Understanding the factors that alter competitive interactions and coexistence between plants is a key issue in ecological research. A pot experiment was conducted to test the effects of root interaction and arbuscular mycorrhizal fungi (AMF) inoculation on the interspecies competition between Trifolium repens and Lolium perenne under different proportions of mixed sowing by the combination treatment of two levels of AMF inoculation (inoculation and non-inoculation) and two levels of root interaction (root interaction and non-root interaction). Overall, the aboveground and belowground biomass of T. repens and L. perenne were not altered by AMF inoculation across planting ratios, probably because the fertile soil reduced the positive effect of AMF on plant growth. Both inter- and intraspecies root interaction significantly decreased the aboveground biomass of T. repens, but tended to increase the aboveground biomass of L. perenne across planting ratios, and thus peaked at the 4:4 polyculture. These results showed that T. repens competed poorly with L. perenne because of inter and intraspecies root interaction. Our results indicate that interspecies root interaction regulates the competitive ability of grass L. perenne and legume T. repens in mixtures and further makes great contribution for overyielding. Furthermore, AMF may not be involved in plant–plant interaction in fertile condition.
Sea buckthorn (Hippophae rhamnoides) is an important deciduous shrub for fruit and ecological restoration in arid and semi-arid regions of China. Twelve Chinese and Russian cultivars (cv. Shenqiuhong, eshi01, ... eshi11) were planted about 1.6 acre area in a seedling nursery, located in Qingyang City of Gansu province in northwest China, where high mortality (more than 70%) of sea buckthorn was observed in late July 2019. Symptoms consisted of massive chlorosis, drooping leaves and dried-up stems on 5-year-old trees. Pieces of tree roots and stems with irregular light-brown discoloration in the xylem vessels were selected. Small pieces of discolored tissue were surface disinfested (1 min in 1% sodium hypochlorite, followed by three rinses with sterile distilled water), air-dried, and placed on potato dextrose agar (PDA) medium for 5 days at 25°C in the dark. A fungus was consistently isolated from both diseased roots and stems tissues. Colonies on PDA grew rapidly. Dense mycelia were pinky-white initially, and became carmine red color with age on the undersurface of the plate. Macroconidia were moderately curved, 3 to 5 marked septa, hyaline, thick walled, and measuring 27.8± 3.6 µm × 4.8 ± 0.5 µm (n = 30). Microconidia were abundant, pear-shaped, ellipsoid to fusoid, often with a papilla at the base, and 8.4 ± 2.2 µm ×3.1 ± 0.3 µm (n = 30). Genomic DNA was extracted for amplification and sequencing of the internal transcribed spacer region (ITS1 and ITS4 primers) (White et al. 1990) of the ribosomal DNA (Accession Nos. MN160235 to MN160238) and translation elongation factor-1 alpha (EF1 and EF2 primers, accession Nos. MN429075 to MN429078) (O’Donnell et al. 1998). The sequences revealed 99% similarity to the sequences of the ITS (AY188917), and 100% identity with EF1-α (JF740808) regions of Fusarium sporotrichioides. Based on morphological and molecular characteristics, the fungus was identified as F. sporotrichioides (Leslie and Summerell 2006). Koch’s postulates were fulfilled on healthy, potted 1-year-old sea buckthorn seedings using two isolates in a greenhouse at 25 °C, 90% relative humidity, and 12-hour light/dark photoperiod. Ten potted seedings were inoculated on the stems by placing a 5-mm-diameter mycelial plug (5-day-old PDA cultures for each isolate) into the surface of a wound created with a needle, and the inoculation sites were covered with Parafilm to maintain moisture. Ten seedings were inoculated with PDA plugs as controls. Seven to ten days after inoculation, typical symptoms of dark-brown necrotic lesions on chlorotic leaf margins were observed. About 2 weeks after inoculation, the inoculated stems were gradually dry up, accompanied by withering and fallen leaves. Control plants remained asymptomatic. Pathogens were successfully isolated from the inoculated stems again, exhibiting morphological characteristics identical to those of F. sporotrichioides. Previous papers reported F. sporotrichioides as a common pathogen caused lavender wilt (Cosic et al. 2012), foliar spots on forage corn (Moya-Elizondo et al. 2013) and maize ear rot (Wang et al. 2019). To our knowledge, this is the first report of sea buckthorn stem wilt caused by F. sporotrichioides on several Chinese and Russian cultivars in Gansu province of China. In Heilongjiang province, the same disease was reported in 2010 (Song et al. 2010), nearly 30 longitudes away from Gansu province. Therefore, this disease appears to be a serious risk for future sea buckthorn production.
The Huajian gold deposit is located in the metallogenic belt of the northern part of the North China block. This deposit's ore bodies are mainly hosted in metamorphosed Neoarchean and Mesoproterozoic sedimentary rocks, of which Mesozoic volcano-intrusive complexes are closely associated with the Gold mineralization. The FIs of the Huajian deposit are primarily aqueous FIs with minor gas FIs. The pure gas or liquid FIs are very few. The ore-forming fluids were characterised by moderate–low temperature, low salinity and high oxygen fugacity and belonged to an H2O–NaCl ± CO2system. The FIs in quartz veins primarily developed in temperature intervals of 202–380°C, 191–407°C and 170–307°C., corresponding to salinities of 3.85wt.% to 11.23 wt.%, 3.69wt.% to 10.99 wt.% and 2.06wt.% to 17 wt.% NaCl eq.., respectively. The trapping pressures of the FIs from high temperature fluids in the quartz veins are 10-90 MPa, corresponding to depths of 1.0–10 km, assuming a density of the overlying rocks of 0.54 g/cm3–0.98 g/cm3. Multiple stages of phase separation or immiscibility of ore-forming fluid was critical for the formation of the Huajian deposit.
The ability of soil and water conservation crops to resist stress is closely related to their abundance of lipid‐soluble chemical components. This study systematically evaluated the composition and content of fatty acids, sterols, squalene, and tocopherol in oils extracted from three varieties of crops growing on the Chinese Loess Plateau with extreme environments. The dominant fatty acids in the wild seabuckthorn pulp oil were oleic acid (29.73%), palmitic acid (26.83%), and palmitoleic acid (25.71%), and those in wild seabuckthorn seed oil were linoleic acid (42.29%), α‐linolenic acid (20.65%), and oleic acid (18.94%). The most abundant fatty acids in wild elaeagnusmollis seed oil were oleic acid (43.29%), linoleic acid (35.93%), and α‐linolenic acid (7.00%). Wild yellowhorn seed oil was rich in linoleic acid (34.14%), oleic acid (25.99%), and erucic acid (8.76%). Seabuckthorn seed oil had the highest levels of total sterols (619.33 mg/100 g), followed by seabuckthorn pulp oil (606.10 mg/100 g), yellowhorn seed oil (249.46 mg/100 g), and elaeagnusmollis seed oil (224.01 mg/100 g). However, the squalene content was highest in elaeagnusmollis seed oil (68.06 mg/100 g) and similarly low in yellowhorn seed oil (9.81 mg/100 g), seabuckthorn pulp oil (4.62 mg/100 g) and seabuckthorn seed oil (4.71 mg/100 g). In addition, seabuckthorn pulp oil had the highest tocopherol content (179.92 mg/100 g), followed by seabuckthorn seed oil (130.57 mg/100 g), elaeagnusmollis seed oil (85.87 mg/100 g), and yellowhorn seed oil (45.44 mg/100 g). This study provides favorable data supporting biomass resource utilization and organic synthesis of bioactive raw chemical composition.
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