IntroductionArbuscular mycorrhizal fungi (AMF) perform a vital role in terrestrial ecosystems.MethodsTo investigate the diversity of AMF communities on the western slope of Helan Mountain at different altitudes and their influence factors, high-throughput sequencing was used to study the structure and diversity of soil AMF communities under different environments and their interrelationships between AMF and environmental factors.ResultsThe results revealed that there were significant differences (p < 0.05) in the physical and chemical properties of the soil along the different altitudes. A total of 1,145 OTUs were obtained by high-throughput sequencing, belonging to 1 phylum, 4 class, 6 orders, 13 families, 18 genera and 135 species, with the dominant genus being Glomus, which accounted for 75.27% of the relative abundance of the community. Soil AMF community structure was shown to be variable at the generic level according to NMDS analysis. Correlation analysis showed that soil pH, water content (WC), organic matter (OM), available K, available P and N were significantly correlated with AMF community diversity and species abundance (p < 0.05, p < 0.01). Based on redundancy analysis (RDA) and Monte Carlo test results, soil pH, WC and OM had highly significant effects (p < 0.01) on AMF community diversity and species abundance.DiscussionThis study investigates the relationship between AMF community structure and diversity and soil physicochemical properties at different elevations on the western slope of Helan Mountain, which is of great significance to the study of the Helan Mountain ecosystem.
Previous research has reported that hypoxic conditions and ethylene treatments greatly trigger programmed cell death (PCD) occurrence and induce the formation of aerenchyma to adapt stress environment in Helianthus annuus stem. Caspase 3‐like protease (CLP) as regulatory signals, also be involved in the process of PCD to adapt the low oxygen environment. However, the relationships between ethylene and CLP have seldom been reported. Herein, To understand the regulatory role of ethylene and CLP signaling molecules in aerenchyma formation, we investigated the effects of exogenous ethephon (ET), ethylene perception inhibitor 1‐methylcyclopropene (1‐MCP), and the treatment of 1‐MCP + ET on morphological, physiological characteristics and aerenchyma formation in H. annuus stem. The results showed that lysigenous aerenchyma formation in H. annuus stem is induced by ET, and immunohistochemistry assay indicate CLP activity is raised at the formation stage of aerenchyma formation, and decreased at the expanding phase of aerenchyma formation. Western blotting illustrate the expression of CLP is also increased within 8 h after ethylene signaling inducing aerenchyma formation, and the activities of CLP are higher in ET treated seedlings than the control and 1‐MCP treated seedlings. The same phenomenon was also observed by caspase‐3 activity assay. These results revealed there is a causal and interdependent relationship between ET and CLP signaling during the process of aerenchyma formation, which regulating PCD initiation in H. annuus stem.
To reveal distribution characteristics of glomalin-related soil protein (GRSP) and it’s influencing factors under different vegetation types in the drought-tolerant shrubland of Helan Mountain, we chose three vegetation types as study subjects: Stipa breviflora (Grassland, G), Amygdalus mongolica (Shrub, S), and Stipa breviflora-Amygdalus mongolica (Grassland-Shrub, G×S) and bare soil was used as the control (CK). The contents of easily extractable glomalin-related soil protein (EE-GRSP) and total glomalin-related soil protein (T-GRSP), soil physicochemical properties, colonization rate, spore density, and species abundance in the rhizosphere soil were determined. The results indicated that EE-GRSP and T-GRSP showed significant difference (p < 0.05) among vegetation types, with GRSP content highest under G×S (5.68 and 6.27 mg·g−1, respectively) and lowest under CK (3.84 and 4.48 mg·g−1, respectively). EE-GRSP/soil organic carbon (SOC) and T-GRSP/SOC showed no significant difference (p > 0.05). The trends of colonization rate, spore density, and species abundance were the same and were significantly different from those of GRSP content (p < 0.05), with maximum values of 75.6%, 20.7 × 10 g−1, and 29.7, and minimum values of 55.6%, 13.0 × 10 g−1, and 12.7, respectively. Pearson correlation analysis showed that EE-GRSP was significantly positively correlated with SOC, total phosphorus, available phosphorus, and colonization rate (p < 0.05), and it showed an extremely significant positive correlation with available potassium, spore density, and species abundance (p < 0.01). T-GRSP was significantly positively correlated with total phosphorus and available phosphorus (p < 0.05), as well as with soil organic carbon, available potassium, spore density, colonization rate, and species abundance (p < 0.01). The redundancy analysis (RDA) showed similar results. Therefore, the distribution characteristics of GRSP and its influencing factors under different vegetation types in the low elevation area of Helan Mountain were influenced by vegetation types, physicochemical properties of rhizosphere soil, and arbuscular mycorrhizal fungi (AMF) colonization, thus providing a scientific basis for soil quality improvement and vegetation restoration.
The purpose of this narrative review was to summarize empirical studies regarding the effects of metacognition on English reading-related outcomes for students who are d/Deaf and hard of hearing (d/Dhh). This review covered the timeframe from the publication of the previous and only narrative review conducted by Strassman (1997) to 2020. Several of Strassman’s assertions were confirmed, including the oft-repeated one: d/Dhh students possess inadequate comprehension-monitoring skills. In fact, the students are not aware of effective metacognitive strategies and, in general, do not know “what they do not know.” Although intervention is strongly recommended, a few later studies asserted that such intervention not only should be based on the recommendations of the National Reading Panel, but also should be differentiated to meet the individual needs of d/Dhh students. It was argued that d/Dhh reading comprehension challenges are due to metacognitive or executive function issues; however, this assumption needs to be contextualized within a framework of reading which entails decoding and comprehension processes.
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