Growth, Physiological, and Photosynthetic Responses of Xanthoceras sorbifolium Bunge Seedlings Under Various Degrees of Salinity

Source leaves are regulated by sink strengths through non-coding RNAs and alternative polyadenylation in cucumber (Cucumis sativus L.)

BACKGROUND

The yield of major crops is generally limited by sink capacity and source strength. Cucumber is a typical raffinose family oligosaccharides (RFOs)-transporting crop. Non-coding RNAs and alternative polyadenylation (APA) play important roles in the regulation of growth process in plants. However, their roles on the sink‒source regulation have not been demonstrated in RFOs-translocating species.

RESULTS

Here, whole-transcriptome sequencing was applied to compare the leaves of cucumber under different sink strength, that is, no fruit-carrying leaves (NFNLs) and fruit-carrying leaves (FNLs) at 12th node from the bottom. The results show that 1101 differentially expressed (DE) mRNAs, 79 DE long non-coding RNAs (lncRNAs) and 23 DE miRNAs were identified, which were enriched in photosynthesis, energy production and conversion, plant hormone signal transduction, starch and carbohydrate metabolism and protein synthesis pathways. Potential co-expression networks like, DE lncRNAs-DE mRNAs/ DE miRNAs-DE mRNAs, and competing endogenous RNA (ceRNA) regulation models (DE lncRNAs-DE miRNAs-DE mRNAs) associated with sink‒source allocation, were constructed. Furthermore, 37 and 48 DE genes, which enriched in MAPK signaling and plant hormone signal transduction pathway, exist differentially APA, and SPS (CsaV3_2G033300), GBSS1 (CsaV3_5G001560), ERS1 (CsaV3_7G029600), PNO1 (CsaV3_3G003950) and Myb (CsaV3_3G022290) may be regulated by both ncRNAs and APA between FNLs and NFNLs, speculating that ncRNAs and APA are involved in the regulation of gene expression of cucumber sink‒source carbon partitioning.

CONCLUSIONS

These results reveal a comprehensive network among mRNAs, ncRNAs, and APA in cucumber sink-source relationships. Our findings also provide valuable information for further research on the molecular mechanism of ncRNA and APA to enhance cucumber yield.

Mitigation of salinity stress in yarrow (Achillea millefolium L.) plants through spermidine application

This study investigated the mitigating effects of spermidine on salinity-stressed yarrow plants (Achillea millefolium L.), an economically important medicinal crop. Plants were treated with four salinity levels (0, 30, 60, 90 mM NaCl) and three spermidine concentrations (0, 1.5, 3 μM). Salinity induced electrolyte leakage in a dose-dependent manner, increasing from 22% at 30 mM to 56% at 90 mM NaCl without spermidine. However, 1.5 μM spermidine significantly reduced leakage across salinities by 1.35-11.2% relative to untreated stressed plants. Photosynthetic pigments (chlorophyll a, b, carotenoids) also exhibited salinity- and spermidine-modulated responses. While salinity decreased chlorophyll a, both spermidine concentrations increased chlorophyll b and carotenoids under most saline conditions. Salinity and spermidine synergistically elevated osmoprotectants proline and total carbohydrates, with 3 μM spermidine augmenting proline and carbohydrates up to 14.4% and 13.1% at 90 mM NaCl, respectively. Antioxidant enzymes CAT, POD and APX displayed complex regulation influenced by treatment factors. Moreover, salinity stress and spermidine also influenced the expression of linalool and pinene synthetase genes, with the highest expression levels observed under 90 mM salt stress and the application of 3 μM spermidine. The findings provide valuable insights into the responses of yarrow plants to salinity stress and highlight the potential of spermidine in mitigating the adverse effects of salinity stress.

Effects of different light conditions on morphological, anatomical, photosynthetic and biochemical parameters of Cypripedium macranthos Sw

In this study, the morphological (plant height, leaf length and width, stem diameter and leaf number), anatomical (epidermal cell density and thickness, Stomatal length and width), photosynthetic (net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, relative humidity, leaf temperature and chlorophyll fluorescence parameters) and biochemical parameters (the content of soluble sugar, soluble protein, proline, malondialdehyde and electrical conductivity) of Cypripedium macranthos Sw. in Changbai Mountain were determined under different light conditions (L10, L30, L50, L100). The results showed that morphological values including plant height, leaf area, stem diameter and leaf number of C. macranthos were smaller under the condition of full light at L100. The epidermal cell density and epidermal thickness of C. macranthos were the highest under L30 and L50 treatments, respectively. It had the highest net photosynthetic rate (Pn) and chlorophyll content under L50 treatment. Meanwhile, correlation analysis indicated that photosynthetically active radiation (PAR) and water use efficiency (WUE) were the main factors influencing Pn. C. macranthos accumulated more soluble sugars and soluble proteins under L100 treatment, while the degree of membrane peroxidation was the highest and the plant was severely damaged. In summary, the adaptability of C. macranthos to light conditions is ranked as follows L50 > L30 > L10 > L100. Appropriate light conditions for C. macranthos are 30%-50% of full light, which should be taken into account in protection and cultivation.

Arbuscular mycorrhizal fungi alleviates salt stress in Xanthoceras sorbifolium through improved osmotic tolerance, antioxidant activity, and photosynthesis

Mycorrhizal inoculation was widely reported to alleviate the damage resulting from NaCl by various physiological ways. However, the symbiotic benefit under distant NaCl concentrations and the relationship among different responsive physiological processes were elusive. In this study, saline resistant plant Xanthoceras sorbifolium was selected as the experimental material and five concentrations of NaCl in the presence or absence of Arbuscular Mycorrhiza Fungi (AMF) were conducted, in order to understand the differences and similarities on the photosynthesis, antioxidant activity, and osmotic adjustment between arbuscular mycorrhizal (AM) plants and non-arbuscular mycorrhizal (NM) plants. Under low salt stress, X. sorbifolium can adapt to salinity by accumulating osmotic adjustment substances, such as soluble protein and proline, increasing superoxide dismutase (SOD), catalase (CAT) activity, and glutathione (GSH). However, under high concentrations of NaCl [240 and 320 mM (mmol·L−1)], the resistant ability of the plants significantly decreased, as evidenced by the significant downregulation of photosynthetic capacity and biomass compared with the control plants in both AM and NM groups. This demonstrates that the regulatory capacity of X. sorbifolium was limiting, and it played a crucial role mainly under the conditions of 0–160 mM NaCl. After inoculation of AMF, the concentration of Na+ in roots was apparently lower than that of NM plants, while Gs (Stomatal conductance) and Ci (Intercellular CO2 concentration) increased, leading to increases in Pn (Net photosynthetic rate) as well. Moreover, under high salt stress, proline, soluble protein, GSH, and reduced ascorbic acid (ASA) in AM plants are higher in comparison with NM plants, revealing that mycorrhizal symbiotic benefits are more crucial against severe salinity toxicity. Meanwhile, X. sorbifolium itself has relatively high tolerance to salinity, and AMF inoculation can significantly increase the resistant ability against NaCl, whose function was more important under high concentrations.