Trees最新文献

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.

Key message

Species interactions should be considered during the design of restoration plans for tropical dry forests.

Abstract

Legume trees dominate old-growth and regenerating tropical dry forests with some pioneers becoming temporarily monodominant during secondary succession. Yet, the mechanisms promoting legume coexistence in this ecosystem are poorly understood but essential to develop restoration strategies for degraded forests. We studied plant–plant interactions in the regeneration niche of an early and a late successional legume tree species, increasingly co-occurring in northwestern Mexico due to persistent climatic and anthropogenic disturbance that is altering forest dynamics. Our experiment comprised two species (Acacia cochliacantha, typical early successional and monodominant, and Lysiloma watsonii, typical late successional) × two habitats (direct light and shade) × three plant interaction treatments (control, intraspecific and interspecific). Each of the 12 experimental units contained 20 pots, totaling 240 replicates. We examined germination, seedling survival, and growth dynamics and determined seedling dry mass (total and root: shoot) at the end of the experiment. Our results suggest that legume monodominance in regenerating tropical dry forests starts early during germination and may be temporarily maintained through the interplay between interspecific facilitation and intraspecific competition. In contrast, late successional species may avoid negative heterospecific interactions by recruiting later (benefiting from neighbors’ shade) and maintaining neutral associations with conspecifics since early ontogenetic stages. Therefore, a cautious selection of early and late successional species and their spatial arrangement should be considered during the planning stage of restoration programs for tropical dry forests. Advancing our understanding of plant interactions in tropical dry forests should lead us to develop better tools for restoring this highly degraded ecosystem.

Key message

The growth rates of current-year shoots, fruits and trunks in apple trees peak sequentially during the growing season. The period of most intense growth coincided with the lowest NSC reserves.

Abstract

Vegetative and reproductive growth and storage are major carbon sinks in fruit trees; however, little is known about their mutual seasonal coordination. In this study, we monitored growth dynamics of trunks, fruits and current-year shoots together with the concentration of non-structural carbohydrates (NSC) in trees subjected to defoliation, early season flower thinning, mid-season fruit thinning and their respective combinations across the season. We found that defoliation had a negative effect on both trunk radial growth and annual fruit yield. Flower and fruit thinning caused lower fruit number per tree, but the individual fruits were larger resulting in a similar annual fruit yield among the treatments. Shoot extension growth was not significantly affected by the defoliation and flower and fruit thinning treatments. The concentration of non-structural carbohydrates was also similar across treatments. Modelled daily growth rates of shoots, fruits and trunks peaked sequentially one after another throughout the growing season with a delay of 15 and 18 days, respectively. The period of most intense growth of tree’s organs corresponded well with the lowest NSC reserves and a temporary depletion of starch in 1-year-old branches. Taken together, our study illustrates a tight temporal coordination of major carbon sinks and improves our understanding of sink/source relations of commercially important apple trees.

Key message

The 164 DAA maturation stage is superior in terms of germination and seedling formation, with gains of 4.2 months in relation to the last stage, and X-ray densitometry is a new and efficient technique to analyze Euterpe edulis seeds.

AbstractEuterpe edulis Martius is an endangered palm species that grows in the Atlantic Forest and the Cerrado of South America. Economic exploitation of its antioxidant-rich fruits could ensure the sustainable management of this species. However, this relies on the rapid selection of high-quality seeds from which to derive seedlings. Image analysis and X-ray densitometry can be quick, practical, and best of all, non-destructive techniques for selecting seeds, ensuring the sustainability of the species. The objective of this study was to investigate the maturation of E. edulis seeds using image analysis and X-ray densitometry. Fruits were harvested from ten matrices at different stages of maturation, from 94 days after anthesis (DAA) to 290 DAA. Seed dry mass, water content, germination, vigor, and density were quantified at each stage. At the same time, seeds were analyzed by GroundEye^® imaging, radiography, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The design was completely randomized and consisted of 29 treatments (maturation stages) and four replications with 10 seeds each. The highest dry mass was detected 255 DAA (0.83 g), in vitro germination began 115 DAA and achieved 100% from 150 DAA, and maximum vigor was observed 164 DAA, whereby 100% of seedlings appeared normal. X-ray imaging revealed dehydrated seeds and small mechanical damage, such as cracking of the pericarp. X-ray densitometry revealed that seed density increased considerably 185 DAA. SEM/EDS detected changes between maturation stages, such as the accumulation of K and Si, in the mesocarp and endocarp. Overall, E. edulis seeds presented maximum in vitro germination, vigor, percentage of normal seedlings, and physicochemical qualities 164 DAA (green epicarp), which corresponds to 126 days earlier compared with the fruits harvested 290 DAA (black epicarp) for ex vitro germination. The analyses proposed in this study, together with the analysis of seed germination and vigor throughout maturation, were promising for increasing the speed, classification accuracy, and selection of E. edulis seeds. Such analyses have a high potential since they are practical and many are non-destructive, adding cost-benefit with accurate results.