Na2CO3 Stress Research Articles

Early Transcriptomic Adaptation to Na2CO3 Stress Altered the Expression of a Quarter of the Total Genes in the Maize Genome and Exhibited Shared and Distinctive Profiles with NaCl and High pH Stresses

Sodium carbonate (Na₂CO₃) presents a huge challenge to plants by the combined damaging effects of Na⁺, high pH, and CO₃²⁻. Little is known about the cellular responses to Na₂CO₃ stress. In this study, the transcriptome of maize (Zea mays L. cv. B73) roots exposed to Na₂CO₃ stress for 5 h was compared with those of NaCl and NaOH stresses. The expression of 8,319 genes, representing over a quarter of the total number of genes in the maize genome, was altered by Na₂CO₃ stress, and the downregulated genes (5,232) outnumbered the upregulated genes (3,087). The effects of Na₂CO₃ differed from those of NaCl and NaOH, primarily by downregulating different categories of genes. Pathways commonly altered by Na₂CO₃, NaCl, and NaOH were enriched in phenylpropanoid biosynthesis, oxidation of unsaturated fatty acids, ATP-binding cassette (ABC) transporters, as well as the metabolism of secondary metabolites. Genes for brassinosteroid biosynthesis were specifically upregulated by Na₂CO₃, while genes involved in ascorbate and aldarate metabolism, protein processing in the endoplasmic reticulum and by N-glycosylation, fatty acid biosynthesis, and the circadian rhythm were downregulated. This work provides the first holistic picture of early transcriptomic adaptation to Na₂CO₃ stress, and highlights potential molecular pathways that could be manipulated to improve tolerance in maize.

Effects of Na2CO3 stress on photosynthesis and antioxidative enzymes in endophyte infected and non-infected rice

Endophyte infected and uninfected seedlings of rice (Oryza sativa L.) were subjected to five different levels of Na2CO3 for 2 weeks. Under both Na2CO3 stress as well as no stress, endophyte-infected plants were higher for above-ground dry weight and shoot length, but lower for root length compared to non-infected controls, and there was no significant difference for below-ground dry weight. Chlorophylls and carotenoid contents, net photosynetic rate, transpiration rate, catalase and peroxidase activities increased, but malondialdehyde content declined in the infected plants compared to non-infected controls under Na2CO3 stress. Compared to non-infected controls, water use efficiency, stomatal conductance, chlorophyll fluorescence parameters (Fv/Fm, Fv/Fo) and superoxide dismutase activity in infected plants increased under high concentrations of Na2CO3 while there was no significant difference under low concentrations of Na2CO3. Endophyte infection was concluded to be beneficial to the growth and antioxidative mechanisms in Oryza sativa under Na2CO3 stress.

Volatile communication between Chlamydomonas reinhardtii cells under salt stress

Although it is known that volatile organic compounds (VOCs) can be released by lower plants, their release and ecological functions are not much studied, especially in aquatic systems under abiotic stress. In the present study, we determined the compositions of VOCs released from Chlamydomonas reinhardtii under both neutral (NaCl) and alkali (Na2CO3) salt stresses. Hexanal was the newly released abundant compound under NaCl stress, while we found 3,4-dimethyl-hexane and 5-methyl-2-heptene under Na2CO3 stress. Under both stress conditions, longifolene was the significantly increased compound. When C. reinhardtii cells were exposed to the VOCs from the salt-stressed cells, the cell density was reduced, but the content of chlorophyll, Fv/Fm and antioxidant enzyme activity were increased. This might indicate that those VOCs can transfer stress signal between C. reinhardtii cells and tell the receptor to prepare against reactive oxygen species (ROS) damage ahead of the stress coming.

Stress of NaCl and Na<SUB>2</SUB>CO<SUB>3</SUB> on seed germination of <I>Bromus cartharticus</I> Vahl new strain

Seed germination of the salinetoloerant Bromus cartharticus Vahl new strain was studied on the condition of neutral and alkaline salt.NaCl and Na2CO3 were applied at concentrations of 0.2%,0.4%,0.6%,0.8%,1.0% and 1.2% for salt stress treatments.The relative germination percentage,germination index and vigor index of Bromus cartharticus Vahl declined with increased salinity.In 0.2%~0.8% NaCl concentrations,the neutral salt had the promoter action to the radicle length.Its length increased about 40.2% while the amplitude of variation reduced with the increase of the concentration.The length of embryo root was greatly restrained under Na2CO3-stress.A large number of non-root plants occurred.The regression analysis was carried by the relative germination percentage under two different kinds of single-salt stress.The preference value,critical value and ultimate value of Bromus cartharticus Vahl new strain's seeds were 0.65%,1.14% and 1.93% respectively under NaCl stress,compared to the Na2CO3 stress under various values(0.38%,0.71% and 1.24%).The ability of Bromus cartharticus Vahl new strain's seeds to bear the neutral salt(NaCl) stress was stronger than alkaline salt(Na2CO3) if all germination indicators were all considered.

Mapping of QTLs Underlying Tolerance to Alkali at Germination and Early Seedling Stages in Rice

A double haploid (DH) population including 120 lines derived from a cross between indica rice (Oryza sativa L.) TN1 and japonica rice CJ06 was used to detect quantitative trait loci (QTLs) for 10-trait relative values of alkali damage at germination period and early seedling stage under 0.15% Na2CO3 stress. Correlation analyses showed that alkali damage rate in germination period (ADG) had significant positive correlation with relative germination energy (RGE), relative germination rate (RGR) and relative germination index (RGI), and alkali damage rate at early seedling stage (ADS) had significantly correlation with relative seedling height (RSH), relative root length (RRL), relative root number (RRN) and relative seedling dry weight (RDW). ADG and ADS can be used as evaluation indexes of alkaline tolerance in rice. By using QTLNetwork 2.0 software, 14 additive QTLs and 13 epistatic QTLs controlling the tolerance to alkali were mapped. Two main effect QTLs were detected in same region, RM251–RM3280, on chromosome 3, and three main effect QTLs were mapped between RM3286 and RM1279 on chromosome 7. Epistasis analysis showed that some epistatic loci, like RM1–RM1195, RM1358–RM290, RM1279–RM505, and RM1246–RM519 on chromosome 1, 2, 7, and 12 respectively were important under alkali stress, included two or more epistatic QTLs, indicating that the QTLs displayed their effects through different ways of interaction. Among the key loci under alkali stress one may be pleiotropic or some closely linked each other. Comparing QTLs with those found in other researches, some alkali resistance QTLs were likely to be in the same region with some salt resistance QTLs. A presume was made that QTLs in this articlemight include two types, one for resistance to ions (K+ or Na+) stress and other for resisttance to high pH stress, the latter may play an important role for tolerance to alkali. Many rice varieties have different resistance QTLs for alkali stress; we can pyramid them through marker-assistant selection to breed varieties suitable to growth in saline-alkalized land.

Effects of Na2CO3 and NaCl stresses on the antioxidant enzymes of chloroplasts and chlorophyll fluorescence parameters of leaves of Puccinellia tenuiflora (Turcz.) scribn.et Merr.

Antioxidant enzymes in chloroplasts and chlorophyll fluorescence parameters of leaves of Puccinellia tenuiflora (Turcz.) scribn.et Merr. under isotonic Na2CO3 and NaCl stresses were studied. Ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities showed a similar increasing trend and then decreased with the decreasing osmotic potential of culture solution, peaking at −4.74 × 105 Pa under NaCl stress and at −3.40 × 105 Pa under Na2CO3 stress. APX, glutathione transferase and SOD activities were higher under NaCl stress than those under Na2CO3 stress, and higher activities of antioxidant enzymes in chloroplasts were accompanied by lower MDA content under NaCl stress. F v/F m, F v/F o and F v′/F m′ all initially increased and then decreased with the decreasing osmotic potential of culture solution, while Φ PSII, qNP and HDR showed a constant increase. F v/F m, F v/F o, Φ PSII and qNP under NaCl stress were also shown to be higher than those under Na2CO3 stress. The present study suggested that acidity played an important role in the hurt toPuccinellia tenuiflora seedlings, which was due to higher activities of antioxidant enzymes, qNP and Φ PSII, and the Na2CO3 resistance to Puccinellia tenuiflora was also supposed to be less than NaCl resistance in present work.