The effect of shade trees on the air and surface-soil temperature reduction under the canopy was studied in a park in subtropical Taipei City, Taiwan. Ten species of trees and two species of bamboo, ...which had tightly clustered tall stems and spreading branches resembling trees in shape, were chosen for the study. In the summer of 2007, we measured leaf and canopy characteristics of each species. The microclimate conditions under the tree canopies and an unshaded open space were measured repeatedly at middays without precipitation. In comparison with the nearby unshaded open space, air temperatures under the canopies were 0.64 to 2.52 °C lower, whereas the surface-soil temperatures were 3.28 to 8.07 °C lower. Regression analysis revealed the relative contributions to air cooling effect by the plant's leaf color lightness, foliage density, leaf thickness, and leaf texture (surface roughness) in decreasing order. Foliage density had the greatest contribution to surface-soil cooling followed by leaf thickness, leaf texture, and leaf color lightness in that order. Regression analysis also revealed that solar radiation, wind velocity, and vapor pressure at the site had significant effects on temperature reduction attributable to shade trees or bamboo.
Phytophthora ramorum, the cause of sudden oak death on oak and ramorum blight on woody ornamentals, has been reported in ornamental nurseries on the West Coast of North America from British Columbia ...to California. Long-distance migration of P. ramorum has occurred via the nursery trade, and shipments of host plants are known to have crossed the U.S.–Canadian border. We investigated the genotypic diversity of P. ramorum in Canadian nurseries and compared the Canadian population with U.S. and European nursery isolates for evidence of migration among populations. All three of the P. ramorum clonal lineages were found in Canada but, unexpectedly, the most common was the NA2 lineage. The NA1 clonal lineage, which has been the most common lineage in U.S. nurseries, was found relatively infrequently in Canada, and these isolates may have been the result of migration from the United States to Canada. The EU1 lineage was observed almost every year and shared multilocus genotypes with isolates from Europe and the United States. Estimation of migration rates between Europe and North America indicated that migration was higher from Europe to North America than vice versa, and that unidirectional migration from Europe to North America was more likely than bidirectional migration.
An understanding of plant domestication history provides insights into general mechanisms of plant adaptation and diversification and can guide breeding programmes that aim to improve cultivated ...species. Cultivated tree peonies (genus Paeonia L.) are among the most popular ornamental plants in the world; yet, the history of their domestication is still unresolved. Here, we explored whether the domestication in China of historically cultivated peonies, that is, the common and flare cultivated tree peonies, was a single event or whether independent domestications occurred. We used 14 nuclear microsatellite markers and a comprehensive set of 553 tree peonies collected across China, including common tree peonies, flare tree peonies and the wild species or subspecies that are potential contributors to the cultivated tree peonies, that is, Paeonia rockii ssp. rockii, P. rockii ssp. atava, P. jishanensis and P. decomposita. Assignment methods, a principal component analysis and approximate Bayesian computations provided clear evidence for independent domestications of these common tree and flare tree peonies from two distinct and allopatric wild species, P. jishanensis and P. rockii ssp. atava, respectively. This study provides the first example of independent domestications of cultivated trees from distinct species and locations. This work also yields crucial insight into the history of domestication of one of the most popular woody ornamental plants. The cultivated peonies represent an interesting case of parallel and convergent evolution. The information obtained in this study will be valuable both for improving current tree peony breeding strategies and for understanding the mechanisms of domestication, diversification and adaptation in plants.
Phytophthora ramorum is an oomycete plant pathogen classified in the kingdom Stramenopila. P. ramorum is the causal agent of sudden oak death on coast live oak and tanoak as well as ramorum blight on ...woody ornamental and forest understorey plants. It causes stem cankers on trees, and leaf blight or stem dieback on ornamentals and understorey forest species. This pathogen is managed in the USA and Europe by eradication where feasible, by containment elsewhere and by quarantine in many parts of the world. Genomic resources provide information on genes of interest to disease management and have improved tremendously since sequencing the genome in 2004. This review provides a current overview of the pathogenicity, population genetics, evolution and genomics of P. ramorum. Phytophthora ramorum (Werres, De Cock & Man in't Veld): kingdom Stramenopila; phylum Oomycota; class Peronosporomycetidae; order Pythiales; family Pythiaceae; genus Phytophthora. The host range is very large and the list of known hosts continues to expand at the time of writing. Coast live oak and tanoak are ecologically, economically and culturally important forest hosts in the USA. Rhododendron, Viburnum, Pieris, Syringa and Camellia are key ornamental hosts on which P. ramorum has been found repeatedly, some of which have been involved in moving the pathogen via nursery shipments. P. ramorum causes two different diseases with differing symptoms: sudden oak death (bleeding lesions, stem cankers) on oaks and ramorum blight (twig dieback and/or foliar lesions) on tree and woody ornamental hosts. http://nature.berkeley.edu/comtf/, http://rapra.csl.gov.uk/, http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/index.shtml, http://genome.jgi-psf.org/Phyra1_1/Phyra1_1.home.html, http://pamgo.vbi.vt.edu/, http://pmgn.vbi.vt.edu/, http://vmd.vbi.vt.edu./, http://web.science.oregonstate.edu/bpp/labs/grunwald/resources.htm, http://www.defra.gov.uk/planth/pramorum.htm, http://www.invasive.org/browse/subject.cfm?sub=4603, http://www.forestry.gov.uk/forestry/WCAS-4Z5JLL
▶Drought treatment significantly reduced net photosynthesis rate (A) and transpiration (E), but increased chlorophyll a (chla), carbon isotope (δ13C), endogenous abscisic acid (ABA), malondialdehyde ...(MDA) and hydrogen peroxide (H2O2) contents, and guaiacol peroxidase (POD) and catalase (CAT) activities. ▶ There was an apparent alleviation of drought effects by shade, as indicated by the lower relative growth rate, and chlorophyll, MDA and H2O2 contents, and increases in indoleacetic acid (IAA) and reduced glutathione (GSH) contents. ▶ The exogenous ABA application under shade induced protective effects on drought-stressed seedlings, as visible in MDA, A, stomatal conductance (gs), E, δ13C, ABA and IAA values. ▶ Our results suggest that seedlings of Cotinus coggygria are more sensitive to drought under full-light than under shade.
We exposed seedlings of Cotinus coggygria var. cinerea to drought and exogenous abscisic acid (ABA) under two different light conditions. Two watering regimes (well-watered and drought), two exogenous ABA applications (no ABA and with ABA) and two light regimes (full sunlight and shade) were employed. Compared with well-watered treatment, drought treatment significantly reduced the relative growth rate, relative water content (RWC), net photosynthesis rate (A) and transpiration (E), but increased chlorophyll a (chla), carbon isotope (δ13C), endogenous ABA, malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, and guaiacol peroxidase (POD) and catalase (CAT) activities. There was an apparent alleviation of drought effects by shade, as indicated by the lower relative growth rate, and chlorophyll, MDA and H2O2 contents, and increases in indoleacetic acid (IAA) and reduced glutathione (GSH) contents. On the other hand, the exogenous ABA application under shade induced protective effects on drought-stressed seedlings, as visible in RWC, MDA, A, stomatal conductance (gs), E, δ13C, ABA and IAA values. In all, our results suggest that seedlings of C. coggygria are more sensitive to drought under full-light than under shade.
We examined invasive, casual (found occasionally outside cultivation) and non‐invasive (found only in cultivation) species to investigate the role of species traits and two forms of biotic resistance ...(plant neighbours and herbivores) in limiting invasion in Hawaiian lowlands. Seeds of 21 species of common woody ornamentals from three plant families (Acanthaceae, Apocynaceae, Bignoniaceae) that are non‐invasive, casual or invasive in Hawai'i were outplanted at two field sites. We measured germination of seeds and growth and survival of seedlings for 1 year in plots with and without neighbours from the naturally assembled community. The presence of neighbours reduced survival in some species, mostly non‐invasive or casual species, and completely excluded two non‐invasive species from community plots. Damage from the existing community of herbivores was correlated with lower survival in the Acanthaceae and Bignoniaceae, but not the Apocynaceae. Non‐invasive and casual species had lower survival and growth rates than invasive species and lower photosynthetic rates in the presence of neighbours than invasive species. Non‐invasives without neighbours also had lower specific leaf area than invasives and casuals. We found evidence for barriers to invasion in some non‐invasive and casual species, including low growth rate, low survival, or low survival in the presence of neighbours. By contrast, five of the six invasives flowered and three began setting fruit within the duration of the experiment, as did one of the casual species. Synthesis. Our research demonstrates biotic resistance, presumably as a result of competition. Neighbouring plants reduced survival and growth for most species. For non‐invasive species with low survival and growth even without competition from neighbouring plants, this resulted in complete exclusion from community plots or such low growth rates that exclusion over longer time frames was likely. We also provide evidence for traits‐based barriers to invasion in non‐invasive and casual species. However, no single barrier to invasion was shared across all non‐invasive and casual species.
Biodiversity conservation is a key factor in meeting sustainable development goals. This is even more important in cities, where green spaces are becoming increasingly scarce. This study analyzes ...Kinshasa’s proliferating ornamental plant nurseries, known as informal horticultural sites (IHSs). The analysis focused on characterizing the profile of horticulturists, their production conditions, and the ornamental species produced. A total of 15 IHSs were sampled using the “snowball” technique, and 178 horticulturists were surveyed. Based on the socio-professional profile of the horticulturists, five groups of IHS are distinguished after a hierarchical clustering of principal components (HCPC). We found that IHSs exclusively employed men, most of whom were new to the trade, from all levels of education, and most of whom ranged from 19 to 45 years old. Production conditions are relatively similar from one site to another. However, all IHSs are characterized by permanent land insecurity, the use of phytosanitary products, plant-conditioning methods that are not very diversified and calibrated to growers’ investment capacities, and diversified seed acquisition methods. A total of 139 ornamental species, most of them exotic, were identified. Of these, 37% are phanerophytes, and 24% are considered potentially invasive. We suggest ways of professionalizing the activity and protecting the urban environment.
In the present study, the chemical and morphological status of eight cultivars of groundcover rose (Rosa xhybrida) with a range of flower colors was investigated. From the methanolic extracts of rose ...petals collected from flowers at four developmental stages, several phenolic compounds were identified via high-performance liquid chromatography/mass spectrometry, including five anthocyanins, which are especially important for the visual attributes of rose flowers. Colorimetric parameters were also measured and correlated with total anthocyanins and cell sap pH levels. During flower development from bud to senescent stage, a significant trend was detected; lightness (L*) increased, b* decreased in all analyzed roses, and a* decreased in pink and red cultivars. Cell sap pH level increased from bud to senescent petals; fresh weight, dry weight, and water content increased to fully open stage and were then reduced in senescent petals. Total anthocyanin and quercetin content increased from bud stage to fully open flowers, and was decreased in senescent ones. However, the highest content of total phenolics was measured in buds and partially opened flowers, respectively. Three distinct groups were formed according to the content of total anthocyanins and quercetins; white cultivars were most distant from the red ones, which were similar to the pink and light red cultivars.
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