75% including interesting criteria. Based on the results of data analysis, it can be concluded that the E-LKPD based on Discovery Learning using the Adobe Acrobat 11 Pro Extended application produced was validated and can be used in high school chemistry subjects on ion balance and pH of salt solution.