Herbaceous Annuals Research Articles

Ectomycorrhizal fungal communities associated with Crocanthemum and Lechea (Cistaceae) in subtropical Florida sandhill habitats.

Cistaceae are shrubs, subshrubs and herbs that often occur in stressful, fire-prone or disturbed environments and form ectomycorrhizal (ECM) associations with symbiotic fungi. Although some Cistaceae are long-lived shrubs that grow to significant size, others are herbaceous annuals or short-lived plants. Thus, Cistaceae are atypical ECM hosts that are fundamentally different in their biology from trees that are the more typically studied ECM hosts. The Mediterranean region is the center of diversity for Cistaceae and the ectomycorrhizal fungi associated with Cistaceae hosts have primarily been studied in Europe, North Africa, and the Middle East. Mediterranean Cistaceae often host diverse communities of ECM fungi, but they also act as hosts for some ECM fungi that putatively show host-specificity or strong host preference for Cistaceae (including species of Delastria, Hebeloma, Terfezia, and Tirmania). The ECM associations of Cistaceae in North America, however, remain highly understudied. Here we use fungal DNA metabarcoding to document the ectomycorrhizal fungal communities associated with Crocanthemum and Lechea (Cistaceae) in open, fire-prone sandhill habitats in north Florida. At each site we also sampled nearby Pinus to determine whether small, herbaceous Cistaceae have specialized ECM fungi or whether they share their ECM fungal community with nearby pines. The ECM communities of Florida Cistaceae are dominated by Cenococcum (Ascomycota) and Russula (Basidiomycota) species but were also significantly associated with Delastria, an understudied genus of mostly truffle-like Pezizales (Ascomycota). Although many Cistaceae ECM fungi were shared with neighboring pines, the ECM communities with Cistaceae were nonetheless significantly different than those of pines.

Effect of simulated extreme rainfall on the vegetative phenology of perennial and annual herbaceous plants from a Brazilian dry forest.

Detecting changes in the phenological responses of herbaceous species as a function of predicted climate change is important for forecasting future scenarios for the functioning of dry tropical forests, especially when predicting an increase in the frequency and intensity of extreme droughts. Because of the sensitivity of plants to water availability, our study hypothesizes that if years become drier or wetter, herbaceous plants will synchronously change the onset, duration, and intensity of their vegetative phenophases. We used a historical series of 60 years of precipitation observations for the Caatinga vegetation to define daily average of precipitation for rainy (Twet), median (Tcontrol), and dry (Tdry) years. We simulated past average daily rainfall (Twet, Tcontrol, and Tdry) while growing two herbaceous perennials and two herbaceous annuals. We monitored plant growth and measured the activity (absence or presence) and intensity of vegetative phenophases. We used circular statistical analysis to assess differences between treatments. Our results revealed that leaf production was seasonal but relatively uniform for perennial species and highly seasonal (wet season) for annual species. Simulated dry years induced lower leaf emergence concentrated over a few months in annual species, but this effect was more strongly significant in one of the two perennial species. Both annual and perennial species can experience delayed and less intense leaf abscission during the rainy season in years with below-average precipitation. In contrast, large voluminous rains in years with above-average precipitation can accelerate and intensify the process of leaf renewal. If future precipitation reductions occur, the changes in phenological response indicate that the cover of annual and perennial herbaceous species in this study will likely decrease, altering the landscape and functioning of dry tropical forests. However, the potential trade-offs observed may help populations of these species to persist during years of severe drought in the Caatinga.

Адвентивный компонент банка семян некоторых лесных сообществ островов реки Волги

The paper presents the results of studying the adventive component of the seed bank of the Oak Mane Island of the Volga River Valley in the vicinity of the city of Saratov. Seeds of 12 species of adventitious plants were registered in the seed bank of the studied forest communities. All identified seeds belong to plant species belonging to one department of Magnoliophyta, 8 families and 12 genera. The Asteraceae family plays a leading role in the taxonomic spectrum of adventitious seed bank species (42%). Mesophytic mesotrophic (63.6%) heliophytic grouping of plants dominates in relation to ecological regimes. Mostly there are species of North American origin (60%). Herbaceous annuals (33% of species) and trees (34%) play a significant role. A significant impact on the composition of seed banks was caused by the unintentional entry of seeds of plants that are “refugees from culture” into this territory. Most adventitious plants, represented by both vegetating individuals and seeds, have penetrated into natural cenoses, and in some cases even partially transformed their structure, which is due to their reproductive potential and ability to compete with representatives of the native flora of natural habitats. In the studied area, foci of the concentration of seeds of drift plants in different communities were revealed, in continuous placement (Acer negundo, Bidens frondosa and Populus alba), disjunctive (Fraxinus pennsylvanica, Parthenocissus quinquefolia, Echinocystis lobáta, Impatiens glandulifera), sporadic – Ambrosia trifida, Artemisia sieversiana, Crataegus sanguinea, Inula caspica and Ulmus pumila. An increase in the number of adventitious species presented in the seed bank was recorded, but the number of seeds decreased.

Observations on the effects of fire on East African Afroalpine vegetation

AbstractAn accidental fire that affected vegetation across an elevational gradient on the eastern slope of Mount Muhabura in Volcanoes National Park (Rwanda) provided a unique opportunity to compare the richness, diversity, composition and elevational distribution of plant taxa across burned and unburned Afromontane habitats 1 and 9 years after the fire. Although richness and local α‐diversity were comparable, community composition differed across burned and unburned habitats with the former having a lower cover of woody perennials and a higher cover of herbaceous annuals. We confirm the role of fire in shaping Afromontane vegetation, which is important information for protected area management.

Structure and seasonal dynamics of the adventitious fraction of the flora of "Gagarin Park" (Dnipro)

Alien species significantly change the structure and functions of green spaces in cities, can affect people's health and cause economic damage to the urban economy. Studies show that the flora of urboecosystems has been significantly transformed by human economic activity, which causes the spread and rapid advancement of invasive species and the reduction of phytodiversity. The object of the study was the grass cover of "Gagarin Park" (Dnipro). The species composition and projective cover of vascular plants of the grass layer were studied in April–May and June–July 2021–2022. Experimental sites measuring 3×3 m were laid in different parts of the park, the total number of spring descriptions – 420, summer – 230. Field work was carried out using classic geobotanical methods of research (route-reconnaissance, detailed-route, geobotanical description, establishment of test plots). 121 species of vascular plants belonging to 45 families were recorded in the grass cover of Gagarin Park (Dnipro). The most numerous are Asteraceae (17%) and Poaceae (12%). At the beginning of the growing season, the families Lamiaceae, Rosaceae, and Scrophulariaceae are characterized by the richest species composition; in the summer, the role of Aceraceae, Brassicaceae, Caryophyllaceae, Fabaceae, and Rosaceae increases. 42 adventive species belonging to 29 families were found in the grass layer of the park. The share of adventitious plants increases during the growing season from 22 to 37% in species composition. In spring, representatives of the Asteraceae, Lamiaceae, and Scrophulariaceae families predominate among the 12 registered adventives (15% each), in summer the number of adventive species increases to 36, and the Asteraceae family dominates (28%). The spectrum of life forms is dominated by herbaceous annuals - 33.3% and perennials - 23.8%, as well as numerous seedlings of woody species – 21.4%. There are much fewer biennials (9.5%) and vines (7.1%), biennials and shrubs are represented singly. American species (33.4%) are the leaders in species diversity by origin: North American and South American migroelements have 13 and 1 species, respectively. There are also numerous representatives of Mediterranean (23.8%) and Asian origin (21.4%). This ratio is more typical for the group of invasive plants than for alien species of Ukraine as a whole. The predominance of species of American origin indicates that plants that grow in similar conditions in their original habitat are best adapted to new conditions. This confirms the proposition that species with a transcontinental habitat type have greater opportunities for adaptation to new conditions than species originating from adjacent floristic regions. The spectrum of adventitious plant biomorphs in «Gagarin Park» is dominated by annuals in the spring, but in the summer the share of woody species seedlings increases. Among the life forms according to K. Raunkier (or climamorph), the largest percentage belongs to therophytes in spring, and phanerophytes and hemcryptophytes in summer. The dominant group of biomorphs is vegetatively immobile plants – 80% in spring and 55% in summer. Cenomorphic analysis of the grass cover indicates the dominance of ruderants throughout the season, which is natural for the analyzed group of adventive plants. Xeromesophytes and mesophytes predominate among hygromorphs, and mesotrophs among tromorphs, which indicates favorable conditions for the growth of tree vegetation in the park. Among the heliomorphs, heliophytes and scioheliophytes predominate, which reflects the increased level of illumination under the canopy of woody park plants compared to typical forest phytocenoses. In the grass cover of the «Gagarin park», representatives of alien species with high and medium indicators of phytocenotic activity were found. Among them, most of them belong to invasive plants and transformative species – Impatiens parviflora, Solidago canadensis, Acer negundo, Erigeron annuus, they are the ones that pose a threat to the phytodiversity of the studied ecosystem, inhibit naturalization processes and require measures to regulate the number of populations. Due to the detected increased phytocenotic activity of Partenocissus quinquefolia and Vitis vinifera, we state that these species acquire invasive properties, therefore they require the attention of researchers and monitoring.

Contrasting anatomical and biochemical controls on mesophyll conductance across plant functional types.

Mesophyll conductance (gm ) limits photosynthesis by restricting CO2 diffusion between the substomatal cavities and chloroplasts. Although it is known that gm is determined by both leaf anatomical and biochemical traits, their relative contribution across plant functional types (PFTs) is still unclear. We compiled a dataset of gm measurements and concomitant leaf traits in unstressed plants comprising 563 studies and 617 species from all major PFTs. We investigated to what extent gm limits photosynthesis across PFTs, how gm relates to structural, anatomical, biochemical, and physiological leaf properties, and whether these relationships differ among PFTs. We found that gm imposes a significant limitation to photosynthesis in all C3 PFTs, ranging from 10-30% in most herbaceous annuals to 25-50% in woody evergreens. Anatomical leaf traits explained a significant proportion of the variation in gm (R2 > 0.3) in all PFTs except annual herbs, in which gm is more strongly related to biochemical factors associated with leaf nitrogen and potassium content. Our results underline the need to elucidate mechanisms underlying the global variability of gm . We emphasise the underestimated potential of gm for improving photosynthesis in crops and identify modifications in leaf biochemistry as the most promising pathway for increasing gm in these species.

A foliar spray application of indole-3-butyric acid promotes rooting of herbaceous annual cuttings similarly or better than a basal dip

Foliar rooting hormone applications containing indole-3-butyric acid (IBA) to unrooted vegetative cuttings have gained popularity as they reduce labor costs and the risk of spreading diseases compared to standard basal dips. The objective of this study was to quantify if foliar applied 20% IBA promotes adventitious rooting of herbaceous annuals similarly to a basal dip application of IBA + 1-napthaleneacetic acid (NAA). Dahlia (Dahlia pinnata) Venti™ ‘Passion Fruit’, osteospermum (Osteospermum ecklonis) Serenity™ ‘Lavender Frost’, scaevola (Scaevola aemula) Scalora® ‘Brilliant’ and geranium (Pelargonium × hortorum) Sunrise™ ‘Lavender + Red Eye’ cuttings received a foliar spray of 0, 150, 300, or 600 mg·L–1 IBA at 0.2 L·m–2; 150 or 300 mg·L–1 IBA at 0.8 L·m–2; or a basal dip of 100 mg·L–1 + 50 mg·L–1 or 200 mg·L–1 + 100 mg·L–1 IBA + NAA. In most cases, cuttings receiving a foliar application of 300 mg·L–1 IBA at 0.8 L·m–2 had either comparable or greater root dry mass than cuttings receiving a basal dip of IBA + NAA and outperformed the control. After 14 d, root dry mass was generally greatest when cutting were treated with 300 mg·L–1 IBA at 0.8 L·m–2 and was an equal or better alternative to a basal dip. For the most effective results, rooting hormones should be utilized when the DLI integral is <12 mol·m–2·d–1.

Molecular Phylogeny and Taxonomic Revision of the Genus Diastatea (Campanulaceae: Lobelioideae)

Abstract— Diastatea (Campanulaceae-Lobelioideae) is a genus of small, herbaceous annuals found mostly in Mexico. Differences in the number of recognized species in the historical treatments, and the lack of a phylogeny, suggested that a revision of the genus was necessary. Species boundaries and species level relationships were tested based on a sampling of nearly 50 individuals. Sequences of the chloroplast spacer regions, atpB-rbcL and ndhF-rpl32, as well as the ITS, were generated and then analyzed using maximum likelihood and Bayesian inference methods. The analyses of the separate datasets produced congruent topologies. Two strongly supported clades of Diastatea are newly recognized as subgenera in the taxonomic treatment. Diastatea Scheidw. subg. Diastatea and Diastatea subg. Angustifolia E.P.Johnson &amp; T.J.Ayers can be distinguished morphologically by leaf shape and pubescence, hypanthium shape, and the presence or absence of a gibbous projection on the ventral side of the corolla. A morphological treatment of the genus corroborated by the molecular analysis revealed one new species, Diastatea aptera E.P.Johnson &amp; T.J.Ayers, one new subspecies, Diastatea tenera subsp. durangensis E.P.Johnson &amp; T.J.Ayers, and elevated an existing subspecies, Diastatea ciliata (McVaugh) E.P.Johnson &amp; T.J.Ayers, to specific rank.

Traditions of growing and using of plants in villages and small towns of Ukraine in the 70–80s of the XX century

Aim. The purpose of the article is to describe the traditions of growing and using plants in the villages and small towns and to highlight the range of plants that were most often planted near houses during the 1970s and 80s in Ukraine. Methods. The study was conducted in the villages of Kyiv (Rogoziv), Zhytomyr (Hardyshivka) regions, in the suburbs of Kyiv (Bilychi, Zhulyany) and Borzna (Chernihiv region) by interviewing and eyewitness based accounts. Results. The article covers the list of traditional agricultural, fruit and ornamental plants for rural areas of Ukraine during the 1970s and 80s. The names of cultivars, methods of cultivation, meaning and traditional use of the plants are given. The peculiarities of the range of cultures depending on the studied area are analyzed. Conclusions. As a result of our research, the list of plants species grown in the villages of Ukraine during the 1970s and 80s included 104 species. Ornamental and food plants that were grown and used in the villages of Ukraine during the 1970s and 80s mostly were herbaceous annuals and perennials. A significant portion of them were vegetable fruit and berry plants. Among ornamental plants, medium- and tall plants with bright flowers and (or) strong aroma became more popular and widespread. These were species and cultivars that are easily propagated by seeds and division, do not require careful care and are resistant to diseases and pests.

Responses of the Plant Cell Wall to Sub-Zero Temperatures: A Brief Update.

Our general understanding of plant responses to sub-zero temperatures focuses on mechanisms that mitigate stress to the plasma membrane. The plant cell wall receives comparatively less attention, and questions surrounding its role in mitigating freezing injury remain unresolved. Despite recent molecular discoveries that provide insight into acclimation responses, the goal of reducing freezing injury in herbaceous and woody crops remains elusive. This is likely due to the complexity associated with adaptations to low temperatures. Understanding how leaf cell walls of herbaceous annuals promote tissue tolerance to ice does not necessarily lead to understanding how meristematic tissues are protected from freezing by tissue-level barriers formed by cell walls in overwintering tree buds. In this mini-review, we provide an overview of biological ice nucleation and explain how plants control the spatiotemporal location of ice formation. We discuss how sugars and pectin side chains alleviate adhesive injury that develops at sub-zero temperatures between the matrix polysaccharides and ice. The importance of site-specific cell-wall elasticity to promote tissue expansion for ice accommodation and control of porosity to impede ice growth and promote supercooling will be presented. How specific cold-induced proteins modify plant cell walls to mitigate freezing injury will also be discussed. The opinions presented in this report emphasize the importance of a plant’s developmental physiology when characterizing mechanisms of freezing survival.

Roadside Vegetation in and Around the Megacity of Kolkata Along an Urbanisation Gradient

Combustion of fossil fuels by the on-road vehicles is major contributor of air pollution which affects the surrounding vegetation and their habitat in addition to human health hazards. Study on the concurrence between vehicular greenhouse gas emissions and associated plant community is important to assess the present day problem scenario on environmental equilibrium. An ecological analysis has been carried out from five locations along roadside of the suburban interiors to the highly vehicle congested urban areas of Kolkata megacity. Quantitative study on naturally grown road side vegetation covering seedlings of tree and shrubby species, herbaceous annuals and perennials along the suitable length of each study area was conducted following standard methodology. Increasing vehicular pollution shows reciprocal correlation with species richness and species diversity. From community structure analyses across the emission gradient it was revealed that a few species exhibited tolerance to withstand increasing air contamination by successful population growth. Nevertheless, the present study might be worthwhile in assessing ecological status of the local plant communities subjected to varying level of vehicle traffic.

IDENTIFIED PLANTS WHICH ARE BELONGS IN INDIGOFERA GENERA IN THOOTHUKUDI DISTRICT, TAMIL NADU, INDIA

The Indigofera are frequently shrubs, and some are small trees or herbaceous perennials or annuals. These have pinnate leaves. Racemes of flowers grow in the leaf axils, in hues of red, but there are a few white- and yellow-flowered species. The fruit is a legume pod of varying size and shape. Botanical description schedule as; Kingdom: Plantae, (unranked): Angiosperms, (unranked): Eudicots, (unranked): Rosids, Order: Fabales, Family: Fabaceae, Subfamily: Faboideae, Tribe: Indigofereae, Genus: Indigofera. 1620 plant name records match your search criteria Indigofera. The names found have these generic epithets: as accepted in the plant list online data base. That plants were; Indigofera argentea / I. articulate, Indigofera aspalathoides Vahl. Indigofera enneaphylla Linn. Indigofera glabra Linn. Indigofera glandulosa Willd. Indigofera linifolia Retz. Indigofera pulchella Roxb. Indigofera tinctoria Linn. Indigofera trifoliata Linn. Indigofera trita Linn. Books mentioned 04 species were not latest updated Plant List Online data base which were; Indigofera caerulea Roxb. Indigofera cordifolia. Indigofera frutescens. Indigofera hirsuta. According to the Results and Discussion this research revealed that, 20 species of Indigofera genera by the evidence of books and 04 species synonyms like updated latest in online data base. However, 16 species available in the Thoothukudi District 16 species available commonly and 04 species were rarely showed in Thoothukudi District by randomly field to all soil types of areas.

Senecio as a model system for integrating studies of genotype, phenotype and fitness.

Two major developments have made it possible to use examples of ecological radiations as model systems to understand evolution and ecology. First, the integration of quantitative genetics with ecological experiments allows detailed connections to be made between genotype, phenotype, and fitness in the field. Second, dramatic advances in molecular genetics have created new possibilities for integrating field and laboratory experiments with detailed genetic sequencing. Combining these approaches allows evolutionary biologists to better study the interplay between genotype, phenotype, and fitness to explore a wide range of evolutionary processes. Here, we present the genus Senecio (Asteraceae) as an excellent system to integrate these developments, and to address fundamental questions in ecology and evolution. Senecio is one of the largest and most phenotypically diverse genera of flowering plants, containing species ranging from woody perennials to herbaceous annuals. These Senecio species exhibit many growth habits, life histories, and morphologies, and they occupy a multitude of environments. Common within the genus are species that have hybridized naturally, undergone polyploidization, and colonized diverse environments, often through rapid phenotypic divergence and adaptive radiation. These diverse experimental attributes make Senecio an attractive model system in which to address a broad range of questions in evolution and ecology.

Tracing insular woodiness in giant Daucus (s.l.) fruit fossils from the Early Pleistocene of Madeira Island (Portugal)

AbstractPlants on oceanic islands can evolve insular syndromes such as secondary woodiness, a generalized trend found in island floras worldwide. This phenomenon occurs through evolution in situ. It is triggered by ecological and physiological stimuli that transform herbaceous annuals into woody perennials. However, well‐dated and informative fossils that could help track and frame the evolution of this syndrome are lacking. Remarkably, in Madeira Island (Portugal), there are good examples of Apiaceae that evolved secondary woodiness, like the giant neoendemic Melanoselinum (≡ Daucus). Apiaceae has a very scarce fossil record, despite being a cosmopolitan family and an economically important crop. Here we describe the oldest Daucus s.l. fossil known to date and the first fossil evidence of a plant with insular woodiness. The fossils are preserved as mummified/compressed mericarps within 1.3‐million‐year‐old fluvio‐lacustrine sediments of the Funchal unit, Upper Volcanic complex, near Porto da Cruz. We assign them to the extant neoendemic species Melanoselinum (≡ Daucus) decipiens. The mericarp morphology shows remarkable stasis since the Calabrian stage of the Early Pleistocene. Our results demonstrate that in the Madeiran Daucinae clade, insular woodiness developed at least 1.3 million years ago, indicating a coeval or earlier immigration to Madeira Island of a Daucus sp. Our results reinforce the role of palaeobotanical research in oceanic islands, supported by stratigraphy and geochronology studies, as a key element for the understanding of plant palaeobiogeography, ecology and evolution worldwide. We expect this contribution to shed light on the evolutionary origins of carrots, and related plant groups, an important element of human food, and to better comprehend the evolution of plant insular woodiness.

Kenaf (Hibiscus cannabinus L., Malvaceae) Research and Development Advances in Bangladesh: A Review

Kenaf originated in India and Africa the plant is best grown in tropics and to some extent in sub-tropics. In Bangladesh, Kenaf is now a promising new fibre crop. Around 0.08-0.09million tons of kenaf produced in the country from 0.04 million hectares of land. The secondary data of kenaf used here were collected from different studies like national and international annual reports, thesis, books and journals during from January to July 2019. The plants are herbaceous annuals; growing to a height of even 5 m. There are some Kenaf varieties of bnagladesh, HC-2, HC-95, BJRI Kenaf-3(Bot Kenaf) and BJRI Kenaf -4 (KE-3). The commercial success of kenaf has important potential economic and environmental benefits in the areas of soil remediation, toxic waste cleanup, removal of oil spills on water, reduced chemical and energy use for paper production, greater recycled paper quality, reduced soil erosion due to wind and water, replacement or reduced use of fiberglass in industrial products, and the increased use of recycled plastics. In Bangladesh day by day demand of kenaf fibre is increasing. Kenaf uses in fibre, forage, paper pulp and also where kenaf is grown in home gardens, the more tender upper leaves and shoots are sometimes eaten either raw or cooked. Kenaf fruits have significant medicinal properties, very high in vitamin-C, antioxidants and phytochemicals. It’s seeds are a good source of fat slouble antioxidants. In future research to be continued for searching kenaf varieties tolerance to problem soil; tolerance to diseases and pests; having small seed size with long duration of seed viability and smoothness and indehiscence type of kenaf fruits.

Grazing animals drove domestication of grain crops.

In addition to large-seeded cereals, humans around the world during the mid-Holocene started to cultivate small-seeded species of herbaceous annuals for grain, including quinoa, amaranth, buckwheat, the millets and several lost crops domesticated in North America. The wild ancestors of these crops have small seeds with indigestible defences and do not germinate readily. Today, these wild plants exist in small fragmentary stands that are not appealing targets for foragers. This combination of traits has led many to argue that they must have been a food of last resort. We propose a new explanation: the domestication of small-seeded annuals involved a switch from endozoochoric dispersal (through animal ingestion) to human dispersal. Humans encountered these plants in dense stands created by grazing megafauna, making them easy to harvest. As humans began to cultivate these plants they took on the functional role of seed dispersers, and traits associated with endozoochory were lost or reduced. The earliest traits of domestication-thinning or loss of indigestible seed protections, loss of dormancy and increased seed size-can all be explained by the loss of the ruminant dispersal process and concomitant human management of wild stands. We demonstrate, by looking at rangeland ecology and herd animal herbivory patterns, that the progenitors of all of these species evolved to be dispersed by megafaunal ruminants and that heavy herbivory leads to dense homogenous clusters of endozoochoric plants. Hence, easily harvested stands on nitrogen hot spots near water sources would have existed in regions where these plants were domesticated. Future experimental and ecological studies could enhance our understanding of the relationships between specific crops and their possible ruminant dispersers.

Gene flow and genetic structure in Acacia stenophylla (Fabaceae): Effects of hydrological connectivity

AbstractAimRiparian ecosystems are regarded as vulnerable to the effects of climate change. Because of their reliance on passive dispersal to migrate from areas where conditions have become unfavourable, plants are particularly susceptible. On dryland river floodplains, the species diversity of herbaceous annuals is often high while that of structurally dominant woody perennials is low. We examined gene flow genetic structure and dispersal in Acacia stenophylla, a small perennial tree widely distributed throughout river systems of inland Australia. The role of the river corridor in shaping patterns of gene flow and genetic structure is also investigated.LocationMurray‐Darling Basin, south eastern AustraliaMethodsA total of 127 individuals, from 12 subpopulations located on seven rivers were genotyped at 13 microsatellite loci. Several population and landscape genetic tools were applied to the microsatellite data to evaluate spatial patterns of gene flow and genetic structure and make inferences regarding possible modes of dispersal.ResultsHigh gene flow and weak genetic structure was identified for the 12 subpopulations of A. stenophylla sampled, a surprising result given large distances between subpopulations. Pairwise genetic distance between subpopulations was low to moderate and could largely be explained (R2 = 0.68) by two variables: distance along the river and the proportion of no flow days. structure analysis revealed two genetic clusters. Subpopulations located on the Darling and Lower Balonne rivers were dominated by cluster one while subpopulations from the Warrego and Paroo rivers showed largely mixed ancestry with individuals descending from both clusters one and two.Main ConclusionsThese results indicate that the river corridor facilitates extensive gene flow between subpopulations of A. stenophylla in this system. Hydrochory appears to be the dominant process; however, upstream movements of propagules most probably via animal movement are sufficient to negate effects expected under unidirectional dispersal.

Does acclimation in cavitation resistance due to mechanical perturbation support the pit area or conduit reinforcement hypotheses in Phaseolus vulgaris?

Two Phaseolus vulgaris L. cultivars were exposed to reduced water and stem mechanical perturbation treatments (flexing) to determine if acclimation to these treatments induced hydraulic changes, altered cavitation resistance and changed stem mechanical properties. Additionally, this study sought to determine if changes in cavitation resistance would support the pit area or conduit reinforcement hypotheses. Flexing reduced biomass, leaf area, xylem vessel area and hydraulic conductivity. One cultivar had greater measures of stem strength and cavitation resistance. Flexing increased cavitation resistance (P50 ) but did not increase Young's modulus, rigidity or flexural strength on dried stems. Stem rigidity and basal diameter were correlated with leaf mass. The ratio of conduit wall thickness to span [(t/b)h 2 ] increased under high water and flexing treatments while rigidity decreased for one cultivar exposed to both flexing and lower water suggesting an inability to compensate for two simultaneous stresses. Although P50 was not correlated with measures of mechanical strength, P50 was correlated with vessel diameter, consistent with the pit area hypothesis. This study confirmed that mechanical perturbation can impact xylem structural properties and result in altered plant water flow characteristics and cavitation resistance. Long-term hydraulic acclimation in these herbaceous annuals was constrained by similar tradeoffs that constrain hydraulic properties across species.

Two sides to every leaf: water and CO2 transport in hypostomatous and amphistomatous leaves.

Leaves with stomata on both upper and lower surfaces, termed amphistomatous, are relatively rare compared with hypostomatous leaves with stomata only on the lower surface. Amphistomaty occurs predominantly in fast-growing herbaceous annuals and in slow-growing perennial shrubs and trees. In this paper, we present the current understanding and hypotheses on the costs and benefits of amphistomaty related to water and CO2 transport in contrasting leaf morphologies. First, there is no evidence that amphistomatous species achieve higher stomatal densities on a projected leaf area basis than hypostomatous species, but two-sided gas exchange is less limited by boundary layer effects. Second, amphistomaty may provide a specific advantage in thick leaves by shortening the pathway for CO2 transport between the atmosphere and the chloroplasts. In thin leaves of fast-growing herbaceous annuals, in which both the adaxial and abaxial pathways are already short, amphistomaty enhances leaf-atmosphere gas-exchange capacity. Third, amphistomaty may help to optimise the leaf-interior water status for CO2 transport by reducing temperature gradients and so preventing the condensation of water that could limit CO2 diffusion. Fourth, a potential cost of amphistomaty is the need for additional investments in leaf water transport tissue to balance the water loss through the adaxial surface.

Plant height control of obligate long day herbaceous annuals using plant growth retardants and light

Plant height control of obligate long day herbaceous annuals using plant growth retardants and light