Search Results (5)

The endemic Patagonian conifer, Austrocedrus chilensis, is threatened by the pathogen Phytophthora austrocedri. This study presents the first histological and histochemical analysis of A. chilensis affected by this pathogen. We examined the stem tissues of naturally infected adult trees (over 30 years old) and artificially inoculated saplings (8–12 years old) to identify the pathogen’s colonization strategies and the tree’s histological responses. Using light and scanning electronic microscopy along with several histochemical techniques (Lugol, toluidine blue, vanillin-HCl, Phloroglucinol, Calcofluor white, and aniline blue), we found that P. austrocedri can grow in all active tissues, leading to cambium and parenchyma necrosis. The pathogen spreads through sieve cells and tracheids, moving to the adjacent cells via sieve plates and bordered pits and colonizing nearby parenchyma cells. We observed loss of starch in necrotic tissues. In contrast, starch accumulation and an increase in the number of polyphenolic cells occur in the healthy areas adjacent to the margins of the lesion, indicating a tree’s induced defense mechanisms. The tree’s responses include cambium reprogramming, which leads to the formation of traumatic resin ducts, alterations in cell shape and size, and the deposition of phenolic compounds. We analyze the tree responses and discuss their potential relationship with a methyl jasmonate-induced defense and a hypersensitive-like response. Full article

Benzoin is a pathologic exudation produced by plants of the family Styrax. It is secreted by traumatic resin ducts after injury, which are derived from parenchymal cells in secondary xylem by schizolysigeny. Some 63 chemical constituents have been isolated and identified from this resin, including balsamic acid esters, lignans and terpenoids. It has a long history of applications, including as incense along with olibanum, a flavor enhancer in the food industry, materials in the daily chemistry industry as well as therapeutic uses. Up to now, high-performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS) have been widely used in qualitative and quantitative analysis of benzoin. Other technologies, including near-infrared reflectance spectroscopy (NIR), proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and Fourier-transform infrared spectroscopy (FT-IR), have also been used to distinguish different resins. Herein, this paper provides a comprehensive overview of the production process, phytochemistry, traditional uses and quality control of benzoin and looks to the future for promoting its further research and applications. Full article

Xylem traumatic resin ducts (TRDs) in Douglas-fir form in response to mechanical injury, fire, and root pathogens, but it is unknown if these form at the stem in response to bark-beetle-associated fungi. Meanwhile, TRDs are rarely documented in lodgepole pine. In the southern Rocky Mountains, TRD formation in the two species from sterile (Control) and fungal inoculation treatments (Aggressive, Weak (Douglas-fir only)) were compared; predicting the following: (1) both trees would produce TRDs in response to fungal treatments; (2) in Douglas-fir, Aggressive treatment would promote denser and larger TRDs than Weak or Control treatments; and (3) interspecifically, Douglas-fir would produce a higher density of TRDs than lodgepole pine in Aggressive treatments. Two months post-treatment, the position of TRDs indicated these were only induced on all Douglas-fir treatments. Aggressive and Weak treatments had similar responses, except a second TRD line formed in two Douglas-fir Aggressive treatments. Douglas-fir produced >7× more resin ducts that were twice the size of those in lodgepole pine. Douglas-fir’s stronger induced response indicates better resistance traits against bark beetle fungal associate colonization. Understanding the characteristics of TRD produced in reaction to specific damage in Douglas-fir can improve past disturbance reconstructions and explain interspecific tree response differences conducive to bark beetle resistance. Full article

Mountain hiking trails are vital components of tourist infrastructure and provide recreational opportunities for a large number of tourists. Exposed roots along the tourist trails in the forested mountains are impacted by tourist trampling and various natural processes, thus becoming even more exposed and eroded. The aim of our study was to estimate the annual erosion rates along three hiking trails in the Făgăraș Mountains using dendrogeomorphological approaches. The three used routes were: Bâlea Hotel—Bâlea Waterfall (BWFHT), Bâlea Hotel—Bâlea Glacial Lake (BLHT), and Bâlea Hotel—Doamnei Glacial Valley (DVHT). The average annual erosion rates in BWFHT, BLHT, and DVHT were 10.6 ± 4.4, 6.8 ± 3.9, and 6.1 ± 3.3 mm·y⁻¹, respectively. Over a 56-year interval (1965–2021), 610 scars were recorded among the annual growth rings of the sampled tree roots; 172, 213, and 225 scars were recorded in BWFHT, BLHT, and DVHT, respectively. Moreover, we identified 1022 rows of traumatic resin ducts (TRDs) associated with scars: 237, 343, and 442 in BWFHT, BLHT, and DVHT, respectively. Additionally, the climate of the Făgăraș Mountains is humid with a multiannual average precipitation of 1366.2 mm; the precipitation in 24 h, between 1979 and 2021 in seven and three cases exceeded 70 mm/24 h and 100 mm/24 h, respectively. Thus, there were synchronous situations of root exposure with 24 h rainfall. However, it is unclear whether precipitation plays a decisive role in root exposure or in triggering erosion processes on tourist trails. We considered that tourist traffic plays a decisive role in root exposure and erosion, however locally and complementarily, 24 h precipitation must also be considered. Full article

The increases in temperature have recently allowed the southern pine beetle (Dendroctonus frontalis Zimm.; SPB) and its associated fungi to expand its natural range to northern pine forests. In this study, vigorous eastern white pine mature trees were used to evaluate constitutive and induced response to the southern pine beetle, using O. minus as a proxy. We evaluated histological and chemical changes in P. strobus in response to the fungus at 28- and 65-days post inoculation (dpi). Inoculation with O. minus resulted in an induced defense response as evidenced by the increased production of traumatic resin duct, and lesion development surrounding the site of infection. Starch granules accumulated in the epithelial cells surrounding the resin ducts of inoculated trees. Chemical analyses showed that among phloem phenolics, epi/catechin and three unknown compounds were significantly upregulated at 28 dpi due to fungal inoculation. Several phloem terpenoids (α-pinene, β-myrcene, limonene, terpinolene and β-pinene) were significantly increased in inoculated trees compared to controls at both, 28- and 65-dpi. Continuous production of these terpenoids (up to 65 dpi) can be energetically costly for P. strobus as carbohydrate reserves fund monoterpene synthesis, reducing carbon availability necessary for tree development. Induced phenolics along with monoterpenes production and traumatic resin ducts observed in these trees, suggests that vigorous white pine may sustain endemic populations of southern pine beetle and vectored fungi. Full article