Deciduous Habit Research Articles

Phylogenomic insights into the origin and evolutionary history of evergreen broadleaved forests in East Asia under Cenozoic climate change.

The evergreen versus deciduous leaf habit is an important functional trait for adaptation of forest trees and has been hypothesized to be related to the evolutionary processes of the component species under paleoclimatic change, and potentially reflected in the dynamic history of evergreen broadleaved forests (EBLFs) in East Asia. However, knowledge about the shift of evergreen versus deciduous leaf with the impact of paleoclimatic change using genomic data remains rare. Here, we focus on the Litsea complex (Lauraceae), a key lineage with dominant species of EBLFs, to gain insights into how evergreen versus deciduous trait shifted, providing insights into the origin and historical dynamics of EBLFs in East Asia under Cenozoic climate change. We reconstructed a robust phylogeny of the Litsea complex using genome-wide single-nucleotide variants (SNVs) with eight clades resolved. Fossil-calibrated analyses, diversification rate shifts, ancestral habit, ecological niche modelling and climate niche reconstruction were employed to estimate its origin and diversification pattern. Taking into account studies on other plant lineages dominating EBLFs of East Asia, it was revealed that the prototype of EBLFs in East Asia probably emerged in the Early Eocene (55-50 million years ago [Ma]), facilitated by the greenhouse warming. As a response to the cooling and drying climate in the Middle to Late Eocene (48-38 Ma), deciduous habits were evolved in the dominant lineages of the EBLFs in East Asia. Up to the Early Miocene (23 Ma), the prevailing of East Asian monsoon increased the extreme seasonal precipitation and accelerated the emergence of evergreen habits of the dominant lineages, and ultimately shaped the vegetation resembling that of today.

Growth phenology adjusts to seasonal changes in water availability in coexisting evergreen and deciduous mediterranean oaks

Different leaf (evergreen vs. deciduous habit) and xylem (diffuse-vs. ring-porous wood) traits represent contrasting strategies to face seasonal changes in water availability and temperature. However, how contrasting leaf and xylem habits of coexisting tree species affect stem wood formation and tree-ring development remains poorly understood. Here, we investigated the spatio-temporal patterns of wood formation in two deciduous oaks (Quercus faginea and Quercus petraea) and two evergreen oaks (Quercus ilex and Quercus suber) coexisting in seasonally dry Mediterranean forests along an aridity gradient in Spain. We hypothesized that growth responses to drought and intra- and inter-annual growth patterns would differ between functional groups. We simulated intra- and inter-annual growth using a modified version of the Vaganov-Shashkin (VS) process-based, growth model. The VS model simulations were used to estimate growth changes under a high emission scenario (RCP 8.5) for the current distribution of the study oak species and to forecast their future performance under warm (4.8 ​°C) conditions in the Iberian Peninsula. Our simulations indicate that climate warming would induce a shortening of the ring-growth season and a reduction of radial growth in evergreen and deciduous Mediterranean oaks, particularly in dry sites from southern and eastern Iberia currently occupied by Q. ilex and Q. faginea. Evergreen oaks may better recover after dry periods than deciduous oaks by resuming growth after the summer drought. Low soil water availability in spring would be more detrimental to growth of deciduous oaks. Process-based growth models should be refined and validated to better forecast changes in tree growth as a function of climate.

Contrasting seasonal dynamics of dormancy, respiratory metabolism and cell cycle state in grapevine buds of a subtropical and Mediterranean climate

AbstractGrapevine (Vitis vinifera L.) is the most widely cultivated fruit crop worldwide, contributing substantially to rural economies. The production cycle and productivity depend on seasonal cues and can range from a strongly deciduous habit in cool‐temperate climates to evergreen in subtropical and tropical climates. The influence of the different seasonal conditions on the dynamics of the perennating bud, including the degree of growth and metabolic quiescence, cell cycle status and internal tissue oxygen status between different climatic zones is largely unknown. This knowledge is important for adapting to changing climate conditions and for crop expansion to wider regions. This study investigated the growth and metabolic physiology of the perennating bud of commercially grown cv. Flame Seedless table grapes from Mediterranean and subtropical climate in Western Australia, from summer until late winter. Climate data were obtained, showing differences in minimum (night) temperature between the two climates, reflected by differences in calculated chilling units. Bud dormancy increased during autumn of both climates;however, the onset and depth of dormancy of buds from the subtropical region were attenuated relative to the Mediterranean condition. Stark contrasts were also observed in metabolism. The respiration of subtropical‐grown buds increased over fivefold during late autumn and winter, while that of Mediterranean‐grown buds increased less than twofold. This was also reflected in less desiccation of the subtropical‐grown buds, and an apparently greater degree of hypoxia within the bud during late winter, prior to bud burst. Collectively, these data show pronounced differences in growth and metabolic physiology of commercially grown table grapes, which provide a foundation for investigating the influence of differing climate and seasonality on the growth and productivity of table grapes and how these may be managed through breeding and agronomy.

Time-varying response of fine root growth to soil temperature and soil moisture in cypress and deciduous oak forests.

Fine root phenology is controlled by complex mechanisms associated with aboveground phenological events and environmental conditions, and therefore, elucidating fine root responses to changing environments remains difficult without considering the dynamics within and among years. This study evaluated the response of fine root growth at variable time scales to the surrounding environments of soil temperature and moisture at ecosystem scales. Optical scanners were used to measure fine root production over 4years in two forests dominated by either cypress or deciduous oak trees. Correlations between fine root production and soil temperature and moisture were analyzed using the state-space model. Fine root phenology varied among years in the cypress stand and showed stable growth patterns in the oak stand as production peaked in spring every year. Soil temperature had a dominant influence on fine root production, while soil moisture enhanced fine root growth especially in the oak stand. Fine root responses to both soil temperature and moisture peaked during the early growing season, indicating its own temperature hysteresis that means different responses under same temperature within a year. The time-varying response of fine root growth to external factors is a key perspective to explain fine root growth mechanisms, and whether evergreen or deciduous habits differentiates the fine root phenology due to a linkage between above- and belowground resource dynamics.

Huchimingia, a new genus segregated from Millettia (Leguminosae, Millettieae) based on morphological and molecular evidence

Millettia Wight & Arn. is a heterogeneous genus within the tribe Millettieae (Leguminosae) and has long been used as a repository to accommodate all undistinctive species of the tribe with elastically dehiscent pods. Millettia sect. Podocarpae Dunn is representative of the heterogeneous genus. This section includes five Asian species that have a unique combination of characters that distinguishes them from all other species of the genus, including the deciduous tree habit, conspicuous buds covered with scales, pseudoracemes or pseudopanicles with very indistinct brachyblasts, two flowers per brachyblast, conspicuous large bracts, ebracteolate calyx, well-developed hypanthium, stipitate ovary, and flat, stipitate and dehiscent pods. Our molecular phylogeny based on plastid matK and nuclear ribosomal ITS sequences also suggested the section is clearly monophyletic, separate from other congeneric species, and is most closely related to Antheroporum Gagnep. with inflated, vacuous pods and Ohashia X.Y. Zhu & R.P. Zhang with indehiscent flat pods. Therefore, we propose a new genus, Huchimingia Z.Q. Song & Shi J. Li, to accommodate this distinct section.

The Ravenscrag Butte flora: Paleoclimate and paleoecology of an early Paleocene (Danian) warm-temperate deciduous forest near the vanishing inland Cannonball Seaway

The Ravenscrag Butte flora in southwestern Saskatchewan, Canada, provides a record of an early Paleocene (Danian) forest ecosystem that followed the K-Pg boundary event. Plant macrofossil collections were investigated to assess the paleoclimate and paleoecology of the forest. An ensemble approach to climate analysis using leaf physiognomic and nearest living relative methods indicates that the forest grew under warm and wet temperate conditions, with mild frost-free winters, and did not experience a significant drying season—although some precipitation seasonality is indicated. Reconstructed leaf mass per area suggests that the woody broadleaf dicot flora had an entirely deciduous habit, despite temperature and precipitation conditions that were suitable for evergreen taxa. The reconstructed climate of the Ravenscrag Butte flora is similar to modern coastal climates with proximity to an inland sea (e.g., Croatia and Slovenia on the Adriatic Sea and Georgia on the Black Sea), suggesting that the Ravenscrag Butte flora was influenced by its proximity to the western margin of the early Paleocene Cannonball Seaway. The leaf physiognomy of the Ravenscrag Butte flora is most similar to contemporaneous fossil macrofloras from throughout western and northern North America, which suggests physiognomic homogeneity over broad latitudes during the early Paleocene, a potential consequence of vegetation reorganization after the K-Pg event.

Florística e fenologia de dez espécies do extrato arbustivo-arbóreo em torno do Apiário-Escola da Universidade Estadual de Alagoas (UNEAL)

RESUMO: Os padrões fenológicos predominantes para a Caatinga são marcados pela rápida reposição das copas durante o início do período chuvoso e por hábito caducifólio no início do período seco. O processo de floração e frutificação está diretamente relacionado ao período de chuvas e principalmente em um ambiente com muitas variações como a Caatinga. O presente trabalho teve por objetivo caracterizar a flora da área onde o apiário/escola está localizado, bem como a fenologia de dez espécies representativas do extrato arbustivoarbóreo de ocorrência em área de Caatinga na mesorregião do Semiárido alagoano. O estudo foi conduzido na estação experimental Curral do Meio (Sementeira), situada no município de Santana do Ipanema, mesorregião do Sertão alagoano. As observações foram realizadas mensalmente no período de abril de 2019 a janeiro de 2020, onde foram registrados dados de floração (botões florais e flores em antese), frutificação (frutos em desenvolvimento e frutos maduros prontos para dispersão), brotamento (surgimento de folhas novas) e queda foliar. Foram constatados nas 50 parcelas amostradas da área experimental 1.626 indivíduos, os quais estão distribuídos em 18 famílias, 36 gêneros, 40 espécies e dois indivíduos indeterminados. Durante o presente estudo e de acordo com os dados obtidos, pode-se verificar que, para as dez espécies, a produção de folhas novas ocorreu durante o período chuvoso e início da estação seca, o que indica que a fase de brotamento está diretamente relacionada com a precipitação. Porém, quando se observa a senescência foliar, pode-se analisar que algumas espécies concentraram as quedas das folhas no período seco e início da estação chuvosa, a exemplo da Catingueira, Baraúna e Umburana de Cheiro, enquanto que no Pereiro esta fenofases foi registrada praticamente ao longo de quase todo o período, o que indica que a espécie apresenta substituição gradual das folhas.
 PALAVRAS-CHAVE: apicultura, flora nativa, Caatinga, atividade sustentável.

Pyrus calleryana allometric equations and stand structure in southwestern Ohio and northern Kentucky

AbstractCallery pear (Pyrus calleryana Decne.), a native of eastern Asia, has recently emerged as an important woody invader in much of the eastern United States. Little is known about its ecology in its new range. Its shade tolerance may be an important indicator of areas it is likely to invade. In this study, allometric equations were first developed to predict aboveground biomass components, including wood, branches, bark, leaves, and fruit, from diameter at stump height (dsh; 25 cm), by destructively harvesting 13 trees, ranging from 0.1 to 19.3 cm dsh. Then, a total of 23 wild-grown stands in the northern Kentucky/southwestern Ohio region were surveyed, with diameters of all woody stems sampled. Pyrus calleryana density, basal area, aboveground biomass, stand density index, size distribution inequality, and importance value were calculated for each site. Two-factor Weibull distributions were fit to diameter distributions. Allometric equations provided good fits for total aboveground biomass as well as individual components. Aboveground biomass levels fell below mean levels of native forest stands found in the United States. Stand density indices yielded values typical of shade-intolerant or midtolerant species. Stands with smaller trees generally had steeply declining monotonic diameter distributions, while stands with larger trees trended toward positively skewed monotonic distributions. These findings are consistent with a species that is either shade-intolerant or midtolerant. Thus, while this species is expected to invade open or disturbed areas, it is not expected to be an important invader under forest canopies. However, its extended deciduous habit is one shared by other understory woody invaders, and so this may allow it to survive under forest canopies.

Heterophyllous Shoots of Japanese Larch Trees: The Seasonal and Yearly Variation in CO2 Assimilation Capacity of the Canopy Top with Changing Environment.

Japanese larch (Larix kaempferi = L. leptolepis) is often characterized by its high growth rate with heterophyllous shoots, but the functional differences of heterophyllous shoots still remain unclear. Recently, abrupt high temperature and drought during spring induced high photosynthetic rate via change in leaf morphology of the deciduous habit. In order to reveal the photosynthetic characteristics of both short and long-shoot needles of sunny canopy of the larch trees using a canopy tower, we calculated the seasonal change of gas exchange characters and leaf mass per area (LMA) and foliar nitrogen content (N) of heterophyllous needles: short and long-shoot needles over 3 years. No marked difference in light-saturated photosynthetic rates (Psat) was observed between short and long shoots after leaf maturation to yellowing, although the difference was obvious in a specific year, which only shows that seasonal change in temperature and soil moisture determines the in situ photosynthetic capacity of needles. The large annual and seasonal variations in Psat in both shoots were found to be mainly determined by climatic variations, while shoot types determined the strategy of their photosynthetic N utilization as well as the stomatal regulation.

Assessment of risk factors for early childhood caries at different ages in Shandong, China and reflections on oral health education: a cross-sectional study

BackgroundThe high prevalence of early childhood caries (ECC) is widespread around the world, and oral health education (OHE) plays a vital role in preventing ECC. Numerous studies on ECC risk factor assessment have assisted us in enriching the content of OHE. The objective of this study was to further assess independent risk factors for ECC at different ages to provide evidence and insights for OHE.MethodsChildren aged 3–5 years old (N = 1301) in Shandong Province were enrolled in this cross-sectional study. Data about oral health status and caregivers’ oral health knowledge, attitude, and practice (KAP) were extracted from the 4th National Oral Health Survey of China. The associations between ECC prevalence and various KAP variables were tested with chi-square tests, bivariate analysis and multivariable logistic regression analyses.ResultsThe ECC prevalence in Shandong Province was 64.6%, and the dmft mean was 3.15. The independent variables with an increased risk for ECC were age, feeding method within 6 months of birth, bedtime sugar frequency, experience of toothache over the past year and dental visits (P < 0.05, chi-square tests). Complete breastfeeding within 6 months of birth primarily contributed to the high ECC risk of the 3-year-old group (OR: 3.39, 95% CI: 1.41–8.17), while high frequency bedtime sweet consumption mainly contributed to that of the 5-year-old group (OR: 3.22, 95% CI: 1.03–10.06; logistic regression analysis). Tooth brushing was not associated with ECC in this study, and some positive knowledge and attitude variables were positively correlated with a high risk of ECC.ConclusionThese data provide evidence to suggest that the ECC-related risk factors at different ages are inconsistent, which provides some insights for OHE. We should highlight the effects of feeding methods in the early stages of deciduous dentition and sugar habits in the late stages of deciduous dentition on ECC, as well as encourage preventive dental visit and supplemental training for oral health practices.

Paleoclimate and paleoecology of the latest Eocene Florissant flora of central Colorado, U.S.A.

The uppermost Eocene Florissant Formation of central Colorado, U.S.A. contains a diverse flora and fauna preserved in lacustrine facies and represents a key episode in Earth history immediately preceding the Eocene-Oligocene boundary. Laminated shales contain impressions of non-monocot angiosperm leaves that were used to estimate paleoecological and paleoclimatic parameters using leaf physiognomic methods including: leaf mass per area (MA), digital leaf physiognomy (DiLP), leaf margin analysis (LMA), and leaf area analysis (LAA). The majority (58%) of the morphotypes analyzed for MA suggested a semi-evergreen leaf lifespan, whereas another 27% indicated a deciduous habit and 15% an evergreen habit. There was no significant relationship between MA and insect damage based on a small subset of Florissant's leaves. Higher MA values (~73% of leaves ≥ one-year lifespan), coupled with a tendency toward long and narrow leaf shapes and small leaf areas, indicate the existence of sclerophyllous vegetation. Using the global regression for mean annual temperature (MAT), the DiLP estimate of MAT was anomalously cold: 5.5 ± 4 °C. However, using a Northern Hemisphere regression the DiLP MAT estimate of 11.6 ± 3.3 °C was more plausible. Using DiLP, mean annual precipitation (MAP) was estimated at 740 + 608/−334 mm∙yr−1, which supports dry conditions. Estimates for MAT and MAP using the univariate LMA and LAA methods overlapped within uncertainty of the DiLP results. In addition, those taxa classified as growing in wet areas (riparian) had significantly more teeth than non-riparian taxa. These paleoclimatic and paleoecological results suggest that outside the riparian forest, the Florissant flora sampled a seasonally dry temperate sclerophyllous shrubland to woodland, perhaps similar to modern chaparral forests, in the western interior of the U.S.A. just before the transition into the cooler Oligocene.

Rehderodendron truongsonense (Styracaceae), a new species from Vietnam

Rehderodendron truongsonense, a new species from Vietnam, is described and illustrated. In the treatment of the Styracaceae for the Flore du Cambodge, du Laos, et du Viêtnam, specimens of this species were recognized as R. macrocarpum Hu. These specimens clearly differ from R. macrocarpum, however, as well as from all other species of Rehderodendron (where these characters are known) by, e.g., an evergreen versus deciduous habit, fewer secondary veins of the leaf blade, shorter inflorescences and corolla lobes, large and conspicuous lowermost bracteoles, the presence of eight ovules per carpel, and a fruit with ca. 10 to 20 ribs that are indistinct. Phylogenetic analysis based on five chloroplast DNA regions (clpP-psbB, ndhD-psaC-ndhE-ndhG, rpl22-rps19, rps18-rpl20, and psbI-trnS-GCU) placed the new species as nested within Rehderodendron and sister to R. gongshanense. This new species is endemic to the Truong Son Mountain Range, from which the epithet is derived, and we assign it an IUCN Red List preliminary status as Near Threatened.

Modelling the seasonal changes in the gas exchange response to CO2 in relation to short-term leaf temperature changes in Vitis vinifera cv. Shiraz grapevines grown in outdoor conditions

Effects of temperature on the photosynthetic response of Vitis vinifera cv. Shiraz leaves to CO2 were investigated across the growing season and modelling was used to determine relationships between photosynthesis and seasonal climate. Results indicated that photosynthetic rates declined from spring to summer, conforming to the deciduous habit of grapevines. Rates of ribulose 1,5-bisphosphate (RuBP) carboxylation and regeneration increased in a temperature dependent pattern throughout the season. However, the maximum rates decreased as the season progressed. There were also marked decreases in temperature sensitivity for each of these processes, consistent with the decreases occurring faster at high compared to low temperatures. There were no correlations between the seasonal climate and each of these photosynthetic processes but the effect of day was significant in all cases. CO2 saturated rates of photosynthesis (Amax) across the season were highly correlated with the maximum rates of RuBP carboxylation and regeneration. The transition temperature between RuBP regeneration and RuBP carboxylation-limited assimilation varied across the growing season, from 23 °C in spring, 35 °C in mid-summer and 30 °C at harvest and were highly correlated with mean day temperature. This suggested dynamic control of assimilation by carboxylation and regeneration processes occurred in these grapevines in tune with the seasonal climate.

Shifting global Larix distributions: Northern expansion and southern retraction as species respond to changing climate

AbstractAimRecent and rapid warming is reorganizing terrestrial vegetation, creating novel species assemblages, and shifting range limits. Relative to the evergreen species that currently dominate much of the boreal forest landscape, Larix (larch) distributions may be particularly responsive to climatic change due to their deciduous habit, and quick growth and reproduction. Here, we amassed data from 83 studies to describe and explain observed patterns of Larix range shifts under contemporary climate change.LocationNorthern hemisphere.TaxonSpecies of the genus Larix, deciduous gymnosperms.MethodsWith 181 observations of Larix range limit dynamics, we used five distribution parameters (tree line advance, stand infilling, tree line recession, stand thinning, no response) and their determinants (climate, land use change, natural disturbance) to describe and explain observed patterns of Larix range shifts under contemporary climate change. We ran a redundancy analysis on the matrix of five distribution parameters considered with other climatic and nonclimatic parameters as explanatory variables. We also characterized the climatic niche of Larix species (temperature and precipitation) and how the niche has changed during the 20th century.ResultsOf 173 sites studied over the full distribution of Larix, 63% experienced Larix population increases, 18% had population decreases, and no response was detected at 19% of sites. Latitudinal Larix tree lines in Siberia and North America appear to be infilling and shifting their distributions northward, whereas Larix recession and thinning was more common in southern regions, suggesting southern populations may be experiencing greater drought stress than their northern counterparts. Climatic niches of most Larix species shifted towards warmer and wetter conditions, with tree line advance/forest infilling in cool/dry climate space, and recession/thinning in warm/dry space.Main conclusionsNorthern expansion is underway or seems imminent for boreal Larix species, primarily L. laricina in North America. Retraction in southern regions and disappearance of some mountainous populations may be inevitable due to their narrow ecological niches. Species restricted to mountainous habitats may expand locally, though will likely not contribute to broad scale range expansion. These changes will depend on suitable climate, disturbance, and dispersal mechanisms.

Species-specific molecular signature of Commiphora species of Saudi Arabia inferred from internal transcribed spacer sequences of nuclear ribosomal DNA.

The deciduous habit and tendency to produce flowers prior to developing leaves, and a predominantly dioecious system of breeding in the genus Commiphora leads to difficulties in its taxonomic identification at species level. The characteristics of easy amplification by universal primer, shorter length and higher discrimination power at the species level makes the internal transcribed spacer (ITS) sequence of nuclear ribosomal DNA (nrDNA) to a smart gene for generating species-specific phylogenetic inferences in most of the plants groups. The present study deals the ITS sequence of nrDNA based molecular genotyping of seven species of the genus Commiphora of Saudi Arabia. The molecular phylogenetic analysis of ITS sequences of nrDNA of Commiphora species distributed in Saudi Arabia reveals the the occurrence of C. madagascariens in Saudi Arabia.

Effects of charcoal hearth soil on forest regeneration: Evidence from a two-year experiment on tree seedlings

Production of wood charcoal is a traditional form of forest use that lasted for millennia in most temperate regions, vanishing only some decades ago in the Mediterranean countries. Here, the abandoned charcoal hearths form a network of microhabitats with peculiar vegetation and soil conditions. Previous observational studies showed that establishment of woody species at these sites is severely hindered for unknown reasons. To test the effects of charcoal hearth soil on tree growth we used a common garden experiment with three major Euro-Mediterranean forest trees with different traits and ecology, one evergreen (Quercus ilex, holm oak) and two deciduous (Fagus sylvatica, beech, and Quercus cerris, Turkey oak). These were sown on control and charcoal-enriched soil collected in forest hearths abandoned since decades. Seed germination, seedling growth, photosynthetic efficiency and mortality were measured over a period of two years. Some responses were species-specific, while others were possibly associated to key traits such as evergreen vs. deciduous habit. Although charcoal soil effects were mainly positive on growth rate (height increase), they were mostly negative on germination of beech seeds, survival of holm oak seedlings, and photosynthetic efficiency. Although total biomass was not significantly affected, the root:shoot ratio was increased as a possible effect of physiological drought on hearth soil. These results support field-based evidence that the long persistence of charcoal remains in the soil may be not a favourable condition for forest regeneration. Management implications concern the use of biochar practices to promote forest restoration, which should be further tested on a wide range of species in different life-stages before applications in the field, also considering its long-term consequences.

Convergence, Consilience, and the Evolution of Temperate Deciduous Forests.

The deciduous habit of northern temperate trees and shrubs provides one of the most obvious examples of convergent evolution, but how did it evolve? Hypotheses based on the fossil record posit that deciduousness evolved first in response to drought or darkness and preadapted certain lineages as cold climates spread. An alternative is that evergreens first established in freezing environments and later evolved the deciduous habit. We monitored phenological patterns of 20 species of Viburnum spanning tropical, lucidophyllous (subtropical montane and warm temperate), and cool temperate Asian forests. In lucidophyllous forests, all viburnums were evergreen plants that exhibited coordinated leaf flushes with the onset of the rainy season but varied greatly in the timing of leaf senescence. In contrast, deciduous species exhibited tight coordination of both flushing and senescence, and we found a perfect correlation between the deciduous habit and prolonged annual freezing. In contrast to previous stepwise hypotheses, a consilience of independent lines of evidence supports a lockstep model in which deciduousness evolved in situ, in parallel, and concurrent with a gradual cooling climate. A pervasive selective force combined with the elevated evolutionary accessibility of a particular response may explain the massive convergence of adaptive strategies that characterizes the world's biomes.

A new Pararistolochia Hutch. &amp; Dalziel (Aristolochiaceae) from the Beanka Tsingy (western Madagascar)

Abstract Luino I., M.W. Callmander, O. Poncy, S. Da-Giau & L. Gautier (2016). A new Pararistolochia Hutch. & Dalziel (Aristolochiaceae) from the Beanka tsingy (western Madagascar). Candollea 71 : 135–141. In English, English and French abstracts. DOI : http ://dx.doi.org/10.15553/c2016v711a16 Pararistolochia Hutc. & Dalziel (Aristolochiaceae) is a genus that comprised about 35 species known until present from continental Africa and Australasia. Two recent inventories carried in the limestone massif of Beanka in western Madagascar have led to the detection of a new species that we describe here as Pararistolochia enricoi Luino, L. Gaut. & Callm. This impressive liana is until today the only malagasy representative of the genus. The deciduous habit, together with the two-lobed perianth and the presence of trichomes covering most parts of the plant are exclusive characters that clearly distinguish Pararistolochia enricoi within the genus. The new species is provided with a preliminary risk assessment of its ...

Photoperiodic phytochrome-mediated vegetative growth responses of container-grown citrus nursery trees

In Florida, most citrus trees are grown on rootstocks with trifoliate orange parentage. Nurserymen have long noted that these rootstocks exhibit much slower growth during the winter than their non-trifoliate counterparts (e.g., ‘Volkamer’ lemon, ‘Sour Orange’). Since 2007 citrus nursery trees in Florida must be grown in greenhouses to protect them from the Asian citrus psyllid, the vector of huanglongbing (citrus greening). Greenhouse production of citrus nursery trees has greatly increased production costs and, thus, the desire to determine why trifoliate-type rootstocks grow poorly during the winter. We hypothesized that trifoliate-type rootstocks, because of their deciduous habit, respond to photoperiod and exhibit slow growth under short days (photoperiods <12h). Our objective was to determine the effect of photoperiod on the growth of container-grown trees of the two most common trifoliate-type rootstocks, ‘Carrizo’ citrange and ‘Swingle’ citrumelo with and without ‘Hamlin’ sweet orange scions. Three weeks after budding, all trees were placed in growth chambers under three different photoperiods: short days (SD – 10h photoperiod), long days (LD – 14h) and short days+night interrupt (SD-NI – 10h photoperiod+1h night interrupt) for 14 weeks, and maintained at 28/21°C day/night temperature. All trees, regardless of being budded or not, had reduced growth under SD conditions, whereas the trees under SD-NI grew similar to those under LD. Average tree growth during the 14-weeks was 19, 52 and 55cm, across all rootstock-scion combinations for SD, LD and SD-NI treatments, respectively. The difference in growth between budded and non-budded trees in the SD treatment was not significant, but was highly significant in LD and SD-NI. Across rootstock-scion combinations, the average numbers of new nodes produced per tree were 13, 30 and 32 nodes in the SD, LD and SD-NI treatments, respectively, indicating that the increased growth under LD and SD-NI conditions was not simply a result of internode elongation. Net CO2 assimilation was higher under the SD and SD-NI treatments compared with LD, but there were no significant differences in whole-plant total nonstructural carbohydrate concentrations as a result. The ability of a 1-h night interrupt to overcome the SD response indicates that the photoperiod effect observed is a phytochrome-mediated response.

Molecular phylogeny of Cotoneaster (Rosaceae) inferred from nuclear ITS and multiple chloroplast sequences

Cotoneaster Medik. (Rosaceae, Maloideae) is distributed in Europe, North Africa, and temperate areas of Asia except Japan. Members of the genus exhibit considerable morphological variation. The infrageneric classification is also obscured by polyploidy, hybridization, and apomixis. In this study, phylogenetic analyses were conducted to test infrageneric classifications of this genus using DNA sequence data from the nuclear ITS (nrITS) region and three chloroplast intergenic spacer regions. Maximum parsimony and Bayesian inference analyses of both datasets agreed with the two sections/subgenera of Koehne’s classification system, and suggested that four subsections (Microphylli, Chaenopetalum, Adpressi, and Cotoneaster) and the series of Koehne’s classification system were non-monophyletic. The incongruence length difference test indicated that the nrITS and cpDNA datasets were significantly incongruent (P = 0.001), and the placement of 14 species was discordant in phylogenetic trees derived from the two datasets. Within Cotoneaster, hybridization was indicated to be an important factor contributing to the incongruence between the nrITS and cpDNA data. By mapping nine morphological characters onto the combined nrITS–cpDNA phylogenetic tree, we inferred that a deciduous habit, glabrous fruit, white anthers, erect and light pink petals, and white filaments are plesiomorphic character states in Cotoneaster.