Trees最新文献

Plant grafting involves naturally or intentionally merging distinct plant parts to form a single organism. Although it is a common horticultural practice used to improve the yield, quality, and resistance of horticultural crops and study the long-distance transport of molecules, the underlying mechanism of graft union formation (GUF) remains poorly understood. In this study, we optimized the in situ analysis method for plant hormones and explored the spatial and temporal distribution of endogenous hormones (IAA, ABA, and ZR) during walnut GUF. The results demonstrated that changes in endogenous IAA and ZR levels in the graft union were consistent, with an increase during the rapid proliferation phase of callus tissue and enrichment in the cambium and cells of the grafting interface. As callus tissue entered the differentiation stage, endogenous IAA and ZR levels rapidly decreased and were mainly distributed in the callus tissue. Conversely, the level and distribution of endogenous ABA showed no significant changes during the rapid proliferation phase of callus tissue. However, they increased rapidly after entering the differentiation stage, mainly in the scion cambium and callus tissue. We also observed "S"-shaped, “M”-shaped, and “N”-shaped trends in the dynamic changes of IAA/ABA, IAA/ZR, and ZR/ABA ratios, respectively. Based on these results, we propose a spatial and temporal distribution model of endogenous hormones during walnut GUF. This provides a foundation for further investigation into the molecular mechanisms of hormone-mediated GUF in walnut and other woody plants.

Tamarix taklamakanensis is an endangered shrub endemic to northwestern China. Single-nucleotide polymorphism (SNP) loci obtained by Genotype-by-sequencing (GBS) method were used to estimate the genetic diversity and population structure of the species for developing conservation strategies. A moderate level of genetic diversity was (mean H_E = 0.16) detected for the species, and sampled sites were grouped into two genetically distinct clusters by Bayesian assignment, principal coordinates analyses, and maximum-likelihood (ML) tree. The moderate level of genetic diversity is likely due to its reproductive characteristics and long-lived life-history traits, and the strong genetic differentiation between the two clusters suggests a positive response to habitat fragmentation. Based on the results, we provide useful conservation strategies for this species.

Key message

We identified seven OfNCEDs and analyzed the potential function of OfNCED4, which is involved in the biosynthesis of carotenoids and abscisic acid in Osmanthus fragrans.

Abstract

In plants, 9-cis-epoxycarotenoid dioxygenases (NCEDs) can cleave carotenoids and are rate-limiting enzymes for the biosynthesis of abscisic acid (ABA). Sweet osmanthus (Osmanthus fragrans Lour.), an important ornamental and fragrant tree, contains abundant carotenoids in its flowers. To examine the function of the 9-cis-epoxycarotenoid dioxygenases (NCEDs) involved in ABA biosynthesis and floral coloration in O. fragrans, the sequences of seven OfNCEDs were isolated from the genomic DNA and cDNA of O. fragrans. A bioinformatics analysis showed that these OfNCEDs encode 422 ~ 591 amino acids, and they all contain the RPE65 domain. These OfNCEDs showed different patterns of expression, and that of OfNCED4 was most consistent to the patterns of ABA accumulation during the flowering process. Moreover, the levels of expression of seven OfNCEDs in the O. fragrans flowers were significantly induced by exogenous ABA. ABA-responsive elements were found in the promoters of OfNCEDs. The overexpression of OfNCED4 resulted in increased contents of chlorophylls, carotenoids and ABA, and up-regulation of NtCRTISO, NtLCYE, NtLCYB, and NtNXS, and down-regulation of NtCCD1 and NtCCD4 in tobacco leaves. It suggests that OfNCED4 probably mediates the biosynthesis of ABA. Taken together, this study systematically identified the bioinformatics, pattern of expression of OfNCED genes and the potential function of OfNCED4, which could provide molecular evidence for further research on the regulation of carotenoid biosynthesis and floral color of O. fragrans.

Key Message

Atlantic Forest tree seedlings with contrasting ecological characteristics present specific growth and physiological responses to nitrogen and phosphorus addition in the soil.

Abstract

Nitrogen (N) and phosphorus (P) are commonly the most limiting nutrients for plant growth in tropical forests. Many of these ecosystems are exposed to increasing rates of anthropogenic nutrient deposition. This study aims to assess how five Atlantic Forest tree species respond to N and P addition to the soil. Five species with different levels of shade tolerance were subjected to nine weekly soil applications of (NH₄)₂SO₄ (84 kg N ha⁻¹ treatment N), NaH₂PO₄ (45 kg P ha⁻¹ treatment P), both nutrients (treatment N + P), or water. Soil, foliar nutrient concentrations, and biometric and gas exchange analyses were performed. No changes in the soil pH or total N and P availability were observed in the soil after N addition, whereas P accumulated in the soil and leaves of three species after P addition. The pioneer species H. popayanensis presented increased total biomass with P and N+P treatments, while C. floribundus increased with P treatment and C. pachystachya increased with N + P treatment. N and P treatments reduced the photosynthesis of C. pachystachya and the stomatal conductance of C. pachystachya and C. floribundus. The growth rate and total biomass of C. estrellensis reduced with N and P treatments and increased with N+P treatment. Aspidosperma polyneuron presented reduced photosynthesis with N treatment, but increased total biomass with all treatments, especially N + P. The diversity of growth and physiological responses to N and P addition suggests that each species has specific nutrient requirements and uses strategies related to the niche occupied by each one.

Key message

The response of herbivore abundance to birch genotypic diversity varies depending on the host specificity of the herbivores. Specialist, but not generalist, herbivores were affected by birch genotypic diversity.

Abstract

Biological control is an important ecosystem service mediated through plant diversity. Responses of herbivore abundance to plant genotypic diversity may depend on host specificity, especially the host-feeding type. We conducted a common-garden experiment by manipulating plot-level genotypic diversity (number of source populations per plot) of Erman’s birch (Betula ermanii) to understand how birch genotypic diversity affected the abundance of three herbivore feeding types (chewers, galls, and suckers). Specifically, we investigated whether the effects of plant genotypic diversity on herbivore abundance were additive or non-additive. Furthermore, we examined this mechanism as a possible change in plant phenotype (plant productivity and/or leaf traits) and/or herbivore foraging behavior (associational resistance with neighboring plant individuals). We found that genotypic diversity had a significant positive effect on condensed tannin concentration; however, it did not affect plant growth. There was no effect of increasing birch genotypic diversity on the density of chewers (generalists) and chewing herbivory, whereas the density of galls and suckers (specialists) decreased significantly. A negative non-additive effect was observed with regard to gall density and a negative additive effect on sucker density was observed. Gall density was not related to the increase in condensed tannins affected by birch genotypic diversity. This implies that associational resistance is more likely to explain the negative non-additive effects on gall density. Our study shows that the loss of birch genotypic diversity due to shrinking population sizes will strongly affect specialist herbivores in the boreal forests of Hokkaido.

Key message

Dendroclimatic sensitivity varies by axial position for Sequoiadendron giganteum: negative correlations with June temperature strengthen with height, while positive correlations with snow water are strongest in the lower trunk.

Increment cores collected along trunks of mature Sequoiadendron giganteum provide new and updated ring-width chronologies ideal for assessing how height above ground affects sensitivity of radial growth to climatic variation. Chronologies from 61 living trees at nine locations across the geographic distribution span 1973 yr. Analyses of subsets of 18–44 trees reveal that correlations between radial increments and climate (temperature, water availability) vary with axial position. Negative correlations with maximum and minimum June temperature intensify with height and are strongest at the highest position analyzed (60 m above ground). Sensitivity to the hydroclimate variable of April-1 snow water equivalent is stronger at lower trunk positions (10 m) compared to breast height or the upper trunk, and a similar relationship is identified for the standardized precipitation evapotranspiration index using a 12-month window ending in September. Drought-induced low-growth years computed as radial increment relative to the mean of 10 yr before and after are more weakly expressed at breast height compared to higher on the trunk (10–60 m). Analysis of regional upper (maximum core height = 87 m) versus lower trunk (above buttress) chronologies corroborate differing inter-annual correlations with climate depending on height above ground. Accounting for axial variation in dendroclimatic sensitivity can maximize the quality of environmental reconstructions using tree rings and improve biophysical understanding of Sequoiadendron, especially in the context of an increasingly arid climate.

Key message

This work belongs to the Tunisian conservation strategies of local fruit tree resources. Results highlighted the important genetic richness of Tunisian peach as an unexplored source for peach future breeding.

Abstract

Tunisia is characterized by a rich genetic heritage of fruit trees. Nevertheless, local Tunisian accessions of different fruit crops face several threats that are causing a dramatic loss of some of these valuable landraces. This study was conducted to evaluate the genetic diversity and population structure of 23 Tunisian peach accessions using 27 microsatellite (SSR) loci. These Tunisian accessions were compared with accessions from America, mainland Spain and the island of La Palma (Canary Islands, Spain). A considerable genetic diversity was observed in Tunisian genotypes with allelic richness value of 0.47. The genetic richness was 0.37 in La Palma genotypes, 0.3 in mainland Spain and 0.38 in the American genotypes. Eight private alleles were obtained in the Tunisian genotypes, while six were observed in the mainland Spanish pool, five in the American pool and six in the La Palma pool. Structure analyses and similarity dendrogram based on SSRs were clearly consistent with a geographic structuring and highlighted the different introduction pathways of Prunus persica into Tunisia.

Key message

Variation in lateral organ morphology identifies the timing of annual transitions between bud scale and needle identity in conifer buds.

Abstract

Vegetative tissue is generated from the shoot apical meristem (SAM) at branch tips. Temperate and boreal conifers have determinate growth, in which a year’s complement of needles all begin to form in the summer of Year 1 (Y1), overwinter in a protective bud, then emerge and mature in spring and summer of Year 2 (Y2). Buds are protected by bud scales (bss), which are initiated in spring Y1 prior to needle initiation. Through the annual cycle of needle and bud formation, the SAM alternately produces needle or bs lateral organs. Detailed classification of vegetative lateral organ morphologies in Picea abies (Norway spruce) showed that while the majority of lateral organs are clearly either of needle or bs type, a number of organs in any given bud are intermediate, having both needle and bs characteristics. These transitional organs form the basal outer protective layers of the bud. This work documents the variety of bs morphologies involved in forming the overall bud. Needle and bs counts show a clear distinction in initiation times for each type. bs initiation coincides with spring bud elongation, while needle initiation lags this by 2–3 months. This suggests distinct, temporally separated signals for bs and needle tissue differentiation. The transitional forms suggest some primordia form at times when they are susceptible to both needle and bs differentiation signals. Measurements of shoot apex dimensions show that, in addition to an increasing number of needle primordia on the shoot apex over the summer, the needle primordia themselves undergo an expansion in the fall prior to dormancy.