Vessel Traits Research Articles

Variation in vessel traits of northern red oak (Quercus rubra L.) provenances revealed high phenotypic plasticity to prevailing environmental conditions

Key messageRed oak provenances responded with high plasticity and intra-annual variability in vessel traits to studied climatic conditions, indicating weak signals of local adaptation and providing opportunities for forest management.The climate change-induced increase in frequency and severity of extreme events has revealed a high vulnerability of various major tree species in Europe, stressing the need for selecting climate-resilient species for forest management. In this context, adaptive strategies of northern red oak (Quercus rubra L.) were examined, using wood anatomical data derived from a provenance trial. We investigated the interannual variation in vessel traits of red oak provenances planted at three sites along a precipitation gradient in Germany. We compared the climate sensitivity of German provenances with those from North America to analyze plasticity and to identify signals of local adaptation in vessel traits. The results revealed variations in vessel traits between all sites, pointing to site-specific responses to prevailing environmental conditions. Differences between provenances were prevalent for vessel size-related traits, with site-specific higher values for German provenances at wet sites. Climate signals, which varied between traits, were strongest for vessel density and the relative conductive area. Vessel traits were found to depend both on previous-year conditions as and on spring climate conditions during the onset of vessel formation. The site-specific response in extreme years deviate significantly between drought and frost events. A trade-off between resistance to extremes and vessel diameter could not be demonstrated, and provenances with larger vessel diameters showed higher frost resistance. The observed high plasticity in vessel traits and the site-specific variation to climate influences point to an adjustment in vessel formation to the prevailing environmental conditions.

Ecological stress memory in wood architecture of two Neotropical hickory species from central-eastern Mexico

BackgroundDrought periods are major evolutionary triggers of wood anatomical adaptive variation in Lower Tropical Montane Cloud Forests tree species. We tested the influence of historical drought events on the effects of ecological stress memory on latewood width and xylem vessel traits in two relict hickory species (Carya palmeri and Carya myristiciformis) from central-eastern Mexico. We hypothesized that latewood width would decrease during historical drought years, establishing correlations between growth and water stress conditions, and that moisture deficit during past tree growth between successive drought events, would impact on wood anatomical features. We analyzed latewood anatomical traits that developed during historical drought and pre- and post-drought years in both species.ResultsWe found that repeated periods of hydric stress left climatic signatures for annual latewood growth and xylem vessel traits that are essential for hydric adaptation in tropical montane hickory species.ConclusionsOur results demonstrate the existence of cause‒effect relationships in wood anatomical architecture and highlight the ecological stress memory linked with historical drought events. Thus, combined time-series analysis of latewood width and xylem vessel traits is a powerful tool for understanding the ecological behavior of hickory species.

Advances in Structural and Functional Retinal Imaging and Biomarkers for Early Detection of Diabetic Retinopathy.

Diabetic retinopathy (DR), a vision-threatening microvascular complication of diabetes mellitus (DM), is a leading cause of blindness worldwide that requires early detection and intervention. However, diagnosing DR early remains challenging due to the subtle nature of initial pathological changes. This review explores developments in multimodal imaging and functional tests for early DR detection. Where conventional color fundus photography is limited in the field of view and resolution, advanced quantitative analysis of retinal vessel traits such as retinal microvascular caliber, tortuosity, and fractal dimension (FD) can provide additional prognostic value. Optical coherence tomography (OCT) has also emerged as a reliable structural imaging tool for assessing retinal and choroidal neurodegenerative changes, which show potential as early DR biomarkers. Optical coherence tomography angiography (OCTA) enables the evaluation of vascular perfusion and the contours of the foveal avascular zone (FAZ), providing valuable insights into early retinal and choroidal vascular changes. Functional tests, including multifocal electroretinography (mfERG), visual evoked potential (VEP), multifocal pupillographic objective perimetry (mfPOP), microperimetry, and contrast sensitivity (CS), offer complementary data on early functional deficits in DR. More importantly, combining structural and functional imaging data may facilitate earlier detection of DR and targeted management strategies based on disease progression. Artificial intelligence (AI) techniques show promise for automated lesion detection, risk stratification, and biomarker discovery from various imaging data. Additionally, hematological parameters, such as neutrophil-lymphocyte ratio (NLR) and neutrophil extracellular traps (NETs), may be useful in predicting DR risk and progression. Although current methods can detect early DR, there is still a need for further research and development of reliable, cost-effective methods for large-scale screening and monitoring of individuals with DM.

Site-specific climate sensitivity of tree-ring width and vessel anatomical features of Juglans regia L. in Bhutan Himalaya

Climate change significantly impacts tree growth in the Himalayas, however, there is little information on how broadleaved tree species in Himalayan regions respond to climate change. Juglans regia L. (Common or Persian walnut) plays a vital economic and ecological role across the Himalayas, but little is known about how environmental changes influence the growth and wood anatomical traits of this species. In this study, we developed chronologies of tree-ring width (TRW) and six quantitative vessel anatomical features of Persian walnut trees from two sites in the Bhutan Himalayas. We evaluated how TRW and vessel anatomical features respond to climatic conditions and extreme climate events for the period 1960–2020. We found the climate sensitivity of tree growth differed at the two study sites, with the southwest-facing Dodeyna site (DOD) exhibiting higher moisture sensitivity than the north-facing Chimithangka site (CHI). The climate sensitivity of vessel traits was much stronger than that of tree-ring widths, particularly at the DOD. Hydraulic efficiency-related vessel traits (Mean vessel area, MVA; theoretical hydraulic conductivity, Kh; and hydraulic diameter, Dh) were positively sensitive to moisture availability, whereas the hydraulic safety-related vessel traits (vessel density, VD; and vessel grouping index, RVGI) were negatively sensitive to moisture availability at the DOD site. We further observed that MVA and Kh were significantly higher during extreme dry events at CHI site but displayed opposite directions at DOD site. Notably higher RVGI at the DOD site during dry years indicated an enhancement of hydraulic safety against drought. These findings highlight that the climate sensitivity of tree-ring width and vessel traits of walnuts were site-specific and mediated by aspects with the drier site (south-facing slope) being more sensitive. Whilst consideration of the aspects and site-specific climate sensitivity of tree species is crucial to developing robust forest conservation strategies at a larger spatial scale in the Himalayan region which is more vulnerable to climate change.

A systems genetic analysis identifies putative mechanisms and candidate genes regulating vessel traits in poplar wood.

Wood is the water conducting tissue of tree stems. Like most angiosperm trees, poplar wood contains water-conducting vessel elements whose functional properties affect water transport and growth rates, as well as susceptibility to embolism and hydraulic failure during water stress and drought. Here we used a unique hybrid poplar pedigree carrying genomically characterized chromosomal insertions and deletions to undertake a systems genomics analysis of vessel traits. We assayed gene expression in wood forming tissues from clonal replicates of genotypes covering dosage quantitative trait loci with insertions and deletions, genotypes with extreme vessel trait phenotypes, and control genotypes. A gene co-expression analysis was used to assign genes to modules, which were then used in integrative analyses to identify modules associated with traits, to identify putative molecular and cellular processes associated with each module, and finally to identify candidate genes using multiple criteria including dosage responsiveness. These analyses identified known processes associated with vessel traits including stress response, abscisic acid and cell wall biosynthesis, and in addition identified previously unexplored processes including cell cycle and protein ubiquitination. We discuss our findings relative to component processes contributing to vessel trait variation including signaling, cell cycle, cell expansion, and cell differentiation.

Root topological order drives variation of fine root vessel traits and hydraulic strategies in tropical trees.

Vessel traits contribute to plant water transport from roots to leaves and thereby influence how plants respond to soil water availability, but the sources of variation in fine root anatomical traits remain poorly understood. Here, we explore the variations of fine root vessel traits along topological orders within and across tropical tree species. Anatomical traits were measured along five root topological orders in 80 individual trees of 20 species from a tropical forest in southwestern China. We found large variations for most root anatomical traits across topological orders, and strong co-variations between vessel traits. Within species, theoretical specific xylem hydraulic conductivity (Kth) increased with topological order due to increased mean vessel diameter, size heterogeneity, and decreased vessel density. Across species, Kth was associated with vessel fraction in low-order roots and correlated with mean vessel diameter and vessel density in high-order roots, suggesting a shift in relative anatomical contributors to Kth from the second- to fifth-order roots. We found no clear relationship between Kth and stele: root diameter ratios. Our study shows strong variations in root vessel traits across topological orders and species, and highlights shifts in the anatomical underpinnings by varying vessel-related anatomical structures for an optimized water supply.

Extreme drought triggers parallel shifts in wood anatomical and physiological traits in upper treeline of the Mediterranean Andes

BackgroundTreeline ecotones of Mediterranean ecoregions have been affected by the increasing intensity and severity of droughts. Even though the effect of droughts on forest dynamics has been widely documented, knowledge is relatively scarce of how extreme climate episodes affect the hydraulic structure and, therefore, the physiology of woody plants. The Mediterranean Andes have experienced an uninterrupted period of drought since 2010, including an extremely dry year in 2019 with approximately 80% rainfall deficit. Here, we investigated shifts in wood anatomical and physiological traits of Kageneckia angustifolia, an endemic treeline species, in response to this drought period.MethodsWe evaluated the xylem plasticity of three K. angustifolia populations across their natural distribution (31–35° SL) based on anatomical (vessel structure and distribution) and physiological (intrinsic water-use efficiency) variables in the tree rings. We focused on the period 2000–2020 that corresponds to before the megadrought (2000–2007), (ii) megadrought (2008–2018) and (iii) hyperdrought (2019–2020). The variables were annualized and analyzed by linear mixed-effects models.ResultsOur results provide insights to the anatomical and physiological mechanisms underlying the resilience of treeline forests to persistent droughts in central Chile. We found that the extreme drought in 2019–2020 triggered shifts in vessel size and frequency that increased hydraulic safety. These significant shifts in vessel traits occurred in parallel with a decrease in pit aperture area and an increase in water-use efficiency, further increasing the resilience of K. angustifolia to extreme drought stress.ConclusionsOur results revealed coordinated shifts in vessel size and frequency and water-use efficiency in response to the megadrought, thereby reducing vulnerability to hydraulic failure. The apparent resilience of K. angustifolia to extreme droughts suggests that this adaptation to drought stress may increase its ability to tolerate novel climatic conditions of treeline environments of the Mediterranean Andes, although it is not clear whether these adaptations will be sufficient to persist in scenarios that predict intensification of climate stress. Finally, our results provide empirical evidence that integrating wood anatomical and physiological traits facilitates the understanding of resilience mechanisms that treeline forests develop in the face of increasing drought stress.

Tree species differ in plant economic spectrum traits in the tropical dry forest of Mexico.

In tropical dry forests, studies on wood anatomical traits have concentrated mainly on variations in vessel diameter and frequency. Recent research suggests that parenchyma and fibers also play an important role in water conduction and in xylem hydraulic safety. However, these relationships are not fully understood, and wood trait variation among different functional profiles as well as their variation under different water availability scenarios have been little studied. In this work, we aim to (1) characterize a set of wood anatomical traits among six selected tree species that represent the economic spectrum of tropical dry forests, (2) assess the variation in these traits under three different rainfall regimes, and (3) determine the relationships between wood anatomical traits and possible functional trade-offs. Differences among species and sites in wood traits were explored. Linear mixed models were fitted, and model comparison was performed. Most variation occurred among species along the economic spectrum. Obligate deciduous, low wood density species were characterized by wood with wide vessels and low frequency, suggesting high water transport capacity but sensitivity to drought. Moreover, high cell fractions of carbon and water storage were also found in these tree species related to the occurrence of abundant parenchyma or septate fibers. Contrary to what most studies show, Cochlospermum vitifolium, a succulent tree species, presented the greatest variation in wood traits. Facultative deciduous, high wood density species were characterized by a sturdy vascular system that may favor resistance to cavitation and low reserve storage. Contrary to our expectations, variation among the rainfall regimes was generally low in all species and was mostly related to vessel traits, while fiber and parenchyma traits presented little variation among species. Strong functional associations between wood anatomical traits and functional trade-offs were found for the six tree species studied along the economic spectrum of tropical dry forests.

Vessel, intervessel pits and vessel-to-fiber pits have significant impact on hydraulic function under different drought conditions and re-irrigation

Although xylem embolism is a key process during drought-induced tree mortality, its relationship to xylem anatomy remains debated. We subjected Syzygium aromaticum to different degrees of drought treatments for three years, followed by short-term and high-intensity drought stress, and then re-irrigation to explore the influence of anatomical structures on hydraulic function. We found that vessel area, vessel diameter, and pit membrane area (APM) of intervessel pits significantly reduced after long-duration severe drought stress, while the APM of vessel-to-fiber pits increased. These variations had a strong effect on hydraulic conductivity and embolism. Drought-adapted plants had higher embolism resistance when exposed to short-term and high-intensity drought stress. Unexpectedly, under extreme drought stress, some exudations presented on the vessel-to-fiber pit membrane, and the aperture area of intervessel pits and vessel-to-fiber pits in each organ decreased by 29–44% and 0.7–30%, respectively. Pit membrane and aperture, especially the intervessel pits, were associated with hydraulic efficiency and embolism resistance under different drought conditions and re-irrigation. These findings suggest that the intervessel pits have a substantial impact on hydraulic function, and the fibers around vessels also play an essential role in embolism resistance. Our study makes an addition to the developing knowledge on xylem plasticity, vessel traits, and their effect on hydraulic function.

Wood anatomy and dendrochronological potentiality of some woody shrubs from the southern Mediterranean coast in Egypt.

In tropical and subtropical regions, much research is still required to explore the dendrochronological potential of their trees. This study aims to evaluate the anatomical structure and dendrochronological potential of three Mediterranean desert shrubs in Egypt (Lycium schweinfurthii var. schweinfurthii, L. europaeum, and Calligonum polygonoides subsp. comosum) supported by X-ray density. The results showed that the target species had distinct growth rings at macroscopic and microscopic levels. The vessel traits reflected the adaptability of each species with the prevailing arid climate conditions. After the exclusion of the non-correlated series, we obtained three site chronologies that cover the years 2013-2022 for L. schweinfurthii, 2012-2022 for L. europaeum, and 2011-2022 for C. comosum. The mean series intercorrelation was 0.746, 0.564, and 0.683 for L. schweinfurthii, L. europaeum, and C. comosum, respectively. The EPS (expressed population signal) values ranged from 0.72 to 0.80, while the SNR (species-to-noise ratio) ranged from 9.1 to 21.5. Compiling all series of L. schweinfurthii raised the EPS value to 0.86. The chronologies developed for the studied species were relatively short since we dealt with multi-stemmed shrubs. The average percentage difference between latewood density (LWD) and earlywood density (EWD) in C. comosum, L. europaeum, and L. schweinfurthii were 11.8% ± 5.5, 5.2%± 1.87, and 3.6% ± 1.86, respectively. X-ray densitometry helped in the precise determination of the ring borders of the studied species. The relationships between the radial growth of the studied species and the climate variables were weak to moderate but mostly not significant (i.e., r < 0.7). Generally, the radial growth of the target species had a weak to moderate positive correlation with temperature and precipitation during the wet season (winter), while negatively correlated with temperature for the rest of the year, particularly in summer. Our data agrees with earlier findings that ring formation starts at the beginning of the long vegetative stage, then the rest of the assimilated carbohydrates are directed to the flowering and fruiting at the end of the vegetative stages. For more efficient dendrochronological studies on subtropical and Mediterranean trees, we recommend carrying out xylogenesis studies, collection of phenological data, sampling 45-80 trees per species, using new techniques, and choosing homogeneous and close sites for wood sampling.

Root and branch hydraulic functioning and trait coordination across organs in drought-deciduous and evergreen tree species of a subtropical highland forest.

Vessel traits are key in understanding trees' hydraulic efficiency, and related characteristics like growth performance and drought tolerance. While most plant hydraulic studies have focused on aboveground organs, our understanding of root hydraulic functioning and trait coordination across organs remains limited. Furthermore, studies from seasonally dry (sub-)tropical ecosystems and mountain forests are virtually lacking and uncertainties remain regarding potentially different hydraulic strategies of plants differing in leaf habit. Here, we compared wood anatomical traits and specific hydraulic conductivities between coarse roots and small branches of five drought-deciduous and eight evergreen angiosperm tree species in a seasonally dry subtropical Afromontane forest in Ethiopia. We hypothesized that largest vessels and highest hydraulic conductivities are found in roots, with greater vessel tapering between roots and equally-sized branches in evergreen angiosperms due to their drought-tolerating strategy. We further hypothesized that the hydraulic efficiencies of root and branches cannot be predicted from wood density, but that wood densities across organs are generally related. Root-to-branch ratios of conduit diameters varied between 0.8 and 2.8, indicating considerable differences in tapering from coarse roots to small branches. While deciduous trees showed larger branch xylem vessels compared to evergreen angiosperms, root-to-branch ratios were highly variable within both leaf habit types, and evergreen species did not show a more pronounced degree of tapering. Empirically determined hydraulic conductivity and corresponding root-to-branch ratios were similar between both leaf habit types. Wood density of angiosperm roots was negatively related to hydraulic efficiency and vessel dimensions; weaker relationships were found in branches. Wood density of small branches was neither related to stem nor coarse root wood densities. We conclude that in seasonally dry subtropical forests, similar-sized coarse roots hold larger xylem vessels than small branches, but the degree of tapering from roots to branches is highly variable. Our results indicate that leaf habit does not necessarily influence the relationship between coarse root and branch hydraulic traits. However, larger conduits in branches and a low carbon investment in less dense wood may be a prerequisite for high growth rates of drought-deciduous trees during their shortened growing season. The correlation of stem and root wood densities with root hydraulic traits but not branch wood points toward large trade-offs in branch xylem towards mechanical properties.

Adaptation potential of Neotropical montane oaks to drought events: Wood anatomy sensitivity in Quercus delgadoana and Quercus meavei

Abstract Climate and local water availability are major evolutionary drivers of adaptive variation and plasticity in the hydraulic architecture of Tropical Montane Cloud Forest (TMCF) tree species. Between‐year xylem vessel variability is key to understanding the adaptation potential of wood anatomy of trees to drought. How wood anatomical features have been influenced by the typical TMCF climate and how tree species persist in these environments remain open questions, particularly in the context of predicted extreme climate events in the future. Here, we evaluated the effects of changes in temperature, precipitation and evapotranspiration during drought events on ring‐width and anatomical vessel traits (hydraulic diameter, vessel density, vessel grouping index and vulnerability index) for two relict endemic and threatened oak species (Quercus delgadoana and Q. meavei) from a Mexican TMCF. The study species differed in their functional and ecological vessel anatomical traits, and their wood anatomical differences are related to specific environmental requirements. However, the ring‐width indices (RWIs) calculated for these species indicate that both have high resistance and recovery, and thus high resilience to drought events. Ring‐width and vessel functional traits show differences in the between‐year variability of xylem traits associated with the hydraulic efficiency of these oak species, which is crucial to understanding how they avoid drought‐induced embolism and cavitation in vessel conduits. These results provide evidence for the existence of specific hydraulic systems that determine functional wood anatomy in response to climatic variation and drought in the study species. Further research assessing the wood anatomical adaptation to different climatic variables and identifying the xylem functional traits that underlie these adaptations, along with the mechanisms allowing tree species persistence in these environments, is essential to gain insight into the responses of TMCF to future drought events. Read the free Plain Language Summary for this article on the Journal blog.

锡林浩特多年生草本根部导管性状与植株生态策略的相关特征

PDF HTML阅读 XML下载 导出引用 引用提醒 锡林浩特多年生草本根部导管性状与植株生态策略的相关特征 DOI: 10.5846/stxb202108262399 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重大项目（41991233）；国家自然科学基金面上项目（41877539，42071125） Vessel traits of main roots are linked to ecological strategies of the perennial herbs in Xilinhot of China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:干旱半干旱区植物的木质部输水系统对维持植物生长发育有重要作用。以中国干旱半干旱区的草本植物为研究对象，旨在探究草本物种根系导管解剖结构与植物生长之间的关系。用石蜡切片法，将在锡林浩特草原采集的草本物种的主根样品制作成切片，得到固定面积内导管解剖结构参量（导管数量、导管分数、平均导管面积、平均水力传导率和水力直径），然后用逐步回归法和Pearson相关分析各导管解剖性状与植物生长特征（年龄、生长速率和平均高度）之间的关系。结果发现（1）生长速率与导管数量（R=-0.494，P<0.01）和导管分数（R=-0.255，P<0.05）显著负相关，与平均导管面积（R=0.274，P<0.05）、平均水力传导率（R=0.263，P<0.05）和水力直径（R=0.245，P<0.05）显著正相关，表明生长快的草本具有大而少的导管，需要较高的水分传输能力，而生长慢的草本具有小而多的导管，水力安全性较高；（2）植株的高度与导管数量（R=-0.354，P<0.01）显著负相关，与平均导管面积（R=0.293，P<0.05）、平均水力传导率（R=0.289，P<0.05）和水力直径（R=0.278，P<0.05）显著正相关，表明高大的植株以较少的导管补偿较大的导管以维持一定的机械强度，而矮小植株的水力安全性较高。 Abstract:The hydraulic system plays an important role in supporting plant growth and development in arid and semiarid regions. In this study, we explored the relationship between vessel anatomical traits and growth characteristics of herbaceous species. We used paraffin sectioning method to make taproot sections, and acquired the characteristics of vessel anatomical structures (including number of vessels, vessel fraction, mean vessel area, mean hydraulic conductivity, and hydraulic diameter) in a fixed area. Pearson correlation and stepwise regression methods were used to analyze the relationship between vessel anatomical traits and plant growth characteristics (age, growth rate, and mean height). The results indicated that (1) the growth rate was significantly negatively correlated with vessel number (R=-0.494, P<0.01) and vessel fraction (R=-0.255, P<0.05), whilist, significantly positively correlated with mean vessel area (R=0.274, P<0.05), mean hydraulic conductivity (R=0.263, P<0.05), and hydraulic diameter (R=0.245, P<0.05), which may indicate that fast-growing herbs form larger and fewer vessels to increase the hydrualic efficiency, while slow-growing herbs form smaller and more vessels to increase hydraulic safety. (2) Mean height was significantly negatively correlated with vessel number (R=-0.354, P<0.01), whilist, significantly positively correlated with mean vessel area (R=0.293, P<0.05), mean hydraulic conductivity (R=0.289, P<0.05), and hydraulic diameter (R=0.278, P<0.05), which may suggest that in order to maintain the mechanical strength, high plants usually form few vessels to compensate for large vessels, while short plants form smaller and more vessels to increase hydraulic safety. 参考文献 相似文献 引证文献

Plastic adjustments in xylem vessel traits to drought events in three Cedrela species from Peruvian Tropical Andean forests

Cedrela species occur within the Tropical montane cloud forest (TMCF) and rainforest in North America (Mexico), Central and South America. We assessed the hypothesis that functional xylem hydraulic architecture might be influenced by specific climatic variations. We investigated the effect of climate on tree-ring width and vessel traits (diameter, vessel density, vulnerability index and hydraulic diameter) of three relict-endemic and threatened Cedrela species (Cedrela fissilis, C. nebulosa and C. angustifolia) inhabiting Peruvian Tropical Andean cloud forests. All Cedrela species showed a significant reduction in radial growth and adjusted vessel trait linked with temperature, precipitation, and evapotranspiration. Ring-width and vessel traits showed adaptation within Cedrela species, crucial to understanding a rough indication of the plant’s ability to withstand drought-induced embolism or cavitation. Our results provide evidence for hydraulic mechanisms that determine specific wood anatomical functionality to climatic variation and drought responses. Therefore, changing the frequency or intensity of future drought events might exceed the adaptive limits of TMCF tree species, resulting in a substantial reduction of hydraulic functionality in Peruvian Cedrela species.

Potassium fertilization enhances xylem plasticity and growth recovery of Eucalyptus grandis trees in response to drastic changes in water availability

Most Eucalyptus plantations in Brazil are located in regions currently experiencing periods of water shortage, where fertilizers such as potassium (K) are intensively used to achieve high productivity. In a changing environment, improving our understanding of the effects of K nutrition on tree growth rates and xylem plasticity across tree ages as a function of climate is crucial for forest management. The objective of this study was to gain insight into the interactive effects of K fertilization, water availability, and tree age on stem growth and changes in xylem traits of E. grandis trees over a full rotation. Changes in growth and xylem traits in response to a severe drought that occurred in 2014 were also studied. An experimental plantation of E. grandis trees was established in São Paulo, Brazil and monitored over a full 6-year rotation period. The experiment consisted of a split-plot design with two water supply regimes (37 % throughfall reduction vs undisturbed throughfall) and two fertilization regimes (K supply vs control). Basal area increment (BAI) was monitored using band dendrometers at 14-day intervals from 1 to 6 years after planting. Xylem traits including wood density (WD), cell wall fraction (CWF), cell density (CDen), theoretical xylem specific hydraulic conductivity (Kst), vessel diameter (VD), vessel density (VDen), vessel area (VA), and the vulnerability index (VI) were measured in 6-month periods (rainy and dry seasons) throughout the rotation. K fertilization increased BAI by a factor of 3 in plots where throughfall was not disturbed but led to an interruption of tree growth during the severe drought in 2014. The growth patterns showed a positive effect of K for growth recovery following drought. Throughfall reduction affected growth only in K-fertilized trees and up to 30 months of age. K fertilization also increased changes in xylem traits in response to drought in E. grandis trees. The main changes occurred in vessel traits, with a 53 % decrease in Kst during the drought but recovery was rapid after the first rainfall events. High plasticity was also observed for WD, CWF, CDen, and VI.

Different-Sized Vessels of Quercus variabilis Blume Respond Diversely to Six-Year Canopy and Understory N Addition in a Warm-Temperate Transitional Zone

Nitrogen is a necessary macroelement in plant growth and is usually considered a limiting factor in many forest ecosystems. Increasing N deposition has been reported to affect tree growth. However, the effects still remain controversial due to variable N fertilization methods used. In order to study the realistic responses of tree growth to increasing N deposition, we investigated effects of canopy and understory N addition on tree-ring growth and vessel traits of Quercus variabilis Blume. Since 2013, 50 kg N ha−1 year was applied monthly from April to December to either the canopy (CN) or understory (UN) of trees in a warm-temperate forest in Central China. During 2013–2018, tree-ring growth and vessel-related traits (mean vessel area, theoretical xylem hydraulic conductivity (KH), relative ratio of KH, etc.) were analyzed. Tree rings were negatively impacted by both CN and UN treatments, but only the effect of UN was significant. Neither CN nor UN significantly impacted the detected vessel traits. However, some diverging influencing trends were still showed in some vessel traits. Both CN and UN treatments positively affected the percentage of annual total vessel area and vessel density, with the effect of UN on vessel density being more severe. All the detected vessel traits of the large vessels formed at the beginning of the tree-ring responded positively to CN, whereas the opposite response to UN was showed on mean vessel area and the relative ratio of KH. All these diverging responses in different vessel traits likely reflected the compensation and trade-off between maximizing growth and adapting to CN and UN treatments. Six-year long N addition negatively and positively affected tree-ring growth and vessel traits of Q. variabilis in Central China, respectively. UN treatment could not fully simulate the real effect on tree growth, especially on the hydraulic architecture.

Could trees change future behaviour in xylogenesis to improve fitness based on past and current conditions? A tropical case of study

Carbon allocation is the Achilles' heel of forest models, due to the difficulty to predict responses induced by environmental changes. Structural-functional models involve the plant's strategy to split its resources between organs and functions. An important functional characteristic is xylem architecture, which is connected to water use strategy and plant productivity besides one of the most important C-sink (that absorbs carbon). Our goal is to use the information present in the tree rings of Schizolobium parahyba, to expand the possibilities of teleonomic approaches in structural-functional models of tree species. In a comparative xylem rings analyses, we established relationships among specific gravity, vessel traits as hydraulic conductivity potential, double wall thickness, and autofluorescence intensity of lignin. The analyses showed that growth ring characteristics seem to have been modulated not only by water availability of the period of wood formation but also by the water availability of previous years. This relationship would be occurring due to the greater capacity of accumulation of reserve carbohydrates in years whose climatic conditions were favourable. This pattern of behaviour entails the formation of two distinct growth ring patterns, one with high and the other with low structural cost. This case study shows that the species can change future behaviour in xylogenesis to improve fitness based on past and current conditions. Our study may help to extend the possibilities of teleonomic approaches in structural-functional models of tree species, which will assist in a greater understanding of how trees balance their carbon allocation in wood according to changes in the environment.

Secondary xylem maturation evaluated by modeling radial variations in anatomical characteristics and wood properties of Shorea macrophylla (De Vr.) Ashton planted in Sarawak, Malaysia

Xylem maturation depends on cambial age rather than diameter growth in Shorea macrophylla by the model selections for radial variations in cell length, wood fiber traits, and basic density. Radial variations in anatomical characteristics and wood properties were investigated in 23-year-old Shorea macrophylla (engkabang) trees planted in Sarawak, Malaysia. The effects of radial growth rates on anatomical characteristics and wood properties and the manner of xylem maturation were determined based on selected mixed-effects models. The best models of radial variation were fitted by linear functions for wood fiber length, wood fiber wall thickness, basic density, and compressive strength. Logarithmic functions were applied for vessel element length and vessel frequency, and quadratic functions were applied for vessel diameter and wood fiber diameter. Vessel diameter and wood fiber length were affected by radial growth rates although these effects on the other properties were minimal. In the fixed part of the models, the results showed small mean absolute error values of radial variation in relation to the distance from the pith according to vessel frequency and vessel diameter. In contrast, in relation to the estimated cambial age, smaller mean absolute error values were obtained for cell length, wood fiber traits, and basic density, suggesting that all properties varied from pith to bark in relation to the cambial age, except for vessel traits. Thus, in S. macrophylla, xylem maturation in cell length, wood fiber traits, and basic density were due to cambial age rather than diameter growth, but xylem maturation in vessel traits depended on diameter growth.

Evaluation of family seed sources and clones of Casuarina junghuhniana and C. cunninghamiana, for growth and wood traits at two contrasting sites in southern India

The growth and wood traits of four taxa (a) 42 Casuarina junghuhniana (Cj) families from four natural provenances, (b) 9 second generation (2G) Cj families, (c) 43 Cj clones and (d) 14 C. cunninghamiana families, were evaluated at two contrasting sites in southern India. Survival was high (>90%) at the dry coastal Ongole site at 48 months for both the seedlings and clones. Overall, growth was better at the higher rainfall, irrigated inland location West Godavari (WG), but the clones had 16% lower mean survival than Cj seed sources. C. cunninghamiana had significantly lower survival at both sites at 72 months. The clones had comparable growth (height and diameter at breast height) and better stem form and axis persistence than natural provenances and 2G seedlots of C. junghuhniana. Provenance variation was significant for growth traits, while narrow and broad-sense heritability estimates were low to moderate in C. junghuhniana, suggesting that both recurrent selection and breeding among appropriate provenances and deployment of clones are likely to result in genetic gain. Genotype-by-environment interaction was low for growth traits. Wood (density and pulp yield), fibre, and vessel traits were evaluated from core samples in 9–10 families/clones of each taxon at 48 months. Fibre length was significantly higher in 2G seedlots and clones than natural Cj provenances, while C. cunninghamiana had the longest fibres at the irrigated inland site. C. cunninghamiana had significantly lower wood density and Runkel ratio due to lower fibre wall thickness and wider cell lumen (fibre and vessel). All taxa had higher wood density at the dry coastal site due to higher fibre wall thickness, but vessel wall thickness was higher at the irrigated WG site. Narrow-sense heritability estimates for wood traits were moderate for fibre length and width, but low and imprecisely estimated for pulp yield and other traits. However, the broad-sense heritability (clonal repeatability) estimate was moderate for pulp yield, with low clone-by-site interaction, suggesting deployment of suitable, stable clones would be an appropriate deployment strategy.

Genetic Regulation of Vessel Morphology in Populus.

During secondary growth, forest trees can modify the anatomy of the wood produced by the vascular cambium in response to environmental conditions. Notably, the trees of the model angiosperm genus, Populus, reduce the risk of cavitation and hydraulic failure under water stress by producing water-conducting vessel elements with narrow lumens, which are more numerous and more interconnected with each other. Here, we determined the genetic architecture of vessel traits affecting hydraulic physiology and resilience to water stress. Vessel traits were measured for clonally replicated genotypes of a unique Populus deltoides x nigra population carrying genomically defined insertions and deletions that create gene dosage variation. We found significant phenotypic variation for all traits measured (mean vessel diameter, height-corrected mean vessel diameter, vessel frequency, height-corrected vessel frequency, vessel grouping index, and mean vessel circularity), and that all traits were under genetic control and showed moderate heritability values, ranging from 0.32 to 0.53. Whole-genome scans of correlations between gene dosage and phenotypic traits identified quantitative trait loci for tree height, mean vessel diameter, height-corrected mean vessel diameter, height-corrected vessel frequency, and vessel grouping index. Our results demonstrate that vessel traits affecting hydraulic physiology are under genetic control, and both pleiotropic and trait-specific quantitative trait loci are found for these traits.