Pomegranate (Punica granatum L.) is widely grown in arid and semiarid regions, where the salinization may have developed through irrigation. A greenhouse experiment was conducted to investigate NaCl stress on growth, photosynthesis, and nutrients of 18 pomegranate cultivars. One group was irrigated twice a week with a nutrient solution. The other group was watered twice a week with the same nutrient solution and 200 mM NaCl for five weeks. Dry weight, shoot length, new shoot number, root length and number, leaf area, leaf relative water content, and net photosynthesis of salt-treated plants were negatively impacted by salt stress, and there was a significant difference among cultivars. Few foliar damages were observed. Na content of plants significantly increased in all cultivars, while P, S, K, Ca, Mg, Si, Al, Zn content of plants decreased under salt stress. Fe, Mn, and Cu content increased in most cultivars. Pomegranate accumulated supraoptimal Na mostly in roots and transported more K and Ca to shoots, which was attributed to maintaining a higher ratio of K/Na and Ca/Na in the aerial part of plants. Ten of the 18 cultivars were considered salt-tolerant, which would offer a reference for pomegranate cultivation on saline lands.

Cadmium (Cd) is a common heavy metal contaminant which seriously affects plant growth and environmental safety. Biochar, as an organic soil amendment, has been shown to effectively mitigate Cd damage to plants. To study the effectiveness of biochar on mitigating Cd stress, Mentha piperita ‘chocolate’ and Mentha spicata were used in a pot experiment of Cd stress with a CdCl₂ solution (10 mg Kg⁻¹), while a biochar suspension (0, 40, 80, and 160 g Kg⁻¹) was applied to the soil. The effects of Cd on the growth, physiological and biochemical properties, and Cd content in plant tissues of both mint species were found to be significant. The application of 40 g Kg⁻¹, 80 g Kg⁻¹, 160 g Kg⁻¹ biochar significantly alleviated Cd damage to both mint species, increased plant height, leaf length, leaf width, biomass, photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content, and decreased antioxidant enzyme activities (including superoxide dismutase, catalase, peroxidase, and polyphenol oxidase) and non-enzymatic antioxidant content (including flavonoids and total phenols). Biochar effectively reduced the Cd uptake by plants and decreased the migration and transformation capacity of Cd in the soil–plant system. In addition, the available nitrogen (available N), available phosphorus (available P), available potassium (available K), and pH in the soil increased after biochar application compared to non-biochar amended soil. The addition of 160 g Kg⁻¹ biochar was shown to have the best performance of the application rates in this experiment and may be considered as an effective way to reduce the damage caused by Cd contamination to M. piperita ‘chocolate’ and M. spicata.

Salicylic acid (SA) plays an important role in regulating salt stress tolerance in plants. However, there are no studies on the effect of exogenous SA on Saponaria officinalis under salt stress. To study the effectiveness of SA on mitigating salt stress, S. officinalis were used in a pot experiment of salt stress simulated with an NaCl solution (100, 200, and 300 mmol L⁻¹), while an SA solution (0, 0.2, 0.4, 0.6, 0.8, 1.0 mmol L⁻¹) was sprayed on leaves. Under salt stress, spraying SA caused an increase in the salt damage index, electrolyte leakage, and a reduction in malondialdehyde and Na⁺ content, but an increase in the rate of photosynthesis, chlorophyll, soluble sugar, soluble protein, free proline, K⁺, Mg²⁺, Ca²⁺ content, the K⁺/Na⁺ ratio, superoxide dismutase, peroxidase, catalase, ascorbate peroxidase activity, and the comprehensive score. The results show that SA improves the salt tolerance capacity of S. officinalis by modulating its photosynthetic rate, osmoprotectants, antioxidant levels, and ion homeostasis. However, the effectiveness of SA was not linearly related to its concentration. In summary, our findings reveal the protective roles of SA against salinity in S. officinalis and suggest that the use of 0.6 mmol L⁻¹ of SA in salt stress conditions could be an effective approach to reduce the damage caused by saline soil in S. officinalis.

Secondary development is a key biological characteristic of woody plants and the basis of wood formation. Exogenous nitrogen can affect the secondary growth of poplar, and some regulatory mechanisms have been found in the secondary xylem. However, the effect of nitrogen on cambium has not been reported. Herein, we investigated the effects of different nitrogen concentrations on cambium development using combined transcriptome and metabolome analysis. The results show that, compared with 1 mM NH₄NO₃ (M), the layers of hybrid poplar cambium cells decreased under the 0.15 mM NH₄NO₃ (L) and 0.3 mM NH₄NO₃ (LM) treatments. However, there was no difference in the layers of hybrid poplar cambium cells under the 3 mM NH₄NO₃ (HM) and 5 mM NH₄NO₃ (H) treatments. Totals of 2365, 824, 649 and 398 DEGs were identified in the M versus (vs.) L, M vs. LM, M vs. HM and M vs. H groups, respectively. Expression profile analysis of the DEGs showed that exogenous nitrogen affected the gene expression involved in plant hormone signal transduction, phenylpropanoid biosynthesis, the starch and sucrose metabolism pathway and the ubiquitin-mediated proteolysis pathway. In M vs. L, M vs. LM, M vs. HM and M vs. H, differential metabolites were enriched in flavonoids, lignans, coumarins and saccharides. The combined analysis of the transcriptome and metabolome showed that some genes and metabolites in plant hormone signal transduction, phenylpropanoid biosynthesis and starch and sucrose metabolism pathways may be involved in nitrogen regulation in cambium development, whose functions need to be verified. In this study, from the point of view that nitrogen influences cambium development to regulate wood formation, the network analysis of the transcriptome and metabolomics of cambium under different nitrogen supply levels was studied for the first time, revealing the potential regulatory and metabolic mechanisms involved in this process and providing new insights into the effects of nitrogen on wood development.

Ryegrass has a relatively high salt tolerance and is considered to be a promising species for both foraging and turf purposes in salt-affected soils in China. While annual ryegrass and perennial ryegrass are two different species, they have similar genomes. However, little is known about their physiological and molecular response mechanisms to salinity stress. Here, biomass, chlorophyll fluorescence, and inorganic ion and organic solute content were measured. 2-DE-based proteomic technology was then used to identify the differentially expressed proteins in the salt-treated seedlings. The results showed that salt stress reduced growth and photosynthesis in the seedlings of both species, but much more so in annual ryegrass. With increasing salinity, the Na⁺ concentration increased while the K⁺ concentration decreased in both species, and the sugars and proline increased as the primary organic solutes used to cope with osmotic stress. Additionally, proteomic analysis revealed 33 and 37 differentially expressed proteins in annual and perennial ryegrass, respectively. Most of the identified proteins were involved in carbohydrate and energy metabolism, photosynthesis, genetic information processes, amino acid metabolism, stress defense, and protein synthesis and folding. The results suggest that the two-ryegrass species had different physiological and proteomic responses. These findings can provide new insights into physiological mechanisms by which ryegrass species respond to salt stress.