Seedlings Of Varieties Research Articles

Urban forests support natural regeneration of cloud forest trees and shrubs, albeit with limited occurrence of late-successional species

In highly diverse tropical landscapes, urban and peri-urban forests can play a crucial role as reservoirs of biodiversity. However, urbanization has negatively impacted the natural and anthropogenic vegetation, including the composition, diversity, and functions of urban forests. Tree regeneration plays an essential role in the long-term functionality of forests. Few studies have investigated how natural regeneration occurs in urbanized tropical landscapes, as well as the factors that drive this process. We assessed whether natural regeneration of the tropical montane cloud forest is occurring in urban and peri-urban forests and examined the influence of environmental factors (elevation, annual precipitation, air temperature, canopy cover, and soil physicochemical characteristics) on the regeneration. We used the density and diversity of seedlings, saplings, and juveniles of trees and shrubs in 42 plots across seven urban and peri-urban sites in the Neotropical city of Xalapa, Mexico. In the natural regeneration, 42 tree and 22 shrub species were recorded. Of these species, 83% were native and 17% were non-native. There was a lower abundance of tree (34%) compared to shrub (66%) individuals. Early-successional species were more abundant (51%) than intermediate (35%) and late-successional (14%) species. The numbers of species in the seedling, sapling, and juvenile stages, and the number of early-successional species, were higher in urban than in peri-urban forests. The species richness of both native and non-native taxa was higher in urban than in peri-urban forests (95% CI). We found no significant differences in the density of the young life stages, the density of successional groups, or the density of native and non-native species, between urban and peri-urban forests, probably due to high variability across the sites. Canopy cover had a consistently positive effect on density in most groups. Forest type, soil phosphorus, and soil bulk density also explained densities, except for the late-successional species, where these factors were not statistically significant. The limited richness and density of late-successional species highlight the need to assist the regeneration of this vulnerable group. Understanding natural regeneration patterns can inform the management and restoration of urbanized areas in the distributional regions of tropical montane cloud forest, one of the most important and threatened tropical ecosystems.

Responses of Plant Species Diversity and Biomass to Forest Management Practices after Pine Wilt Disease

Pine wilt disease (PWD), which is caused by the Bursaphelenchus xylophilus, is one of the most serious biological invasions in East Asia. Removal of infected pine trees is generally used to prevent the spread of PWD. However, how this strategy affects plant species diversity and ecosystem functions needs to be clarified. We compared alpha diversity, species composition, and biomass for all woody plant species, adults, saplings, and seedlings in infected Masson pine forests where removal of infected trees occurred (CTD) and where infected trees were retained (UTD), uninfected Masson pine forests (PMF), and evergreen broad-leaved forests (EBF). UTD had the highest alpha diversity of all species and saplings, and UTD and PMF had the lowest alpha diversity of seedlings. CTD and EBF had a similar composition of seedlings, and CTD and UTD had similar species composition of all plant species and saplings. UTD had the lowest biomass for all species and adults but had the highest saplings biomass. Soil properties were significantly related to plant biomass. The retention of infected trees likely maintained soil fertility which increased species alpha diversity and the biomass of saplings, and unchanged species composition compared to the removal of infected trees, indicating that the retention strategy could help to maintain ecosystem functions.

A lack of ecological diversity in forest nurseries limits the achievement of tree-planting objectives in response to global change

Abstract Tree planting is increasingly being adopted as a strategy to address global change, including mitigation, adaptation, and restoration. Although reforestation has long been central to forest management, the desired outcomes of traditional and emerging tree-planting strategies face barriers linked to a lack of ecological diversity in forest nurseries. In the present article, we outline how insufficient diversity in nursery seedlings among species, genotypes, and stock types has impeded and will continue to hinder the implementation of diverse ecological or climate-suitable planting targets, now and into the future. To support this, we demonstrate disparities in seedling diversity among nursery inventories, focusing on the northern United States. To overcome these challenges, we recommend avenues for improving policy and financing, informational resources and training, and research and monitoring. Absent these advances, current seedling production and practices will fall short of ambitious tree-planting goals proposed for forest restoration and global change mitigation and adaptation.

Transcriptome and Metabolome Analyses Reveal Mechanisms Underlying the Response of Quinoa Seedlings to Nitrogen Fertilizers.

Quinoa (Chenopodium quinoa Willd.) is a dicotyledonous annual amaranth herb that belongs to the family Chenopodiaceae. Quinoa can be cultivated across a wide range of climatic conditions. With regard to its cultivation, nitrogen-based fertilizers have a demonstrable effect on the growth and development of quinoa. How crops respond to the application of nitrogen affects grain quality and yield. Therefore, to explore the regulatory mechanisms that underlie the responses of quinoa seedlings to the application of nitrogen, we selected two varieties (i.e., Dianli-1299 and Dianli-71) of quinoa seedlings and analyzed them using metabolomic and transcriptomic techniques. Specifically, we studied the mechanisms underlying the responses of quinoa seedlings to varying concentrations of nitrogen by analyzing the dynamics of metabolites and genes involved in arginine biosynthesis; carbon fixation; and alanine, aspartate, and glutamate biosynthetic pathways. Overall, we found that differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) of quinoa are affected by the concentration of nitrogen. We detected 1057 metabolites, and 29,012 genes were annotated for the KEGG. We also found that 15 DEMs and 8 DEGs were key determinants of the differences observed in quinoa seedlings under different nitrogen concentrations. These contribute toward a deeper understanding of the metabolic processes of plants under different nitrogen treatments and provide a theoretical basis for improving the nitrogen use efficiency (NUE) of quinoa.

The Effect of Nano-Fertilization and Tube Size on the Qualitative Characteristics of Two Types of Strawberry (Fragaria ananassa Duch)

This experiment was conducted in the unheated plastic house of the Horticulture and Landscaping Department of the College of Agriculture / University of Tikrit in the agricultural season 2021-2022. To study the effect of nano-fertilization at a concentration of 0, 1.5, and 3 g, and planting with different sizes of plastic tubes with a diameter of 4, 6, and 8 inches on the qualitative characteristics of two varieties of seedlings of the Fragaria ananassa Duch plant. Anthocyanins reached 18.16 mg 100gm-1, tube 6 inch was superior in terms of total acidity and reached 1.26%, while tubes 6 and 8 inch were superior in percentage of soluble solids, total sugars and percentage of dry matter in fruits. The cultivar Albion was significantly superior to the cultivar Rubygem in terms of total acidity, reaching 1.25%, while the cultivar Rubygem was superior to Albion in the percentage of total sugars, amounting to 2.23%, and the percentage of anthocyanins in the fruits, amounting to 17.51 mg 100g-1. Significant in the percentage of total solids, which amounted to 12.00%, and the percentage of total sugars, which amounted to 2.24%.

Understory plant growth forms respond independently to combined natural and anthropogenic disturbances

Natural disturbances can maintain forest diversity by creating a heterogeneous resource landscape, which can contribute to coexistence of early- and late-successional species. However, almost all forested ecosystems are also subject to multiple anthropogenic stressors, which could inhibit plant diversity and forest recovery after natural disturbances. Here, we present the first large-scale replicated field experiment testing the interactions among two natural and two anthropogenic disturbances in a mature secondary temperate forest. Specifically, we test the extent to which: 1. a natural windthrow (tornado), 2. deer browsing, 3. salvage logging, a common forestry practice to generate revenue after natural disturbances, and 4. mechanical removal of the understory, drive subsequent plant community assembly, diversity, and abundance. Our results have two clear messages. First, the combined disturbances, especially salvage logging, increased plant species richness and abundance; we found 65 more species in 0.1 ha of the disturbed areas versus the same area of reference forest. Second, we found that it was critical to analyze plant growth forms separately; each major plant growth form responded to the disturbances differently. Surprisingly, salvage logging, browsing, and vegetation removal had negligible effects on the diversity and abundance of tree seedlings or saplings. In contrast, salvaging increased herb richness by 30% (six extra species per 36 m2 plot), and shrubs were twice as abundant in salvaged versus unsalvaged plots. The combined disturbances created unique plant communities in comparison to adjacent undisturbed reference sites, but plant growth forms differed in which combination of disturbances shifted community composition the most. We did not find that non-native invasive species substantially increased in abundance in response to the disturbances, nor were invasive species unique to the salvaged areas. Together, our results demonstrate that a patchwork of combined natural and anthropogenic disturbances can promote plant diversity in a human-modified temperate forest. In particular, the combination of a natural wind disturbance and salvage logging benefited native herbaceous species, the plant group that represents the vast majority of vascular plant species (∼80%) in temperate forests across the world.

Taxonomic and phylogenetic shifts following an inland derecho

In 2009, a derecho occurred in southern Illinois, affecting large areas of the regional forest systems. Previous research reported multi-strata species compositional shifts post-derecho at LaRue Pine Hills/Otter Pond Research Natural Area but did not investigate how these changes varied within the RNA. These observations are expanded here to include phylogenetic and spatial relationships to show how compositional shifts can vary within a landscape. Surveys were conducted the year before and after the derecho. Univariate and multivariate analyses identified elevation as an environmental driver of diversity and community composition. Spatial analyses identified spatial patterns in taxonomic (TSR) and phylogenetic (PSR) species richness, and metrics of phylogenetic clustering and overdispersion (net relatedness index and nearest taxon index; NRI and NTI, respectively), in seedling, sapling, and tree communities. Tree TSR and PSR and sapling PSR decreases and sapling NTI increases occurred post-derecho. Seedling diversity-elevational relationships exhibited humped-backed relationships, while saplings showed positive linear relationships between phylogenetic metrics and elevation. Local Moran’s I analysis showed post-derecho clustering in the north-central extent for seedling, sapling, and tree strata. Co-Kriging interpolation predicted seedling diversity increases in the southwestern extent, with sapling and tree diversity increases in the eastern extent and the north-central extent respectively post-derecho, indicating competitive interactions at lower elevations and environmental filtering at higher elevations. Seedling and tree NRI and NTI increased in the southern extent, whereas sapling clustering increased in the northeastern extent. These relationships indicate how community assembly processes (i.e., competition or environmental filtering) are altered following large-scale disturbance.

Biotic pressures and environmental heterogeneity shape beta‐diversity of seedling communities in tropical montane forests

Many theories have been proposed to explain the high diversity of plants in the tropics. However, we lack an understanding of the processes that drive plant diversity and community assembly at different spatial scales. Here, we applied beta‐diversity partitioning to test how biotic and abiotic factors are associated with seedling beta‐diversity in a tropical montane forest in southern Ecuador. We recorded seedling communities on 81 subplots in nine plots located at three elevations along a 2000 m elevational gradient. We measured biotic pressures (i.e. herbivory and fungal pathogen attacks) and environmental conditions (i.e. soil moisture and canopy closure) in all subplots and related them to species turnover and richness differences in seedling communities within and between elevations. We found that species turnover increased with differences in biotic dissimilarity within elevations, while differences in species richness within elevations increased with increasing environmental dissimilarity. Between elevations, species turnover increased with increasing environmental dissimilarity. Our findings show that species turnover and changes in species richness are related differently to abiotic and biotic factors, and that the importance of these factors for shaping seedling diversity is scale‐dependent. Our study contributes to better understand the processes driving seedling beta‐diversity and the assembly of plant communities in highly diverse tropical montane forests.

Adaptive Trait Variation in Seedlings of Rare Endemic Mexican Spruce Provenances under Nursery Conditions

The distributions of the three Mexican spruces are fragmented, possibly leading to phenological, morphological and genetic differentiation, which is partly caused by local adaptation. In this study, we estimated for the first time the intra- and inter-specific phenotypic variation in 5641 seedlings from provenances of the three Mexican spruces. We examined (i) provenance-related differences in the seedling survival rate, diameter (D), height (H) and seed weight (SW) as quantitative traits, (ii) the association between the survival rate, D, H and SW and climatic and soil variables in the Picea provenances and (iii) (narrow-sense) heritability (within-provenance) based on D and H under the same nursery conditions, assuming that the response can be considered as a proxy for quantitative genetic differentiation between provenances. All Mexican spruce species differed significantly in H, and all eight provenances studied were significantly different in D and H, except for two neighboring provenances of P. mexicana. Very strong, significant correlations (up to R2 = 0.96) were found between H, the survival rate and SW with respect to environmental factors of provenance/seed origin. Additionally, the heritability index explained a high percentage of the provenance-related variance. The use of germplasm for restoration in different sites and with different populations requires collecting seeds from numerous trees from as many provenances as possible, but should be carried out with caution owing to the apparently strong local adaptation in provenances of the Mexican spruces.

Spatial ionomics provides new insights into the accumulation and transport of mineral ions in rice (Oryza sativa L.) under Cadmium stress

The distribution of various elements in different organs is spatially specific, and the distribution of elements in different organs of rice under Cadmium (Cd) stress and nutrient deficiency conditions is unknown, these limit the creation of ideal crops. In this study, spatially-specific ionomics study was applied to the spatial distribution of ions in different organs of 14 different varieties of hybrid rice seedlings under Cd stress. Under Cd stress, magnesium (Mg), manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe) were found to accumulate mainly in the nodes, while Ca accumulated mainly in the mature leaves, and K mainly in the leaf sheaths and new leaves. Under Cd stress, the contents of Mg and Mn in all organs and Mg, Mn, Zn, Ca, Cu, and Fe in nodes decreased, but the accumulation of Fe in roots increased. In all organs, the concentrations of calcium (Ca), Mg, Mn, and Fe were almost positively correlated. Moreover, the ion transfer factors of Mg/Mn, Mg/Cu, and Zn/potassium (K) all showed positive correlations, indicating that these elements had similar chemical properties or biological functions. The accumulation of Cd in different organs of 4 varieties under Cd stress and K/Mn/Ca/Mg deficiency treatments was studied. Under Mg deficiency stress, the Cd concentration increased significantly. Under Ca deficiency stress, Cd transport was reduced. In conclusion, spatial ionomics was used to investigate the transport and accumulation of elements in different organs of O. sativa L., and these results provided theoretical support for the creation and production of ideal crops under Cd stress.

Indeks Nilai Penting dan Keanekaragaman Komunitas Vegetasi Penyusun Hutan di Alas Burno SUBKPH Lumajang

The importance value index and diversity are important indicators to determine the dynamics and stability of the vegetation community. The objectives of the study were (1) to determine the importance value index of seedlings, saplings, poles and trees composing the Bruno Forest community in SUBKPH Lumajang (2) to know the diversity of seedlings, saplings, poles and trees composing the Bruno Forest community in SUBKPH Lumajang. The research was conducted in the Bruno Forest Area, SUBKPH Lumajang, East Java. The plot method was used in this study with nested plots measuring 2x2m2 for seedlings, 5x5m2 for saplings, 10x10m2 for poles, and 20x20m2 for trees. The number of samples was 30 plots placed systematically, with a distance between plots of 20m. The conclusions of this study are (1) the forest vegetation community of Bruno Forest area is composed of 9 species belonging to 6 families, at tree level dominated by Pinus merkusii, at pole level by Swietenia macrophylla species, saplings and seedling level dominated by Calliandra surinamensis (2) Diversity at tree and pole level was categorized as high while at sapling and seedling level was categorized as moderate. The species evenness index at the tree, pole and saplling level was categorized as high, while at the seedling level it was categorized as medium.

Light effects on seedling growth in simulated forest canopy gaps vary across species from different successional stages

Tropical forests continue to suffer from various kinds of disturbances in the Anthropocene. An immediate impact of disturbances on forest ecosystems is the creation of numerous large and small canopy gaps, which dramatically affect forest structure and function. Yet, we know little about the effect of canopy gaps on forest successional trajectory. More specifically, the responses of seedlings from different successional stages to increased light intensity under large and small canopy gaps in understory remain unclear. In this study, dominant tree seedlings from early-, mid-, and late-successional stages were selected, respectively from a tropical montane forest in Hainan Island, China to study their growth rate, biomass and traits. Our results showed that the light condition under small canopy gaps (SG, 10–15% of full sunlight) and large canopy gaps (LG, 40–50% of full sunlight) induced greater increment of relative growth rates for seedlings from early- and mid-successional stages relative to that in late-successional stage. Both SG and LG also significantly increased photosynthesis rate, leaf area (LA), light saturation point (LSP), root mass ratio (RMR) and root: shoot ratio, but decreased specific leaf area (SLA) of seedlings across successional stages. Tree seedlings from the early-successional stage displayed the greatest decrease in leaf mass ratio, increase in LA, LSP, and RMR, in comparison to those from mid- and late- successional stages. Light condition and SLA were the most important factors for seedlings’ relative growth rate across successional stages. SLA connected the interaction between the light condition and successional stage on seedlings’ growth, thereby jointly explaining the 93% variation of seedlings’ growth, combining with area-based light saturated rate of CO2 assimilation. Our study highlights the distinct effect of disturbance-induced canopy gaps on seedling regeneration in the understory in tropical forest due to the variation of light intensity. We suspect that the seedlings from late-successional stage will recover relatively slow after disturbances causing canopy losses, which can have detrimental impacts on structure feature and successional trajectory in tropical forest, as well as forest-based ecosystem services.

Tree Diversity and Regeneration in Sacred Groves and Nature Reserves in Xishuangbanna, Southwest China

Holy Hills, sacred groves protected by ethnic minority Dai people, have garnered great interest for conservation in Xishuangbanna—a region containing some of the world's northernmost tropical rain forests and China's richest biodiversity, though much of it has been threatened by deforestation from rubber cultivation. As some of the only remaining forest fragments outside nature reserves, Holy Hills have been documented to contain rare species and ecosystems underrepresented in protected areas. Although previous studies provided some insight into fragmentation impacts, they lacked data to examine population structures. Accordingly, this study uses continuous metrics of tree regeneration for the first time in sacred groves, while also drawing on ethnographic understandings of socioecological contexts of human disturbance, to examine biodiversity and regeneration in three Holy Hills and two nature reserves. Contrary to expectations that smaller area and fragmentation effects would decrease biodiversity in Holy Hills, we found no significant difference in diversity between Holy Hills and nature reserves, though we detected marginally significantly less diversity in seedlings, and certain Holy Hills displayed a shift towards light-demanding species. Common and dominant species varied by site, speaking to the importance of inter-patch beta diversity captured among Holy Hills that can support the maintenance of a regional species pool. Our results also indicated considerable regeneration opportunity in Holy Hills, though individual site conditions and histories had a strong influence. We recommend collaborating with communities and local institutions not only to safeguard existing forest, but also to regenerate and restore fragments whose protection is bolstered with cultural meaning.

The species diversity and composition of seedlings for degraded land rehabilitation in different phytogeographical regions in Indonesia

Abstract. Wirnoyo, Lukman AH, Nurliana S. 2022. The species diversity and composition of seedlings for degraded land rehabilitation in different phytogeographical regions in Indonesia. Biodiversitas 23: 5771-5781. Forest clearing and conversion into cropland without implementing conservation measures have caused land degradation. The total area of degraded land in Indonesia is 14 million hectares. The responsible institution for land rehabilitation in Indonesia is Balai Pengelolaan Daerah Aliran Sungai dan Hutan Lindung (Agency for Watershed and Protection Forest Management), abbreviated as BPDASHL. This study aimed to analyze seedlings' species diversity and composition for degraded land rehabilitation provided by six BPDASHLs located in different phytogeographic regions, i.e., Sunda Shelf, Wallacea, and Sahul Shelf. Data were collected through questionnaires distributed to BPDASHL offices in Papua, West Papua, Gorontalo, Bangka Belitung Islands, Riau, and Aceh. They were analyzed to determine the species richness, indexes of species diversity, equity, and similarity. The clustering of sites based on species composition was done using a dendrogram. This study found that the species richness of seedlings in each site ranged from 25 to 47, the diversity index of Shannon from 2.39 to 2.96, and a Simpson diversity index from 0.80 to 0.94. The species composition differed from one site to another, with similarity indexes of Bray-Curtis and Jaccard of < 0.35. The dendrogram separated western Indonesia (Sunda Shelf) from eastern Indonesia (Sahul Shelf and Wallacea), except for Bangka Belitung Islands, which was clustered in eastern Indonesia despite its location in western Indonesia. Three study sites had more native dominant species, while the other three had more introduced dominant species. We recommend that more native species of seedlings should be provided.

The effect of water volume on growth of several oil palm varieties (Elaeis guineensis Jacq.) aged of 8-14 months in main nursery

Oil palm plantation has an important role for the development of national plantation in Indonesia, in purpose to create job opportunities that lead to community welfare and also become the source of foreign exchange or tax for the country. Over the last four years, the area of oil palm plantation in Indonesia has increased from 10.4 million hectares since 2013 and continued to 12.30 million hectares in 2017 with total production 34.47 million tons of Crude Palm Oil (CPO). This research was conducted using experimental research by applying the form of the two-stage nested plot with the treatment arrangement of factor 2 into factor 1. The first factor was oil palm variety which includes of 3 levels, namely V1: Tenera DxP Marihat variety, V2: Tenera DxP Topaz 3 variety, and V3: Tenera DxP Socfindo Lame variety. The second factor was the volume of water supply which consists of 4 levels, namely A1 = 1000 ml per day per plant, A2 = 1500 ml per day per plant, A3 = 2000 ml per day per plant, and A4 = 2500 ml per day per plant. The Observation parameters are photosynthetic rate, leaf area, seedling height, and diminutive diameter of trunk, number of leaves, wet weight, plant roots, root crown ratio, and seed quality index. The results showed that the volume of water affected all growth components of several varieties of oil palm seedlings, both on the variables of photosynthesis rate, leaf area, seedling height, and diminutive diameter of trunk, number of leaves, wet weight, plant root volume, root crown ratio, and seed quality index.

PEG-induced physiological drought for screening winter wheat genotypes sensitivity - integrated biochemical and chlorophyll a fluorescence analysis.

This study aimed to screen different winter wheat genotypes at the onset of metabolic changes induced by water deficit to comprehend possible adaptive features of photosynthetic apparatus function and structure to physiological drought. The drought treatment was the most influential variable affecting plant growth and relative water content, and genotype variability determined with what intensity varieties of winter wheat seedlings responded to water deficit. PEG-induced drought, as expected, changed phenomenological energy fluxes and the efficiency with which an electron is transferred to final PSI acceptors. Based on the effect size, fluorescence parameters were grouped to represent photochemical parameters, that is, the donor and acceptor side of PSII (PC1); the thermal phase of the photosynthetic process, or the electron flow around PSI, and the chain of electrons between PSII and PSI (PC2); and phenomenological energy fluxes per cross-section (PC3). Furthermore, four distinct clusters of genotypes were discerned based on their response to imposed physiological drought, and integrated analysis enabled an explanation of their reactions’ specificity. The most reliable JIP-test parameters for detecting and comparing the drought impact among tested genotypes were the variable fluorescence at K, L, I step, and PITOT. To conclude, developing and improving screening methods for identifying and evaluating functional relationships of relevant characteristics that are useful for acclimation, acclimatization, and adaptation to different types of drought stress can contribute to the progress in breeding research of winter wheat drought-tolerant lines.

Performance Test of Cassava Cutting Machine Type of Double Block Cutter

Preparation of cassava seeds using a machete or hand saw takes a long time, the results are not uniform, and there is a potential for damage to cassava seedlings. The double block cutter type cassava stem cutting machine has been designed to produce high capacity and good quality cassava seeds. This study aims to test the performance of the cassava stem cutting machine with the double block cutter type. Performance tests include measuring machine working capacity, fuel consumption, seed uniformity, and planting test. The cutting test was carried out using 3 varieties of cassava seedlings. The machine works at a rotational speed of 3800 rpm and the test was carried out with various feeding loads, namely 3 rods, 4 rods, and 5 rods with. Each test was repeated 3 times. Cassava stem cutting machine (Petokong) is suitable for producing cassava stems with an average working capacity of 16275 seeds/hour. The results of the Anova test showed that the number of baits and varieties of cassava seeds and their interaction had a significant effect on the working capacity of the Petokong machine. Variations in fuel consumption are thought to be influenced by the variety of cassava stem used, which is influenced by the stem diameter of each variety. The Petokong machine is far superior to manual cutting using a machete or saw which can only produce 815 and 3005 seeds/hour per hour. The average fuel consumption is 1.82 liters per hour. Seed uniformity is about 98% and seedling damage can be minimized to 2%. The seeds produced by the Petokong machine can grow well, which is indicated by the appearance of shoots and an even distribution of roots. Keywords: Cassava seeds, Cassava stem cutter, Double block cutter, Petokong

Transcriptomic and alternative splicing analyses provide insights into the roles of exogenous salicylic acid ameliorating waxy maize seedling growth under heat stress

BackgroundSalicylic acid (SA) is a phytohormone which works to regulate the abiotic stress response of plants. However, the molecular mechanism by which SA mediates heat tolerance in waxy maize (Zea mays L. sinsensis Kulesh) remains unknown.ResultsTwo varieties of waxy maize seedlings, heat-tolerant ‘Yunuo7’ (Y7) and heat-sensitive ‘Suyunuo5’ (S5), were pretreated with SA prior to heat stress (HTS). After treatment, physiological and transcriptomic changes were analyzed. Compared with HTS, the exogenous application of SA enhanced the shoot dry weight, the activities of antioxidant enzymes (e.g., SOD, POD, CAT and APX), and the concentration of endogenous phytohormones (e.g., SA, ABA, IAA, GA3), while decreased the MDA content. Transcriptome analysis showed that the number of differentially expressed genes (DEGs) identified in the control (CK) vs HTS and HTS vs HTS + SA comparisons were more in S5 than in Y7. HTS induced the downregulation of genes involved in photosynthesis and the upregulation of genes encoding heat shock transcription factors (HSFs) and heat shock proteins (HSPs). Compared with HTS, SA pretreatment reversed the expression of 5 photosynthesis-related genes, 26 phytohormone-related genes, and all genes encoding HSFs and HSPs in S5. Furthermore, the number of alternative splicing (AS) events increased under HTS treatment for both varieties, while decreased under SA pretreatment of S5. Differentially spliced genes (DSGs) showed little overlap with DEGs, and DEGs and DSGs differed significantly in functional enrichment.ConclusionsPhysiological and transcriptional together indicated that HTS and SA pretreatment had a greater effect on S5 than Y7. Additionally, it appears that transcriptional regulation and AS work synergistically to enhance thermotolerance in heat-sensitive waxy maize. Our study revealed the regulatory effects and underlying molecular mechanisms of SA on waxy maize seedling under HTS.

Woody seedling community responses to deer herbivory, introduced shrubs, and ash mortality depend on canopy competition and site wetness

Emerald ash borer (EAB) (Agrilus planipennis), non-native shrubs, and white-tailed deer (Odocoileus virginianus) have been independently shown to affect woody seedling communities. Our objective was to determine the relative importance as well as additive and interactive-effects of these stressors in the context of two environmental factors, canopy tree competition and site wetness. We sampled 24 sites, representing three natural non-congruent gradients in ash mortality, deer browse, and introduced shrub invasion. We explored the responses of seedling species abundance, diversity and richness to an array of deer herbivory, ash mortality, and introduced shrubs and varying levels of canopy tree competition, site wetness. The effects of each stressor on the differences in the relative abundance of seedling species was also evaluated. Our results indicate a persistent negative effect of non-native shrubs in drier forest plots on native seedling abundance, richness, and diversity. In wetter forests, non-native shrubs had no effect on native seedling richness or abundance and were positively related to diversity. Deer browse had a negative effect on seedling diversity in wetter forests and no effect in drier forests. Canopy tree competition had a positive effect on seedling diversity in drier forest plots, but negatively affected diversity in wetter forest plots. Ordination analysis revealed that site wetness, non-native shrubs and the total basal area of trees in the stand had the largest impacts on the species composition of seedlings found at each site. Our results suggest that site wetness and chronic stressors like deer and introduced shrubs are interacting to shift seedling communities towards fewer native species as well as to reduce seedling species richness and diversity.

Microbiome-metabolome analysis directed isolation of rhizobacteria capable of enhancing salt tolerance of Sea Rice 86

Soil salinization has been recognized as one of the main factors causing the decrease of cultivated land area and global plant productivity. Application of salt tolerant plants and improvement of plant salt tolerance are recognized as the major routes for saline soil restoration and utilization. Sea rice 86 (SR86) is known as a rice cultivar capable of growing in saline soil. Genome sequencing and transcriptome analysis of SR86 have been conducted to explore its salt tolerance mechanisms while the contribution of rhizobacteria is underexplored. In the present study, we examined the rhizosphere bacterial diversity and soil metabolome of SR86 seedlings under different salinity to understand their contribution to plant salt tolerance. We found that salt stress could significantly change rhizobacterial diversity and rhizosphere metabolites. Keystone taxa were identified via co-occurrence analysis and the correlation analysis between keystone taxa and rhizosphere metabolites indicated lipids and their derivatives might play an important role in plant salt tolerance. Further, four plant growth promoting rhizobacteria (PGPR), capable of promoting the salt tolerance of SR86, were isolated and characterized. These findings might provide novel insights into the mechanisms of plant salt tolerance mediated by plant-microbe interaction, and promote the isolation and application of PGPR in the restoration and utilization of saline soil.