Tree-based Research Articles

Crossings

Crossings

New paromomyids (Mammalia, Primates) from the Paleocene of southwestern Alberta, Canada, and an analysis of paromomyid interrelationships

AbstractParomomyidae are one of several families of plesiadapiforms that flourished during the Paleocene in North America soon after the extinction of non-avian dinosaurs some 66 million years ago. Although they are often among the best-represented plesiadapiforms in mammalian faunas in both North America and Europe, the early history of paromomyids is poorly understood, and their fossil record at higher latitudes is comparatively depauperate. We report here on the discovery of two new species of paromomyids from Paleocene deposits in southwestern Alberta: Edworthia greggi new species is the second known species of the basal paromomyid Edworthia Fox, Scott, and Rankin, 2010 whereas Ignacius glenbowensis new species is among the most abundantly represented species of Ignacius Matthew and Granger, 1921. These new discoveries document, for the first time, parts of the upper dentition of Edworthia, and the new species of Ignacius represents the first new, pre-Clarkforkian species of the genus to be described in nearly 100 years. A comprehensive phylogenetic analysis of nearly all known paromomyid taxa (including the new species described herein) recovered both species of Edworthia near the base of the paromomyid tree in a polytomy with Paromomys depressidens Gidley, 1923 and a paraphyletic Ignacius. The new paromomyids from Alberta not only increase the known taxonomic diversity of Edworthia and Ignacius but also add significantly to knowledge of the dental anatomy of these poorly known genera and further add to a uniquely Canadian complement of Paleocene plesiadapiforms.UUID: http://zoobank.org/a2f31cfe-09b9-4168-b09f-9d0c3d0af342

Overwintering Migration of the Double-Spined Spruce Bark Beetle Ips duplicatus (Sahlberg, 1836) (Coleoptera; Curculionidae)

The double-spined bark beetle, Ips duplicatus, is an example of a species whose economic importance has increased in many European countries over the past decade. Many aspects of its life cycle remain unknown, complicating its management. I. duplicatus adults overwinter in forest litter, which makes the removal of infested trees during winter ineffective. Therefore, this study focuses on the mechanisms and timing of I. duplicatus overwintering migration into the forest litter. Only 2.2% of adult I. duplicatus overwintered under the bark of spruce logs stored outdoors from August 2016 to March 2017. In all, 94.4% of the beetles emerged and burrowed in forest litter. Migration began in late August, peaked in mid-September, and lasted until mid-October. At that time, forest litter collected at the base of an infested tree contained an average of 154.7 ± 23.9 I. duplicatus. Catches of migrating adults on glue stripes proved that the beetles walked down the trunk on days when the average daily temperature reached 10–15 °C. Based on the results, we suggest that trees infested with I. duplicatus that have completed their development into adults should be removed no later than September. Sanitation cutting in the following months is not effective against this pest.

Revision and analysis of the chromosome variability in the speciose genus Akodon (Rodentia, Sigmodontinae), including new data from Argentina.

Rodentia has a high species number and chromosomal variability. The South American genus Akodon is one of the most speciose muroids, with more than 40 species included in several species groups. Here, we characterize cytogenetically specimens of Akodon from central-western Argentina. Subsequently, we reviewed and analyzed the cytogenetic data for this genus, build a phylogeny and mapped chromosome changes to interpret its evolution. Specimens of A. dolores from central-western Argentina have 2n=42-44/FNa=44 (46, 48) due to a Robertsonian rearrangement. Our data expand the distribution range known for this polymorphism and confirm its geographic structure. Other specimens had 2n=40/FNa=40, representing populations of A. oenos, A. polopi, and A. spegazzinii. All karyotypes have a low amount of heterochromatin, concentrated in centromeres and sex chromosomes, as in other rodents. The complement with 2n=40/FNa=40 is the most frequent in Akodon and is shared by most species in some groups. Chromosome numbers are very diverse. The FNa shows less variability; FNa=42 was recovered as ancestral, excluding A. mimus, which was connected at the base of the Akodon tree and has FNa=44. This indicates a complex chromosome evolution in Akodon, and suggests that reductions and increases in the 2n and FNa evolved independently in some lineages.

Genetic population structure of Cheilolejeunea rigidula (Lejeuneaceae) in the Amazon region

We studied the community structure and diversity of epiphytic bryophytes in a vertical gradient from tree base to canopy in four lowland rain forest sites of the Colombian Amazon (Amazonas, Caquetá, Putumayo, and Vaupés). Each of the 64 sampled phorophytes was divided into six height zones from the base (Z1) to the outer canopy (Z6). As a subproject, we carried out a genetic population study using the liverwort Cheilolejeunea rigidula (Lejeuneaceae) as our model species, which occurred in all six height zones. In addition to 65 successfully sequenced samples from the study sites, we included individuals of C. rigidula from Guiana and Brazil (Manaus and Tapajos) to investigate the connectivity and genetic structure of this species across the Amazon region and to evaluate the genetic structure based on phorophyte height zones. Each site in Colombia, Brazil and Guiana was considered a subpopulation. The sequenced chloroplast markers (partial atpB gene, partial psbA gene/psbA-trnH spacer) showed little variation across the Amazon and the height zones on the trees. The nuclear marker (ITS) showed a spatial structure indicating genetic differentiation of subpopulations across the Amazon, but little genetic differentiation of C. rigidula along the height of the trees. The gradient across the Amazon shows a relationship between genetic distance and geographic distance, indicating dispersal limitations (P<0.001). At local and regional scales, our results suggest that dispersal can have a dominant effect on populations and communities, increasing connectivity.

Contrasting effects of low-severity fire on stemflow production between coexisting pine and oak trees

As climate change intensifies, fires events are predicted to increase in forest ecosystems. Fire alters the ecosystem structure and consequently, the hydrological cycle. However, little is known about the impacts of forest fire on stemflow. A field experiment was conducted to evaluate the short-term response of stemflow production to low-severity fire in a coniferous and broadleaved mixed forest. Results demonstrated low-severity fire changed stemflow yield and had insignificant effect on the correlation between stemflow efficiency and rainfall or plant morphological variables. In unburned site Quercus acutissima and Pinus massoniana and in burned site Q. acutissima and P. massoniana, stemflow percentage averaged 3.86, 0.37, 1.20, and 0.47 %, whereas funneling ratio averaged 38.8, 4.2, 11.4, and 5.1, respectively. Fire substantially decreased the stemflow percentage and funneling ratio of Q. acutissima (P < 0.05) and slightly enhanced P. massoniana (P > 0.05). The responses of stemflow production to fire differed significantly between oak and pine trees. Fire made Q. acutissima become less effective in funneling rain to the forest ground, which is attributed to that the scaly bark was burned to highly furrowed bark that delivers less water to tree base. Burned P. massoniana was more productive in draining stemflow relative to unburned trees and is attributed to the bark which was still flaky regardless of. Additionally, the higher canopy openness allows more rain to funnel to the trunk. Stemflow efficiency was reduced in response to fire and limited the transfer of water and nutrients from canopy to soil and can reduce the competitiveness of Q. acutissima after fire disturbance.

Effect of Direction and Distance of Moringa oleifera on Growth and Yield of Cabbage (Brassica oleracea)

A field experiment was conducted at the moringa-based experimental farm of the Department of Agroforestry and Environment, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur from November 2020 to September 2021. The aim of the study was to assess how well cabbage performed and adapted to various orientations and distances from the moringa tree. The experiment was carried out in a Randomized Complete Block Design (RCBD) with three replications. Four different directions along with one control plot were used as factor A and different distances from tree base was treated as factor B. The data of some ecophysiological parameters like maximum light intensity and soil temperature were noticed in south direction and the widest distance from tree base. The highest soil moisture was found at north direction. Most of the growth parameters showed better performance in open field compared to shade condition. In the case of interaction effect, the south direction and the widest distance (180 cm) from moringa tree base showed the highest number of outer leaves, head length, width, head diameter, head length, and head weight compared to other directions and distances. Concurrently, the maximum total yield and marketable yield were recorded from 180 cm in south direction whereas the lowest yield was found at the closest distance (80 cm) and east direction. The marketable yield of south, west, north, and east directions were reduced by 8.43, 14.87, 23.86 and 31.52% as compared to open field. At 130 cm and 80 cm distance the yield was reduced by 16.42 and 32.26% as compared to 180 cm distance from tree base. The current findings suggested that cabbage may be grown in partial shade in moringa-based agroforestry production systems without enduring significant yield losses.

Comparative mitogenomes provide new insights into phylogeny and taxonomy of the subfamily Xenocyprinae (Cypriniformes: Cyprinidae).

Xenocyprinae is a cyprinid subfamily that not only has a discrete geographic distribution but also has a long history dating to the Early Miocene. However, it is controversial whether systematic classification and some species validity of Xenocyprinae exist, as well as its phylogenetic relationships and evolutionary history. In the present study, we first reviewed the description and taxonomic history of Xenocyprinae, and then the complete mitochondrial genome of Distoechodon compressus, an endemic and locally distributed species belonging to Xenocyprinae, was sequenced and annotated. Finally, all the mitogenomes of Xenocyprinae were compared to reconstruct the phylogenetic relationship and estimate the divergence time. The results showed that the mitogenomes are similar in organization and structure with 16618-16630 bp length from 12 mitogenomes of eight species. Phylogenetic analysis confirmed the monology of Xenocyprinae and illustrated three clades within the Xenocyprinae to consist of ambiguous generic classification. Plagiognathops is a valid genus located at the base of the phylogenetic tree. The genus Xenocypris was originally monophyletic, but X. fangi was excluded. Divergence time estimation revealed that the earliest divergence within Xenocyprinae occurred approximately 12.1 Mya when Plagiognathops separated from the primitive Xenocypris. The main two clades (Xenocypris and (Distoechodon + Pseudobrama + X. fangi)) diverged 10.0 Mya. The major divergence of Xenocyprinae species possibly occurred in the Middle to Late Miocene and Late Pliocene, suggesting that speciation and diversifications could be attributed to the Asian monsoon climate. This study clarifies some controversial issues of systematics and provides essential information on the taxonomy and phylogeny of the subfamily Xenocyprinae.

Microclimatic variation in tropical canopies: A glimpse into the processes of community assembly in epiphytic bryophyte communities

Abstract Epiphytic communities offer an original framework to disentangle the contributions of environmental filters, biotic interactions and dispersal limitations to community structure at fine spatial scales. We determine here whether variations in light, microclimatic conditions and host tree size affect the variation in species composition and phylogenetic structure of epiphytic bryophyte communities, and hence, assess the contribution of environmental filtering, phylogenetic constraints and competition to community assembly. A canopy crane giving access to 1.1 ha of tropical rainforest in Yunnan (China) was employed to record hourly light and microclimatic conditions from 54 dataloggers and epiphytic bryophyte communities from 408 plots. Generalized Dissimilarity Modelling was implemented to analyse the relationship between taxonomic and phylogenetic turnover among epiphytic communities, host‐tree characteristics and microclimatic variation. Within‐tree vertical turnover of bryophyte communities was significantly about 30% higher than horizontal turnover among‐trees. Thus, the sharp vertical variations in microclimatic conditions from tree base to canopy are more important than differences in age, reflecting the likelihood of colonization, area, and habitat conditions between young and old trees, in shaping the composition of epiphytic bryophyte communities. Our models, to which microclimatic factors contributed most (83–98%), accounted for 33% and 18% of the variation in vertical turnover in mosses and liverworts, respectively. Phylogenetic turnover shifted from significantly negative or non‐significant within communities to significantly positive among communities, and was slightly, but significantly, correlated with microclimatic variation. These patterns highlight the crucial role of microclimates in determining the composition and phylogenetic structure of epiphytic communities. Synthesis. The mostly non‐significant phylogenetic turnover observed within communities does not support the idea that competition plays an important role in epiphytic bryophytes. Instead, microclimatic variation is the main driver of community composition and phylogenetic structure, evidencing the role of phylogenetic niche conservatism in community assembly.

Lepilemur petteri latrine placement in Tsimanampetsotse National Park, Madagascar

Abstract Latrine behaviour in lemurs has been interpreted as a means of olfactory communication linked to energy efficient resource defence against neighbouring individuals and/or social bonding within social groups. For social bonding, latrines might best be placed at the core of home ranges, while resource defence could be based on defending the most important part of the home range, i.e., the core area or by establishing olfactory landmarks at the periphery of the home range. Most studies on lemurs describe deposition of urine and faeces in latrines in the core of the home range. In a study at the limit of the distributional range of Lepilemur petteri, at a site with unpredictable weather conditions, we radio-tracked 12 individuals and located latrines within their home ranges. In our study, latrines were located at the periphery of the home ranges. This is interpreted as a means to defend a larger area rather than specific resource rich sites that may or may not provide food in a given year. Regardless of the flexible spatial pattern, and in common with other mammals, lemur latrines are characterized by conspicuous trees, even though urine and faeces are deposited at the base of trees. This indicates some kind of optimal structure of latrines to convey information most effectively, possibly by combining visual and olfactory cues.

Vessel tapering is conserved along a precipitation gradient in tropical trees of the genus Cedrela

Key messageThe rate of vessel tapering is highly conserved across a precipitation gradient in tropical trees, pointing to a limit on tree height determined by a maximum basal vessel diameter.Maximum tree height in the tropics decreases strongly with decreasing precipitation. The role of hydraulic architecture in controlling this variation in tree height remains unclear. The widening of conducting xylem vessels from the apex to the base of trees, also known as tapering, is important for maintaining the hydraulic conductivity along the tree stem. If in contrast vessel diameter were constant, then resistance would increase with path length constraining flow rates as tree height increases. Whilst previous research has shown that vessel diameter scales with tree height at a similar rate (similar power law exponent) across biomes and taxa, knowledge on these relationships across precipitation gradients within a single species is incomplete, especially for the tropics. Here we report how vessel density and diameter at the tree base differ for two tropical Cedrela species across four sites varying in precipitation from 1014 to 2585 mm year−1. We find that maximum tree height decreases with decreasing precipitation across sites from 42 to 13 m. Despite the strong differences between sites in maximum tree height and water availability, tapering is indeed remarkably conserved and close to published scaling with height based on multi-species analyses. Thus, for a given tree height, basal vessel diameter does not vary between sites, whilst the maximum basal vessel size is two times smaller at the drier site (with the shortest trees) compared to the wettest site (with the tallest trees). This suggests a possible limitation of tree height determined by a maximum basal vessel diameter that can be sustained, given increasing embolism risk with increasing dryness. Our results show no hydraulic adaptation across this wetness gradient and reveal a clear relationship between maximum tree height and maximum basal vessel size.

Lycorisinsularis (Amaryllidaceae), a new species from eastern China revealed by morphological and molecular evidence.

Lycorisinsularis S.Y.Zhang & J.W.Shao, a new fertile diploid species from coastal provinces in eastern China is described. This new species is most similar to L.sprengeri in morphology and has been misidentified as the latter for a long time. However, it can be distinguished from the latter by the relatively longer perianth tube (1.5‒2.5 cm vs. less than 1.3 cm), a characteristic that was overlooked before. Phylogenetic analysis, based on complete plastid genome, showed that L.insularis is not genetically related to L.sprengeri in the genus. The former was a sister group of L.sanguinea, while the latter was closely related to L.longituba and L.chinensis and they were respectively located on different clades that were separated at the base of the phylogenetic tree. The chromosome number of L.insularis is 2n = 22. At present, as the new species is relatively widely distributed and the wild population can normally reproduce by seeds, we evaluate it as LC (Least Concern) according to criteria of the IUCN Red List.

Sirtuin Evolution at the Dawn of Animal Life.

Sirtuins are a family of proteins that protect against cellular injury and aging; understanding their evolution should reveal fundamental mechanisms governing longevity. “Early-branching” animals such as sea sponges and jellyfish have been understudied in previous analyses of sirtuin diversity. These organisms not only hold important positions at the base of the evolutionary tree, but also have unique aging dynamics that defy convention, such as quasi-immortality and high regenerative capacity. In this study, we survey the evolution of sirtuin proteins in animals, with a focus on the oldest living lineages. We describe previously unrecognized expansions of “Class IV” and “Class I” sirtuins around the origin of animals, raising the number of sirtuin families in the last common ancestor to at least nine. Most of these undescribed sirtuins have been lost in vertebrates and other bilaterian animals. Our work also clarifies the evolution of PNC1 and NAMPT enzymes that carry out the rate-limiting step in sirtuin-related NAD+ biosynthesis. The genes for PNC1 and NAMPT enzymes were both present in the first animals, with the genes being lost a minimum of 11 and 13 times, respectively, over the course of animal evolution. We propose that species with these ancestral gene repertoires are ideal model organisms for studying the genetic regulation of animal longevity and will provide clues to increasing longevity in humans.

Commercial Eucalyptus Plantations with Taungya System: Analysis of Tree Root Biomass

The increasing demand for wood, fiber, and pulp, coupled with efforts to mitigate greenhouse gas emissions, has placed immense importance on the development of forest plantations. The rapidly growing human population faces shortages of food, particularly in the developing world where agricultural productivity is generally low. The taungya system, an age-old agroforestry practice involving the intercropping of crops with trees on the same unit of land, is opined as a win-win strategy to meet the need for wood products and food at the same time. In recent years, the taungya system has gained increasing attention from large forest companies as a tool and an opportunity to contribute to the social well-being of the local community. However, the effects of intercropping on the tree component are largely unexplored. Thus, this study was conducted to examine whether intercropping after 2 and 7 years has an effect on the root system of trees, thereby generating knowledge that supports evidence-based plantation management decisions involving the taungya system. To characterize the root system architecture, trenches were made on six young trees in both a pure Eucalyptus camaldulensis monoculture and intercropped stands (1111 trees/ha in both stands). To quantitatively estimate root biomass, a total of 324 soil cores (6 stands × 6 trees × 3 distances × 3 soil depths) were collected, and roots were sorted and dried to constant mass in an oven at 60 °C for 48 h. The root dry mass data were subjected to analysis of variance to examine the significant effects of intercropping, spacing, and stand age. The results show that the root system of E. camaldulensis was mainly confined to shallow depth but well elongated horizontally in both pure and intercropped stands with 4–6 thick lateral roots. The intercropping of rice/cassava with eucalypt had no effect on the total root dry mass of the tree component (p &gt; 0.05) irrespective of the plantation spacing (5 m × 2 m or 9 m × 1 m); however, root biomass decreased with increasing horizontal distance from the tree base and in deeper soil layers, particularly for trees in young stands. The effects of spacing between trees, wide (5 m × 2 m) versus narrow (9 m × 1 m), on root dry mass were dependent on the horizontal and vertical distribution of the root system, and root biomass appeared to be higher at 40 cm soil depth for the stand with wide spacing between trees than for stands with narrow spacing. Root biomass was larger for older rather than younger trees in both monoculture and intercropped stands, suggesting the lack of a carry-over effect of intercropping on root biomass. In conclusion, this study provides evidence in support of intercropping as a win-win strategy to meet the short-term needs of food production while producing wood in the end. As root biomass varies with horizontal distribution, further research is recommended to test buffer zones between trees and crops other than 1m, which is currently used.

Species boundary and phylogeographical pattern provide new insights into the management efforts of Megacopta cribraria (Hemiptera: Plataspidae), a bean bug invading North America.

Correct identification together with information on distribution range, geographical origin and evolutionary history are the necessary basis for the management and control of invasive species. The bean bug Megacopta cribraria is a crucial agricultural pest of soybean. Recently, M. cribraria has invaded the United States and spread rapidly, causing severe reductions in soybean yields. However, the species boundary and phylogeographical pattern of this invasive bean bug are still unclear. The results of different species delimitation methods (Automatic Barcode Gap Discovery, Assemble Species by Automatic Partitioning, Bayesian Poisson Tree Processes and Bayesian Phylogenetics and Phylogeography) strongly demonstrated that M. cribraria and Megacopta punctatissima represent the same species. M. punctatissima should not be considered a distinct species but rather a variety of M. cribraria. Phylogenetic analyses revealed three well-supported clades (Southeast Asia [SEA], East Asia continent [EAC] and Japan [JA]) with distinct geographical structures in the M. cribraria-M. punctatissima complex. The SEA clade was at the base of the phylogenetic tree, and the sister relationship between the EAC clade and JA clade was strongly supported. The split between the EAC clade and JA clade occurred at approximately 0.71 Ma, corresponding to the submergence period of the East China Sea land bridge. This study clarified the species boundary between M. cribraria and its closely related species and revealed the phylogeographical pattern and evolutionary history of M. cribraria. The species delimitation and phylogeography results achieved in this study could provide new insights into the monitoring and management of this agricultural pest. © 2022 Society of Chemical Industry.

An Inherent Coordination between the Leaf Size and the Hydraulic Architecture of Angiosperm Trees

Leaf veins are the continuation of twigs, and the hydraulic system of a leaf is part of, and the continuation of, the hydraulic architecture of a tree. Previous studies have demonstrated that the vessel diameter of the widest part at the tree base is tightly related to the total stem length of a tree. Here, we demonstrate that: the vessel diameter of the narrowest part at the distal end of the tree (the terminal twigs) is closely correlated to the leaf size for an angiosperm tree. Consequently, the basic feature of the hydraulic system of an angiosperm tree may be predicted by two simple parameters: the stem length (or tree height) and the leaf size, with the tree height predicting the size of the widest vessel at the tree base and the leaf size predicting the size of the narrowest vessel at the terminal trig. Namely, there is an inherent coordination between the leaf size and the hydraulic architecture of the angiosperm tree. As leaves are replacing themselves every year, their responses to climate are direct and immediate, while the woody part of a tree is there for years and more, and thus can only respond passively to climate change. This may cause a mismatch between the woody part and leaf part of the hydraulic system, and thus endanger the hydraulic coordination between leaves and the woody part.

Dynamics of fine roots and soil nitrogen in Mangifera indica‐based agroforestry systems in the Central Himalayan region, India

AbstractThis study estimated seasonal variations among several parameters of the fine roots and N dynamics in Mangifera indica‐based agroforestry systems; we examined homegarden (HG), agri‐horticulture (AH) and agri‐horti‐silviculture (AHS) systems in the Bhabhar area of the Indian Central Himalayan region. Fine roots biomass (FRB) and fine roots production (FRP) of M. indica were highest in the AH system and lowest in the HG system while fine roots turnover (FRT) showed a reverse trend. FRB, FRP and FRT rates decreased with soil depth and distance from the tree base, with larger variations in the AH system. The biomass: necromass ratio varied between 1.91 and 2.42 for HG, between 2.27 and 3.29 for AH and between 2.09 and 2.46 for AHS systems. Among all the selected agroforestry systems, concentrations of mineral N (NH4‐N and NO3‐N) were higher in the AH system and lower in the AHS system while net N mineralization rates were higher in the AHS system. In HGs, FRB it was significantly correlated with ammonification, nitrification and N mineralization while in the AH system it was positively correlated with nitrification and N mineralization. In the AHS system, it was positively correlated with ammonification only. Thus, it can be concluded that in agroforestry systems FRB was enhanced by rapid N mineralization. The variability in FRB and N mineralization between selected agroforestry systems were possibly due to the differences in soil characteristics and management practices. For enrichment of soil nutrients, the contribution of fine roots could be of more importance through the process of decomposition under the prevailing agroforestry systems.

Light-Dependence of Formate (C1) and Acetate (C2) Transport and Oxidation in Poplar Trees.

Although apparent light inhibition of leaf day respiration is a widespread reported phenomenon, the mechanisms involved, including utilization of alternate respiratory pathways and substrates and light inhibition of TCA cycle enzymes are under active investigation. Recently, acetate fermentation was highlighted as a key drought survival strategy mediated through protein acetylation and jasmonate signaling. Here, we evaluate the light-dependence of acetate transport and assimilation in Populus trichocarpa trees using the dynamic xylem solution injection (DXSI) method developed here for continuous studies of C1 and C2 organic acid transport and light-dependent metabolism. Over 7 days, 1.0 L of [13C]formate and [13C2]acetate solutions were delivered to the stem base of 2-year old potted poplar trees, while continuous diurnal observations were made in the canopy of CO2, H2O, and isoprene gas exchange together with δ13CO2. Stem base injection of 10 mM [13C2]acetate induced an overall pattern of canopy branch headspace 13CO2 enrichment (δ13CO2 +27‰) with a diurnal structure in δ13CO2 reaching a mid-day minimum followed by a maximum shortly after darkening where δ13CO2 values rapidly increased up to +12‰. In contrast, 50 mM injections of [13C]formate were required to reach similar δ13CO2 enrichment levels in the canopy with δ13CO2 following diurnal patterns of transpiration. Illuminated leaves of detached poplar branches pretreated with 10 mM [13C2]acetate showed lower δ13CO2 (+20‰) compared to leaves treated with 10 mM [13C]formate (+320‰), the opposite pattern observed at the whole plant scale. Following dark/light cycles at the leaf-scale, rapid, strong, and reversible enhancements in headspace δ13CO2 by up to +60‰ were observed in [13C2]acetate-treated leaves which showed enhanced dihydrojasmonic acid and TCA cycle intermediate concentrations. The results are consistent with acetate in the transpiration stream as an effective activator of the jasmonate signaling pathway and respiratory substrate. The shorter lifetime of formate relative to acetate in the transpiration stream suggests rapid formate oxidation to CO2 during transport to the canopy. In contrast, acetate is efficiently transported to the canopy where an increased allocation towards mitochondrial dark respiration occurs at night. The results highlight the potential for an effective integration of acetate into glyoxylate and TCA cycles and the light-inhibition of citrate synthase as a potential regulatory mechanism controlling the diurnal allocation of acetate between anabolic and catabolic processes.

Root distribution pattern studies to assess the foraging zone in Melia dubia Cav.

Melia dubia is one of the important tree species in agroforestry models across India owing to its multifarious utilities, compatibility with various agricultural, horticultural and forage crops. Inspite of its pan India prevalence, research data pertaining to the spatial distribution of its root system is scarce which is primarily responsible for determination of the capacity to absorb water and nutrients preferentially over other allied crops. Belowground competitions are the major constraints to successful intercropping in woody/agroforestry ecosystems and thus spatial distribution of tree roots assumes paramount importance. The root distribution pattern of selected trees in a twelve-year-old Malabar neem (Melia dubia Cav.) plantation grown at 4 m x 4 m spacing was studied using the logarithmic spiral trench technique to assess the level of competitive/complementary impacts of the root system. Root intensity decreased steadily as the root diameter classes increased with function to soil depth as well as lateral distance. It was observed that 65.07 % of the total roots observed on the profile wall of the trench were fine roots (size class 2.5 to5.0 mm). Major share of the fine roots occupied near to the base of tree and 60.14% of fine roots were found to be accumulated in upper 20 cm layer of soil. In terms of lateral distance, maximum number of fine roots were recorded near the tree at 0.26 m with root intensity 431.1 m-2, and 65.85% of fine roots were found to be concentrated within 80 cm lateral distance from the tree.

The origin of human epithelial tissue.

The histological structure of human epithelial tissue is complex, but all epithelia share three major features: cohesion, polarity and attachment. These functions are mainly achieved by the presence of specialized structures such as intercellular junctions, polarity protein complexes and basement membranes. In the present review, we have analyzed the presence of each of these structures in several groups of animals that are considered to be at the base of the animal evolution tree. Interestingly, these characters seem to have evolved independently, and a careful histological and structural analysis of the phylogenetic tree shows different groups of animals in which epithelia are absent and groups in which cells show only some of the specialized structures found in differentiated epithelia. These findings could contribute to understand how epithelial tissues evolved and determine their current protective functions.