Stem Circumference Research Articles

Identifying the relationships of climate and physiological responses of a beech forest using the Standardised Precipitation Index: a case study for Slovakia

Abstract The paper presents relationship between the Standardised Precipitation Index (SPI) and physiological responses of individual trees in a beech stand using an example of an experimental plot in Bienska valley (Zvolen, Slovakia). SPI is a widely used tool for monitoring both short-term and long-term droughts, and for the assessments of drought impacts on agriculture. Due to the complex ecosystem bonds, monitoring of drought in forests often requires a sophisticated technological approach. The aim of the paper was to correlate the SPI on the physiological responses of trees that were recorded during the performed physiological research (sap flow, and stem circumference increment) at the site in the growing seasons (May to September) of the years 2012-2014. The results revealed a relationship between the index and the physiological responses, although the problem with the impact of other environmental factors has also come up. The secondary correlation, in which soil water potential that significantly affects physiological responses of forest tree species was used as a dependent variable, showed a tighter relationship with the SPI. We found the highest correlation between the soil water potential and the values of SPI aggregated for five weeks. This indicates that the beech forest has a five week resistance to drought stress. The results also enable simple monitoring of the initiation of the drought stress by applying SPI for five weeks.

Genome-Wide Association Study for Nine Plant Architecture Traits in Sorghum.

Sorghum [ (L) Moench], an important grain and forage crop, is receiving significant attention as a lignocellulosic feedstock because of its water-use efficiency and high biomass yield potential. Because of the advancement of genotyping and sequencing technologies, genome-wide association study (GWAS) has become a routinely used method to investigate the genetic mechanisms underlying natural phenotypic variation. In this study, we performed a GWAS for nine grain and biomass-related plant architecture traits to determine their overall genetic architecture and the specific association of allelic variants in gibberellin (GA) biosynthesis and signaling genes with these phenotypes. A total of 101 single-nucleotide polymorphism (SNP) representative regions were associated with at least one of the nine traits, and two of the significant markers correspond to GA candidate genes, () and (), affecting plant height and seed number, respectively. The resolution of a previously reported quantitative trait loci (QTL) for leaf angle on chromosome 7 was increased to a 1.67 Mb region containing seven candidate genes with good prospects for further investigation. This study provides new knowledge of the association of GA genes with plant architecture traits and the genomic regions controlling variation in leaf angle, stem circumference, internode number, tiller number, seed number, panicle exsertion, and panicle length. The GA gene affecting seed number variation () and the genomic region on chromosome 7 associated with variation in leaf angle are also important outcomes of this study and represent the foundation of future validation studies needed to apply this knowledge in breeding programs.

Morphological diversity of mango germplasm from the upper Athi River region of Eastern Kenya: An analysis based on non- fruit descriptors

Phenotypic variation in plants can be evaluated by morphological characterization using visual attributes. Fruits have been the major descriptors for identification of different varieties of fruit crops. However, even in their absence, farmers, breeders and interested stakeholders require to distinguish between different mango varieties. This study aimed at determining diversity in mango germplasm from the Upper Athi River (UAR) and providing useful alternative descriptors for the identification of different mango varieties in the absence of fruits. A total of 20 International Plant Genetic Resources Institute (IPGRI) descriptors for mango were selected for use in the visual assessment of 98 mango accessions from 15 sites of the UAR region of eastern Kenya. Purposive sampling was used to identify farmers growing diverse varieties of mangoes. Evaluation of the descriptors was performed on-site and the data collected were then subjected to multivariate analysis including Principal Component Analysis (PCA) and Cluster analysis, one- way analysis of variance (ANOVA) and Chi square tests. Results classified the accessions into two major groups corresponding to indigenous and exotic varieties. The PCA showed the first six principal components accounting for 75.12% of the total variance. A strong and highly significant correlation was observed between the color of fully grown leaves, leaf blade width, leaf blade length and petiole length and also between the leaf attitude, color of young leaf, stem circumference, tree height, leaf margin, growth habit and fragrance. Useful descriptors for morphological evaluation were 14 out of the selected 20; however, ANOVA and Chi square test revealed that diversity in the accessions was majorly as a result of variations in color of young leaves, leaf attitude, leaf texture, growth habit, leaf blade length, leaf blade width and petiole length traits. These results reveal that mango germplasm in the UAR has significant diversity and that other morphological traits apart from fruits can be useful in morphological characterization of mango. Keywords: Mango, morphological characterization, Principal Component Analysis, IPGRI, eastern Kenya

Growth dynamics of rubber tree clones in northwestern Minas Gerais, Brazil

ABSTRACT: This study aimed to evaluate the growth of rubber tree clones ( Hevea brasiliensis (Willd.exA.Juss.) Müll. Arg.) in the Northwest region of Minas Gerais, Brazil. Randomized blocks, constituted of three treatments (rubber tree clones) and four repetitions were used, and evaluated as plots subdivided in time. Subplots represent the evaluations carried out at the ages 62, 77, 87, 99, 113 and 128 months after planting. It was evaluated survival, stem circumference and total plant height. Current annual increment and average annual increment of circumference and also the number of trees fit for rubber tapping were calculated. Results obtained indicate that clones GT 1, IAN 2880, IAC 15, RRIM 600, PB 235 and IAN 3156 have potential to establish under local edaphoclimatic conditions. Increase in plant height and stem circumference throughout the evaluation period makes it evident that the clones have different growing paces in the studied region. Clones GT 1, IAN 3087, IAN 3156 and PR 255 had larger stalk circumference at 128 months, and PR 255 was the only one fit for rubber tapping at the age of 128 months after planting.

Concentrations of sulphur and trace elements in semi-arid soils and plants in relation to geothermal power plants at Olkaria, Kenya

Exploitation of geothermal energy is considered to have minimal ecological impacts. However, this assumption has not been widely studied. We tested the hypothesis that emitted elements from geothermal power plants would be enriched in both plant tissue and soil close to the power plants with consequences for plant health. The concentrations of sulphur, arsenic, boron, antimony and mercury in the soil and leaves of the dominating shrub, Tarchonanthus camphoratus, were assayed and associated foliar injury and growth traits assessed at variable distances and directions from two geothermal power plants in Kenya, Olkaria I (operated since 1981) and Olkaria II (since 2003). Sulphur concentration in the leaves was elevated close to the power plants and decreased with increasing distance, implying atmospheric input of sulphur to the ecosystem from the power plants. Similar trends were not detected in soil and with the other elements. Our study design did not support the observed higher degree of leaf injury close to the power plants. Similarly, any association of growth traits with distance or location was not detected. The results were compared with data from a reference site well out of the range of element deposition from the power plants. Overall, the levels of sulphur, arsenic, boron and antimony in leaves of T. camphoratus and sulphur, and boron concentration in soil around the Olkaria I and Olkaria II geothermal power plants were higher than at the reference site. Furthermore, the number of healthy leaves per shrub and stem circumference were lower around the power plants than the reference site, while leaf damage and other plant growth traits did not differ. In spite of relatively weak indication of the harmful effects of the geothermal power plants on the dominating shrub species, follow-up experimental studies and studies on more sensitive ecosystem components are recommended to advise existing mitigation measures against chronic exposure from the emitted gases and associated impacts.

Mutation breeding as an effective tool for papaya improvement in South Africa

Previous plant improvement efforts at the Institute for Tropical and Sub Tropical crops of the Agricultural Research Council (ARC-ITSC) concentrated on conventional breeding of papaya which subsequently led to the release of 'Bh65' and 'Selection 42' to the local industry. Gamma irradiation has proved to be an effective method to improve cultivars in several crops and in recent years, the seed of promising papaya selections were irradiated in order to develop dwarfed and/or disease-resistant selections. Seeds were irradiated at different dosages ranging from 0 to 120 Gy. Results showed that gamma irradiation has an effect on seed germination. The higher dosages of 100 and 120 Gy were lethal and almost no seeds germinated. Furthermore the different irradiation dosages showed a correlation between higher irradiation dosage and lower plant height and stem circumference on cultivars 'Bh65', 'Maradol' and 'Sunrise Solo' whereas the cultivars 'OShew Mee', 'Tainung' and 'V3' were less affected by radiation. The higher dosage of 80 Gy had the most profound effects, reduced plant height and stem circumference. Radiation did not affect yield negatively except for 'Shew Mee' and 'V3' where some differences were observed. The higher dosages especially 80 Gy resulted in smaller fruit. No effect on disease resistance for black spot (Asperisporium spp.) was observed in the irradiated treatments as the leaves on all the plants were infected.

PLANTING ROSEWOOD FOR SUSTAINABLE ESSENTIAL OIL PRODUCTION: INFLUENCE OF SURROUNDING FOREST AND SEED PROVENANCE ON TREE GROWTH AND ESSENTIAL OIL YIELDS

L’huile essentielle de bois de rose (Aniba rosaeodora Ducke) recherchée pour ses propriétés olfactives est un ingrédient majeur de la parfumerie de luxe. En raison d’une surexploitation ces dernières décen- nies, le bois de rose est désormais consi- déré comme une espèce en voie de dis- parition. Envisager de produire de l’huile essentielle à partir de plantations s’avère une alternative pertinente. Nous avons planté 605 arbres de bois de rose issus de graines de deux provenances de Guyane française sur une parcelle de 5 445 m². La plantation présente la particularité d’être entourée de forêt primaire. Après une période de 9 ans, nous avons évalué l’effet de la position de l’arbre par rap- port à la forêt environnante et de la prove- nance des graines sur les traits dendromé- triques (hauteur, circonférence, biomasse ligneuse) et le rendement en huile essen- tielle. Les arbres présentent une crois- sance moyenne enhauteurde 0,7 m/an, en circonférence de 2,5 cm/an, avec une pro- duction de biomasse aérienne de 990,5 kg de masse sèche/ha/an. Les rendements en huile essentielle varient entre 0,6 % et 3,6 %, avec une production moyenne de 2,1 %. La position de l’arbre par rapport à la forêt environnante est le principal fac- teur affectant la croissance des arbres et la production d’huile essentielle : les arbres situés en bordure de la forêt environnante sont significativement plus petits et accu- mulent moins d’huile essentielle du fait de l’influence de la disponibilité de lumière. La provenance des graines a peu d’in- fluence sur les caractéristiques dendro- métriques et le rendement en huile essen- tielle. En conclusion, la mise en place de plantations pourrait être un système opti- mal et économiquement avantageux si l’on vise la production d’huile essentielle mais il importe d’éviter leseffetsdebordliés à la proximité de la forêt

Phenotypic variation of flowering and vegetative morphological traits along the distribution for the endemic species Yucca capensis (Agavaceae)

Phenotypic variation across the geographic range of a species depends upon genetic differences within and between populations as well as environmental heterogeneity. Estimating the variation in morphological and reproductive traits and determining the influence of abiotic factors on the expression of phenotype is particularly important in endemic species as a means of inferring their response to different environmental scenarios. This study analyzes the interpopulation variation in oral and vegetative traits of Yucca capensis Lenz and their relation to altitude and precipitation. At 2 different sites total plant length, stem length, stem circumference, rosette length, rosette diameter, leaf length and leaf width were measured and the number of plants with inflorescences and fruits was recorded. The results showed higher coefficients of variation for plant length, stem length and rosette length and lower coefficients of variation for leaf length and width. All of the vegetative traits differed significantly between sites. It was found that 31 % and 12 % of the plants produced inflorescences and fruits respectively and inflorescence production differed between sites, presenting a positive relation with average annual precipitation. This study shows that there is large phenotypic variation in vegetative traits and that levels of rainfall have a clear influence on the production of reproductive structures throughout the geographic range of the endemic species Y. capensis .

Ecological segregation of bark beetle (Coleoptera, Curculionidae, Scolytinae) infested Scots pine

AbstractBark beetles infest several pine tree species, often creating major economic losses. Biotic interactions between Scolytinae populations inhabiting Pinus sylvestris were analyzed using a new sampling method involving a two dimensional division of tree space resources into units and sections. The goal was to evaluate the effects of the type of available reproduction material on insect infestation. The P. sylvestris stands in this study included an analysis of bark beetles colonizing dead trees and uninfested living trees (trap trees). Analyzed trees were harvested and their stems divided into ten equal units; each unit was halved into two sections (half of the stem circumference). The colonization of dead trees by insects was evaluated immediately after cutting for infested trees and 2 months after cutting for trap trees. The type of breeding material significantly affected the species composition of bark beetles infesting P. sylvestris. The dead trees were colonized mostly by Trypodendron lineatum and Tomicus minor, and to a lesser extent by Tomicus piniperda, which dominated in trap trees. Tomicus piniperda and T. lineatum preferred thicker stems; however, T. minor, Hylurgops palliatus and Pityogenes bidentatus preferred thinner ones. The application of the new sampling method helped to increase the accuracy of niche segregation among insect species. The results of niche segregation indicate bark beetles exhibited spatial specialization in the use of resources, mainly related to the moisture content of breeding material and the availability of food resources which is the main factor determining the coexistence of bark beetles in the same environment.

Efecto de <i>Trichoderma</i> spp., <i>Paecilomyces lilacinus</i> y la inyección de nematicida en el pseudotallo en el combate de <i>Radopholus similis</i> y la producción de banano

Se evaluó el efecto de las cepas PB17 y B23 de Trichoderma spp., de la cepa UNA de Paecilomyces lilacinus y de la inyección de oxamil 24 SL en el pseudotallo, sobre el combate de nematodos y la producción de banano (Musa AAA). Se seleccionó una plantación comercial infestada con nematodos y sembrada con el cultivar Grande Naine. Se usó un diseño de bloques completos al azar con 6 repeticiones. De cada cepa se realizaron aplicaciones mensuales a 1 * 109 ufc.ml-1 durante 20 meses. El nematicida químico se aplicó sobre la superficie del suelo cada 4 meses y la inyección de oxamil 24SL en el pseudotallo se realizó cada 3 meses. Muestras de raíces se tomaron cada mes en cada repetición para análisis de nematodos. No se redujeron las poblaciones de nematodos en las plantas tratadas con la cepa UNA de P. lilacinus ni con las cepas PB17 y B23 de Trichoderma spp. Sin embargo, las plantas tratadas con estas cepas mostraron mayor peso del racimo (p=0,0375) y circunferencia (p=0,0402) de la planta madre, respecto a las plantas sin esa aplicación. Las plantas inyectadas con oxamil y las tratadas con la rotación de nematicidas sobre la superficie del suelo mostraron un mayor porcentaje de raíz funcional (p<0,0241) y redujeron (p<0,0001) el número de nematodos totales en 43 y 41% respectivamente, respecto al testigo. Las plantas inyectadas con oxamil aumentaron en 3,2 kg el peso del racimo (p=0,0006), mostraron mayor (p<0,0478) número de manos, calibración, longitud del fruto y circunferencia de la madre respecto a las plantas sin aplicación. No se encontraron diferencias en las variables de producción evaluadas al comparar la rotación de nematicidas sobre la superficie del suelo con la inyección de oxamil en el pseudotallo.

DATING OF ROCKFALL EVENTS USING VESSEL LUMEN AREA IN BETULA PENDULA

Vessel lumen area is influenced by both genetic and environmental forces. Its alterations balance hydraulic water transport efficiency and safety from cavitation or embolism. We tested the hypothesis that environmental stress inflicted by rockfall injury influences average vessel lumen area in newly formed tree rings of Betula pendula Roth, which would make it useful for retrospective detection of rockfall events. We took samples from 11 trees injured by a rockfall that occurred in the winter of 2010–2011, specifically from the stem area adjacent to the injury, parts of the stem located perpendicular to the injury, parts located opposite to the injury, and from four undisturbed trees. We measured the mean vessel lumen area of each tree ring in every sample, comprising up to 10 pre-event tree rings and generally 3 tree rings formed after rock injury. On average, 115 vessels were measured in each tree ring. We then compared the vessel lumen area in tree rings formed after the event with that of rings formed before it as well as with values predicted by an age-trend model inferred from vessel lumen area chronologies. Our results show a strong reduction in vessel lumen area in the first tree ring formed after the event regardless of the position around the stem circumference. This reduction is strongest in wood just next to the callus tissue zone, with decreasing significance in distal parts of the stem circumference. During the three years after the rockfall, the trees mostly recovered their pre-event vessel lumen area, even right next to the place of injury. Still, this value is significantly lower than the value predicted for growth without injury. Abrupt reductions of vessel lumen area turn out to be potentially useful for identifying former rockfall events and can improve on results obtained by traditional methods of dendrogeomorphological dating.

Estimating tree and stand sapwood area in spatially heterogeneous southeastern Australian forests

Aims: Natural and anthropogenic changes in forests can have important influences on transpiration and water production. Understanding the effects of increasing disturbances, due for example to climate change and forest harvesting, requires detailed information on how forest density and structural attributes relate to transpiration. Mean annual transpiration of eucalypt forest communities is often strongly correlated with total cross-sectional sapwood area. Our aim was to test an efficient method for estimating sapwood area at 1.3 m height (SA 1.3 ) in a large number of trees to understand the spatial heterogeneity of tree and stand sapwood area within and between forest communities, and develop allometric relationships that predict SA1.3 with forest inventory data. We also apply tree competition models to determine the degree to which the relationship between SA 1.3 and tree basal area at 1.3 m height (BA 1.3 ) is influenced by competition. Methods: We visited 25 recently harvested southeastern Australian forest sites consisting of 1379 trees and 5 Eucalyptus species to evaluate a new efficient data collection method for estimating SA 1.3 with tree taper and stump dimensions data using mixed effects models. The locations of 784 stumps within one 5-ha site were accurately mapped using an unmanned aerial vehicle (UAV), and four distance-dependent tree competition models were applied across the site to explain within-stand variation in the ratio of SA 1.3 to BA 1.3 . Data from 24 additional sites, consisting of ten 15 m radial plots per site, were used to analyse within-site variation in R Ha (the ratio of stand sapwood area SA Ha to stand basal area BA Ha ). The radial plots were merged within each site to evaluate between-site variations in R Ha across the landscape. For predicting SA Ha with forest inventory data, we computed the relationship between SA Ha and a new index of total stem perimeter per hectare, defined as BA Ha N T , where N T is tree stocking density. Important Findings: Our 1379 measured stems represent the most comprehensive measure of sapwood area, surpassing the 757 measured stems in native eucalypt forests published in literature. The species-specific R Ha varied considerably across sites and therefore extrapolating SA Ha with spatially distributed BA Ha maps and a generalized R H a would introduce local uncertainty. We found that the species-specific stem perimeter index was more effective at capturing variability in SA Ha across the landscape using forest composition, structure and density data ( R 2 : 0.72-0.77). The strong correlation between tree SA 1.3 and BA 1.3 improved slightly using tree competition models ( R 2 increased from 0.86 to 0.88). Relating SA Ha to routinely measured forest inventory attributes within permanent plots and Light Detection and Ranging (LiDAR) data may provide opportunities to map forest water use in time and space across large areas disturbed by wildfire and logging.

Effect of conventional and organic orchard floor management practices on arbuscular mycorrhizal fungi in a ‘Cripp’s Pink’/M7 apple orchard soil

Arbuscular mycorrhizal (AM) fungi are key components of agricultural soil–plant systems, which may be affected by agricultural practices. In organically managed (ORG) orchards, nutrients are supplied in the form of compost, and weeds are suppressed with mulches, whereas synthetic fertilizers and herbicides are used for these respective purposes in conventional (CON) orchards. The effects of ORG and CON orchard floor management practices on native AM fungi in apple orchards were investigated in a randomized field trial. AM root colonization, spore abundance, infectivity potentials and soil glomalin contents were determined in the 0–30cm soil depth interval, in tree rows, over consecutive seasons. Root colonization was higher in the ORG than the CON treatments, but intermediate where straw mulch was substituted for green work-row covers. Glomalin levels were not affected by the treatments. Root colonization by AM fungi increased with increasing soil pH, P, C, K, Zn, and Mn concentrations, but were suppressed by Cu. Colonization correlated positively with leaf P, Ca and Mg, and with stem circumference, but negatively with leaf N and yield. ORG orchard floor management practices therefore, promoted functional AM associations more effectively than CON practices.

Intra-annual patterns of weather and daily radial growth changes of Norway spruce and their relationship in the Western Carpathian mountain region over a period of 2008-2012

The contribution presents the results of a 5-year (2008–2012) dendroecological research in a Norway spruce (Picea abies [L.] Karst.) clone forest (Northern Slovakia). Due to different climatic and soil moisture conditions in the monitored years, different seasonal courses of stem increment formation were observed using band dendrometers with continuous data recording. The lack of precipitation affected growth processes mainly during the growth culmination and at the end of summer. The multiple regression analysis of the impact of individual factors on stem circumference changes on the basis of their partial correlation coefficients revealed that the individual environmental characteristics influenced daily stem radial changes with time lags of one to ten days. The results of the analysis of variance showed that the stem radial reactions to climatic and soil moisture factors were not significantly different between the clones.

English

Field experiment was carried out during 2010-2011 at All India Coordinated Research Programme Water Management block, Agricultural College and Research Institute, Madurai. There were eleven treatments replicated three times in randomized block design using banana cv. Rasthali as a test crop. In recent years, fertigation a technique of application of both water and fertilizers via an irrigation system was shown to be very effective in achieving higher water and fertilizer use efficiency. In this method, both water and fertilizer are delivered precisely in the crop root zone as per the crop need and according to crop developmental phase. Increased growth and yield with sub surface drip irrigation has been reported earlier in several crops. The current results revealed that pseudostem girth increased markedly with nitrogen and potassium fertigation levels. Significantly higher plant height was observed with the application of nitrogen and potassium each at the rate of 200 g per plant. The increase in plant height and girth could be largely due to regular supply of nutrients through fertigation. The 75% RDF through drip fertigation increased plant height (278.8 cm) and stem circumference (68.54 cm) of banana as compared to a plant height of 253.7 cm and stem circumference of 64.23 cm observed under soil application. Key words: Subsurface drip fertigation, growth, yield, banana.

English

Collar rot is a disease difficult to control that has hindered passion fruit cultivation in many regions of Brazil. Therefore, this study aimed to find genetic resistance to the fungus Fusarium solani in Passiflora species using the multivariate analysis methodology to discriminate the most resistant species. The following fourteen Passiflora species were assessed: P. quadrangularis, P. nitida, P. foetida, P. tenuifila, P. alata, P. setacea, P. cincinnata, P. mucronata, P. micropetala, P. suberosa, P. morifolia, P. eichleriana , P. edulis and P. coccinea. These plants were arranged in a casualized block design with 14 treatments (species), three replications and three plants per plot. The reactions of the inoculated species of Passiflora were evaluated with the use of 12 resistance traits. The generalized Mahalanobis distance was used to form groupings by the UPGMA method. 3D projection with the canonical variables and quantification of the relative contribution of characters were also conducted. The UPGMA method revealed the formation of three distinct groups of species, which composed the susceptible, moderately resistant and resistant groups. The groups formed by three-dimensional dispersion were similar to those formed by the dendrogram. The following traits contributed most to genetic diversity: inoculation time until the lesion reached more than 50% of the circumference of the injured stem and area under the curve of the expansion of the lesion width. The use of the set of traits and their joint assessment through multivariate analysis allowed greater accuracy in the inference of the most resistant species, mainly P. nitida and P. cincinnata .

Karakter Fenotipik Tanaman Stroberi Festival (Fragaria x ananassa D.) Hasil Induksi Kolkisin Pada Konsentrasi 0,05% dan 0,01%

Strawberries were a lot of holticulture commodities consumed by the people of Indonesia. Strawberry consumption continues to increase over time in Indonesia but not matched by production. This it because the strawberry is native to subtropical climate so that production in Indonesia limited in the plateau regional still affected by the tropical climate. Therefore, it is necessary to increase the production of both quality and quantity of strawberries, one with plant breeding through the induction of colchicine. The objective of this research were to determine the differences in phenotypic characters of strawberry plants with the control and induction results to determine the length of time and the induction colchicine 0,05% and 0,01% on the Festival cultivar of strawberry most effective. Research were done by inducing with 0,05% and 0,01% colchicine in leaves, roots 24 hours and 36 hour, the root and leaves of 24 and 36 hour. The observed for 6 months long leaf growth, leaf width, number of leaves, stem circumference, plant height, bloom vast flower and volumes of the fruit. The results indicate that the induction of the leaf growth at the optimal parameter leaf lenghth, leaf width and number of leaves. While 24-hour induction of root growth at optimum height and volume of fruit plants, then root induction at 36 hour to flowers bloom. Induction in root and leaves 36 hour optimum growth on trunck circumference. From this study it could be concluded that there are differences in the character of the strawberry crop cultivar Festival phenotype induction results colchicine 0,05% and 0,01% with control. Induction for 36 hours and induction on leaves was most effective for induction of strawberry cultivar Festival. Key words : Character phenotype, Festival, Colchicine.

Epiphytic lichens onJuniperus communis– an unexplored component of biodiversity in threatened alvar grassland

Semi‐natural grasslands, among them thin‐soil calcareous grasslands (alvars), have great conservation value but have become increasingly rare in Europe. The main threat to alvar grasslands is the encroachment by juniperJuniperus communisand therefore it is usually removed during the restoration practice. Juniper can also be a host plant for many epiphytic lichens, but its role as a phorophyte is poorly known. We studied epiphytic lichen diversity on 126 junipers in 17 sites in western Estonia and found 140 lichenized taxa including several rare and red‐listed species. Using indirect and direct multivariate analyses (DCA, pCCA) and general linear models we revealed that both habitat and phorophyte properties affect lichen assemblies on juniper. Lichen species richness per site showed a unimodal relationship with compound factors of site productivity and juniper characteristics (stem circumference and juniper width). Lichen species richness per phorophyte was increasing with its size and with the proportion of dead branches, and was twice higher in plate alvars than in ryhk alvars. Also, the species composition in plate alvars differed from ryhk alvars by having 42 characteristic lichen species in plate alvars vs three indicators of ryhk alvars. The composition of lichens was significantly influenced by encroachment of alvars, e.g. by high juniper cover and shrub layer height, as well as by the proportion of dead branches and stem circumference of juniper. We conclude that the epiphytic lichen assemblies on junipers are threatened by grassland encroachment similarly to ground layer lichen assemblies. We suggest that some old and scencent junipers should be preserved during the restoration of alvar grasslands.

The use of fresh and saline water sources by the mangrove Avicennia marina

Mangroves are distributed along tropical and subtropical riverine and coastal shores. Although mangroves are highly adapted to saline environments, maintaining water uptake under saline conditions is energetically expensive. Therefore, salinity is a lim- iting factor for mangrove growth and productivity, and access to fresh water sources, such as rainwater and groundwater, which reduce water salinity, increase mangrove ecosystem productivity. Here, we investi- gated the extent of fresh water utilization by man- groves to better predict current and future mangrove productivity. We used the abundance of 18 O isotope in stem water to assess: (1) the extent of fresh water utilization by Avicennia marina (Forssk.) Vierh across hydrological settings; and (2) whether growth, mea- sured as increments in stem circumference, is sensitive to variation in rainfall availability. The d 18 O isotopic composition of stem water indicated mangroves use both fresh and saline water sources for metabolic processes. However, our results suggest that the proportion of fresh water used by mangroves increases with the availability of fresh water. Growth of the main stems of trees was correlated with rainfall (r 2 = 0.34 and r 2 = 0.37, P = 0.001). Our results

Association mapping of brassinosteroid candidate genes and plant architecture in a diverse panel of Sorghum bicolor.

This first association analysis between plant architecture and BR candidate genes in sorghum suggests that natural allelic variation has significant and pleiotropic effects on plant architecture phenotypes. Sorghum bicolor (L) Moench is a self-pollinated species traditionally used as a staple crop for human consumption and as a forage crop for livestock feed. Recently, sorghum has received attention as a bioenergy crop due to its water use efficiency and biomass yield potential. Breeding for superior bioenergy-type lines requires knowledge of the genetic mechanisms controlling plant architecture. Brassinosteroids (BRs) are a group of hormones that determine plant growth, development, and architecture. Biochemical and genetic information on BRs are available from model species but the application of that knowledge to crop species has been very limited. A candidate gene association mapping approach and a diverse sorghum collection of 315 accessions were used to assess marker-trait associations between BR biosynthesis and signaling genes and six plant architecture traits. A total of 263 single nucleotide polymorphisms (SNPs) from 26 BR genes were tested, 73 SNPs were significantly associated with the phenotypes of interest and 18 of those were associated with more than one trait. An analysis of the phenotypic variation explained by each BR pathway revealed that the signaling pathway had a larger effect for most phenotypes (R (2)=0.05-0.23). This study constitutes the first association analysis between plant architecture and BR genes in sorghum and the first LD mapping for leaf angle, stem circumference, panicle exsertion and panicle length. Markers on or close to BKI1 associated with all phenotypes and thus, they are the most important outcomes of this study and will be further validated for their future application in breeding programs.