Rubra Seedlings Research Articles

Total Polyphenol Content and Antioxidant Activity of Leaves and Fine Roots as Indicators of Drought Resistance in the Native Quercus robur and Alien Quercus rubra

Research Highlights: Environmental abiotic stressors generate secondary stresses in plants, such as osmotic and oxidative stresses, which negatively influence their normal growth, development, and metabolism. Research about other non-enzymatic components with antioxidant capacity has recently focused on polyphenols. However, their role as indicators of drought and shade tolerance in woody species leaves and roots has been poorly explored or was limited to leaves only. Background and Objectives: Under a scenario of increasing drought, understanding the seedling responses in terms of total polyphenols and their antioxidant activity, in particular at the fine root system level, may help to elucidate the native–alien species interaction. Materials and Methods: At the beginning of July, 5-month-old native Quercus robur and alien Quercus rubra seedlings were transferred indoors to the growth chamber and subjected to progressive soil drying for 21 days. Results: The decrease in soil water content was more pronounced for Q. robur (9%) than for Q. rubra (34% of field capacity). Leaf water potential significantly decreased over time in Q. robur but did not differ from the control in Q. rubra. The total polyphenol concentration in Q. robur was markedly lower in the leaves and significantly higher in the fine roots than in Q. rubra. For the leaves, both species showed markedly higher values if well-watered, and the values significantly decreased in response to drought only in Q. rubra. In contrast, the fine root values for both species were markedly higher if droughted and decreased significantly in time only in Q. robur. Differently from the polyphenol concentration, the antioxidant capacity of Q. rubra was always higher in both the leaves and fine roots. Conclusions: The higher antioxidant activity of the alien species Q. rubra revealed by this work, combined with its isohydric behaviour, could further shed some light on our understanding of its competitive performance at the seedling stage against the native Q. robur.

The Fungal Pathogen Gnomoniopsis castaneae Induces Damaging Cankers in Multiple Domestic Fagaceae Species.

Gnomoniopsis castaneae is internationally recognized as a destructive pathogen of chestnut species. Primarily associated with nut rot, it has also been associated with branch and stem cankers of chestnut and as an endophyte of multiple additional hardwood species. The present study evaluated implications of the recently reported United States presence of the pathogen for domestic Fagaceae species. Stem inoculation assays of Castanea dentata, C. mollissima, C. dentata × C. mollissima, and Quercus rubra (red oak) seedlings were utilized to examine the cankering ability of a regional isolate of the pathogen. The pathogen induced damaging cankers in all assessed species and significant stem girdling in all chestnut species. No previous study has associated the pathogen with damaging infection in Quercus species, and its presence in the United States has the potential to compound ongoing chestnut recovery programs and oak regeneration problems within forest systems.

Common garden study reveals frost-tolerant northern seed sources are best suited to expand range of Quercus rubra

Climate change is shifting the potential suitable range of northern red oak (Quercus rubra L.) faster than it can migrate, creating an adaptation lag.Quercus rubrais prominent in eastern North American forests and important for its carbon sequestration, ecological functions, and economic significance. Our study addresses which populations ofQ. rubraare best suited for climatic conditions at its northern and central United States range limits. Our findings can inform management decisions involving assisted migration, where species are transferred within their native range to mitigate the effects of climate change. We planted over 800 Q. rubra seedlings from twelve populations representing the current Q. rubra geographic range in two common gardens, one at the northern range limit (Alberta, Michigan, USA) and one in the central range (Kalamazoo, Michigan, USA). We observed Q. rubra aboveground growth, phenology (senescence, budburst), and frost damage for three years.At the central range site, southern seed source populations from warmer and wetter locations showed greater relative growth rate. At the northern range site, northern seed sources, from colder, drier locations, had greater relative growth rate. Southern seed sources generally had later phenological events which resulted in them sustaining more frost damage than northern seed source populations in the spring and autumn. Northern seed sources had earlier budburst and were able to utilize early growing season snow melt and higher solar radiation. Northern seed sources also senesced earlier, avoiding autumn frosts. More extreme weather events are predicted with climate change, which favors the phenology, frost tolerance, and greater growth rate of northern seed sources for assisted migration at the northern range limit.

First Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in China

HomePlant DiseaseAhead of PrintFirst Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in ChinaYuhang Qiao, Xiangrong Zheng, Huan Li, and Fengmao ChenYuhang QiaoCo-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, Xiangrong Zhenghttps://orcid.org/0000-0002-9574-9449Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, Huan LiCo-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, and Fengmao Chen†Corresponding author: F. Chen; E-mail Address: [email protected]https://orcid.org/0000-0003-2412-7607Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations Yuhang Qiao Xiangrong Zheng Huan Li Fengmao Chen † Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China Published Online:10 Apr 2023https://doi.org/10.1094/PDIS-08-22-1845-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleAcer rubrum belongs to the family Aceraceae. It was introduced from North America by Chinese researchers in 2000 to promote the economic growth and value of forests (Lu et al. 2020). Since 2019, a serious leaf spot disease was observed on the petioles of A. rubrum in the Xuzhou Red Maple Park (34.28°N, 118.03°E) of Jiangsu Province. Lesions initially appeared black, surrounding more than half of the petioles of A. rubrum, and gradually expanded toward the branches and along the veins of leaves. Diseased leaves were sterilized in 10% sodium hypochlorite for 120 s, then rinsed in ddH2O twice for 30 s each time, and dried with sterile distilled paper. Afterward, the tissues were cultured on 2% potato dextrose agar (PDA), which was amended with 100 mg/liter ampicillin sodium and incubated in the dark at 25°C for 3 days. Twenty-four single-spore isolates were obtained as described by Cai et al. (2009). The colony morphology of 24 isolates was almost identical, so three isolates (XZC05, XZC15, and XZC27) were selected randomly for further study. Both sides of the colonies of the three isolates were white. Conidia were single-celled, hyaline, straight, cylindrical with circular ends, measuring 14.5 to 16.9 × 5.5 to 6.7 μm (n = 50). Appressoria were single-celled, subcircular or irregular, light brown to dark brown, thick-walled, measuring 6.1 to 11.8 × 5.5 to 11.6 μm (n = 50). Asci were clavate, eight-spored, thin-walled, measuring 74.5 to 52.4 × 14.7 to 9.2 μm (n = 50). Ascospores were one-celled, slightly curved, measuring 14.1 to 18.6 × 5.1 to 7.5 μm (n = 100). The morphology of the three isolates was basically the same. The morphological features were consistent with the description of Colletotrichum sp. (Weir et al. 2012). Six nuclear gene regions were amplified and sequenced, including ITS, CAL, GAPDH, TUB2, ACT, and CHS (Weir et al. 2012). The sequences were deposited in GenBank (accession nos. OM663716, OM681224, OM681272, OM681248, OM681200, and OM681296 for XZC05; OM663726, OM681234, OM681282, OM681258, OM681210, and OM681306 for XZC15; OM663736, OM681244, OM681292, OM681268, OM681220, and OM681316 for XZC27). IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 were used for phylogenetic reconstruction. The concatenated sequences placed XZC05, XZC15, and XZC27 in the clade of Colletotrichum aenigma with a high confidence level (ML/BI = 100/1). Pathogenicity assay was selected XZC15 and tested on 3-year-old A. rubrum seedlings. A. rubrum leaves were wounded by a sterilized needle (0.5-mm diameter) and inoculated with spore suspension (106 conidia/ml), and A. rubrum leaves inoculated with sterile water were used as the control group. Each treatment had five leaves and was incubated at 25°C under high moisture conditions. The experiments were conducted three times. After 7 days, all of the inoculated petioles showed lesions similar to the previous symptoms observed in the nursery, while the controls remained healthy. The fungus was reisolated from the lesions and morphologically identified, confirming Koch’s postulates. The leaf diseases caused by C. aenigma were widely distributed in China, with a variety of host plants, such as Cyclocarya paliurus (Zheng et al. 2021) and Aquilaria sinensis (Lour.) Spreng (Li et al. 2021). This is the first report of C. aenigma associated with leaf blight on Acer rubrum. The finding provides clear pathogen information for further evaluation of disease control strategies.The author(s) declare no conflict of interest.

First Report of Leaf Spot on Basella rubra Caused by Fusarium proliferatum in Malaysia.

Basella rubra (family Basellaceae), locally known as 'Remayong Merah', is the edible perennial vine served as leafy vegetable in Malaysia. In May 2021, B. rubra's leaves with circular to subcircular purple spots (ranging from 1-10 mm wide) were collected in Lido (5°56'44.6"N 116°04'46.5"E), Sabah province. The disease severity was about 60% with 20% disease incidence on fifty plants. As disease developed, the spots grew larger and necrosis were formed within the purple spots. Small pieces (5 x 5 mm) of five diseased spots were excised, and then surface sterilized based on Khoo et al. (2022b) before plating on water agar at 25°C. Once obtained the pure cultures from all diseased spots, they were incubated on potato dextrose agar at 25°C. After 7 days, white aerial mycelium with light violet pigmentation on lower side were observed on PDA. Then, the fungi were cultured on Carnation leaf agar (CLA) at 25°C and 12-h light/dark photoperiod for 10 days. Thin-walled slender and slightly curved macroconidia (n= 20) with 3 to 5 septa were ranged from 2.3 to 2.6 µm wide by 26.8 to 44.5 µm long in size. Oval microconidia (n= 20) with no septa were 2 to 2.2 µm wide by 9.5 to 15 µm long in size. Chlamydospores were absent. Monophialids with false head were observed. Isolate Lido and Lido02 were kept in the Laboratory of Genetics, Faculty of Science and Natural Resources, Universiti Malaysia Sabah for public request. Their genomic DNA were extracted from fresh mycelia of isolates based on Khoo et al. (2022a). EF1/EF2, RPB1-Fa/RPB1-G2R and RPB2-5f2/RPB2-7cr (Jiang et al. 2021) were used to amplify the translation elongation factor 1-α (TEF1) region, RNA polymerase largest subunit gene (RPB1) and RNA polymerase second largest subunit gene (RPB2) based on PCR condition in Khoo et al. (2022b). The isolate's sequences were deposited in GenBank as OM048109, OM634654 (TEF1), OM634655, OM634657 (RPB1) and OM634656, OM634658 (RPB2). They were 99 to 100% homology to TEF1 of isolate DPCT0102-2 (LC581453) (657/657 bp), RPB1 of strain ZJ05 (MT560605) (1558/1558 bp) and RPB2 of isolate GR_FP248 (MT305154) (1867/1869 bp) sequences. These sequences were polyphasic identified at the Fusarium MLST (https://fusarium.mycobank.org/), and were more than 99% similarity to Gibberella fujikuroi species complex (NRRL 25200). Gibberella fujikuroi and Fusarium fujikuroi are synonymous with Fusarium proliferatum (Leslie and Summerell 2006). The pathogen was identified as F. proliferatum based on morphological characterization, molecular data and phylogenetic analysis. Two non-wounded leaves of three one-month-old B. rubra seedlings were inoculated with mycelium plug (10 x 10 mm). Additional three B. rubra seedlings received sterile PDA agar plug (10 x 10 mm) to serve as controls. They were incubated in a glasshouse at room temperature 25°C with a relative humidity of 80 to 90%. After 8 days of inoculation, all inoculated leaves exhibited the symptoms as observed in the field, while the controls showed no symptoms, thus confirming the Koch's postulates. The experiment was repeated two more times. The reisolated pathogens were identified as F. proliferatum via PDA macroscopically, CLA microscopically and PCR amplification. F. proliferatum was reported previously causing leaf spot disease on Cymbidium orchids (Wang et al. 2018), tobacco (Li et al. 2017) and tomato (Gao et al. 2017). To our knowledge, this is the first report of F. proliferatum causing leaf spot on B. rubra in Malaysia. Infections of leaves reduce plant vigor and marketability. The identification of leaf spot caused by F. proliferatun will enable plant health authorities and farmers to identify practices to minimize disease on this important crop.

First Report of Fusarium oxysporum Causing leaf spot on Basella rubra in Malaysia.

Basella rubra (family Basellaceae), locally known as 'Remayong Merah', is an edible perennial vine served as leafy greens in Malaysia. In May 2021, leaves with circular brown spots ranging from 3 to 10 mm wide with purple borders were found on B. rubra growing in Penampang (5°56'55.6"N 116°04'33.5"E), Sabah province. The disease severity was 80% with 10% disease incidence on 50 plants. As the disease developed, the lesions grew larger and they developed necrotic centers. Leaves with brown spot symptoms from five plants were collected from the field. Five leaf pieces (5 x 5 mm) were excised from lesion margins, surface sterilized based on Khoo et al. (2022b), before incubation on water agar at 25°C. When five pure cultures were obtained, the fungi were cultured on potato dextrose agar (PDA) at 25°C. After 5 days, fluffy white mycelia tinged with pink pigmentation showing on the underside of the colony were observed on PDA. Mycelia became violet in color as the culture aged. The isolates were incubated on carnation leaf agar at 25°C with a 12-hour light/dark photoperiod for 10 days. Sickle-shaped, thin-walled and delicate macroconidia (n= 30), predominantly 3 septate, ranging from 21.6 to 38.3 μm long by 2.7 to 4.2 μm wide in size were observed. Kidney-shaped, aseptate microconidia (n= 30) ranged from 6.2 to 11 μm long by 2.6 to 3.9 μm wide in size, and were formed on monophialides in false heads. Chlamydospores were detected both terminally and intercalarily, singly or in pairs, with smooth or rough walls. Genomic DNA was extracted from fresh mycelia of a representative isolate from Penampang based on Khoo et al. (2022a). The primers ITS1/ITS4 (White et al. 1990) and EF1/EF2 (O'Donnell et al. 1998) were used to amplify the internal transcribed spacer (ITS) rDNA and translation elongation factor 1-α (TEF1α) region, respectively based on PCR conditions as described previously (Khoo et al. 2022b). The products were sent to Apical Scientific Sdn. Bhd. for sequencing. In BLASTn analysis, ITS sequence (OK469301) was 99% (506/507 bp) identical to isolate TSE07 (MT481761) of Fusarium oxysporum, and the TEF1α sequence (OM743433) was 100% (705/705 bp) identical to isolate BLBL5 of Fusarium oxysporum. The TEF1α sequence of Penampang was analyzed at the Fusarium MLST site (https://fusarium.mycobank.org/), and had 98% similarity to TEF1α of F. oxysporum (NRRL 22551). The pathogen was identified as F. oxysporum based on morphological (Leslie and Summerell 2006) and molecular data. A volume of 0.16 ml of spore suspensions (1 × 106 conidia/ml) were inoculated on a spot on each leaf of every three healthy B. rubra seedlings at the two-leaf stage. An additional three B. rubra seedlings were mock inoculated by pipetting sterile distilled water on similar aged leaf. The seedlings were maintained in a greenhouse at 25°C with a relative humidity of 80 to 90%. Six days after inoculation, all inoculated leaves exhibited the same symptoms as observed in the field, while the controls showed no symptoms. The experiment was repeated two more times. The reisolated fungi had the same morphology and DNA sequences as the original isolate obtained from the field samples, completing Koch's postulates. F. oxysporum has been reported previously in Bangladesh and India causing leaf spot disease on B. rubra (Dhar et al. 2015; Shova et al. 2020). To our knowledge, this is the first report of F. oxysporum causing leaf spot on B. rubra in Malaysia. The identification of leaf spot caused by F. oxysporum will enable plant health authorities and farmers to identify practices to minimize disease on this important crop.

Effects of exogenous bacterial quorum-sensing signal molecule/messenger N-hexanoyl-L-homoserine lactone (C-HSL) on acorn germination and plant growth of Quercus robur and Q. rubra (Fagaceae)

The effect of pre-sowing priming with N-hexanoyl-L-homoserine lactone (C6-HSL) solution (300 mg/L) on acorn germination and morpho-phenological characteristics of Quercus robur and Q. rubra was studied under laboratory conditions. After priming, 93.4% of Q. robur acorns germinated that exceeded the control by 32.2%, while the number of sprouted acorns of Q. rubra increased within error limits by 5% more than the control and amounted to 90%. According to morphological characteristics, the 47-day-old plants of Q. robur were divided into the following groups: germinated acorns, sprouts and seedlings with juvenile leaves, whereas among the plants of Q. rubra, sprouts and seedlings with true leaves were selected. A group of plants with juvenile leaves was detected only in the samples primed with C6-HSL. Priming induced differential changes in cotyledon biomass of both species and accelerated nutrient utilization by Q. robur seedlings. We observed a positive effect on the growth and biomass accumulation of Q. robur plants and a negative effect, except for plants of the third group, on those of Q. rubra. The dry weight of seedling roots of Q. robur and shoots of Q. rubra increased, respectively, by 103% and 153%. Priming of acorns with C6-HSL solution induced an increase in number, length, biomass and total area of leaves. These changes were more pronounced in Q. rubra seedlings. Alterations in the root system architecture towards formation of numerous additional lateral roots were recorded for both species. Thus, priming with C6-HSL solution activated acorn germination and stimulated growth of Q. robur plants and decelerated growth of plants of Q. rubra. Exogenous C6-HSL did not eliminate the syndrome of unfriendly seedlings of both studied oak species, but improved the viability of acorns and increased the number of seedlings.

Seedling Response to Simulated Browsing and Reduced Water Availability: Insights for Assisted Migration Plantations

To facilitate forest transition to future climate conditions, managers can use adaptive silvicultural tools, for example the assisted translocation of tree species and genotypes to areas with suitable future climate conditions (i.e., assisted migration). Like traditional plantations, however, assisted migration plantations are at risk of failure because of browsing by ungulate herbivores. The ability of seedlings to tolerate browsing could also be hampered by low water availability, as is expected under climate change. Using a greenhouse experiment with five eastern North American tree species, we evaluated the effects of simulated winter browsing and reduced water availability on the growth (total biomass, shoot:root ratio), survival, and chemical composition (nitrogen, total phenolics, flavonoids) of seedlings. We compared seedlings from three geographic provenances representing three climate analogues, i.e., locations with a current climate similar to the climate predicted at the plantation site at a specific time (here: current, mid-century and end of the century). We hypothesized that seedlings would allocate resources to the system (shoots or roots) affected by the most limiting treatment (simulated browsing or reduced water availability). Additionally, we evaluated whether the combination of treatments would have an additive or non-additive effect on the growth, survival and chemical composition of the seedlings. Quercus rubra seedlings reacted only to the water reduction treatment (changes in biomass and N concentration, dependent on geographic provenance) while Pinus strobus reacted only to the simulated browsing treatment (biomass and chemical composition). We also observed non-additive effects of reduced water availability and simulated browsing on Prunus serotina, Acer saccharum and Thuja occidentalis. In general, shoot:root ratio and investment in chemical defense did not vary in response to treatments. The regrowth response observed in Q. rubra and A. saccharum suggests that these species could tolerate periodic browsing events, even when water availability is reduced. More information is required to understand their long-term tolerance to repeated browsing events and to harsher and more frequent water stress. We highlight the importance of species-specific growth and allocation responses that vary with geographic provenance, which should be considered by managers when planning climate-adapted strategies, such as assisted migration.

Limited evidence that larger acorns buffer Quercus rubra seedlings from density-dependent biotic stressors.

Plant performance and functional traits vary considerably within species, particularly in response to environmental variation. Plant responses may reflect life-history trade-offs, such as between resource acquisition and resource conservation. Larger seeds may buffer young plants from the negative effects of environmental variation, such as limitations in nutrients or water. However, whether seed size plays a similar role in how plants respond to variation in their biotic environment, including competition and soil microbial communities, remains poorly understood. We used a greenhouse experiment to test the interactive effects of intraspecific competition, the origin of the soil microbial community, and seed size on performance and functional traits in Quercus rubra L. seedlings. Intraspecific variation in seedling traits weakly aligned with a resource acquisition-conservation trade-off. Across the wide range of initial acorn mass, competition decreased seedling biomass by about 35%. Competition directly decreased the root mass ratio and indirectly increased specific leaf area and specific root length, via the negative effects on total biomass. In contrast, soil microbial communities had minor effects on seedlings, and we found no differences between plants receiving soil originating from a conspecific adult and plants receiving soil originating from a heterospecific adult. Competition is a more important driver of intraspecific variation in young Quercus rubra seedling performance and traits, both directly and by delaying ontogenetic development, than soil microbial communities. Seed size is an important predictor of seedling biomass, but a larger seed does not necessarily buffer seedlings from the effects of competition.

Transcriptomic study of the night break in Chenopodium rubrum reveals possible upstream regulators of the floral activator CrFTL1

The transition from vegetative to reproductive phases is the most fundamental and tightly controlled switch in the life of flowering plants. The short-day plant Chenopodium rubrum is a fast cycling annual plant lacking a juvenile phase. It can be induced to flowering at the seedling stage by exposure to a single period of darkness. This floral induction may then be cancelled by a short pulse of red light at midnight called night break (NB), which also inhibits the floral activator FLOWERING LOCUS T LIKE 1 (CrFTL1). We performed a comparative transcriptomic study between C. rubrum seedlings treated by NB and ones growing through uninterrupted night, and found about six hundred differentially expressed genes, including the B-BOX DOMAIN (BBX) genes. We focused on the CrBBX19 and BOLTING TIME CONTROL 1 (BTC1) genes, homologous to the upstream regulators of the BvFT2, a floral inducer in sugar beet. The transcription patterns of the two genes were compatible with their putative role as a sensor of the dark period length optimal for flowering (CrBBX19), and a signal of lights-on (CrBTC1), but the participation of other genes cannot be excluded. The expression profiles of CrBBX19 and the homolog of the core endogenous clock gene LATE ELONGATED HYPOCOTYL (LHY) were highly similar, which suggested their co-regulation.

Response of Growth and Chemical Composition of Quercus robur,L.Seedlings to Organic and Inorganic Fertilizers.

This research aims to create a method for increasing the growth of Quercus robur, L seedlings, therfore pot experiment was conducted to study the response of growth and chemical composition for Quercus rubra seedlings to organic (potassium humate 5 or compost tea 15 cm 3 /seedling) and inorganic fertilizers 50% (NPK at 15g/seedling), 75%(NPK at 22.5g/seedling) and 100 %(NPK at 30g/seedling)in the Experimental Farm of Horticultural Research Station of El-Kanater El-Khyria, Qaluobia Governorate, Egypt throughout two successive seasons of 2017/2018 and 2018/2019. The obtained results indicated that the significant values of increment height growth, stem diameter, root length ,biomass fresh and dry weight declared as a result to apply the treatment of 50% NPK mineral plus compost tea 15 cm 3 and K-humate 5 cm 3 /seedlings followed by those of 75% NPK +compost tea the intermediate values were exhibited with applying 75% NPK +compost tea or 75% NPK +K-humate and the latest in ranking was control, meaning that applying 50% NPK plus compost tea and K-humate produced the superior seedlings more than the others. So it can be saved mineral nutrients by applying organic nutrients. Similar trend approximately revealed with total chlorophyll but total carbohydrates in stem pronounced the highest value with the treatment of compost tea alone. Concerning the content of N,P and K levels in plant it can be observed that a different values were occurred due to utilizing organic or inorganic nutrients and there is no clear trend and insignificant differences among the treatments. However N,P,K slightly increased with adding NPK at the different levels + compost tea or K-humate. It can be recommended from the above mentioned results that adding half dose of inorganic nutrients as 50% NPK alongside compost tea and K-humate represented organic nutrients enhanced soil conditions led to producing healthy seedling of Quercus robur and reducing the doses of NPK as mineral nutrients.

Low stringency tests revealed differential gene expression in red maple (Acer rubrum) treated with low doses of nickel

Recent field studies have revealed that Acer rubrum is a nickel (Ni) avoider and it does not store Ni in its tissues. Analysis of nickel toxicity at low and high doses in this species is limited. The main objectives of this study were to 1) determine the effect of low and high Ni doses on A. rubrum seedlings, 2) to assess the effects of low doses of nickel on gene expression using a less stringent test based on P-values, and 3) to identify differential gene expression in resistant and susceptible genotypes. All the Ni toxicity tests were conducted in growth chambers. No morphological damage or change in plant growth were observed when A. rubrum where treated with a low dose (150 mg/kg) and high doses (800 mg/kg, and 1600 mg/kg) of Ni. Differential gene expression from the transcriptome analysis using P-values revealed that 464 genes were downregulated and 609 upregulated in samples treated with 150 mg/kg Ni compared to water. These numbers were 994 down regulated and 1569 upregulated genes when the 800 mg/kg dose was compared to water and 3760 down regulated and 7098 when 1600 mg/kg was compared to the same water control. There were more upregulated genes (1482) than downregulated (623) when Ni-resistant and Ni-susceptible genotypes were compared based on low stringency test (P-values). Among the top 50 most upregulated, Serine/threonine-protein kinase, O-methyltransferase, sugar transporter, glutathione-s-transferase and s-adenosylmethioninie-dependent methyltransferase were the only ones that could be relevant for Ni toxicity based on their role in plants. On the other hand, the top 50 most downregulated genes that could be associated with environmental stress include Peroxisomal ascorbate peroxidase, Glycine-rich protein DC7.1, Aquaporin NIP6.1 family protein, Putative membrane protein (Fragment), and Serine/threonine protein kinase. Overall, the study shows that a less stringent test such as P-Values could be a good tool to study gene expression when the effects of Ni or other metals on global gene transcription are low.

Nanoscale Zero-Valent Iron Has Minimum Toxicological Risk on the Germination and Early Growth of Two Grass Species with Potential for Phytostabilization.

Two Poaceae species, Agrostis capillaris and Festuca rubra, were selected for their potential as phytostabilizing plants in multicontaminated soils. These species are resistant to contamination and maintain high concentrations of contaminants at the root level. Nanoscale zero-valent iron (nZVI) is an engineered nanomaterial with the ability to stabilize metal(loid)s in soils; its potential toxicological effects in the selected species were studied in a germination test using: (i) control variant without soil; (ii) soil contaminated with Pb and Zn; and (iii) contaminated soil amended with 1% nZVI, as well as in an hydroponic experiment with the addition of nZVI 0, 25, 50 and 100 mg L−1. nZVI had no negative effects on seed germination or seedling growth, but was associated with an increase in shoot growth and reduction of the elongation inhibition rate (root-dependent) of F. rubra seedlings. However, applications of nZVI in the hydroponic solution had no effects on F. rubra but A. capillaris developed longer roots and more biomass. Increasing nZVI concentrations in the growing solution increased Mg and Fe uptake and reduced the Fe translocation factor. Our results indicate that nZVI has few toxic effects on the studied species.

The Spread and Role of the Invasive Alien Tree Quercus rubra (L.) in Novel Forest Ecosystems in Central Europe

Research Highlights: The factors that control the spread and regeneration of Quercus rubra (L.) and the functional diversity of invaded forest were studied in order to indicate the significant role of disturbances in a forest and the low functional richness and evenness of sites that are occupied by red oak. Background and Objectives: Red oak is one of the most frequent invasive trees from North America in Central Europe. It is also one of the most efficient self-regenerating invasive alien species in forests. The main goal of the study is to identify the characteristics of forest communities with a contribution of Q. rubra, and to assess its role in shaping the species diversity of these novel phytocoenoses. Materials and Methods: A total of 180 phytosociological records that have a share of Q. rubra in southern Poland were collected, including 100 randomly chosen plots from which soil samples were taken. In addition, vegetation sampling was performed in 55 plots in the vicinities that were uninvaded. Results: The probability of the self-regeneration and cover of Q. rubra seedlings depends mainly on the availability of maternal trees, and the abundance of seedlings was highest in cutting areas. The vegetation with Q. rubra differed in the plant functional types and environmental factors. According to the three-table ordination method, while the cover of red oak only affected the canopy of the remaining species, a comparison of the invaded and uninvaded plots demonstrated that the sites that were occupied by Q. rubra had lower values of functional richness and evenness, thus indicating higher habitat filtering and a lower importance of competition. Conclusions: Forest management practices play the most crucial role in the self-regeneration and occurrence of Q. rubra. However, the role of red oak in shaping the species composition and functional diversity is rather low.

Red oak seedlings as indicators of deer browse pressure: Gauging the outcome of different white-tailed deer management approaches.

After decades of high deer populations, North American forests have lost much of their previous biodiversity. Any landscape‐level recovery requires substantial reductions in deer herds, but modern societies and wildlife management agencies appear unable to devise appropriate solutions to this chronic ecological and human health crisis. We evaluated the effectiveness of fertility control and hunting in reducing deer impacts at Cornell University. We estimated spring deer populations and planted Quercus rubra seedlings to assess deer browse pressure, rodent attack, and other factors compromising seedling performance. Oak seedlings protected in cages grew well, but deer annually browsed ≥60% of unprotected seedlings. Despite female sterilization rates of >90%, the deer population remained stable. Neither sterilization nor recreational hunting reduced deer browse rates and neither appears able to achieve reductions in deer populations or their impacts. We eliminated deer sterilization and recreational hunting in a core management area in favor of allowing volunteer archers to shoot deer over bait, including at night. This resulted in a substantial reduction in the deer population and a linear decline in browse rates as a function of spring deer abundance. Public trust stewardship of North American landscapes will require a fundamental overhaul in deer management to provide for a brighter future, and oak seedlings may be a promising metric to assess success. These changes will require intense public debate and may require new approaches such as regulated commercial hunting, natural dispersal, or intentional release of important deer predators (e.g., wolves and mountain lions). Such drastic changes in deer management will be highly controversial, and at present, likely difficult to implement in North America. However, the future of our forest ecosystems and their associated biodiversity will depend on evidence to guide change in landscape management and stewardship.

Assessing the Efficacy of Seedling Planting as a Forest Restoration Technique in Temperate Hardwood Forests Impacted by Invasive Species

The emerald ash borer (Agrilus planipennis Fairmaire; EAB) is an invasive insect that causes mortality of trees in the genus Fraxinus, creating canopy gaps that may facilitate invasion by exotic plants. Planting native tree seedlings under EAB-infested Fraxinus may accelerate succession and preclude invasive plant expansion; however, the effectiveness of this approach has not been experimentally tested. We assessed understory seedling planting of Quercus rubra, Carya laciniosa, and Juglans cinerea in EAB-infested forests, where the invasive shrub Lonicera maackii (Amur honeysuckle) was removed. We tested whether the use of plastic tree shelters (“tree tubes”) or planting season (fall versus spring) contributed to the success of the reforestation plan by measuring growth rates (cm/yr) and survivorship two and seven years after planting. After seven years, seedling survivorship was <25% for all species and planting techniques. Quercus rubra exhibited poor survivorship with one seedling surviving to the conclusion of the experiment. Juglans cinerea and C. laciniosa had higher survivability and growth rates than did Q. rubra after two and seven years. Effects of tree tubes were weak and temporary. After 2 years, Q. rubra seedling survivorship was higher in tree tubes; however, by the end of the experiment 29 of the 30 Q. rubra seedlings in tree tubes had died. Juglans cinerea seedlings grew faster when planted in the fall compared to the spring, but overall survivorship of these seedlings was unaffected by planting season. Neither the use of tree shelters nor the planting season contributed to the growth or survival of C. laciniosa seedlings. In summary, our results indicate that seedling planting of Carya and Juglans may be a useful way to increase biodiversity in regenerating forests; however, the resource-expensive processes of over-wintering seedlings and using tree shelters may not increase the success of reforestation efforts.

Seedling survival of Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L. in temperate forests of Western Poland

Although invasive trees species spread effectively across different habitats, data on survival of their seedlings are scarce. We compared seedling survival after the first year from germination for the three most invasive tree species in temperate Europe. We also assessed the impact of light availability, parental tree stands and intra- and inter-specific competition. We studied seedlings of three invasive species: Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L., in a set of 186 study plots in W Poland over three years (2015–2018). In total, we labelled 11,135 seedlings. We assessed importance of variables using machine learning techniques. Mean seedling survival was 3.9 ± 1.2%, 12.5 ± 2.2% and 0.1 ± 0.1% for P. serotina, Q. rubra and R. pseudoacacia respectively, and was higher than for native species. Survival of Q. rubra seedlings depended mostly on intraspecific competition in understory, light availability and parental trees availability. Survival of P. serotina seedlings depended mostly on intra- and inter-specific competition, germination year (precipitation seasonality) and light availability. Our study explained that despite the high seedling densities of invasive species beneath parental tree canopies, their survival was lower than in surrounding forests. These two aspects of the establishment process (seedling abundance and survival) contribute to the dynamic equilibrium between limiting (low survival beneath maternal tree canopies) and facilitating (high seedling densities beneath maternal trees canopies) the growth of young generations of invasive tree species.

The effects of lead on photosynthetic performance of waxberry seedlings (Myrica rubra)

The photosynthesis was investigated 30 d after Pb treatment in Myrica rubra seedlings. The Pb treatment resulted in significantly increased Pb concentrations in shoots. Low Pb concentration exposure (≤2 mM) reduced the net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) without affecting the intercellular CO2 concentration (Ci), chlorophyll (Chl) content, and Chl fluorescence parameters. At 10 d after severe Pb treatment (≥4 mM), PN was inhibited and accompanied by Chl damage, while at 30 d, the inhibition of PN was followed by an increase of Ci and a decrease of gs, E, Chl content, and Chl fluorescence parameters. M. rubra showed a promising prospect for use in the soil phytoremediation, when Pb concentration is low, but the remediation efficiency of M. rubra is limited if Pb exceeds 2 mM.

Tree seedling responses to multiple environmental stresses: Interactive effects of soil warming, nitrogen fertilization, and plant invasion

Temperate deciduous forest ecosystems in northeastern North America are under increasing biotic and abiotic stresses that can have interactive effects on understory vegetation, and thus impact the next generation of forest canopy trees. We examined seedling responses of the common and increasingly dominant species Acer rubrum (red maple) to the combined effects of soil warming (+5°C), chronic nitrogen fertilization (+50kgNha−1yr−1), and invasion by the phytotoxic plant Alliaria petiolata (garlic mustard), and their interactions. We planted 296 first-year A. rubrum seedlings in a multifactorial field experiment to examine the effects of all combinations of the experimental treatments. Second-year Acer rubrum seedlings demonstrated higher aboveground growth under soil warming conditions. Further, soil warming positively influenced plant-soil feedbacks through higher arbuscular mycorrhizal colonization in fine roots. However, the positive growth responses and mycorrhizal colonization observed under soil warming were moderated by both N fertilization and A. petiolata invasion. Our results highlight the importance of developing management plans that consider how multiple environmental change factors affect tree seedling performance, particularly via the plant-soil interface.

Individual and interactive effects of white-tailed deer and an exotic shrub on artificial and natural regeneration in mixed hardwood forests.

Underplanting tree seedlings in areas where natural regeneration is limited may offer a tool by which desired overstory composition can be maintained or restored in forests. However, invasive plant species and ungulate browsing may limit the effectiveness of underplanting, and in-turn, the successful restoration of forest ecosystems. Individually, the invasive shrub Lonicera maackii and browsing by white-tailed deer (Odocoileus virginianus) have been found to negatively affect the regeneration of native tree species in the Midwestern United States, but few studies have examined their interactive or cumulative effects. Using exclosures and shrub removal at five sites, we examined the effects of white-tailed deer and L. maackii both on underplanted seedlings of Castanea dentata and Quercus rubra and on the composition, species richness and diversity of naturally regenerated native tree seedlings. Individually, both deer and L. maackii had negative effects on the survival of underplanted seedlings, but we identified no interactive effects. The presence of L. maackii or deer alone resulted in similar declines in the survivorship of Q. rubra seedlings, but the presence of deer alone resulted in lower survival of C. dentata seedlings than the presence of L. maackii alone. Lonicera maackii reduced light levels, increased seedling moisture stress and decreased relative basal diameter growth for Q. rubra seedlings. Deer reduced the relative growth in height of underplanted C. dentata and Q. rubra seedlings and increased moisture stress of C. dentata seedlings. No effects of L. maackii or deer were found on soil or foliar nitrogen or the overall abundance, species richness and diversity of naturally regenerated seedlings. However, L. maackii and white-tailed deer did affect the abundance of individual tree species, shifting composition of the regeneration layer towards shade tolerant and unpalatable and/or browse tolerant species.