During highway slope ecological restoration, selecting restoration plants is important to maintain the soil medium and trace element content, as well as to improve the slope ecological environment. In this study, Amorpha fruticosa, a typical slope protection species on expressways, was examined. Root soil was collected as the research object, and the effective content of major medium and trace elements in the rhizosphere and non-rhizosphere soils of A. fruticosa at different soil depths, and their root enrichment effects, were analyzed. The results showed that the content of trace elements such as Fe and Cu and that of medium elements such as Mg in the rhizosphere was significantly higher than that in the non-rhizosphere, while the content of Mn and Zn in the rhizosphere was significantly lower than that in the non-rhizosphere. There was no significant difference in Ca content between the rhizosphere and non-rhizosphere. With increasing soil depth, the content of Fe, Mn, Cu, and Mg decreased gradually, while that of Zn and Ca showed no obvious trend. A correlation between A. fruticosa rhizosphere and non-rhizosphere soil elements was confirmed, and Fe, Cu, Ca, and Mg were enriched to different degrees in the roots. The results showed that planting A. fruticosa on the slope of the expressway had potential effects in terms of maintaining and improving medium and trace element content in the soil and resisting slope soil erosion.
The relationship between plateau pika disturbance and the value of alpine meadow ecosystem services can be used to comprehensively evaluate the status and role of plateau pika in an alpine meadow ecosystem. In this study, the effects of plateau pika disturbance on the ecosystem service values of alpine meadows–including livestock food production, water conservation, carbon sequestration, soil nutrient cycling, and biodiversity maintenance–were evaluated simultaneously based on the value equivalent factor per unit area and the service function price per unit area to determine the appropriate method for evaluating the effect of pika on the value of alpine meadow ecosystem services. The results showed that plateau pika disturbance decreased livestock food production and water conservation. Using the value equivalent factor per unit area showed that plateau pika disturbance decreased carbon sequestration, soil nutrient cycling, and biodiversity maintenance; however, using the service function price per unit area showed that the same increased carbon sequestration, soil nutrient cycling, and biodiversity maintenance. These results indicated that value equivalent factor per unit area and service function price per unit area both converged and diverged in terms of how they evaluated the effect of plateau pika disturbance on the value of alpine meadow ecosystem services. By analyzing the advantages and disadvantages of the two methods to assess ecosystem service values, this study found that service function price per unit area was more suitable to reflect the effect of plateau pika disturbance on the former in terms of alpine meadow ecosystems.
To explore the effect of the silage time of maize (Zea mays) on silage quality in the Inner Mongolia Plateau (East and North China), we determined the most suitable maize varieties for silage and the optimal silage time to promote the development of animal husbandry. The fermentation quality and nutrient composition of ‘Xianfeng 38P05’, ‘Xianyu 1409’, ‘Haiyu 11’, and ‘Lihe 228’ and ‘A6565’ were selected for assessment after 0, 15, 30, 45, 60, and 90 days of silage. The results showed that after 30 days, the pH of each variety was lower than 4.00. During silage, there were significant differences (P < 0.05) in the lactic acid (LA) and acetic acid (AA) content between all varieties, but no significant differences (P > 0.05) in propionic acid (PA) content and ammonium nitrogen/total nitrogen ratio (AN/TN). The highest LA content was 6.18 mg·g−1 fresh matter (FM) (‘Xianyu 1409’ after 45 days of silage). Each index was stable after 45 days of silage. After 90 days of silage, ‘Xianyu 1409’ had the highest dry matter (DM), ether extract (EE), and relative feeding value (RFV), which were 21.73% DM, 5.43% DM, and 170.36% DM, respectively. The CP loss rate and acid detergent fiber (ADF) content were 36.63% and 23.21% DM, respectively. In conclusion, the quality of maize silage reached a stable state after 45 days. ‘Xianyu 1409’ was selected as the raw material for silage in the Inner Mongolia Plateau (East and North China) as it showed the best silage effect.
SUPPRESOR OF OVEREXPRESSION OF CO 1 (SOC1) encodes the MADS-box transcription factor, which has important functions of inducing flowering in plants, preventing premature maturation of floral meristems, and regulating the development of floral organs by integrating flowering signals. SOC1 transcription factor is regulated by proteins or nucleic acids, forms a complex with other transcription factors to enter the nucleus, targets flowering genes to regulate flowering time, and has a complex flowering time regulatory network. This study mainly analyzed the structural characteristics of SOC1 and its protein, predicted the protein interaction network of SOC1, and mainly reviewed the molecular mechanism of SOC1 regulation of flowering time. Results showed that SOC1 was directly regulated by FT, CO, FLC, MAFs, SVPs, SPL, and AGL24 and indirectly regulated by DELLA, miR156, miR172, AP2, MYC3, and nutrient signals. SOC1 formed a dimer with AGL24 to upregulate LFY expression to accelerate flowering induction in plants. Results of this study provide a reference for future research on how SOC1 regulate the flowering time of other plants.
Perennial ryegrass (Lolium perenne) is widely grown as a forage and turf grass species. To understand the genetic diversity of perennial ryegrass germplasm, we used SSR markers to analyze 10 self-bred lines of L. perenne and 75 germplasm materials collected from 23 different countries. The results showed that 91 polymorphic bands were amplified using 26 pairs of SSR(simple sequence repeats) primers, accounting for 69.5% of all amplified bands. The PIC value of each SSR pair varied between 0.156～0.722 with a mean value of 0.455. The genetic similarity index of the 85 germplasm materials was 0.700～0.900. The NTSYS phylogenetic analysis showed that by setting the cutting value of the genetic similarity coefficient (GS) at 0.738, five clades could be clustered from the 85 materials. Comprehensive cluster analysis and Structure population genetic structure analysis revealed that there was no significant association between the genetic relationships and the geographic origins of these germplasm materials. The results of this study provide a theoretical foundation for germplasm evaluation and parental plant selection in breeding programs.
This study analyzed the spatiotemporal pattern of precipitation and its future trends in the Three-River Headwater region using the linear regression, moving average, climate trend rate, and recalibration range methods with 59 years (1961–2019) of precipitation data. The data were taken from 13 meteorological stations in the Three-River Headwater region. The results indicated that the average annual precipitation was 470.7 mm in this region and had an increasing trend of 10.31 mm·10 a−1 . The Yellow River had the highest precipitation in spring, the Lancang River had the highest precipitation in the other three seasons, and the Yangtze River had the lowest precipitation in all four seasons. Precipitation in all source regions showed an increasing trend, and the greatest climatic trends in the rate of precipitation, which was seen in spring, were 2.69 mm·10 a−1, 2.11 mm·10 a−1, and 2.80 mm·10 a−1 for the Yangtze, Yellow, and Lancang rivers, respectively. The cumulative precipitation anomaly showed decreasing trends from 1961 to 2002 and an increasing trend from 2003 to 2019. Catastrophic precipitation occurred in 2002. The average annual minimum and maximum precipitation in different years occurred in the periods 1961–1970 and 2011–2019 and were 452.23 mm and 512.82 mm, respectively. Annual and seasonal precipitation increased from northwest to southeast, and the range in the spatial variation in precipitation was greatest in the Yellow River source region. The climatic trends in precipitation rates during spring, summer, and autumn decreased from northwest to southeast, but the opposite was observed during winter; this indicated that precipitation increased strongly in source regions with less precipitation. The Hurst value of the long-term change in precipitation was larger than 0.5, indicating that future changes in precipitation would be consistent with past trends. A spatiotemporal pattern in precipitation was observed in the Three-River Headwater region, where future precipitation will present an increasing trend.
Changes in global precipitation patterns are bound to affect the functions of terrestrial ecosystems. The carbon sink function of grasslands is very sensitive to changes in the soil water content. To study the effects of precipitation on ecosystem carbon exchange in a desert steppe ecosystem, four different precipitation gradients were set up in a desert grassland using a random group design (50% reduced precipitation, natural precipitation, and 50% and 100% increased precipitation), and each precipitation gradient had three replicates. The net ecosystem carbon exchange (NEE), ecosystem respiration (ER), and gross ecosystem productivity (GEP), were measured during the growing season of 2017 using the portable optical LI-6400 and the static chamber method. The results showed that: 1) Soil moisture content and above-ground biomass significantly increased, and soil temperature significantly decreased, in treatments with increasing water availability (P < 0.05). 2) Under 50% water reduction, NEE was the carbon source; whereas under natural precipitation, and 50% and 100% increased precipitation, NEE was a carbon sink (P < 0.05). Furthermore, with an increase in precipitation, ER and GEP increased significantly (P < 0.05). The determination coefficient of GEP and soil water content was greater than that of ER and soil water content. 3) The correlation coefficient between NEE and soil temperature was the largest, so was the correlation coefficient between ER, GEP, and above-ground biomass. The results indicate that water can promote ecosystem carbon exchange in a desert steppe by increasing the above-ground biomass and reducing the soil temperature.
To explore the mitigation effects of ground temperature regulation on turf heat stress, three different treatments were set at the soil depth of 20 cm with 27, 24, and 21 ℃. The bentgrass turf maintained under normal growth conditions was used as the control, and the effects of temperature on turf soil temperature, quality, and root system were explored. During the high-temperature season, ground temperature regulation significantly reduced turf soil temperature (P < 0.05), alleviated the decline in turf quality, and recovered root growth under heat stress. Moreover, these mitigation effects reached statistical significance when the temperature was maintained below 24 ℃ (P < 0.05), with the best cooling effect observed at 21 ℃. Soil temperature at 5 and 20 cm was reduced by respectively 2 ~ 4.5 ℃ and 5 ~ 7 ℃ under the 21 ℃ cooling treatment compared with that under the control treatment. Additionally, under the same treatment, the turf color and normalized difference vegetation index were increased by respectively 17.8% and 28.2%. Likewise, the underground biomass, total root length, root surface area, root volume, and root vitality of the turf were increased up to 58.2%, 84.5%, 97.8%, 112.7%, and 46.9%, respectively. Therefore, ground temperature regulation effectively alleviated the decline in bentgrass turf growth under heat stress, and this strategy can effectively improve bentgrass survival during high-temperature seasons. Specifically, maintaining the ground temperature below 24 ℃ is the most suitable mitigation strategy.
Using a total of 503 geographical distribution points and 29 environmental variables, this study employed ArcGIS and the maximum entropy model (MaxEnt) to analyze the potential adaptability areas, driving factors, and niche parameters for five Kalidium species under different climate scenarios in baseline and future periods, and overlaid land use data with the highly suitable areas of the five Kalidium species under the baseline climate scenario. The results showed that: 1) the main factors driving the distribution of areas suitable for the five Kalidium species were different, but climate factors were dominant for them all, and topography and soil affected the distribution of suitable areas; 2) compared with the baseline climate scenario, only the middle- and high-suitability areas for Kalidium caspicum had shrunk in the 2050 period under the RCP8.5 climate scenario, whereas the middle and high fitness areas for the five species in the other time periods under different climate scenarios exhibited different degrees of expansion; 3) the niche parameters of the main factors driving the five species and the high fitness area were different; and 4) part of the land was developed and utilized in the high-suitability areas of the five species under the baseline climate scenario. This study has a certain theoretical significance and reference value for the management, protection, and utilization of the distribution area for Kalidium species.
The aim of this study was to investigate the expression pattern of the m6A RNA methylesterases, METTL3 and WTAP, in different tissues, and yak (Bos grunniens) preadipocyte proliferation and differentiation, as well as the level of mRNA m6A during preadipocyte differentiation. In this study, qRT-PCR was used to detect mRNA expression levels of METTL3 and WTAP in the subcutaneous fat, muscle, heart, liver, spleen, lung, kidney, and subcutaneous adipose tissue of yaks at 18 and 30 months of age. The type I collagenase digestion method was used to obtain yak preadipocytes, Oil Red O staining was used to identify lipid-containing cells, and adipogenesis marker genes were detected to establish a differentiation model of yak preadipocytes. qRT-PCR was used to detect the mRNA expression levels of METTL3 and WTAP in the proliferation and differentiation stages of preadipocytes. The results showed that METTL3 expression was the highest in the liver tissue (P < 0.05) and the lowest in the subcutaneous adipose tissue (P < 0.05). WTAP expression was most abundant in the subcutaneous adipose tissue and lowest in the spleen (P < 0.05). The expression of METTL3 and WTAP was higher in subcutaneous adipose tissue at 30 months than at 18 months of age. After 12 days of preadipocyte-induced differentiation, multiple and dense lipid rings appeared in the cells, and the expression of the adipocyte differentiation-specific marker genes, FABP4, C/EBPα, and PPARγ, was significantly higher on day 12 than on day 0 (P < 0.05). Expression of METTL3 and WTAP at the cell proliferation stage (24, 48, and 72 h) showed a decreasing trend (P < 0.05). At the differentiation stage of yak preadipocytes (0, 4, 8, and 12 d), METTL3 expression showed a rising-declining-rising trend, and WTAP showed a rising-declining trend. The mRNA m6A level showed a gradual increase at the differentiation stage, and the highest intracellular mRNA m6A abundance was observed after 12 days of differentiation (P < 0.05). Our results show the changes in METTL3 and WTAP in different tissues and yak preadipocytes and the changes in mRNA m6A levels during preadipocyte differentiation and revealed that WTAP and METTL3 have important regulatory roles in yak lipid metabolism.
Nitrogen (N) and phosphorus (P) are key elements that affect plant growth, development, and reproduction. To investigate the response of leaf N : P stoichiometry characteristics to soil N : P nutrient addition ratios and gradients in artificial grasses in northern Tibet, two typical forage (Hordeum vulgare and Elymus nutans) were studied using nutrient addition experiments (N : P input levels : 0.5, 1.5, 4.5, 13.5, 40.5, and 121.5; nutrient gradients : high, medium, and low), greenhouse incubation, and indoor analysis. Our objectives were to quantify the N concentration, P concentration, N : P ratio, and resorption efficiency in the leaves of the two forage species with multiple nutrient additions. The results showed that green leaf N concentrations of the two species increased significantly with increasing N : P input level (P < 0.001), and nutrient gradient and its interaction with N : P input level had significant effects on green leaf P concentrations and N : P (P < 0.01). Results also indicated that the N concentration in senesced leaves of Hordeum vulgare showed an overall increasing trend with increasing N : P input level, while the change in N concentration of Elymus nutans was not significant (P > 0.05). The P concentration in senesced leaves of the two species decreased and then increased with increasing N : P input level. The interaction between the nutrient gradient and N : P input level had significant effects on the N : P stoichiometry of senesced leaves of both species (P < 0.05). With the increase in N : P input level, the N resorption efficiency of Hordeum vulgare showed a decreasing trend, but the N resorption efficiency of Elymus nutans showed an increasing trend. The mean values of P resorption efficiency : N resorption efficiency ratios of Hordeum vulgare and Elymus nutans were 1.93 and 0.61, respectively. The results indicated that Hordeum vulgare had a more conservative P utilization strategy, while Elymus nutans showed a more conservative N utilization strategy. This differential response may be determined by species attributes, reflecting the diverse nutrient utilization and allocation strategies of plants. In this study, the response patterns of plant nutrient utilization to multiple nutrient gradients could provide a scientific basis for clarifying the utilization strategies of typical forage species in alpine nutrient-poor environments.
A total of 116 strains of Pseudomonas isolated from raw milk in different regions were identified by rpoD gene sequencing, Pseudomonas fluorescens accounted for 75.8%. Of Pseudomonas isolates, we obtained proteolytic ability from 68.9% at 4 ℃, 81.9% at 10 ℃, 85.3% at 25 ℃. 60.3% Pseudomonas strains with aprX gene were identified, and the proteolytic enzyme secreted by them were heat-resistant. Therefore, it is necessary to formulate good management measures to inhibit the growth and reproduction of Pseudomonas in raw milk and improve the quality of milk and dairy products.
Seed pests have severely hindered afforestation with and the industrial utilization of Caragana shrubs in North China. Therefore, in the initial (June 9), middle (June 18), late (June 27), and last (July 6) bearing phases of Caragana microphylla grown in Horqin Sandy Land, we investigated damage induced by seed pests in these plants while the latter were under different orientations (east, south, west, and north) and examined the effect of the damage on seed quality. Next, we analyzed the occurrence characteristics of seed pests and formulated a specific prevention measure. The results showed that there was no significant difference (P > 0.05) between the seed-set amount, pest rate, and seed quality at different plant orientations. The seed-set amount decreased significantly (P < 0.05) in the initial bearing phase and tended to stabilize in the middle bearing phase. The successful seed set rate stabilized at 89.17%. The pest rate increased sharply from 7.4% in the initial bearing phase to 19.3% in the last bearing phase before stabilizing at 22.8% in the late bearing phase. Pests reduced seed quality significantly (P < 0.05), causing the thousand-seed weight, germination rate, and germination potential to decrease by 30.7%, 17.2%, and 34.7%, respectively, but there was no significant difference (P > 0.05) between seedling emergence and germination rate. This study clarified the degree of damage caused by seed pests and occurrence characteristics of seed pests in C. microphylla, contributing to the investigation and prevention of seed pest infestation in Caragana shrubs in the arid and semi-arid areas of northern China.
Alpine Merino growing rams grazing in the Qilian Mountains, the research object in this study, were used to measure forage intake, nutrient digestibility, and rumen parameters in herbage regreening and grassy stages to determine the forage nutrition supply law and the nutritional status of the rams during these stages. The dominance index of plant communities in the grazing grassland and the diversity index, richness index, evenness index, and aboveground biomass of pasture in the grassy stage were higher than those in the regreening stage (P < 0.05). Additionally, the grading index (GI), crude protein, and crude ash were higher in the grassy stage than in the regreening stage (P < 0.05). There was no difference in the dry matter and crude protein intake of Alpine Merino growing rams, but the metabolic energy intake was higher in the herbage grassy stage than in the regreening stage (P < 0.05). In terms of digestibility in the two stages, there was no significant differences between the dry and organic matter (P > 0.05), but the crude protein, neutral detergent fiber, and acid detergent fiber were higher in the regreening stage (P < 0.05). The total volatile acid content was higher in the regreening stage than in the grassy stage (P < 0.05), but the isobutyric acid, butyric acid, isovaleric acid, and ammonia nitrogen content were higher in the grassy stage than in the regreening stage (P < 0.05). In the regreening stage, the metabolizable energy intake and crude protein intake of the Alpine Merino growing rams were 9.32 and 45.23 MJ·d−1 per sheep lower than the nutritional requirements, respectively, according to the feeding standard of Chinese Merino sheep (body weight 70 kg, daily gain 100 g). In the grassy stage, the metabolizable energy intake and crude protein intake were 7.32 and 32.64 MJ·d−1 per sheep lower than the nutritional requirements, respectively. In conclusion, the GI value and productivity of pasture in the grassy stage were higher than those in the regreening stage. Furthermore, when the daily gain reached 100 g in 70 kg Alpine Merino sheep, the metabolizable energy intake and crude protein were insufficient, and a certain amount of this energy and protein feed needed to be supplemented.
To determine the relationship between the growth and development of crimson clover (Trifolium incarnatum) and different sowing dates, the effects of different sowing dates on overwintering status, flowering date, plant height, grass yield, and seed yield were analyzed through field experiments. The results showed that within the range of the sowing dates applied in this experiment, delays in the sowing date led to later emergence and flowering time of crimson clover the next spring, but the growth period was shortened. Sowing before October 22 not only ensures a high crimson clover emergence rate but also that the overwintering rate reaches more than 84%. The highest yield of crimson clover sown on October 15 was 12.01 g per plant; when sown on October 22, the empty crimson clover pod rate was the lowest (15.40%), and the highest seed yield was 0.6632 g per plant. Therefore, sowing on dates from October 15 to October 22 in the Yangzhou region is beneficial for advancing flowering date and ensuring high grass yield and seed yield at harvest.
Suitable soil water content and plant density are key factors in the management of cultivated grassland. In this study, pot experiments were used to analyze the effects of different soil moisture (85%～90%, 75%～80%, 60%～65%, 35%～40% saturated soil moisture) and plant density (10, 15, 20 plants per pot) on plant and leaf characteristics of alfalfa (Medicago sativa). The results showed that the plant height, branch number, root neck diameter, main root length, and chlorophyll content of alfalfa increased first and then decreased with the increase of soil water content, while the leaf area and leaf dry weight showed an increasing trend. The root neck diameter, main root diameter, leaf area and leaf dry weight of alfalfa decreased with the increase of plant density, while chlorophyll a and chlorophyll b increased first and then decreased. Soil moisture and plant density interactions significantly affected only the root collar diameter (P < 0.05), and optimization results found that plant density was 15.1 plants per pot, and soil water content for soil saturated water capacity was 75.6% when root collar diameter was at its maximum, about 2.21 mm. This provides a scientific basis for regulating soil moisture and plant density in the field management of alfalfa.
Tall fescue (Festuca arundinacea Schred) is an important cool-season turfgrass and forage grass that is widely used in forage production, turf greening, and ecological restoration. In this study, 36 tall fescue germplasms from different sources were collected and analyzed for genetic diversity using EST-SSR primers and combined with seed phenotypic characteristics to comprehensively evaluate and analyze their germplasm diversity. The results showed that 14 pairs of EST-SSR primers amplified a total of 140 bands, and the total number of polymorphic bands was 133, with 95% polymorphic band percentage; the clustering results showed a certain geographical trend, but it was not obvious. In addition, when the genetic distance was 0.54, the clustering results were similar to the K-means clustering results of seed characteristics: the European population had the highest coefficient of variation for seed thickness and thousand seed weight, with values of 25.02% and 23.35%, respectively, and the thousand-grain weight of the European population was significantly lower than that of the Asian and North American populations (P < 0.05). Multifaceted genetic analysis showed that the 36 materials were highly heterogeneous. Multifaceted genetic analysis is important for the scientific evaluation of tall fescue genetic resources, core germplasm innovation, and new variety selection.
The purpose of this experiment was to study the effects of different roughage, supplemented with concentrate, on fattening donkeys raised for meat and to determine the effects of alfalfa hay, corn straw, wheat straw, and reed–supplemented with concentrate–on the dry matter intake (DMI), apparent nutrient digestibility, growth performance, and production benefit of the same. Therefore, 25 donkeys raised for meat (aged 2～3 years and weighing 145～150 kg) set to be fattened were randomly divided into the following 5 groups (5 replicates in each): control (alfalfa hay), group A (alfalfa hay + mixed concentrate), group B (corn straw + mixed concentrate), group C (wheat straw + mixed concentrate), and group D (reed + mixed concentrate). The results showed the following. 1) The DMI of the animals in group A was significantly higher than those of groups B, C, and D (P < 0.05), and there was no significant difference between group A and the control group (P > 0.05). The average daily gain in group A was significantly higher than those in groups B, C, and D (P < 0.01) and the control group (P < 0.05). The feed to weight ratio in group D was significantly higher than those in the other groups (P < 0.01) while that in group C was significantly higher than those in groups A and B and the control (P < 0.05). There was no significant difference between groups A and B and the control (P > 0.05). 2) The dry matter digestibility in group C was significantly lower than those in the other groups (P < 0.05). The crude protein digestibility in group A was the highest and more significant than those in groups B and D (P < 0.05); however, there was no significant difference between groups A and C (P > 0.05). The digestibility of acid detergent fiber in group D was significantly higher than those in the other groups (P < 0.05), and there was no significant difference in the digestibility of neutral detergent fiber in each group (P > 0.05); 3) The control group yielded maximum profit while group D produced a loss. The income from the control group was significantly higher than those from groups A and B (P < 0.05) and group C (P < 0.01). There was no significant difference between groups A and B (P > 0.05). In summary, alfalfa hay can be used as the single dietary item fed to donkeys during the fattening stage, with no need to supplement it with concentrate. Corn straw can be used as a basal diet for fattening donkeys; however, proper supplementation with concentrate could improve digestibility and economic benefits. Wheat straw and reed are not suitable as basal diets for fattening donkeys.
Plants communicate with each other and cooperate or compete with their relatives through identity recognition. The aim of this study was to clarify the identification differences of Stylosanthes guianensis Reyan No. 2 on root exudates of different plant relatives. In this study, the effects of root exudates from Stylosanthes guianensis Reyan No. 2 itself and its close and distant relatives on seedling growth of this taxa were studied. This was undertaken by culturing them in seven nutrient solutions containing root exudates of different relatives of Stylosanthes. Results showed that the average values of lateral root number, total biomass, stem leaf biomass, and root biomass (fresh weight) in the close relative treatment group were significantly higher than those in the self-treatment group (P < 0.05). For the self-treatment group, the average values of lateral root number and root biomass increased by 250.00% and 41.85%, respectively. Meanwhile, the average values of plant height, root length, and root-shoot ratio were not significantly different (P > 0.05). Compared with the self-treatment group, the average values of root length, lateral root number, root biomass, and root-shoot ratio in the distant treatment group significantly increased (P < 0.05). In this group, plant height significantly decreased by 10.52% (P < 0.05). There were differences in the specific response results for each species/variety in the close relative and distant relative treatment groups. Grey correlation analysis showed that the response of S. guianensis Reyan No. 2 to the root exudates of seven Stylosanthes species was ranked as follows: S. hamata > S. guianensis Reyan No. 24 > S. gracilis > S. scabra Seca > S. grandifolia > S. guianensis Reyan No. 5 > S. guianensis Reyan No. 21. It is suggested that kin recognition is an important mechanism for the competition and interaction between Stylosanthes and neighboring plants. In production, it is possible to develop new technologies for forage mixed sowing and increase forage yield per unit area by mixing Stylosanthes species with close relatives, such as mixed planting S. guianensis Reyan No. 2, S. guianensis Reyan No. 5, and S. guianensis Reyan No. 21.
Studying the functional characteristics and culture conditions is essential for successfully exploiting and industrializing plant growth-promoting rhizobacteria (PGPR). To further develop and utilize the strains, five strains obtained from the rhizosphere of Polygonum viviparum, Koeleria glauca, Trifolium pratense, and Poa pratensis were selected as materials in a previous study. The functional characteristics of the strains included the ability to dissolve phosphorus, fix nitrogen, and secrete indoleacetic acid (IAA). The taxonomic status of the strains was confirmed by 16S rDNA molecular biotechnology. The growth characteristics, temperature tolerance, pH tolerance, gas producing characteristics, and acid producing characteristics of the strains were determined, as well as their most appropriate culture conditions. The results showed that M1 had the highest amount of soluble organic phosphorus, 170.37 µg·mL−1, and Y3 had the highest amount of soluble inorganic phosphorus, 308.50 µg·mL−1. The strains had the ability to secrete IAA, and the amount secreted was between 24.23 and 104.74 µg·mL−1. Furthermore, the Y1 and Y3 strains had the ability to fix nitrogen, and produced 175.30 and 255.55 nmol (C2H4)·(h·mL)−1 from nitrogenase activities, respectively. From the determination of the growth characteristics of the strains, it was found that the five strains had entered the stable growth phase at 40 h, the suitable growth temperature was between 25 and 31 ℃, the suitable growth pH range was between 6.5 and 7.5, and there was no gas production when they were grown in LB medium. The pH was stable between 6.23 and 7.52 during the growth process, indicating their potential as industrial fermentation strains. The 16S rDNA identification confirmed that Y5 and Y3 were Bacillus subtilis, Y1 was Bacillus mycoides, M1 was Pseudomonas synxantha, and M6 was Pseudomonas simiae. This study lays the foundation for the industrial production of the strains.
The application of nitrogen fertilizers has a notable effect on the quality of lawns under low-light stress. To investigate the effects of low light and different nitrogen levels on the growth and carbon–nitrogen metabolism of tall fescue (Festuca arundinacea), two light levels (normal light and low light) and three nitrogen levels: low nitrogen (1 mmol·L−1), moderate nitrogen (6 mmol·L−1), and high nitrogen (18 mmol·L−1) were investigated. To provide a theoretical basis for urban landscaping and the management of lawns, the effects of light and nitrogen interactions on the morphology, physiology, and carbon–nitrogen metabolism of tall fescue were studied. The results showed that, compared to normal light exposure, the tiller number, leaf width, total biomass, soluble sugar content, soluble protein content, and nitrate reductase activity decreased in tall fescue under low light. Furthermore, the low nitrogen treatment could induce good blade width and increased the root cap ratio, carbon and nitrogen ratio, and the activity of glutamine synthetase in tall fescue under low-light stress. However, compared to the normal light treatment, the difference in tiller number and soluble sugar content of tall fescue under low light conditions was lower. Compared to the moderate or high nitrogen levels, the total biomass, nitrate reductase activity, and total carbon content of tall fescue under the low nitrogen treatment were not significantly different. Therefore, under low-light stress, tall fescue treated with low amounts of nitrogen had a good appearance and environmental adaptability, and the carbon–nitrogen metabolism of the plant tended to be balanced, which was conducive to the ideal growth of the plant.
In field experiments, three planting systems consisting of jujube (Ziziphus jujuba)–alfalfa (Medicago sativa) intercropping (JA), alfalfa monocropping (SA), and jujube monocropping (SJ) were applied to examine the effects of the different planting systems on soil nutrients and soil microbial properties. The results showed that under the JA system, the soil pH value tended to initially decrease, then increase; soil alkalinity nitrogen content varied in the order SA > JA > SJ; and available potassium and available phosphorus content in the soil differed in the order JA > SJ > SA. The number of soil microorganisms was the highest under the JA system, showing a pattern of an initial increase followed by a decrease. The number of soil fungi and actinomycetes peaked on July 21, and the number of soil bacteria peaked on June 19; in terms of yield, the yield under the JA system was 73% higher than that under either the SA or SJ systems. These findings show that the JA system significantly (P < 0.05) increased soil nutrient content, land use efficiency, and yield while also promoting microbial activity.
Understanding the salt tolerance of forage grass at the seedling stage is essential for the success of cultivated grassland planting. In this study, the growth rate, chlorophyll content, seedling height, survival rate, dry weight, and number of green leaves were measured under various salt concentrations (0, 50, 100, 150, 200 mmol·L−1) at the seedling stage using a hydroponic method. Moreover, the salt tolerance comprehensive evaluation value (D value) of 68 Melilotus officinalis germplasms was comprehensively calculated using principal component analysis, the subordination function, and the index weight method, based on the salt tolerance coefficient of each individual index. The results revealed that the single index of different germplasm materials showed a significant positive correlation under salt stress (P < 0.01). Based on a cluster analysis of the D value, the 68 Melilotus officinalis germplasms were divided into 6 highly salt-tolerant, 20 moderately salt-tolerant, 27 mildly salt-sensitive, and 15 salt-sensitive accessions. Moreover, stepwise regression analysis was performed on the D value and salt tolerance coefficient, and the survival rate, chlorophyll content, and number of green leaves were determined to be good criteria for salt tolerance evaluation in Melilotus officinalis accessions at the seedling stage. This study provides a theoretical basis for the establishment of Melilotus officinalis-cultivated grasslands on saline-alkaline land.
This study aimed to explore the effects of Zygophyllum xanthoxylum tonoplast Na+ compartmentalization gene ZxNHX1, H+-PPase (H+-pyrophosphatase) encoding gene ZxVP1-1, and cuticular wax transport gene ZxABCG11 on alfalfa “Xinjiang daye” growth, development and forage quality. We measured the indicators of growth, development and forage quality of wild type, ZxNHX1-VP1-1 transgenic, and ZxABCG11 transgenic alfalfa under field conditions. The results showed that: 1) Leaf area and hay yield of ZxNHX1-VP1-1 transgenic alfalfa were 56.4% and 74.5% higher than those of the wild type (WT), respectively; the net photosynthesis rate and water use efficiency were significantly higher than those of the WT (P < 0.05). The flowering period was 19 days longer than that of the WT. 2) The leaf area and stem diameter of ZxABCG11 transgenic alfalfa were significantly higher than those of the WT (P < 0.05). The net photosynthesis rate and water use efficiency were 81.7% and 80.5% higher than those of the WT (P < 0.05), respectively. The flowering period was 38 days longer than that of the WT. 3) Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) of ZxNHX1-VP1-1 transgenic alfalfa were significantly lower than those of the WT (P < 0.05). The relative feed value of ZxNHX1-VP1-1 transgenic alfalfa was 35.4% higher than that of the WT. These results showed that overexpression of ZxNHX1 and ZxVP1-1 increased the biomass and nutritional quality of alfalfa and prolonged flowering time. Overexpression of ZxABCG11 affected the leaf area, stem diameter and photosynthetic capacity of alfalfa. Meanwhile, the flowering period of ZxABCG11 transgenic alfalfa was longer than that of the WT.