Trees最新文献

Key message

SSR-based characterization revealed a high genetic diversity, negligible genetic differentiation, insignificant inbreeding, and subtle genetic structure in Myrica esculenta populations of Western Himalayas, indicating a high adaptive and evolutionary potential.

Myrica esculenta is a high-valued wild edible fruit-bearing tree of sub-Himalayan region experiencing noticeable deterioration in its stand structure. This study aimed to unveil the gene diversity and spatial genetic structure of M. esculenta populations in the Western Himalayas under the state of Uttarakhand (India) using nuclear simple sequence repeat (SSR) markers. By investigating 23 populations at 8 SSR loci, high genetic diversity (expected heterozygosity, He = 0.90; allelic richness, Ar = 13.65) was recorded with little genetic differentiation (fixation index, F_ST = 0. 025). Bayesian analysis revealed a weak genetic structure with no discrete genetic lineages from which ancestry can be inferred. Furthermore, genetic clustering among populations was conspicuous but not in accordance with their spatial distribution. Geographically separated populations are genetically well connected due to long-distance gene flow via pollen as well as seed. Hence, the meta-population in the Western Himalayas demonstrated a subtle spatial genetic structure with negligible genetic divergence, where genetic admixing is not modulated by geographical constraints. Viewing the substantial anthropogenic pressure over wild populations, conservation strategies must be adopted synergistically based on scientific knowledge. As center of diversity is centered toward the Kumaon region capturing higher allelic richness, we recommend the populations of this region to be prioritized for in situ conservation. Further, it will be important to harvest seeds from genetically diverse populations for raising plantations or ex situ field gene banks. As its fruits are mostly harvested from wild, local communities need to be sensitized and encouraged to establish private plantations or orchards.

Key message

Differences in architectural traits of European beech saplings submitted to different levels of competition intensity and neighborhood diversity show a shift toward lateral growth exploration for overtopped trees but less expressed apical control is maintained for beech grown with conifers.

Abstract

Crown plasticity is a fundamental process to optimize the acquisition of light in forests, where it is often the limiting factor for growth. The processes leading to crown dynamics in response to biotic interaction are controlled by the competitive status of a tree, as well as the species diversity of the neighborhood. Yet, the ontogenic diversity of the different branches leading to crown structure makes it difficult to model crown plasticity. In this study, we used single-image photogrammetry and a semi-automatic topology reconstruction software to map the architecture of 3-year-old European beech trees (Fagus sylvatica L.) grown in pure pots or mixed with Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) or Norway spruce (Picea abies L. H.Karst). Further, we investigated the effect of competition intensity (estimated with height rank) and neighbourhood diversity on architectural traits. To do so, we quantified the mean volume, slenderness, number of branches, branching rate, internode length, and diameter ratio for each stem and branch, up to the order three. Overtopped trees developed fewer branches and biomass but allocated more biomass to branches of a higher order than to the stem. The increase in the ramification of the stem and the diameter ratio of the first-order branches for overtopped trees indicate a shift in the growth strategy and a decrease in apical control. As competition intensity and neighbour identity have opposite effects on stem traits, it seems that the positive effect of plant diversity on growth can be attributed to the intrinsic effects of species identity rather than to competition release.

There’s a lack of studies on the structure–function aspect of linking non-structural carbohydrates to temperature, in particular phloem structure is yet a largely neglected subject. We studied gas exchange parameters and in parallel examined functional anatomy and non-structural carbohydrates status in leaf blades, petioles and branches in ‘Cabernet Sauvignon’ grapevines grown under three temperature regimes (22/16 °C, 28/22 °C, 34/28 °C day/night).

After  two months of growth, water use efficiency was the highest at 34 ºC. The individual organs size became progressively smaller as the temperatures increased, and was the smallest at 34 ºC for branch and petiole diameter, and for leaf thickness. The relative xylem cross-sectional area was largely not influenced by the temperature regime. In contrast, phloem cross-sectional area was significantly increased at high temperature in branches and petioles, and became 30% higher at 34 ºC in branches compared to 22 °C. The leaves had the highest non-structural carbohydrates concentration compared to petioles and branches. Sucrose content exhibited a temperature-dependent increase both in branches and petioles, and to some extent also in leaves, while starch, fructose and glucose content did not exhibit any statistically significant temperature trends.

In grapevine, sucrose is the main non-structural carbohydrate used for long-distance transport. Our results indicate temperature dependent increased investment in phloem development in parallel with increased main long-distance transported sugar (sucrose) accumulation. Phloem and xylem development were apparently uncoupled, implying a differential cambium activity for each tissue. Our study could have wide structural–functional implications in the ongoing climate change scenario.

Key message

Early rewetting influenced growth variability and hydraulic uniformity in Pedunculate oak wood on disturbed peatland. Long-term study highlighted vessel widening's importance in adapting to water availability changes.

Abstract

Pedunculate oak (Quercus robur L.) is a widely recognized flood-tolerant tree that thrives on fertile and moist soil conditions, such as on or close to peatland ecosystems. In the frame of climate change counteracting policies, rewetting peatland ecosystems is gaining increasing interest, while the ecological consequences are not always clear. Whereas the effect of flooding on wood anatomical traits of pedunculate oak is widely documented, little is known about the effect of permanent rewetting. In this study, we investigated the wood anatomical responses of 12 pedunculate oak trees located on a formerly drained peatland in NE Germany, that experienced flooding and a consequent rewetting. Wood anatomical traits were analyzed via CARROT, a tool that employs the accuracy and efficiency of artificial intelligence to identify tree rings and vessels. Growth anatomical traits (e.g., tree ring width) showed a sudden increase after the rewetting started in 1995, while hydraulic traits (Dh and Ks) displayed a decreasing trend only after the rewetting process was fostered by the opening of an artificial canal in 2004. Variance analysis highlighted subtle changes in the trait’s distribution over time: high soil water content triggered variability in the growth anatomical traits and, simultaneously, homogeneity in the hydraulic traits. Results suggest the relevance of the “vessel widening” mechanisms to develop coping strategies in response to the later stage of the rewetting, and pose relevant insights concerning the importance of specific site conditions for the implementation of rewetting policies in peatlands with presence of pedunculate oak.

Key message

The pyroligneous acid of Acacia mearnsii enhanced the rooting, promoted higher carbon allocation and quality of rooted cuttings representing a novel, natural input for subtropical Eucalyptus clone production.

Abstract

The development of strategies aimed at optimizing the clonal propagation of Eucalyptus species, especially those that are difficult to root, is of great importance. In this context, the present study aimed to evaluate the effect of applying different concentrations of the pyroligneous acid (PA) of Acacia mearnsii De Wild, through foliar spraying, on mini-cuttings of E. benthamii, E. dunnii, and the hybrid, E. urophylla × E. dunnii, during the summer and winter periods in southern Brazil. The experiments were carried out in a greenhouse in a factorial scheme, testing four PA concentrations (0 [control], 2%, 4%, and 6%) and five clones, E. benthamii (B1 and B2), E. dunnii (D1 and D2), and E. urophylla × E. dunnii (UD). Thirty days after staking, the percentage survival of the mini-cuttings was evaluated, and at 50 days, adventitious rooting and callogenesis, as well as the morphological attributes of the mini-cuttings were evaluated. Chemical analysis of the PA revealed the presence of phenolic compounds, primarily syringol, pyrocatechol, and guaiacol derivatives. The PA of A. mearnsii was shown to be a potential alternative input for maximizing the rooting percentages of subtropical Eucalyptus clones that are difficult to propagate. PA contributed to greater allocation of dry matter and quality (Dickson Quality Index) of clonal seedlings, except for clone D2. Spraying concentrations between 2 and 4% PA, applied twice a week, optimized the subtropical eucalyptus mini-cuttings, with the dose of maximum technical efficiency being (DMTE) estimated between 3.5 and 4.5% PA. PA represents a novel, natural input for the production of clones of E. benthamii, E. dunnii, and the hybrid, E. urophylla × E. dunnii.

Key message

Repeated bending stimulations applied on poplar stem drives wood formation toward egg-shaped cross sections, thicker fiber cell walls and more fibers developing a G-layer; but cells sensitivity accommodates to avoid overresponses.

Abstract

Trees acclimate to mechanical stimulations (e.g. wind) through thigmomorphogenesis. Recent studies have demonstrated that repetitive unidirectional bending treatments applied to poplar stems result in the production of two distinct types of wood: tensile flexure wood (TFW) on the stretched side and compressive flexure wood (CFW) on the compressed side of the stem. However, the dose-effect responses of wood formation to repeated unidirectional bending treatments have not been established. In this study, we show that the number of bending events plays a crucial role in wood formation. To investigate this, young poplar stems were subjected to two different treatments involving different numbers of transient and unidirectional elastic bends. The radial growth of the stems was monitored throughout the treatments, and wood anatomy was quantitatively analysed and compared to control trees. The elliptic shape of poplar stem cross section, observed in response to the lowest dose, transformed into egg-shaped cross section in response to the highest dose. At the tissue level, the proportion of vessels vs fibers and their sizes were not differentially altered between the two treatments. However, there were notable differences in the proportion of G-fibers and the thickening of secondary cell walls, showing that the different traits of flexure wood have independent mechanosensitive control. Overall, our findings demonstrate that, in addition to their ability to respond to the intensity and direction of local mechanical strains, poplars adjust wood formation based on the number of bending events. These modifications likely enhance stem resistance against breakage when exposed to strong wind gusts.

Key message

A gradual change exists in the altitudinal response of earlywood growth of Abies fargesii to hydrothermal conditions, with temperature being the main climatic factor controlling its latewood growth.

Abstract

The Tibetan Plateau, as the “Third Pole”, has witnessed profound and intricate effects of climate change in recent decades. This may result in different responses of tree radial growth to climatic factors in this region, varying with elevation and growth stages. To accurately reveal these different responses we established totalwood, earlywood and latewood width chronologies of Abies fargesii at four elevations. Our results showed that: (1) As the elevation increases, the response of radial growth of Abies fargesii to climatic factors shifted from restriction primarily by water deficiency caused by rapid warming, to weak restriction by winter precipitation with favorable hydrothermal conditions, and then to double restriction owing to insufficient heat and excessive moisture. This pattern was inconsistent with the relationship between the radial growth and climatic factors for latewood observed at the low and middle–low elevations. (2) There existed a temporal variability in the relationship between tree radial growth and restrictive climate factors. This unstable relationship was mainly observed in the middle–low elevation within suitable ecological conditions and during the later stages of tree radial growth with lower growth rates. This is related to the fact that more suitable ecological conditions and lower growth rates make tree growth more susceptible to climatic fluctuations. Considering these findings, if the climate would experience further cooling and humidity increasing in the study region, the growth of Abies fargesii might be more adversely affected at high elevation. For economic and ecological considerations, the afforestation of Abies fargesii should be prioritized in the middle–low elevation zones where favorable for the population distribution.

The pecan tree is a globally recognized fruit-bearing tree of significant economic value. This paper focused on the dynamic changes that occur during the germination stages of pecan seeds. To investigate alterations in transcription and metabolism during the germination process, this paper employed UPLC–MS/MS technology to evaluate the shifts in the metabolite composition of pecan seeds during four different germination processes. This paper unveiled a total of 1426 metabolites, encompassing various categories such as flavonoids, phenolic acids, amino acid derivatives, lipids, and alkaloids. Furthermore, the exploration of the transcriptome through GO and KEGG enrichment analyses revealed a common pathway across all control groups—the “phytohormone signal transduction” pathway. This finding underscores the pivotal role of phytohormones in regulating diverse stages of pecan seed germination. In addition, the investigation into the interplay between differentially expressed genes and metabolites highlighted two key plant hormones, ABA and GA3, as essential drivers of seed germination. Within the ABA synthesis pathway, we observed elevated expression of NCED during the S1 stage, leading us to speculate that NCED is a key enzyme in ABA synthesis. Conversely, GA3ox and GGPPS displayed heightened expression during the S2 and S4 stages, respectively, signifying their critical roles in the GA3 synthesis pathway. To validate our findings, we performed qRT-PCR analysis on nine key genes. In conclusion, this study integrated metabolomics and transcriptomics techniques, furnishing a vital foundational framework for unraveling the intricate molecular mechanisms governing metabolite accumulation in pecan seeds at various stages of germination.

Key message

Despite the better performance in wood growth compared with Siberian larch, Siberian spruce may be more vulnerable to ongoing climate change.

Abstract

Understanding the species-specific wood formation kinetics is critical to assess forest growth and carbon sequestration under climate warming; however, such knowledge is still scarce in the fragile forest ecosystems of arid and semi-arid central Asia. Here, we monitored wood formation in two dominant tree species Siberian spruce (Picea obovata Ledeb.) and Siberian larch (Larix sibirica Ledeb.) during 2018 and 2019 at two sites in the southern Altai Mountains, northwest China, and aimed to describe the intra-annual dynamics of wood formation and to understand the annual variation in growth and carbon sequestration of these two species. Results show that the differences in wood production between species were remarkable. Siberian spruce produced 68.5–87.6 cells year⁻¹ at an average rate of 0.82–0.95 cells day⁻¹, about twofold higher than Siberian larch. The differences between species in terms of the onset, cessation timing, and duration of cell production were marginal. Cell production of both species started from mid-May to early June, ceased from early to mid-August, and lasted for about 64 to 70 days. The higher growth rate of spruce led to greater wood production compared to larch. The longer growing seasons induced by climate warming may not result in increased forest growth, thereby failing to enhance carbon sequestration in arid and semi-arid taiga of Central Asia.