Individual Shoots Research Articles

Does apple canker develop independently on leaf scars of a single apple shoot?

European apple canker, caused by Neonectria ditissima, causes serious damage to apple trees, particularly young trees. Canker management is difficult because of the limited availability of effective fungicides, the long latency period, inoculum abundance and host resistance in commercial cultivars as well as the need for costly manual pruning interventions. To understand disease aggregation for more effective pruning management, we assessed whether canker infection and subsequent lesion development on leaf scars are independent from each other on the same shoot. Four inoculation experiments were conducted: one in glasshouse, and three in orchards. On each shoot, 10 consecutive leaf scars were inoculated and assessed for visible cankers over time in situ. Number of cankers developed per shoot as well as spatial distribution of these cankers within a shoot was statistically analysed. Most data of the number of visible canker lesions on a single shoot failed to fit binomial distributions (indicator for independence) and were fitted much better by beta binomial distributions. In a number of cases (4–20%), there appeared to be positive association between lesion development on neighbouring leaf scars. However, in one experiment where laboratory incubation and isolation of N. ditissima from inoculated but asymptomatic leaf scars (after eight months’ field incubation) were used the results suggested independence of canker development on a single shoot. We conclude that apparent aggregation of canker lesions on individual shoots is likely to originate from host responses. Such aggregation of canker lesions on individual shoots should be taken into consideration for field disease assessment and management.

Herbaceous Layer Net Primary Production of Oak-Hornbeam Forest: Comparing Six Methods of Assessment Based on the Seasonal Dynamics of Biomass Increments

Proper estimation of the herb layer annual net primary production (ANPP) can help to appreciate the role of this layer in carbon assimilation and nutrient cycling. Simple methods of ANPP estimation often understate its value. More accurate methods take into account biomass increments of individual species but are more laborious. We conducted our study in an oak-hornbeam forest (site area 12 ha) dominated by beech in NW Poland during two growing seasons (2010 and 2011). We collected herb layer biomass from 7 to 10 square frames (0.6 × 0.6 m). We collected plant biomass every week in April and May and every two weeks for the rest of the growing season. We compared six methods of calculating ANPP. The highest current-year standing biomass (1st method of ANPP calculation) was obtained on May 15, 2010—37.8 g m−2 and May 7, 2011—41.0 g m−2. The highest values of ANPP were obtained by the 6th method based on the sum of the highest products of shoot biomass and density for individual species: 74.3 g m−2 year−1 in 2010 and 94.0 g m−2 year−1 in 2011. The spring ephemeral Anemone nemorosa had the highest share of ANPP with 50% of the total ANPP. Two summer-greens, Galeobdolon luteum and Galium odoratum, each had a ca. 10% share of ANPP. The best results of ANPP calculation resulted from laborious tracking of dynamics of biomass and density of individual shoots.

Propagation of an Epigenetic Age-Related Disorder in Almond Is Governed by Vegetative Bud Ontogeny Rather Than Chimera-Type Cell Lineage

Almond (Prunus dulcis [Mill.] D.A. Webb) represents a model system for the study of epigenetic age-related disorders in perennial plants because the economically important noninfectious bud-failure disorder is well characterized and shown to be associated with the clonal-age of the propagation source. Epigenetic changes regulating disorders such as changes in methylation or telomere-length shortening would be expected to occur in shoot apical meristem initial cells since subsequent daughter cells including those in ensuing shoot axillary meristems show an irreversible advance in epigenetic aging. Because multiple initial cells are involved in meristem development and growth, such ‘mutations’ would be expected to occur in some initial cells but not others, resulting in mericlinal or sectorial chimeras during subsequent shoot development that, in turn, would differentially affect vegetative buds present in the leaf axils of the shoot. To test this developmental pattern, 2180 trees propagated from axillary buds of known position within asymptomatic noninfectious bud-failure budstick sources were evaluated for the disorder. Results demonstrate that relative bud position was not a determinant of successful trait propagation, but rather all axillary buds within individual shoots showed very similar degrees of noninfectious bud-failure. Control is thus more analogous to tissue-wide imprinting rather than being restricted to discrete cell lineages as would be predicted by standard meristem cell fate-mapping.

Dissection of floral transition by single-meristem transcriptomes at high temporal resolution.

The vegetative-to-floral transition is a dramatic developmental change of the shoot apical meristem, promoted by the systemic florigen signal. However, poor molecular temporal resolution of this dynamic process has precluded characterization of how meristems respond to florigen induction. Here, we develop a technology that allows sensitive transcriptional profiling of individual shoot apical meristems. Computational ordering of hundreds of tomato samples reconstructed the floral transition process at fine temporal resolution and uncovered novel short-lived gene expression programs that are activated before flowering. These programs are annulled only when both florigen and a parallel signalling pathway are eliminated. Functional screening identified genes acting at the onset of pre-flowering programs that are involved in the regulation of meristem morphogenetic changes but dispensable for the timing of floral transition. Induced expression of these short-lived transition-state genes allowed us to determine their genetic hierarchies and to bypass the need for the main flowering pathways. Our findings illuminate how systemic and autonomous pathways are integrated to control a critical developmental switch.

Phenotypic and marker-assisted characterization of new apple genotypes with high resistance to fire blight

In the period 2016–2018 the susceptibility to fire blight of seven apple genotypes, including four recently bred was assessed. The studies showed that two of the genotypes (J-2003-05 and ‘Early Szampion’) are highly resistant to the disease. The indicator of assessment was evaluated by the size of necrotized part of terminal shoots after their inoculation with strain Ea659 of Erwinia amylovora. The analysis of disease incidence on individual shoots of both genotypes showed no symptoms on 92% and 100% of shoots inoculated in 2016, 83.8 and 77.0% of shoots in 2017, and 87.8 and 77.3% of shoots inoculated in 2018, respectively. Molecular tests based on 16 genetic markers revealed that genotype J-2003-05 possesses 10 resistance alleles (covering the region of interest from LG 3, 5, 7, 10 and 12). This genotype is derived from the cross between ‘Melfree’ and ‘Sawa’ and produces very large dark-red tasty fruits. Genotype ‘Early Szampion’ representing the selected hybrid from the cross of ‘Gold Milenium’ and ‘Šampion’, producing large, bright red, attractive fruits, was found to possess 10 resistance alleles (covering the region of interest from LG 3, 7, 10 and 12), Both genotypes have the prospect of being used in breeding programs and commercial planting.

ПОБЕГООБРАЗОВАНИЕ EPILOBIUM HIRSUTUM L. В СВЯЗИ С АДАПТАЦИЯМИ ТРАВ СЕЗОННОГО КЛИМАТА К УСЛОВИЯМ ПЕРЕМЕННОГО УВЛАЖНЕНИЯ / ОБВОДНЕНИЯ

One of the fundamental problems of modern biology is the identification of adaptations of organisms to existence in different environments of the biosphere, the mechanisms and methods of the formation of their adaptations. A comparative analysis of shoot formation and ontogenesis of individuals makes it possible to reveal these features in plant biomorphs, including during the development of reservoirs by herbs by mesophytes. The article describes the shoot formation of the hygromesophyte Epilobium hirsutum L. The development and structural-functional zoning of shoots were assessed from the standpoint of modular organization and compared with the peculiarities of shoots formation in mesophytic and hydrophyte grasses. Shown: their similarity with monocarpic shoots of mesophytic herbs at the initial stages; further prolongation in the form of basipetal development through heterochronies and heterotopies with the development of lateral sylleptic shoots as in hydrophytes; increasing the area of the assimilating surface of an individual and ensuring the autonomy of individual shoot systems due to this with early morphological disintegration of the individual. It is proposed to distinguish the following stages in the development of the terrestrial part of the shoot system: vegetative uniaxial shoot - monocarpic shoot - disjunctive system of monopodial shoot - synflorescence system (double heterothetical frondose-frondular brush) at the shoot apex and replacement shoots in the transitional phase of its development in the zone of renewal , broken by the middle zone of inhibition, is more multicomponent and branched in comparison with those in mesohygrophytes like Veronica longifolia L., but less complexity than in hydrophytes - the aquatic form of V. anagallis-aquatica L. It is noted that the early transformation of the universal module (monocarpic shoot) into the main module (the shoot system formed on its basis) is provided by polyvariance in the development of leaf rudiments and axillary structures of elementary modules (elementary metameres) in connection with the conditions of the location of the apex and demonstrates possible mechanisms of adaptation of flowering plants with a sympodial long-shoot model of shoot formation to life in water bodies: abbreviation of ontogeny of an individual and monocarpity of ramet with polycarpicity of an organism (prolongation of ontogeny of an individual).

EFFECTS OF BROWSING PRESSURE ON THE TEXTURAL CHARACTERISTICS OF JUNIPERUS COMMUNIS L. BRANCHES

In the Montseny Natural Park junipers scattered in the grasslands can be found. In some of these areas of the park, the breeding of small ruminants is allowed, while in others only find wildlife exists. Junipers develop differently if browsed, adopting spherical or conical morphotypes. This paper studies the mechanical characteristics of the shoots according to the sex of the bush and the branching regime to which they are subjected. 729 individual shoots were taken from male and female junipers exposed to browsing from goats and ewes and those not grazed and sampled at a different position from each bush. All the leaves were taken off the non-lignified end of the shot to be studied by a simulated bite. The strength needed to cut the apical twigs of junipers was measured using a Volodkevich jaw, which mimics the way incisors act, using a texturometer. The diameter of the branches differs according to bushes’ sex being larger for females and the individuals not exposed to predation pressure. Although the differences induced by sex were significant, differences due to grazing pressure were larger. The annual branches were thicker and longer in non-grazed junipers. This difference was not due to the partial consumption of the studied branches, as all the samples were collected in full. The continued browsing pressure leads to a survival strategy of growing, with branches tighter packaged as was evident in the analysis of the branching structure. The longer annual branches in non-grazed bushes allow for a more open structure. The force necessary to break the branch was significantly higher on females. This could be related to the fact that the females must bear the weight of the fruits. The elasticity of the annual shots was significantly higher on non-grazed junipers, a fact that could be considered as a way to tolerate herbivory.

Effect of activated charcoal and phytohormones to improve in vitro regeneration in Vanda tessellata (Roxb.) Hook. ex G. Don

Vanda tessellata (Roxb.) Hook. ex G. Don. (Orchidaceae) is an epiphytic orchid species, commonly known as grey orchid, and explored enormously for its significant horticultural, medicinal, phytochemical and pharmacological properties. The present study describes an in vitro culture approach via asymbiotic seed germination assisted by phytohormones and enhanced proliferation of shoots and roots using activated charcoal for large scale production of V. tessellata. The maximum frequency of seed germination (100%) was achieved on Murashige and Skoog’s (MS) medium fortified with 1.5 mg L−1 indole-3 butyric acid (IBA). The seedlings developed from the protocorms were used for further proliferation and development of multiple shoots (24.8 ± 0.52 shoots per protocorm with 5.2 ± 0.35 cm average length) on MS medium augmented with 0.5 mg L−1 each of 6-benzylaminopurine (BAP) and indole-3 acetic acid (IAA) + 100 mg L−1 activated charcoal (AC) after 4th sub-culture. The optimal rooting of individual shoots was achieved on MS medium with 1.0 mg L−1 IBA. The well-developed plantlets were hardened using soilrite® + cocopeat + coconut husk complex in a greenhouse for 4 weeks. The plantlets were acclimatized under relatively increased temperature and low humidity for 4–5 weeks in the greenhouse with 98% survival rate. The protocol can be utilized for the development of strategies for large scale stable production of V. tessellata plantlets.

Forest land use discontinuity and northern red oak Quercus rubra introduction change biomass allocation and life strategy of lingonberry Vaccinium vitis-idaea

BackgroundMulti-purpose use of forests in a sustainable way forces a recognition of how introduction of alien woody species in forests with different land use histories affect native plants other than trees. Lingonberry Vaccinium vitis-idaea is an important understory component of temperate and boreal forests and provider of valuable non-wood forest products. Here we studied effects of land use changes and introduction of Northern red oak Quercus rubra on lingonberry in mesic Scots pine forests (in central Poland). We measured lingonberry cover, height of shoots, biomass of stems and leaves, and fruit productivity. Shoots were collected within 200 research plots located in recent and ancient Scots pine forests, with and without Q. rubra.ResultsWe found that V. vitis-idaea reached lower cover, aboveground biomass and fruit production in recent than ancient forests and in forests with than without Q. rubra. The fruit production in recent pine forest was only 2% of that reported in ancient pine forest, and V. vitis-idaea did not reproduce generatively in forests with Q. rubra. Biomass and carbon sequestration of V. vitis-idaea in forests with alien (invasive) trees decreased by 75% compared to ancient pine forest. Effects were also clear at the individual shoot level – in less suitable conditions we found taller heights and higher biomass allocation into stems than foliage. Biomass allocation in fruiting and non-fruiting shoots in pine forests was also different – less of the dry biomass of fruiting shoots was allocated to leaves than to stems.ConclusionsIn the age of high interest in ecosystem services and discussions about usage of alien tree species as alternatives in forest management, our results clearly indicate disruption of ecosystem services provided by V. vitis-idaea in the presence of Q. rubra. Lingonberry benefited from the continuity of forest land use, however, regardless of land-use legacy, alien tree introduction led to decline in abundance of species crucial for ecosystem functioning. Therefore, to maintain valuable native species and for conservation of ecosystem services delivery, we suggest limiting the introduction of Q. rubra in areas with abundant V. vitis-idaea, especially in forests with continuous forest land-use history.

Development and performance evaluation of a machine vision system and an integrated prototype for automated green shoot thinning in vineyards

AbstractGreen shoot thinning in vineyards is an essential, perennial operation for maintaining canopy health and optimizing yield and quality of wine grapes. Use of mechanized thinning system, which is essential to reduce labor dependency and associated cost, causes high variability in shoot removal efficiency due to difficulty in precisely positioning the thinning end‐effector along cordon trajectories. Automated/robotic solution for precise positioning of the thinning end‐effector could significantly improve the performance and efficiency of mechanical green shoot thinning. This study presents: (i) a machine vision‐based cordon detection system that can estimate cordon trajectories at different shoot growth stages in a vineyard; and (ii) evaluation of an integrated green shoot thinning system capable of automatically positioning the thinning end‐effector following vine cordon trajectories. The developed machine vision system uses deep learning‐based techniques that could accurately estimate cordon trajectories with root mean square error (RMSE) of 7.3, 10.3, and 16.1 pixels for canopy images captured in 2–4 weeks of shoot growth, respectively. Then, a control strategy was presented for the integrated system, which receives the computed cordon trajectories from machine vision system to automatically position the thinning end‐effector to cordon trajectories. Field evaluations in a research vineyard showed that the integrated system can achieve an RMSE of 1.47 cm in following the cordon trajectories at 6.6 cm·s−1forward speed. Future work will incorporate additional sensing system to detect individual shoot on cordon and integrating it with an existing system to achieve higher level of precision in green shoot thinning.

Intelligent Bionic Optimization Algorithm Based on the Growth Characteristics of Tree Branches

To improve the performance of bionic algorithms, an intelligent bionic optimization algorithm is proposed based on the morphological characteristics of trees growing toward light. The growth organ of the tree is mapped into the coding of the tree growth algorithm, and the entire tree is formed by selecting the fastest growing individual to form the next level of the tree. When the tree growth reaches a certain level, the individual code of the shoot tip is added to enhance the search ability of the individual shoot tip in the growth space of the entire tree. This method achieves a near-optimal solution. The experimental results were compared with the optimization results of the genetic algorithm and the ant colony algorithm using the classic optimization function. The experimental results show that this algorithm has fewer iterations, a faster convergence speed, higher precision, and a better optimization ability than the genetic algorithm or the ant colony algorithm.

A Nonparametric Model for Analysis of Flowering Patterns of Herbaceous Multi-flowered Monocarpic Shoots.

One of the approaches to plant development description involves phenological curves, which represent the time variations of certain traits. Most models applied to various plant taxa and life forms describe their phenology, including flowering, at the population level, and insufficient attention is paid to the modeling at the individual one. Individual modeling is more complicated than populational one owing to the multilevel structure of a phenotype. And as a result, it is accompanied by a significant increase in the number of model parameters, many of which are both interdependent and non-transferable between species. Here, we present a simple structural-dynamic data-driven model to describe the flowering patterns of individual monocarpic shoots of herbaceous plants with multi-flowered inflorescences. This model is nonparametric, thus being convenient and applicable to various plant species. Our results showed the operability of the proposed model and its potential in the detection of hidden trends in the input data. This is illustrated by the example of the herbaceous polycarpic Campanula sarmatica, Campanulaceae family, whose inflorescences demonstrate a wide variability in the structure and dynamics of flowering. For example, using our model, we found that the shape of the flowering curve of C. sarmatica shoots as a whole is determined by only two factors, the ratio of the number of flowers on the main and lateral axes, and the time of the flowering shift from the main axis to the lateral axes. The proposed model accurately mimics the individual flowering pattern with due natural variability. It can be used to simulate the flowering of a group of individuals in cenopopulational studies or practical tasks, e.g., in landscape design. Flowering patterns that characterize inflorescence development at the individual level can serve as informative phenotypic traits in anthoecological and developmental studies, and in inflorescence diagnostics.

Seasonal dynamics of shoot biomass of dominant clonal herb species in an oak\u2013hornbeam forest herb layer

Seasonal fluctuations of light availability, nutrient concentrations, and moisture affect plant population traits like density, standing biomass, and flowering. We analyzed seasonal changes of density and shoot biomass of the four most frequent herb species growing in an oak–hornbeam forest community, i.e., Anemone nemorosa, Ficaria verna, Galeobdolon luteum, and Galium odoratum. In 2010 and 2011 plant biomass was harvested from 7 to 10 randomly situated square sample plots (0.36 m2) in the homogenous oak–hornbeam forest community every week in the spring and every two weeks in the summer and autumn. The highest abundance of Anemone nemorosa reached over 1000 shoots per m2, of Ficaria verna 459.5 shoots per m2, of Galium odoratum 83.6 shoots per m2, and of Galeobdolon luteum 98.4 shoots per m2 (means for 2010 and 2011, based on all sample plots). We did not observe negative correlation between density and shoot biomass. Growth rates of vegetative shoot biomass amounted to 0.857 mg day−1 for Anemone nemorosa, 0.467 mg day−1 for Ficaria verna, 0.722 mg day−1 for Galium odoratum, and 0.448 mg day−1 for Galeobdolon luteum (means for 2010 and 2011). Spring ephemerals had much higher densities of shoots than summer-greens. Summer-greens reached higher biomass of individual shoots than spring ephemerals. Flowering shoots constituted only 4, 2, and 11% of all shoots for A. nemorosa, F. verna, and G. odoratum, respectively. More resource availability resulting in high shoot biomass did not translate to higher share of flowering shoots.

Germination seeds of millet genotypes under the influences of PEG 6000 solution on the 3<sup>d</sup> and 6<sup>th</sup> days

Purpose. To determine the drought resistance of five millet varieties (ʻOmriyaneʼ, ʻKharkivske 57ʼ, ʻKonstantinovskeʼ, ʻIR 5ʼ, ʻSlobozhanskeʼ) using PEG 6000 as osmotic stress.Methods. To obtain the effect of drought, five concentrations of PEG 6000 solutions were used: 0.0% (control), 11.5%, 15.3%, 19.6%, 23.5% and 28.9%, which corresponds to 0.0, 115, 153, 196, 235 and 289 g of solute in 1000 ml of distilled water or 0.0, -1.9, - 3.1, - 4.8, - 6.6 and - 9.7 bar. Results. Osmotic stress strongly suppressed the germination of millet seeds at -3.1 bars (46.8%) and at -4.8 bars (28.66%) on the third day, but on the sixth day the number of germinated seeds increased to 92.8% and 84.0% respectively. The millet genotypes of differed significantly in the percentage of germination at various concentrations of the PEG 6000 osmotic solution. The minimum germination capacity was observed in variety Omriyane at -3.1, - 4.8, - 6.6 bars. ʻIR 5ʼ, ʻKonstantinovskeʼ and ʻKharkivske 57ʼ showed higher germination potential at the different concentrations of water stress. A decrease in root elongation in all genotypes compared to control was observed in -1.9 bars osmotic stress and then at -3.1 and -4.8 bars of osmotic stress the root length had the same value from 6.6 mm to 13.5 mm on the 3d day and from 25.3 mm to 34.7 mm on the 6th day. Variety ʻSlobozhanskeʼ showed higher mean root length at -3.1 and -4.8 bars of water stress induced by PEG on the 3d day (8,7 mm-12,5 mm) and on the 6th day (35.7 mm-32.3 mm). It is not observed shoot of millet at -9.7 bars on the 3d and on the 6th days. ʻKharkivske 57ʼ, ʻIR 5ʼ, ʻSlobozhanskeʼ showed higher individual shoot length of 23.1 mm, 25.5 mm, 25.6 mm, respectively at -4.8 bars of PEG 6000 on the 6th day. At -6.6 bars of osmotic stress ʻKonstantinоvskeʼ and ʻSlobozhanskeʼ had lowest root length/shoot length ratio 2.58 and 2.61, respectively. Variety ʻOmriyaneʼ (3.54) and ʻIR 5ʼ (3.31) had the maximum deviation from unity (3.54 and 3.31, respectively).Conclusions. Genotypes' ʻKonstantinоvskeʼ and ʻSlobozhanskeʼ, which showed a high level of drought resistance, were selected as a result of this study in breeding for drought resistance. Variety ʻIR 5ʼ, ʻKonstantinovskeʼ and ʻKharkivske 57ʼ were characterized highest seed germination percentage at the different water stress.

Estimating Fresh Weight of Individual Pea Shoots Using Measurable Morphological Characteristics

Nondestructive estimation of individual shoot fresh weight (FW) from its measurable morphological traits is useful for a wide variety of purposes in pea shoot production. To predict individual shoot FW, nine regression models in total were developed, including two power models using stem diameter (SMD) or stem length (SML) as a variable, and seven linear models using part or all the following variables: SMD, SML, leaflet length (LL), leaflet width (LW), stipule length (SEL), and stipule width (SEW). Among the nine models, the 6-variable linear equation had the highest coefficient of determination, R2 = 0.92, indicating it is most effective at explaining the variation in FW. The linear equations including only one variable, SMD or SML, were equally the least effective as nonlinear equations (i.e., power models). This finding suggests that there was a linear rather than nonlinear relationship between FW and the morphological variables. During stepwise regression, SEW and LW together were first removed from the 6-variable linear models without reducing the R2, and then SEL, SMD, SML were further removed one-by-one, which reduced the R2 from 0.92 to 0.90, 0.85, and 0.71, respectively. The result suggests that SMD, SML, SEL, and LL were the most important four predictor variables for multivariable linear regression models to estimate FW, an idea that was also supported by path analysis. For the four linear models with 1–4 predictor variables from stepwise regression, the prediction accuracy of FW was evaluated based on the agreement between the predicted and measured values using another independent dataset. The 4- and 3-variable linear models (i.e., FW = −1.437 + 0.276 SMD + 0.010 SML + 0.022 LL + 0.013 SEL and FW = −1.383 + 0.308 SMD + 0.011 SML + 0.030 LL, respectively) were selected for their more accurate prediction than 1- and 2-variable linear models and relatively simpler forms than a 6-variable linear model. Although the prediction accuracy can be potentially affected by air temperature, light conditions, and harvesting time, the multilinear regression model is an effective approach for estimating fresh weight of individual pea shoots using its measurable morphological traits.

In Vitro Screening and Characterization of Selected Elite Clones of Eucalyptus tereticornis Sm. for Salt Stress

The present investigation aimed to determine the salt tolerance level of six already selected elite clones of Eucalyptus tereticornis. The response of individual shoot cultures was evaluated on basal MS medium supplemented with different concentrations of NaCl (0, 100, 200, 300, 400, and 500 mM) for 28 days. The increase in NaCl concentration affected the survival of microshoots along with inhibition in shoot and root growth in all the clones. A better performance of clone ‘KE8’ was evident with higher survival of microshoots (65.18%) in comparison to clones ‘CE2’ (36.29%), and ‘Y8’ (10.37%) on medium containing 500 mM NaCl. The highest salt tolerance index (0.30) was recorded for clone ‘KE8’, followed by 0.24 for clone ‘CE2’ and 0.10 for clone ‘Y8’ on medium containing 500 mM NaCl. The 50% growth inhibition dose of NaCl was also found to be 479 mM for clone ‘KE8’, as compared to 385 mM and 206 mM for clones ‘CE2’ and ‘Y8’, respectively. Various physiological and biochemical parameters were investigated in microshoots of putatively higher salt-tolerant clone ‘KE8’, moderately salt-tolerant clone ‘CE2’ and less salt-tolerant clone ‘Y8’ at different intervals of culture period (7, 14, 21, 28 days). The relative water content and pigment levels (chlorophyll and carotenoid) declined significantly during culture on medium containing 500 mM NaCl with increasing culture period. Furthermore, the decline was higher in the case of clone ‘Y8’ than ‘CE2’ followed by ‘KE8’. A significant increase in the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), accumulation of proline and lower levels of malondialdehyde content were recorded in clone ‘KE8’ as compared to the other clones ‘CE2’ and ‘Y8’. The present study suggested that clone ‘KE8’ is more tolerant to salt stress, which can be commercially grown in saline soils.

Intraspecific variation influences performance of moss transplants along microclimate gradients.

Identifying the environmental drivers of population dynamics is crucial to predict changes in species abundances and distributions under climate change. Populations of the same species might differ in their responses as a result of intraspecific variation. Yet the importance of such differences remains largely unexplored. We examined the responses of latitudinally distant populations of the forest moss Hylocomiastrum umbratum along microclimate gradients in Sweden. We transplanted moss mats from southern and northern populations to 30 sites with contrasting microclimates (i.e., replicated field common gardens) within a forest landscape, and recorded growth and survival of individual shoots over 3 yr. To evaluate the importance of intraspecific variation in responses to environmental factors, we assessed effects of the interactions between population origin and microclimate drivers on growth and survival. Effects on overall performance of transplanted populations were estimated using the product of survival and growth. We found differences between southern and northern populations in the response to summer temperature and snowmelt date in one of three yearly transitions. In this year, southern populations performed better in warm, southern‐like conditions than in cold, northern‐like conditions; and the reverse pattern was true for northern populations. Survival of all populations decreased with evaporation, consistent with the high hydric demands and poikilohydric nature of mosses. Our results are consistent with population adaptation to local climate, and suggest that intraspecific variation among populations can have important effects on the response of species to microclimate drivers. These findings highlight the need to account for differential responses in predictions of species abundance and distribution under climate change.

Citrus dwarfing viroid reduces canopy volume by affecting shoot apical growth of navel orange trees grown on trifoliate orange rootstock

Author(s): Lavagi-Craddock, I; Campos, R; Pagliaccia, D; Kapaun, T; Lovatt, C; Vidalakis, G | Abstract: Citrus dwarfing viroid (CDVd) infection of navel orange trees (Citrus sinensis (L.) Osb.) on ‘Rich 16-6’ trifoliate orange (Poncirus trifoliata (L.) Raf.) rootstock has been previously reported to reduce canopy volume by approximately 50%. We demonstrated that the reduction in tree size of CDVd-infected citrus resulted from a g20% reduction in the apical growth of individual shoots within the tree canopy. We also demonstrated that the reduced canopy volume of the CDVd-infected trees is a long lasting phenotype comparable to that of ‘Flying Dragon’ rootstock, which is known to reduce citrus tree size.

Assessing methods for restoring seagrass (Zostera muelleri) in Australia’s subtropical waters

Zostera muelleri, the dominant seagrass species along the eastern coastline of Australia, has declined due to anthropogenic stressors, including reduced water clarity. Water quality has improved in recent years, but restoration efforts are hampered by limited knowledge of transplantation methods. To support future restoration efforts, we tested multiple techniques for transplanting mature seagrass shoots: (1) sediment cores with intact seagrass plants (plug); (2) individual shoots anchored on frames (frame); (3) frame methods combined with subsurface mats to exclude bioturbating animals (mat+frame); (4) above-ground cages to exclude grazing fish (cage+frame); and (5) combined treatment of above-ground cages and subsurface mats (cage+mat+frame). Transplant success over 10 months showed considerable variability among locations. At one site, seagrass persisted in all treatments, with highest growth in the mat+frame treatment. At two locations, uncaged shoots were lost within 6–35 days of transplanting, presumably due to grazing by fish. In treatments with cages, growth was again highest in the mat+frame treatment. At the fourth location, all seagrass was lost due to physical stress. Thus, we conclude that transplantation success is highest using the mat+frame technique, but overall success depends on careful assessment of biotic and abiotic stressors at the chosen locations.

All for One: The Role of Colony Morphology in Bryophyte Desiccation Tolerance.

In the last decade, several works showed that even bryophytes from aquatic environments, if slowly dehydrated, can cope with desiccation in a response like the one from desert bryophytes. This led to the hypothesis that, if bryophytes from contrasting habitats can have similar responses, desiccation tolerance (DT) is partially inductive and not only constitutive as previously proposed and, therefore, colony morphology might be the key trait responsible for controlling dehydration rate essential for DT induction. Morphology and life form may be determinant traits in the adaptation of bryophytes to habitats with different water availabilities and corresponding predicted levels in the DT inducibility spectrum. Bryophytes from habitats with different water availabilities were dried as individual shoots and as a colony. The bryophyte Fontinalis antipyretica is fully aquatic presenting a streamer life form, while the three terrestrial species present turf life form with different sizes and degrees of space between individuals in the colony. Two species were collected under trees with moist soil presenting short turf (Tortella tortuosa) and long turf (Campylopus pyriformis) life forms. Another species was completely exposed to sun light with no surrounding trees and a tall turf life form (Pleurochaete squarrosa). We used chlorophyll a fluorescence parameter Fv/Fm (maximum potential quantum efficiency of Photosystem II) as a proxy to photosynthetic fitness throughout the contrasting dehydration rates (fast and slow). These bryophytes with different life forms were submitted to an X-ray computed microtomography (µ-XCT) to assess the three-dimensional inner structure and visualize locations for water storage. Shoots dried slow or fast according to the dehydration they were exposed to, as expected, but they presented similar dehydration rates across different species. However, the aquatic moss F. antipyretica, was unable to recover from fast drying, and after 24 h the recovery following slow drying was lower than the other species. The other three species presented full recovery after 24 h, either at the individual or colony level, and either from slow or fast drying. The only exception was the colonies of Campylopus pyriformis following fast drying that presented a slightly lower recovery, probably due to a looser colony structure.