EjRAV1/2 Delay Flowering Through Transcriptional Repression of EjFTs and EjSOC1s in Loquat

Most species in Rosaceae usually need to undergo several years of juvenile phase before the initiation of flowering. After 4–6 years’ juvenile phase, cultivated loquat (Eriobotrya japonica), a species in Rosaceae, enters the reproductive phase, blooms in the autumn and sets fruits during the winter. However, the mechanisms of the transition from a seedling to an adult tree remain obscure in loquat. The regulation networks controlling seasonal flowering are also largely unknown. Here, we report two RELATED TO ABI3 AND VP1 (RAV) homologs controlling juvenility and seasonal flowering in loquat. The expressions of EjRAV1/2 were relatively high during the juvenile or vegetative phase and low at the adult or reproductive phase. Overexpression of the two EjRAVs in Arabidopsis prolonged (about threefold) the juvenile period by repressing the expressions of flowering activator genes. Additionally, the transformed plants produced more lateral branches than the wild type plants. Molecular assays revealed that the nucleus localized EjRAVs could bind to the CAACA motif of the promoters of flower signal integrators, EjFT1/2, to repress their expression levels. These findings suggest that EjRAVs play critical roles in maintaining juvenility and repressing flower initiation in the early life cycle of loquat as well as in regulating seasonal flowering. Results from this study not only shed light on the control and maintenance of the juvenile phase, but also provided potential targets for manipulation of flowering time and accelerated breeding in loquat.

Land use impacts on Boswellia dalzielii Hutch. an African frankincense tree in Burkina Faso

Boswellia dalzielii Hutch., an African frankincense tree, is a socio-economically important aromatic and medicinal tree. It is currently threatened by uncontrolled exploitation, and therefore requires action to ensure its sustainable management. This study assessed the population structure and regeneration of its natural stands across three land use types in Burkina Faso: woodlands, fallows and farmlands. Sixty, fifty and fifty 50 m × 20 m plots were established respectively in woodlands, fallows and farmlands. All the plots were surveyed for adult tree (dbh ≥ 5 cm) density, dbh, total height and health conditions. Data on regeneration density (dbh < 5 cm), source (generative, stem shoots, suckers), total height and collar diameter were also collected. The results show similar total tree heights (7.0 m-9.0 m) but significantly (p < 0.05) smaller tree dbh in woodlands (mean ± SD: 20.5 ± 0.49 cm) and fallows (29.3 ± 0.64 cm) than in farmlands (32.8 ± 0.15 cm). Adult tree density (trees/ha) was 1.3 and 2.7 times higher in woodlands (82.37 ± 6.57) than in fallows (62.00 ± 3.98) and farmlands (30.02 ± 1.63), respectively. The density of regeneration in woodlands was 28 and 6 times higher than in fallows and farmlands, respectively. The majority (> 50%) of regenerating plants were suckers and no seedling regeneration was found in farmlands. The distribution of trees in diameter classes was J-shaped in woodlands, bell-shaped in farmlands and positive asymmetric in fallows, indicating recruitment bottlenecks. We found that 80.18% of individuals encountered were unhealthy. Intensive debarking and cutting were the main threats to the species and no conservation strategy was in place in the study region. We suggest measures to reduce intensive debarking and cutting, which should contribute to better management of the species.

The functional form of specialized predation dramatically affects whether Janzen-Connell effects can prevent competitive exclusion

Janzen Connell Effects (JCEs), specialized predation of seeds and seedlings near conspecific trees, are hypothesized to promote high species richness. While past modeling studies show JCEs can maintain higher diversity than a neutral community, recent theoretical work indicates JCEs may weakly inhibit competitive exclusion when species exhibit interspecific fitness variation. However, recent models make somewhat restrictive assumptions about the functional form of specialized predation -- that JCEs occur at a fixed rate when seeds/seedlings are within a fixed distance of a conspecific tree. Using a theoretical model, I show that the functional form of JCEs largely impacts their ability to promote coexistence. If specialized predation pressure increases additively with adult tree density and decays exponentially with distance, JCEs maintain considerably higher diversity than predicted by recent models. Parameterizing the model with values from a Panamanian tree community indicates JCEs can maintain high diversity in communities exhibiting high interspecific fitness variation.

Seeds and seedlings of oaks suffer from mammals and molluscs close to phylogenetically isolated, old adults

Background and Aims Mammals and molluscs (MaM) are abundant herbivores of tree seeds and seedlings, but how the trees and their environment affect MaM herbivory has been little studied. MaM tend to move much larger distances during the feeding stage than the more frequently studied insect herbivores. We hypothesize that MaM (1) select and stay within the patches that promise to be relatively the richest in seeds and seedlings, i.e. patches around adult trees that are old and within a distantly related, less productive neighborhood; and (2) try to remain sheltered from predators while foraging, i.e. mammals remain close to adult trees or to cover by herbs while foraging, and might force their mollusc prey to show the opposite distribution. Methods We exposed oak acorns and seedlings in a temperate forest along transects from adult conspecifics in different neighbourhoods. We followed acorn removal and leaf herbivory. We used exclusion experiments to separate acorn removal by ungulates vs. rodents and leaf herbivory by insects vs. molluscs. We measured the size of the closest conspecific adult tree, its phylogenetic isolation from the neighbourhood and the herbaceous ground cover. Key Results Consistent with our hypothesis, rodents removed seeds around adult trees surrounded by phylogenetically distant trees and by a dense herb cover. Molluscs grazed seedlings surrounding large conspecific adults and where herb cover is scarce. Contrary to our hypothesis, the impact of MaM did not change from 1 to 5 m distance from adult trees. Conclusions We suggest that foraging decisions of MaM repulse seedlings from old adults, and mediate the negative effects of herbaceous vegetation on tree recruitment. Also, an increase in mammalian seed predation might prevent trees from establishing in the niches of phylogenetically distantly related species, contrary to what is known from insect enemies.

Carob tree micropropagation essays (Ceratonia siliqua L.)

Carob tree (Ceratonia siliqua L.) is an agro-sylvo-pastoral species that has been classified among the most efficient trees. The first publications on the "in-vitro" multiplication of Carob are very recent and show conflicting results. Mastery of this technique seems necessary to provide the increased demand of the international market for the gum extracted from the endosperm of the seed, a polyoside called galactomannan. This work aimed to study micropropagation from adult tree micro cuttings. Our results showed that the most favorable disinfectant is HgCl2 with 93% surface sterile explants. Comparison of the effect of various hormones with different concentrations (BAP, Zeatin, GA3, TDZ, and ANA) has shown that the addition of BAP on MS medium gave a good response of axillary bud development (58,3%±6,42) while BAP supplemented with activated charcoal gave the best results (87,3%±4,23). As for rooting, the different alternatives of hormones types and concentrations must be later considered to initiate rooting of the buds.

Investigation of Bunch Cut at Different Times After Pollination and Flower Position in the Spikelet in Date Palm ‘Sukkary’ Variety

As many studies on other crops showed an acropetal decline of fruit-set and fruit size in the inflorescence, this paper investigates the effect of flower position in spikelets in the ‘Sukkary’ variety of date palm on fruit-set and final fruit weight. Also studied was the best time to apply strand-cut (bunch cut) as an alternative to hand thinning, to increase final fruit weight. Hand thinning is a labor cost operation and worker productivity operation is one adult tree per day maximum. To study fruit-set in relation to fruit position, three types of pollen were used to pollinate female trees: new pollen harvested in March 2018, pollen stored for one year at room temperature (25-35° C), and pollen stored for two years at room temperature. Four weeks after pollination, fruits aborted and those non-aborted in every bunch were counted. Recording was done in every spikelet from proximal to distal. To study the effect of fruit position in spikelet on fruit weight, fresh pollen was used to pollinate ‘Sukkary’ females. Every two days, fruit weight was measured from pollination to harvest, and fruit growth pattern was drawn. An analysis of variance (ANOVA) was carried out for the final fruit weight in every spikelet part. This investigation showed no pattern in fruit-set or in final fruit weight when using new pollen. When pollinated with old pollen that was one and two years old, the proximal ‘Sukkary’ flowers of the spikelets showed less fruit-set compared to those of the middle and distal part. This basipetal decline is explained by low viability of old pollen, combined with the basipetal opening of the spathes in date palm...

Long-Term Impact of Forest Fragmentation on Tree Functional Diversity, Trait Composition and Aboveground Biomass.

Background: Community composition on fragmented forest remnants has been shown to diverge from their natural successional path, revealing an alternative state which has been known as retrogressive succession. Here we show the long-term monitoring of a small forest fragment concerning community structure, species richness, functional diversity and composition throughout 17 years to offer a means to generalize community performance under the impacts of forest fragmentation. Results: The adult tree community showed shifts on its functional composition: reduction in species’ maximum height and percentage of simple leaves, indicating an investment in resource-acquisitive and disturbance adapted traits. However, we also found a gradual increase in wood density throughout the years for the adult community. For the overall community, functional composition analysis indicated a gradual reduction in the percentage of simple leaves and a significant increase in aboveground biomass. The decrease in Hmax and simple leaves, especially for the adult tree community, are mostly related do microenvironmental conditions caused by edge effects, as desiccation and tree canopy damage.Conclusion: Our results show that natural regeneration is being negatively affected, except for aboveground biomass. Although these findings could have resulted from a transient dynamic, they constitute a warning to future conservation policies around the ecological integrity of small forest fragments.

CAN ARAUCARIA FOREST REMNANTS REGENERATE AFTER 70 YEARS OF ANIMAL HUSBANDRY? A CASE STUDY ON CAÍVAS IN SOUTHERN BRAZIL

In Southern Brazil, forest fragments are commonly used for agroforestry systems (AFS) - called caívas - focused on erva-mate and livestock production. Although the caívas have helped maintain forest cover, there is a general lack of understanding of the effects of this system on species diversity and their potential for ecological restoration. Aiming to contribute to a better understanding of the forest dynamics (trees and regeneration) of these AFS, we present a six-year case study in which we monitored a caíva that has been used for animal husbandry for 70 years. We observe that forest management in the caíva modified the population structure mostly through reductions in the density of a few adult tree species. On the other hand, the potential regeneration shows consistent growth, including several species not found in the adult population. The caíva showed high levels of resilience in terms of regeneration, despite the extractive use of these remnants over several decades. This result demonstrates that the strategies used herein can help to restore forests with a dense and diverse forest cover within caívas. With the correct management of this regeneration potential, it is possible to maintain healthy and diverse forests that are being conserved through use.

Phytosociology, Diversity and Ecological Groups of the Adult Tree Component of a Forest Remnant in Pernambuco – Brazil

The main objective of this study is to characterize the floristic richness, phytosociological structure, and classify the ecological groups of the adult tree component species in an area of ecological tension (Seasonal Forest and Caatinga) in Pernambuco - Brazil. The study was conducted in Atlantic Forest stretch in Pernambuco – Brazil, from April 2019 to February 2020. Methods adopted for this study includes the allocation of 20 plots, with dimensions of 10 m x 25 m, spaced in 25 m. Each adult individual, with a circumference at breast height (CBH 1.30 m) ≥ 15 cm, was identified in the field. The softwares Mata Nativa version 2 and Excel 2019 were used to process the collected data. Sample sufficiency, classification of ecological groups, diversity and phytosociology were analyzed. As a result of the research, the density of the adult tree component in the fragment was 1,888 indha-1 and the dominance was 21.64 m².ha-1. These values are following the standards of other studies in Atlantic Forest in the State of Pernambuco. The botanical families with greatest richness are, respectively, Fabaceae, Myrtaceae, Annonaceae, Lauraceae, Elaeocarpaceae, Sapindaceae and Sapotaceae. Regarding the ecological groups, 46% of the species were classified as initial secondary. The species of greatest Value of Importance were Guapira nitida, Buchenavia tetraphylla, Manilkara sp., Byrsonima crassifolia and Sloanea obtusifolia, respectively. The Shannon-Wiener Diversity Index (H') value was 3.21 nats.ind-1 and the Pielou Uniformity Index (J) was 0.73. According to the results obtained, the development process of the adult tree component of the fragment was directly affected by the pasture matrix. However, species diversity has not been compromised, indicating the area's resilience potential.

Divergent DNA Methylation Signatures of Juvenile Seedlings, Grafts and Adult Apple Trees

The vast majority of previous studies on epigenetics in plants have centered on the study of inheritance of DNA methylation patterns in annual plants. In contrast, perennial plants may have the ability to accumulate changes in DNA methylation patterns over numerous years. However, currently little is known about long-lived perennial and clonally reproducing plants that may have evolved different DNA methylation inheritance mechanisms as compared to annual plants. To study the transmission of DNA methylation patterns in a perennial plant, we used apple (Malus domestica) as a model plant. First, we investigated the inheritance of DNA methylation patterns during sexual reproduction in apple by comparing DNA methylation patterns of mature trees to juvenile seedlings resulting from selfing. While we did not observe a drastic genome-wide change in DNA methylation levels, we found clear variations in DNA methylation patterns localized in regions enriched for genes involved in photosynthesis. Using transcriptomics, we also observed that genes involved in this pathway were overexpressed in seedlings. To assess how DNA methylation patterns are transmitted during clonal propagation we then compared global DNA methylation of a newly grafted tree to its mature donor tree. We identified significant, albeit weak DNA methylation changes resulting from grafting. Overall, we found that a majority of DNA methylation patterns from the mature donor tree are transmitted to newly grafted plants, however with detectable specific local differences. Both the epigenomic and transcriptomic data indicate that grafted plants are at an intermediate phase between an adult tree and seedling and inherit part of the epigenomic history of their donor tree.