BRANCH GEOMETRY AND EFFECTIVE LEAF AREA: A STUDY OF TERMINAUA-BRANCHING PATTERN. 1. THEORETICAL TREES

Single lateral branches and branch tiers of Terminalia catappa L. are simulated and drawn by computer. Leaf clusters on the branches are approximated by discs, and the effective leaf areas are determined by use of Dirichlet domains. Theoretical optimal branching angles which produce the maximum effective leaf area are obtained from simulations. Symmetrical and asymmetrical branching angles are contrasted; the latter characterize real trees. Varying leaf disc radius and ratio of branch-unit lengths affects optimal branching angles, as does the symmetry of a tier of five branches. Leaf area indices for individual branches and branch tiers are given for all simulations. The number of branches in a tier has a major effect on leaf area index and effective leaf area. The theoretical optimal branching angles of many simulations are very close to the values observed in real trees of T. catappa. We conclude that the observed branching angles and number of branches in a tier of this species optimize light interception within constraints of a fixed pattern of branching, one that is widespread among tropical trees.     

The effects of coalescence on survival and development of <Emphasis Type="Italic">Mazzaella laminarioides</Emphasis> (Rhodophyta,Gigartinales)

The potential benefits associated with coalescence in red algae have been best documented with early stages of development. In this study, we report on the effects of the original number of spores on branching and fertility during later stages of development. Measurements for 20 months of survival rates, field growth, and fertility of a set of 96 sporelings produced in the laboratory with different number of spores, and outplanted at mid levels of the Mazzaella laminarioides belt at a locality in central Chile, indicate significant differences between multisporic holdfasts (50 and 100 coalescing spores) and uni- or oligosporic (ten spore) holdfasts in the number of branches and erect axes produced 10 and 15 months after germination. The difference is related to the persistence of clusters of axes and branch initials in deep portions of holdfasts of multisporic plantlets and their absence from equivalent portions of uni- or oligosporic holdfasts. This is an example in macroalgae of an event occurring during germination and expressing its effects in the next growing season (some 10 months after).     

Shoot P status regulates cluster-root growth and citrate exudation in Lupinus albus grown with a divided root system

The present study was carried out to investigate whether the P concentration in the roots or the shoots controls the growth and citrate exudation of cluster roots in white lupin (Lupinus albus L). Foliar P application indicated that low P concentration in the shoots enhanced cluster‐root growth and citrate‐exudation rate more so than low P concentration in the roots. In the split‐root study, the P concentration in the shoots increased with increased P supply (1, 25 or 75 mmol m^?3 P), to the ‘privileged’ root halves. Roots ‘deprived’ of P invariably had the same low P concentrations, whereas those in the ‘privileged’ roots increased with increasing P supply (1, 25 or 75 mmol m^?3 P). Nevertheless, the proportion of the total root mass allocated to cluster roots, and the citrate‐exudation rates from the root halves were always similar on both root halves, irrespective of P supply, and decreased with increasing shoot P concentrations. Peak citrate exudation rates from developing cluster roots were significantly faster from cluster roots on the ‘deprived’ root halves when the ‘privileged’ half was exposed to 1 mmol m^?3 P as compared with 25 or 75 mmol m^?3 P. The possibility that changes in the concentrations of P fractions in the root halves influenced cluster‐root growth and citrate exudation was discounted, because there were no significant differences in insoluble organic P, ester‐P and inorganic P among all ‘deprived’ root halves. The results indicate that cluster‐root proportions and citrate exudation rates were regulated systemically by the P status of the shoot, and that P concentrations in the roots had little influence on growth and citrate exudation of cluster roots in L. albus.     

PpeTAC1 promotes the horizontal growth of branches in peach trees and is a member of a functionally conserved gene family found in diverse plants species

Trees are capable of tremendous architectural plasticity, allowing them to maximize their light exposure under highly competitive environments. One key component of tree architecture is the branch angle, yet little is known about the molecular basis for the spatial patterning of branches in trees. Here, we report the identification of a candidate gene for the br mutation in Prunus persica (peach) associated with vertically oriented growth of branches, referred to as ‘pillar’ or ‘broomy’. Ppa010082, annotated as hypothetical protein in the peach genome sequence, was identified as a candidate gene for br using a next generation sequence‐based mapping approach. Sequence similarity searches identified rice TAC1 (tiller angle control 1) as a putative ortholog, and we thus named it PpeTAC1. In monocots, TAC1 is known to lead to less compact growth by increasing the tiller angle. In Arabidopsis, an attac1 mutant showed more vertical branch growth angles, suggesting that the gene functions universally to promote the horizontal growth of branches. TAC1 genes belong to a gene family (here named IGT for a shared conserved motif) found in all plant genomes, consisting of two clades: one containing TAC1‐like genes; the other containing LAZY1, which contains an EAR motif, and promotes vertical shoot growth in Oryza sativa (rice) and Arabidopsis through influencing polar auxin transport. The data suggest that IGT genes are ancient, and play conserved roles in determining shoot growth angles in plants. Understanding how IGT genes modulate branch angles will provide insights into how different architectural growth habits evolved in terrestrial plants.     

Changes in growth,porosity, and radial oxygen loss from adventitious roots of selected mono‐ and dicotyledonous wetland species with contrasting types of aerenchyma

Growth in stagnant, oxygen‐deficient nutrient solution increased porosity in adventitious roots of two monocotyledonous (Carex acuta and Juncus effusus) and three dicotyledonous species (Caltha palustris, Ranunculus sceleratus and Rumex palustris) wetland species from 10 to 30% under aerated conditions to 20–45%. The spatial patterns of radial oxygen loss (ROL), determined with root‐sleeving oxygen electrodes, indicated a strong constitutive ‘barrier’ to ROL in the basal root zones of the two monocotyledonous species. In contrast, roots of the dicotyledonous species showed no significant ‘barrier’ to ROL when grown in aerated solution, and only a partial ‘barrier’ when grown in stagnant conditions. This partial ‘barrier’ was strongest in C. palustris, so that ROL from basal zones of roots of R. sceleratus and R. palustris was substantial when compared to the monocotyledonous species. ROL from the basal zones would decrease longitudinal diffusion of oxygen to the root apex, and therefore limit the maximum penetration depth of these roots into anaerobic soil. Further studies of a larger number of dicotyledonous wetland species from a range of substrates are required to elucidate the ecophysiological consequences of developing a partial, rather than a strong, ‘barrier’ to ROL.     

DcMYB113, a root‐specific R2R3‐MYB,conditions anthocyanin biosynthesis and modification in carrot

Purple carrots, the original domesticated carrots, accumulate highly glycosylated and acylated anthocyanins in root and/or petiole. Previously, a quantitative trait locus (QTL) for root‐specific anthocyanin pigmentation was genetically mapped to chromosome 3 of carrot. In this study, an R2R3‐MYB gene, namely DcMYB113, was identified within this QTL region. DcMYB113 expressed in the root of ‘Purple haze’, a carrot cultivar with purple root and nonpurple petiole, but not in the roots of two carrot cultivars with a purple root and petiole (Deep purple and Cosmic purple) and orange carrot ‘Kurodagosun’, which appeared to be caused by variation in the promoter region. The function of DcMYB113 from ‘Purple haze’ was verified by transformation in ‘Cosmic purple’ and ‘Kurodagosun’, resulting in anthocyanin biosynthesis. Transgenic ‘Kurodagosun’ carrying DcMYB113 driven by the CaMV 35S promoter had a purple root and petiole, while transgenic ‘Kurodagosun’ expressing DcMYB113 driven by its own promoter had a purple root and nonpurple petiole, suggesting that root‐specific expression of DcMYB113 was determined by its promoter. DcMYB113 could activate the expression of DcbHLH3 and structural genes related to anthocyanin biosynthesis. DcUCGXT1 and DcSAT1, which were confirmed to be responsible for anthocyanins glycosylation and acylation, respectively, were also activated by DcMYB113. The WGCNA identified several genes co‐expressed with anthocyanin biosynthesis and the results indicated that DcMYB113 may regulate anthocyanin transport. Our findings provide insight into the molecular mechanism underlying root‐specific anthocyanin biosynthesis and further modification in carrot and even other root crops.     

Maintenance mechanisms of the pipe model relationship and Leonardo da Vinci’s rule in the branching architecture of <Emphasis Type="Italic">Acer rufinerve</Emphasis> trees

The pipe model relationship (constancy of branch cross-sectional area/leaf area) and Leonardo da Vinci’s rule (equality of total cross-sectional area of the daughter branches and cross-sectional area of their mother branch) are empirical rules of tree branching. Effects of branch manipulation on the pipe model relationships were examined using five Acer rufinerve trees. Half the branches in each tree were untreated (control branches, CBs), and, for the others (manipulated branches, MBs), either light intensity or leaf area (both relating to photosynthetic source activity), or shoot elongation (source + sink activities), was reduced, and responses of the pipe model relationships were followed for 2 years. The pipe model relationship in MBs changed by suppression of source activity, but not by simultaneous suppression of source + sink activities. The manipulations also affected CBs in the year of manipulation and both branches in the next year. The branch diameter growth was most affected by light, followed by shoot elongation and leaf area, in that order. Because of the decussate phyllotaxis of A. rufinerve, one branching node can potentially have one main and two lateral branches. Analysis of 295 branching nodes from 13 untreated trees revealed that the da Vinci’s rule held in branching nodes having one shed branch but not in the nodes without branch shedding, indicating the necessity of natural shedding of branches for da Vinci’s rule to hold. These analyses highlight the importance of the source–sink balance and branch shedding in maintenance of these empirical rules. This article was contributed at the invitation of the Editorial Committee.     

New crinoids from the Baltic region (Estonia): fossil tip‐dating phylogenetics constrains the origin and Ordovician–Silurian diversification of the Flexibilia (Echinodermata)

This study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end‐Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high‐resolution temporal, taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end‐Ordovician mass extinction. A Bayesian ‘fossil tip‐dating’ analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via ‘budding’ cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from ‘taxocrinid’ grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post‐Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade‐based phylogenetic studies and improving estimates of global biodiversity through geological time.     

Root tubercles in apostasiad orchids

Tubercles are swollen, stalked, warty branches arising from the main elongated roots of species in the terrestrial orchid genus Apostasia (subfamily Apostasioideae). Generalized anatomy resembles that of the main roots, except tubercles lack a velamen and conductive strands are few. There are multinucleate cortical cells, and stomata occur in the epidermis. Pores of stomata appear to be permanently open and thus may enhance the interchange of gases between root tissues and soil under the moist conditions in which apostasias grow. Multicellular warts seem to function as holdfasts and are points of entry for mycorrhizal fungi.     

Arabidopsis MPK6 is involved in cell division plane control during early root development,and localizes to the pre‐prophase band,phragmoplast, trans‐Golgi network and plasma membrane

The proper spatial and temporal expression and localization of mitogen‐activated protein kinases (MAPKs) is essential for developmental and cellular signalling in all eukaryotes. Here, we analysed expression, subcellular localization and function of MPK6 in roots of Arabidopsis thaliana using wild‐type plants and three mpk6 knock‐out mutant lines. The MPK6 promoter showed two expression maxima in the most apical part of the root meristem and in the root transition zone. This expression pattern was highly consistent with ‘no root’ and ‘short root’ phenotypes, as well as with ectopic cell divisions and aberrant cell division planes, resulting in disordered cell files in the roots of these mpk6 knock‐out mutants. In dividing root cells, MPK6 was localized on the subcellular level to distinct fine spots in the pre‐prophase band and phragmoplast, representing the two most important cytoskeletal structures controlling the cell division plane. By combining subcellular fractionation and microscopic in situ and in vivo co‐localization methods, MPK6 was localized to the plasma membrane (PM) and the trans‐Golgi network (TGN). In summary, these data suggest that MPK6 localizing to mitotic microtubules, secretory TGN vesicles and the PM is involved in cell division plane control and root development in Arabidopsis.     

Roothairless5, which functions in maize (Zea mays L.) root hair initiation and elongation encodes a monocot‐specific NADPH oxidase

Root hairs are instrumental for nutrient uptake in monocot cereals. The maize (Zea mays L.) roothairless5 (rth5) mutant displays defects in root hair initiation and elongation manifested by a reduced density and length of root hairs. Map‐based cloning revealed that the rth5 gene encodes a monocot‐specific NADPH oxidase. RNA‐Seq, in situ hybridization and qRT‐PCR experiments demonstrated that the rth5 gene displays preferential expression in root hairs but also accumulates to low levels in other tissues. Immunolocalization detected RTH5 proteins in the epidermis of the elongation and differentiation zone of primary roots. Because superoxide and hydrogen peroxide levels are reduced in the tips of growing rth5 mutant root hairs as compared with wild‐type, and Reactive oxygen species (ROS) is known to be involved in tip growth, we hypothesize that the RTH5 protein is responsible for establishing the high levels of ROS in the tips of growing root hairs required for elongation. Consistent with this hypothesis, a comparative RNA‐Seq analysis of 6‐day‐old rth5 versus wild‐type primary roots revealed significant over‐representation of only two gene ontology (GO) classes related to the biological functions (i.e. oxidation/reduction and carbohydrate metabolism) among 893 differentially expressed genes (FDR <5%). Within these two classes the subgroups ‘response to oxidative stress’ and ‘cellulose biosynthesis’ were most prominently represented.     

The importance of anatomical structural study of roots for the understanding of physiological processes

Abstract

Besides being species‐specific, the inner structure of the root is influenced by the place and time of origin during the growth period. From the root tip up to the base of a particular root, the zones of cell division, cell elongation, formation of root hairs and root branching can be distinguished. The root tip that is covered by a root cap and mucilage is protected against evaporation and water contact. From the end of the lateral parts of the root cap, the cells become exposed to the surrounding environment. The cells can elongate by water uptake or can shrink by water loss. All processes of geotropic growth take place there. In this study, some differences are illustrated using Zea mays plants. Radicle and roots emerging from several nodes of the shoot as well as lateral roots are compared. The distances from the tip and from the base of the root are also very important for characterization of particular root functions. Distinctive features such as root diameter, size of the stele and of the cortex, ratio of cortex to stele, number and width of the xylem vessels, size of cells, special thickenings and stage of lignification as well as symptoms of maturation are observed.     

The role of nodal roots in prostrate clonal herbs: ‘phalanx’ versus ‘guerrilla’

The influence of nodal rooting on branching was studied in three evolutionarily and morphologically diverse species of prostrate clonal herbs: Tradescantia fluminensis (a monocotyledonous extreme ‘phalanx’ species), Calystegia silvatica (a dicotyledonous extreme ‘guerrilla’ species) and Trifolium repens (a dicotyledonous intermediate species). In all three, branch development from axillary buds is regulated by a positive signal produced by roots together with inhibitory influences from both pre-existing branches and shoot apical buds (apical dominance). Responses to nodal roots are cumulative and increased root activity leads to more vigorous bud outgrowth. In the absence of nodal roots, a single basal root system is unable to maintain continued extension growth of the shoot. We suggest that as individual nodal roots and stem internodes are both short-lived in these nodally-rooting clonal species, the plants’ investment in them is minimal. Thus, in contrast to perennial species lacking nodal roots, individual root systems in prostrate clonal herbs are small and stems have little secondary thickening and development of long-distance transport tissues. Hence the decline in extension growth of the shoot in the absence of nodal roots could be linked to the weak development of long-distance transport tissues in their relatively thin horizontal stems and to resource sharing between primary stems and lateral branches (as suggested by the greater retardation of primary stem growth in the more profusely branched ‘phalanx’ species (Trifolium and Tradescantia) than in the weakly branched ‘guerrilla’ species, Calystegia). These findings are consistent with the view that the long-term persistence of genotypes of nodally-rooting prostrate species is dependent upon them encountering the moist conditions required to facilitate the continual development of new young nodal root systems.     

Relationships among root branch order, carbon, and nitrogen in four temperate species

The objective of this study was to examine how root length, diameter, specific root length, and root carbon and nitrogen concentrations were related to root branching patterns. The branching root systems of two temperate tree species, Acer saccharum Marsh. and Fraxinus americana L., and two perennial herbs from horizontal rhizomes, Hydrophyllum canadense L. and Viola pubescens Ait., were quantified by dissecting entire root systems collected from the understory of an A. saccharum-Fagus grandifolia Ehrh. forest. The root systems of each species grew according to a simple branching process, with laterals emerging from the main roots some distance behind the tip. Root systems normally consisted of only 4–6 branches (orders). Root diameter, length, and number of branches declined with increasing order and there were significant differences among species. Specific root length increased with order in all species. Nitrogen concentration increased with order in the trees, but remained constant in the perennial herbs. More than 75% of the cumulative root length of tree seedling root systems was accounted for by short (2–10 mm) lateral roots almost always <0.3 mm in diameter. Simple assumptions suggest that many tree roots normally considered part of the dynamic fine-root pool (e.g., all roots <2.0 mm in diameter) are too large to exhibit rapid rates of production and mortality. The smallest tree roots may be the least expensive to construct but the most expensive to maintain based on an increase in N concentration with order. Received: 25 November 1996 / Accepted: 27 March 1997     

Root damage to apple plants by cockchafer larvae induces a change in volatile signals below‐ and above‐ground

Volatile organic compounds (VOCs) mediate communication between plants and insects. Plants under insect herbivore attack release VOCs either at the site of attack or systemically, indicating within‐plant communication. Some of these VOCs, which may be induced only upon herbivore attack, recruit parasitoids and predatory insects to feed on the attacking insects. Moreover, some plants are able to ‘eavesdrop’ on herbivore‐induced plant volatiles (HIPVs) to prime themselves against impending attack; such eavesdropping exemplifies plant–plant communication. In apple orchards, the beetle Melolontha melolontha L. (Coleoptera: Scarabaeidae) is an important insect pest whose larvae live and feed on roots for about 4 years. In this study, we investigated whether the feeding activity of M. melolontha larvae (1) alters the volatile profile of apple roots, (2) induces the release of HIPVs systemically in the leaves, and (3) whether infested plants communicate to neighbouring non‐infested conspecifics through HIPVs. To answer these questions, we collected constitutive VOCs from intact M9 roots as well as M. melolontha larvae‐damaged roots using a newly designed ‘rhizobox’, to collect root‐released volatiles in situ, without damaging the plant root system. We also collected VOCs from the leaf‐bearing shoots of M9 whose roots were under attack by M. melolontha larvae and from shoots of neighbouring non‐infested conspecifics. Gas chromatography‐mass spectrometry analysis showed that feeding activity of M. melolontha larvae induces the release of specific HIPVs; for instance, camphor was found in the roots only after larvae caused root damage. Melolontha melolontha also induced the systemic release of methyl salicylate and (E,E)‐α‐farnesene from the leaf‐bearing shoots. Methyl salicylate and (E,E)‐α‐farnesene were also released by the shoots of non‐infested neighbouring conspecifics. These phenomena indicate the induction of specific VOCs below‐ and above‐ground upon M. melolontha larvae feeding on apple roots as well as plant–plant communication in apple plants.     

SlCCD7 controls strigolactone biosynthesis,shoot branching and mycorrhiza‐induced apocarotenoid formation in tomato

The regulation of shoot branching is an essential determinant of plant architecture, integrating multiple external and internal signals. One of the signaling pathways regulating branching involves the MAX (more axillary branches) genes. Two of the genes within this pathway, MAX3/CCD7 and MAX4/CCD8, encode carotenoid cleavage enzymes involved in generating a branch‐inhibiting hormone, recently identified as strigolactone. Here, we report the cloning of SlCCD7 from tomato. As in other species, SlCCD7 encodes an enzyme capable of cleaving cyclic and acyclic carotenoids. However, the SlCCD7 protein has 30 additional amino acids of unknown function at its C terminus. Tomato plants expressing a SlCCD7 antisense construct display greatly increased branching. To reveal the underlying changes of this strong physiological phenotype, a metabolomic screen was conducted. With the exception of a reduction of stem amino acid content in the transgenic lines, no major changes were observed. In contrast, targeted analysis of the same plants revealed significantly decreased levels of strigolactone. There were no significant changes in root carotenoids, indicating that relatively little substrate is required to produce the bioactive strigolactones. The germination rate of Orobanche ramosa seeds was reduced by up to 90% on application of extract from the SlCCD7 antisense lines, compared with the wild type. Additionally, upon mycorrhizal colonization, C₁₃ cyclohexenone and C₁₄ mycorradicin apocarotenoid levels were greatly reduced in the roots of the antisense lines, implicating SlCCD7 in their biosynthesis. This work demonstrates the diverse roles of MAX3/CCD7 in strigolactone production, shoot branching, source–sink interactions and production of arbuscular mycorrhiza‐induced apocarotenoids.     

Fine root architecture, morphology, and biomass of different branch orders of two Chinese temperate tree species

We have limited understanding of architecture and morphology of fine root systems in large woody trees. This study investigated architecture, morphology, and biomass of different fine root branch orders of two temperate tree species from Northeastern China—Larix gmelinii Rupr and Fraxinus mandshurica Rupr —by sampling up to five fine root branch orders three times during the 2003 growing season from two soil depths (i.e., 0–10 and.10–20 cm). Branching ratio (R _b) differed with the level of branching: R _b values from the fifth to the second order of branching were approximately three in both species, but markedly higher for the first two orders of branching, reaching a value of 10.4 for L. gmelinii and 18.6 for F. mandshurica. Fine root diameter, length, SRL and root length density not only had systematic changes with root order, but also varied significantly with season and soil depth. Total biomass per order did not change systematically with branch order. Compared to the second, third and/or fourth order, the first order roots exhibited higher biomass throughout the growing season and soil depths, a pattern related to consistently higher R _b values for the first two orders of branching than the other levels of branching. Moreover, the differences in architecture and morphology across order, season, and soil depth between the two species were consistent with the morphological disparity between gymnosperms and angiosperms reported previously. The results of this study suggest that root architecture and morphology, especially those of the first order roots, should be important for understanding the complexity and multi-functionality of tree fine roots with respect to root nutrient and water uptake, and fine root dynamics in forest ecosystems.     

Influence of Position and Number of Nodal Roots on Outgrowth of Axillary Buds and Development of Branches in Trifolium repens (L.)

The implications of the presence of a root, either at the parentnode or at neighbour nodes, on branch formation of Trifoliumrepens (white clover) was investigated. Plants were freely rootedor rooting was restricted to every sixth or every twelfth nodealong the parent axis. The absence of a root at the parent nodehad little influence on the probability of the subtending axillarybud forming a branch but, on average, delayed the outgrowthof the bud. The probability that an axillary bud, emerging froma non-rooted parent node, developed to a lateral branch (branchwith elongated internodes) decreased with decreasing proximityof the parent node to a rooted node. Lateral branches emergingfrom non-rooted parent nodes which were two nodes distal toa rooted node had a higher rate of node appearance, a greatermean internode length and area per leaf, and were more branchedthan lateral branches emerging from other non-rooted parentnodes. The dry mass of each single root and of branches grownat rooted parent nodes were significantly higher in plants withrestricted rooting than in freely rooted plants. Restrictionin the number of rooted nodes per plant increased the numberof inflorescences. It is concluded that the whole plant responseto restricted root formation was continuous growth of the parentaxis and compensatory growth of the branch at the rooted node.In general, growth was slow for axillary buds whose developmentwas dependent on the basipetal movement or cross-transport withinthe stolons of resources exported from roots. Trifolium repens (L.); white clover; axillary bud outgrowth; branch development; clonal growth; nodal root     

The peu‐miR160a−PeARF17.1/PeARF17.2 module participates in the adventitious root development of poplar

Deep roots give rise to flourishing leaves, and the two complement each other. However, the genetic mechanisms underlying adventitious rooting for forest trees have remained elusive. In this study, we verified that peu‐miR160a targets six poplar genes AUXIN RESPONSE FACTORS (ARFs), PeARF10.1, PeARF16.1, PeARF16.2, PeARF16.3, PeARF17.1 and PeARF17.2, using 5’RLM‐RACE. Interaction experiments with peu‐miR160a and PeARFs in poplar protoplasts further confirmed that peu‐miR160a targets and negatively regulates the six PeARFs. Peu‐miR160a and its target genes exhibited obvious temporal expression in different stages of adventitious root development, and they could also be induced by IAA and abscisic acid. Peu‐miR160a‐overexpressing lines exhibited a significant shortening of adventitious root length, an increase in the number of lateral roots, severe dwarfing and shortened internodes. In addition, the overexpression of PeARF17.1 or mPeARF17.2 (peu‐miR160a‐resistant version of PeARF17.2) significantly increased the number of adventitious roots. Furthermore, PeARF17.1‐overexpressing lines had multiple branches with no visible trunk, although the adventitious root length of the PeARF17.1‐overexpressing lines was significantly increased. Our findings reveal that the peu‐miR160a ? PeARF17.1/PeARF17.2 module is an important regulator involved in the development of the adventitious roots of poplar.     

Aspects of the semantics of emotions and feelings in Dalabon (South‐Western Arnhem Land,Australia)

This article describes two of the principal roots allowing the expression of emotions and feelings in Dalabon, an endangered language of South‐Western Arnhem Land. The first root, kangu, ‘belly’, is depicted linguistically as the location of emotions induced by interpersonal relationships. The belly is thus presented as the locus of good and bad moods generally and of conflict more specifically. Furthermore, the material properties of the belly—its fluidity in particular—impact on one’s temper and ability to deal with others in an ideologically prescribed manner. Speakers describe ritual manipulations undertaken on the belly of young infants in order to shape their temper. Kangu‐no may thus be described as a malleable interface between the person and the outside world, principally other people. The second root, yolh, may at first sight translate as ‘feelings’, either good or bad, but also means ‘appetite’, ‘drive’, ‘pep’. Yolh‐no is associated with the most intimate part of the person, one’s own aspirations that are independent of interactions with others. Although yolh‐no connotes the core self and kangu‐no, the belly, connotes relatedness to others, they are conceived as physiologically connected, so that material properties of the belly impact on the self. Thus, the semantic analysis of Dalabon, along with related anthropological observations, unveils an explicit conceptual and cultural attention to the distinction between emotions and feelings (as respectively defined in the article) and to the autonomy of the person within a constraining social framework. The article shows how this concern echoes and challenges both anthropological and philosophical considerations.