Branch Apices Research Articles

Impact of Fruit Load on the Replenishment Dynamics of Internal Water Reserves in Olive Trees

Stem refilling has been studied in many forest species, but its impact on olive trees remains underexplored. This study aims to examine the effect of varying fruit loads on stem refilling rates in olive trees. The experiment was conducted in a commercial olive orchard over two years, characterized by a biennial bearing cycle with minimal fruit production in 2021 (“OFF” year) and maximal fruit production in 2022 (“ON” year). Sap flow sensors measured the water volume differences traversing the apex and base of main branches in two experimental trees. Tree water status was monitored using psychrometers, and soil moisture content was continuously recorded. Results suggest that alternate bearing significantly affects the stem refilling process, while soil moisture availability also plays a pivotal role. During the “ON” year, water reserve consumption increased to 63.6% compared to the “OFF” year to meet the water requirements of developing fruits. Replenishment occurred at various times throughout the 24 h period, including early morning, afternoon, and night when stomatal conductance measurements indicated stomatal closure. During the “ON” year, olive trees experienced intense nocturnal replenishment of reserves, regardless of soil moisture, water vapor pressure deficit, or fruit development stage. These findings offer novel insights into olive trees’ rehydration dynamics that can be used to optimize irrigation scheduling and improve water use efficiency.

Three new species of the genus Clavulina (Hydnaceae, Cantharellales) from North China based on morphological and phylogenetic analysis.

Clavulina possesses important ecological and economic value and has attracted extensive attention from mycologists. Macrofungal diversity is high in China, but Clavulina species have not been thoroughly studied. In this study, based on morphological evidence and phylogenetic analyses of the nucleotide sequences of three loci (nrITS, nrLSU, and rpb2), three new species of Clavulina from North China were identified. Morphologically, Clavulinachengdeensis is characterized by its white to dirty white basidiomata with somewhat pale orange tips and somewhat wrinkled hymenium. Clavulinagriseoviolacea is characterized by its gray to dark grayish violet basidiomata, with a sometimes-white stipe base, monopodial or irregularly polychotomous toward branch apices. Clavulinapallida is characterized by its white to pale cream white basidiomata with somewhat orange tips. Phylogenetically, the three new species form three independent branches with high support values in the phylogenetic tree.

(2947) Proposal to reject the name Bryophyllum triangulare (Crassulaceae: Kalanchooideae)

(2947) Proposal to reject the name <i>Bryophyllum triangulare</i> (<i>Crassulaceae</i>: <i>Kalanchooideae</i>)

A new record for Guyana reveals the disjunct distribution of&nbsp;Tragia cearensis Pax &amp; K. Hoffm. (Euphorbiaceae)&nbsp;

Tragia cearensis, which was known only from northeastern Brazil in caatinga (dryland) vegetation, has its distribution expanded after the discovery of its presence in the savanna of Guyana, providing the first evidence of a disjunct distribution between those dry areas among Tragia species. Tragia cearensis could be recognized by having long, capitate, glandular trichomes at the apex of the petiole, the absence of glandular trichomes on the inflorescences and apices of the branches, and verrucose seeds. A detailed description, additional taxonomic notes, illustrations, and a distribution map are presented.

Study of the phylogeny and distribution of Pterocladiella (Pterocladiaceae, Rhodophyta) from China

ABSTRACTIn the current study, 334 specimens of Pterocladiella from China representing historical herbarium specimens and recent field collections were re-examined based upon morphological and molecular data analyses. Both datasets revealed the presence of P. beachiae, P. capillacea, P. caerulescens, and P. musciformis. Of these species, P. beachiae and P. musciformis were new records for China. Pterocladiella beachiae was characterised by a complanate thallus, with first-order short branches opposite or alternate in the upper part of the plant and marginal proliferations in the upper axis and branches; Pterocladiella musciformis had distinctive acute branch apices, cylindrical or slightly compressed lower axes, compressed upper axes, and simple irregular branches occurring either laterally or clustered. P. caerulescens had a corymbose outline and was monoecious. In the field, P. capillacea was the most common species of Pterocladiella, being widely distributed along Chinese coasts, whereas other Pterocladiella species were geographically limited in southern China. In P. capillacea, the tetrasporophyte was the dominant reproductive type while gametophytes were less common and more likely occurred in the East China Sea and South China Sea at lower latitudes.

Frequent fires alter tree architecture and impair reproduction of a common fire‐tolerant savanna tree

Several Cerrado tree species have traits and structures that protect from fires. The effectiveness of a trait depends on the fire regime, especially the frequency. We used Vochysia elliptica, a common Cerrado tree, as a model to test whether different fire frequencies alter crown architecture and flower, fruit and seed production. We analysed the effect of fire on the production of inflorescences, fruits and seeds, as well as seed germination and tree architecture of 20 trees in each of three plots of a long-term ecological experiment managed with different fire regimes: burned every 2years (B), burned every 4years (Q) in mid-dry season and an area protected from fire (C). We found a large negative effect of fire frequency on crown architecture and on flower and fruit production. Trees in C and Q had significantly more main branches and a larger crown area than trees in B. At its peak, a tree in C was expected to produce 2.4 times more inflorescences than Q, and 15.5 times more than B, with similar magnitudes for fruits. Sixty per cent of trees in B and 10% in Q produced no fruits. The differences in architecture might explain the reduction in sexual reproduction due to a smaller physical space to produce flowers at the branch apices. Resource limitation due to plant investment to replace burned vegetative parts may also decrease sexual reproduction. Our results indicate potentially severe consequences of high fire frequencies for population dynamics and species persistence in Cerrado communities.

Laurencia longiramea sp. nov. for Brazil and an emendation of the generic delineation of Corynecladia (Ceramiales, Rhodophyta)

ABSTRACTStudies of the Laurencia complex based on phylogenetic and DNA barcoding analyses revealed a new species, Laurencia longiramea Cassano, G.N. Santos, J.M.C. Nunes, M.C. Oliveira & M.T. Fujii sp. nov., on the Brazilian coast. The rbcL phylogenetic analysis resolved L. longiramea as sister to Laurencia species from the North Atlantic (L. pyramidalis, L. viridis and L. obtusa) and the Caribbean Sea and Gulf of Mexico (L. intricata), with a divergence of 2.4%–3.7%. Using the DNA barcode COI-5P, L. longiramea was closest to L. pacifica from the United States, with a divergence of 4.2%. The new species has the typical features of the genus Laurencia and is characterised by: sparse branching, axes smaller than 1 mm diameter, often long branchlets, lenticular thickenings always present and abundant, and absence of cortical cells projected near branch apices. Morphologically, L. longiramea is similar to Laurencia filiformis. However, an rbcL sequence of L. filiformis from the type locality (Western Australia) confirmed that they are distinct species, with 4.3% divergence. Examination of Laurencia clavata from Brazil, deposited in the University of São Paulo (SPF) herbarium, were misidentified and corresponded to the new species, L. longiramea. In addition, the rbcL and COI-5P sequences of L. clavata from the type locality (Australia) did not join with L. longiramea. Laurencia clavata formed a well-supported clade with the two species of Coronaphycus. Priority supported the recognition of Corynecladia over Coronaphycus, requiring the new combinations Corynecladia elata (C.Agardh) comb. nov. and Corynecladia nova (Metti) comb. nov. Based on our results, Corynecladia clavata does not occur in the Brazilian marine flora.

First Report of Neofusicoccum parvum Causing Stem Necrosis of ‘Ōhi‘a Trees (Metrosideros polymorpha) on O‘ahu, Hawai‘i, U.S.A.

‘Ōhi‘a lehua (Metrosideros polymorpha) is the most abundant and ecologically important native tree in the Hawaiian Islands (Friday and Herbert 2006). In November 2016, extensive ‘ōhi‘a mortality was reported in the ‘Ewa Forest Reserve in the Ko‘olau Mountains of O‘ahu. A site visit revealed 150+ (≈50% disease incidence) ‘ōhi‘a trees along the Poamoho Trail with branch dieback and defoliated crowns, often with epicormic sprouts emerging below dead branch terminals (157°55′31.98″W, 21°31′58.905″N). Trees showed evidence of prior leaf infection by Austropuccinia psidii (pustules with urediniospores), which is likely associated with the widespread defoliation. Stem sections (>2.5 cm diameter) containing the margin between healthy and necrotic xylem were collected from five symptomatic trees for diagnosis. Woody stems were externally asymptomatic; however, when debarked, an extensive brown to black necrotic vascular discoloration was visible from the branch apex downward several centimeters on stems. Additional isolated lesions were found lower on the stems away from branch terminals. Sections of discolored xylem were surface disinfested in 3% sodium hypochlorite and plated onto potato dextrose agar (PDA). Within 4 days, tissue from four of five trees yielded a similar fungus containing white, aerial mycelium that later turned gray. Single-spore isolates (P17-79 and P17-80) were derived from two of four infected trees. To identify the isolates, the internal transcribed spacer of the rDNA (ITS), partial β-tubulin (tub2), and translation elongation factor 1-α (tef1) gene regions were amplified by polymerase chain reaction (PCR) and sequenced using primers ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R, respectively. Both fungal isolates were identical to each other and were 99% (ITS) and 100% (tub2 and tef1) similar the ex-type isolate (CMW9081 and ICMP 8003) in a BLASTn comparison. Sequences were deposited in GenBank with accessions numbers MF631021 and MF631022 (ITS), MF631023 and MF631024 (tub2), and MF631025 and MF631026 (tef1). Pathogenicity tests were conducted by inoculating 1-year-old ‘ōhi‘a seedlings with PDA plugs containing 7-day-old mycelium of Neofusicoccum parvum (P17-79 and P17-80) into wounds made by a 5-mm cork borer and wrapped in Parafilm. Each N. parvum isolate was inoculated into five plants. Five negative control plants were inoculated with sterile PDA plugs. Plants were kept in a greenhouse (21.8 ± 1.0°C) with daily mist irrigation. After 4 months, inoculated stems were debarked, and the extent of xylem necrosis was measured. The necrosis was identical to that observed in the field samples. This experiment was conducted twice. For both experiments combined, mean length of xylem lesions was significantly higher (P < 0.001) for N. parvum-inoculated seedlings (P17-79 = 4.0 ± 0.5 cm and P17-80 = 3.7 ± 0.4 cm) versus controls (mean = 0.6 ± 0.1 cm). Fungi reisolated from inoculated tissue were molecularly analyzed using ITS PCR and sequencing, confirming the fungus as N. parvum, thus completing Koch’s postulates. Control plants showed no symptoms. N. parvum is an endophyte or latent pathogen of woody hosts and has been reported in Hawai‘i on Eucalyptus (Sakalidis et al. 2013). To our knowledge, this is the first report of N. parvum on ‘ōhi‘a in Hawai‘i, and causing stem necrosis. We suspect N. parvum is acting as a stress-induced pathogen (Slippers and Wingfield 2007) and not a primary tree killer. Further investigation is needed to determine the interaction of N. parvum with other pathogens of ‘ōhi‘a, especially A. psidii, which is believed to play a significant role in the defoliation and dieback on O‘ahu.

Selaginella germinans (Selaginellaceae), a new articulate species from Chapada dos Veadeiros region in the State of Goiás, Brazil

ABSTRACTWe describe a new articulate Selaginella species (i.e. S. germinans) from the Chapada dos Veadeiros region in the State of Goiás, Brazil. This species is characterized by articulate stems, dorsal rhizophores, flagelliform stems and branch apices that form flattened buds or gemmae at their tips, as well as a single basal megasporangium on each strobilus, which is subtended by a megasporophyll and few other infertile sporophylls. We also discuss the taxonomic affinity, habitat, distribution, and conservation status of this new species, which is illustrated with digitized micrograph images of stem sections, leaves, and megaspores taken with a Scanning Electron Microscope (SEM). We propose that the formation of buds or gemmae in this new species is probably an adaptive vegetative reproductive mechanism to adverse natural or man-induced environmental conditions (e.g. fires and drought periods) in its habitat.http://www.ipni.org/urn:lsid:ipni.org:names:77186979-1

Floral phenology and floral induction in Leptospermum scoparium

ABSTRACTLeptospermum scoparium is a species found throughout New Zealand and southeastern Australia. It typically flowers in the spring and early summer, although occasional flowers can often be seen on plants throughout the year. A study of bud phenology revealed that floral bract primordia initiated development at apices of sub-terminal branches soon after the longest day, and that floral bud development progressed throughout the summer, autumn and winter months. Flower bud opening then occurred the following spring with the resumption of vegetative growth. A controlled environment study indicated that L. scoparium acted as a ‘short day plant’. When plants were maintained under a 16 h photoperiod (16 h of light and 8 h of dark per day) they remained vegetative. Shorter photoperiods were then tested and values less than 11.5 h were found to be inductive for the two varieties tested (‘Crimson Glory’ and ‘Nanum Ruru’). Plants needed to be subjected to this treatment for at least 4 weeks before induction was observed. An interaction with temperature was also detected. Plants were induced to flower by a 9.5 h photoperiod administered at a constant 20 °C but either failed to flower, or did so very poorly when the 9.5 h photoperiod was administered at a constant 10 °C.

Application of floral microcharacters to solving taxonomic problems in Argentinean species of the genus Senecio (Asteraceae, Senecioneae)

Senecio L., the largest genus in the tribe Senecioneae (Asteraceae), contains a significant number of taxonomic difficulties, given that its boundaries are not clearly defined and species identification is sometimes complicated. A study was carried out to evaluate the importance of micromorphological characters in the resolution of such taxonomic problems. The study included 18 South American taxa from series Xerosenecio, Corymbosi and Otoperi. The characters studied include the stigmatic surface and apices of the stylar branches, the filament collar, base and appendages of the anthers, and the pollen shape, size, sculpture and aperture. The microcharacters of the stamens (filaments and anthers) and the presence of margo in the pollen provide taxonomically useful traits for the differentiation of related taxa and infraspecific entities in the genus Senecio. The mesoaperture in the pollen grain in eight Argentinean taxa of Senecio is recorded for the first time. Finally, unique floral microcharacters (sagittate anther base) and palynological features (cavea not evident, long spines) in S. otites were observed.

A Remarkable New Species of Microlicia (Melastomataceae) Including an Identification Key to Species of the Genus from the Chapada dos Veadeiros National Park, Goiás, Brazil

Abstract Microlicia stenodonoides is herein described and illustrated. It is distinguished from other Microlicia species by its remarkable dwarf arboreal habit, main stem 5–10 cm in diameter with leaf scars, leaves up to 4.5 cm long, grouped in the apex of terminal branches, and large flowers (up to 4 cm in diameter). The set of characters presented by M. stenodonoides is similar to that of species of the genus Stenodon. However, it is ascribed to the genus Microlicia especially due to stems without thickened cortex, 4–6-merous flowers with conspicuously dimorphic stamens, and visible ventral appendages. Comments on ecology, distribution, conservation status, period of flowering and fruiting of the new species are provided. Additionally, images and a key for the identification of species of Microlicia that occur in the Chapada dos Veadeiros National Park are presented.

Description of two new species of Ochtodes (Rhodophyta: Gigartinales) from Caribbean Mexico on the basis of morphological and molecular evidence

Abstract The species diversity of the red algal genus Ochtodes from Caribbean Mexico is reconsidered after a new collection in this region. A combined analysis of plastid rbcL sequences together with detailed morphological studies has confirmed the presence of two undescribed species in addition to Ochtodes secundiramea. Ochtodes akumalensis sp. nov. has abundant spiny branches, especially on the main axis, and robust cystocarps densely aggregate at the branch tips. In contrast, Ochtodes maguachaveziae sp. nov. lacks spiny branches and gland cells, and bears scattered cystocarps near the branch apices. Both species develop cruciately to obliquely divided zonate tetrasporangia. The molecular analysis showed that O. maguachaveziae and O. akumalensis represent separate taxonomic entities with a 1.8% sequence divergence between them. The description of two new species of Ochtodes from Caribbean Mexico suggest that our knowledge of the regional diversity of this genus is still incomplete.

Neosiphonia yongpilii sp. nov. (Rhodomelaceae, Rhodophyta), known as Neosiphonia simplex from Korea, with an emphasis on cystocarp development

:A critical re-examination of recent collections and herbarium specimens from Korea previously referred to Neosiphonia simplex (Hollenberg) Y.Lee showed them to be incorrectly identified. The phylogenetic analyses of rbcL sequences demonstrated that ‘N. simplex’ from Korea formed a clade distinct from other species in Polysiphonia sensu lato, and was clearly separate from N. simplex from California, with high sequence divergence. We propose N. simplex sensu Y.Lee from Korea as the new species, Neosiphonia yongpilii sp. nov. This novel species was characterized by severely twisted erect axes, with two to three pinkish sterile cells at apices of spermatangial branches. We also noted that lateral and basal sterile cell groups remain until maturation of the gonimoblast, and that the origin of inner and outer cortical filaments of the pericarp are central cells and pericentral cells respectively.

A Taxonomic Synthesis of the &lt;I&gt;Tovomita weddelliana&lt;/I&gt; (Clusiaceae) Species Complex

Abstract Phenetic analyses were the basis for recognizing several distinct species within the Tovomita weddelliana species complex, requiring resurrection of synonyms and description of new taxa. The Tovomita weddelliana complex is characterized vegetatively by terminal leaves clustered near the branch apex, subsessile leaves, stipule-like scars around branches (observed to form from the developmental breaking away of the leaf blade bases from the stem at maturity), and prominent midrib with inconspicuous lateral veins. The coriaceous persistent sepals may also help distinguish the complex. Numerous herbarium specimens spanning all morphological variation and geographic distribution in the complex were measured for continuous morphological characters and subjected to multivariate and univariate analyses. Measured traits included vegetative and reproductive characters such as internode length, branch diameter, leaf morphology, pedicel length and thickness, peduncle length, and bud diameter. Canonical varia...

Koenigia chuanzangensis(Polygonaceae), a New Species from Western Sichuan and Eastern Xizang, China

Koenigia chuanzangensis Z. Z. Zhou & Y. J. Min (Polygonaceae) from southeastern Xizang and western Sichuan Provinces, China, is described and illustrated. The new species morphologically resembles K. islandica L. and K. fertilis Maxim., sharing a habit of dwarf annual herbs, the leaf margins entire, pollen echinate and pantoporate, and the achene slightly exceeding a persistent perianth and brown, dull, narrowly ovoid, and biconvex. Koenigia chuanzangensis differs mainly in the pilose indument of its four tepals, tender stems, and leaves. Plants of the new species are usually 1–3 cm tall, commonly as separate plants, and leaf blades are ovate to elliptic and often as several fascicles at branch apices. In contrast, K. islandica and K. fertilis have glabrous plants that are taller, with glabrous adaxial leaf blade surfaces, and tepals that are especially glabrous. Stems of both species are tufted, with alternate leaves and leaf blades that are obovate.

The South African estuarine specialist Codium tenue (Bryopsidales, Chlorophyta) discovered in a south-western Australian estuary

Abstract Codium tenue, previously known reliably only from estuarine habitats in South Africa, is recorded from a similar habitat in the Walpole and Nornalup Inlet system, on the south coast of Western Australia. The Australian C. tenue has a repeatedly divaricately dichotomously branched thallus to 11.5 cm in height, with markedly compressed axes up to 1 cm in width at branch dichotomies, but distally attenuating to terete branch apices. Structurally, thalli have cortices with distinctive cuneate utricles up to 1310 μm long and 650 μm in diameter. Both the habit and structural morphology essentially agree with C. tenue as known in South Africa. Sequences generated from the Australian specimens are also wholly comparable with those of South African specimens newly generated in this study. While similarly disjunct South African/Western Australian distributions are known for other algae, that of C. tenue is particularly remarkable in that the species is apparently an estuarine specialist.

Optimization of the nitrate reductase activity assay for citrus trees

The aim of this study was to assess factors that can affect the in vivo and in vitro assays of the nitrate reductase activity (NRA) in sweet orange trees and then standardize conditions for tissue sampling and analysis. Seven-month-old plants grown in pots were used, of which, mature and healthy leaves between the third and the fifth position from the branch apex, stems, and roots were assessed. One half of each leaf was used for in vivo tests, and the other half was used for in vitro tests. In addition to varied incubation time and temperature, in vivo KNO3 and n-propanol concentrations and in vitro KNO3 and NADH concentrations were evaluated. The optimum conditions for the in vivo NRA assay in leaves were: 200 mmol L−1 KNO3 and 1 % n-propanol at 40 °C for 20 min. The highest leaf NRA occurred at 11:00 h for the in vivo assay and at 13:00 h for the in vitro assay, with both analysis showing similar results. Overestimation of the in vitro NRA occurred as compared to the in vivo analysis when accessed early morning and late afternoon. Branches bearing fruits show reduced NRA in young mature leaves, whereas sprouting significantly increases NRA in correspondent leaves. For the root assays, the optimized conditions for the NRA estimation were the same as for leaves. Although roots and stems (bark) have shown some NRA, it was six times lower than leaf NRA. Our data indicate that NO3 − reduction occurs mostly in leaves and there is a significant effect of daytime and leaf position in relation to fruit or sprouts on NRA of citrus trees.

A new species of Miconia (Miconieae, Melastomataceae) from the Brazilian Amazon

A new species of Miconia sect. Miconia subsection Seriatiflorae. was collected in Igapó Forest from the Purus-Madeira interfluve, in the state of Amazonas, Brazil. This new species, Miconia suberosa, can be distinguished from other species in the subsection by a variety of morphological features, namely: (i) treelet habit; (ii) deeply fissured bark with a thick cork; (iii) long dendritic hairs with short arms on young branches, inflorescences and leaves; (iv) petiolated leaves with rounded to obtuse bases, and ciliate margins, congested at the branch apices; and, (v) truncated stigmas.

Genotypic and Morphometric Effect on Fruit Oil Content in Seventeen Natural Population of Seabuckthorn (Hippophae rhamnoides L.) from Trans-Himalaya

Seventeen natural population of Seabuckthorn (SBT), which comprised 187 plants from trans-Himalaya, were studied to find out the variability, genotypic and morphometric effect on fruit oil content. The soft part of the fruit was found to be rich in oil content ranging from 3.16 to 17.3 %. A variation of 1–5.5-folds in oil content among the examined fruit and univariate two-way ANOVA analysis underlines the important role played by genetic background for determining oil content in SBT fruit. At population level, the highest oil content (12.02 %) was observed in TYX while the lowest was found in CHO population (6.84 %). The overall mean oil content was 9.74 %. Oil content in berry was significantly correlated with fruit weight (–0.203, p ≤ 0.05), fruit width (–0.195, p ≤ 0.05), tree habit (0.216, p ≤ 0.05), seed weight (–0.151, p ≤ 01), seed length (–0.177, p ≤ 0.01), leaf area (–0.162, p ≤ 0.01), number of leaf per 10 cm2 (–0.151, p ≤ 0.01), secondary branch apex (–0.144, p ≤ 0.01) and mature stem colour (0.186, p ≤ 0.01). However, none of the values were highly significant.