Plant polysaccharides are widely found in nature and have a variety of biological activities, including immunomodulatory, antioxidative, and antitumoral. Due to their low toxicity and easy absorption, they are widely used in the health food and pharmaceutical industries. However, low activity hinders the wide application. Chemical modification is an important method to improve plant polysaccharides’ physical and chemical properties. Through chemical modification, the antioxidant and immunomodulatory abilities of polysaccharides were significantly improved. Some polysaccharides with poor water solubility also significantly improved their water solubility after modification. Chemical modification of plant polysaccharides has become an important research direction. Research on the modification of plant polysaccharides is currently increasing, but a review of the various modification studies is absent. This paper reviews the research progress of chemical modification (sulfation, phosphorylation, acetylation, selenization, and carboxymethylation modification) of land plant polysaccharides (excluding marine plant polysaccharides and fungi plant polysaccharides) during the period of January 2012–June 2022, including the preparation, characterization, and biological activity of modified polysaccharides. This study will provide a basis for the deep application of land plant polysaccharides in food, nutraceuticals, and pharmaceuticals.

Background: Geographical variation in morphological traits may reflect evolutionary patterns of morphological adaptability along environmental gradients. Comprehensive information on longitudinal patterns of morphological trait variation is very meaningful to explore morphological diversity and evolutionary trends in widespread bermudagrass. Methods: To explore the spatial patterns of morphological traits, we investigated 10 morphological traits of bermudagrass and 10 soil nutrient indexes and collected local climate data for 13 different regions from 119°E to 105°E along the latitude 34°N. Results: Considerable variations in morphological traits were observed at different longitudes, and the variations in most of the evaluated traits within populations were lower than those among populations. All of the 13 different longitudinal sites were divided into three groups based on morphological traits by cluster analysis. The major sources of diversity at the different longitudes were leaf length of the erect shoot, leaf width of the erect shoot, and the internode lengths of the erect shoot and stolon as determined by principal component analysis. Pearson correlation analysis also indicated that longitude was significantly and negatively correlated with these traits as well. Mean average rainfall was significantly correlated with leaf length of the erect shoot and the internode lengths of the erect shoot and stolon, while mean average temperature was only significantly correlated with internode length of the erect shoots. Available sulfur was significantly correlated with internode length of the erect shoot, plant height, and reproductive branch height, while the exchangeable Ca was significantly correlated with internode lengths of the erect shoot and stolon. Soil pH was significantly correlated with the internode length of the stolon. Longitude is an important factor that affects morphological trait variation in wild bermudagrass, and the leaves of the erect shoot and the internode length enlarged significantly with the collection sites moving from east to west. Conclusion: Different combinations and interactions of environmental factors (soil and climate) along a longitudinal gradient may have strong effects on one or more morphological traits of bermudagrass.

Nitrogen fertilization is a simple and effective field management strategy for increasing plant productivity, but the regulatory mechanisms of nitrogen forms and proportions on soil nutrients and plant growth remain unclear. Therefore, we investigated soil enzyme activities and nutrient contents of alfalfa under different forms and proportions of exogenous nitrogen addition. Results showed that nitrogen input significantly increased the activity of three oxidoreductases (hydroxylamine reductase, nitrate reductase, and nitrite reductase) while having no significant effects on urease. A high proportion of ammonium nitrogen significantly increased neutral protease activity. The amylase activity markedly increased under mixed-nitrogen addition but decreased under single-nitrogen addition. Additionally, the contents of soil nutrients (soil organic matter, total nitrogen, nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium) were significantly increased under different exogenous nitrogen inputs, which drove the changes in enzyme activities. Further, nitrogen addition also improved the biomass and nitrogen content of alfalfa. These findings indicated that applying different forms and proportions of exogenous nitrogen may stimulate soil enzyme activities, which will accelerate the transformation of nutrients and then promote alfalfa growth.

Aluminium (Al) and fluoride (F) are phytotoxic elements that can inhibit plant growth and development. Al³⁺ and F^- can react with each other to form complexes in the soil which will induce alteration of toxicity of single element. However, the mechanisms of plant response to aluminium fluoride induced toxicity are not very clear. In the present study, tall fescue (Festuca arundinacea Schreb) cultivar 'Houndog 5' was treated by 0, 0.4, 4, 20 mg·L^-1 Al₂(SO₄)₃ and 0, 0.5, 5 mg·L^-1 NaF, respectively. After 25 days of treatment, leaf samples were collected for physiological evaluation. The results showed that several forms of Al-OH and Al-F complexes such as Al(OH)₂⁺, AlOH²⁺, Al(OH)₃, Al(OH)^4-, Al₂(OH)₂⁴⁺, Al₃(OH)₄⁵⁺, AlF²⁺, AlF₂⁺, AlF₃ and AlF^4- were formed in Al³⁺ and F^- combined solution. The nutrient uptake including Al, P and K were improved by Al³⁺ and F^-. Under Al³⁺ stress, the MDA (malondialdehyde) content and EL (electrolyte leakage) dramatically increased after high concentration of F^- treatment, while relative low concentration of F induced decrease of MDA content and EL. On the contrary, chlorophyll content decreased significantly after high concentration of F treatment. The photosynthesis efficiency parameters, including φ_P0 (Fv/Fm), δ_R0 and PI_ABS, decreased remarkably after high concentration of Al and F treatment. However, L-band incresed after high concentration of Al³⁺ and F^- treatment. The results of correlation analysis showed that MDA content and EL negatively correlated with other indexes, and Al-F complex significantly correlated with MDA, Pro and EL but negatively correlated with Chl and φ_P0. These results suggested that low concentration of F could alleviate the damage induced by Al stress in tall fescue, but high concentration of Al and F combined solution had negative effects on the growth and development of tall fescue.