Timing of reproductive and vegetative development in Saxifraga oppositifolia in an alpine and a subnival climate

Morphogenesis of floral structures, dynamics of reproductive development from floral initiation until fruit maturation, and leaf turnover in vegetative short-stem shoots of Saxifraga oppositifolia were studied in three consecutive years at an alpine site (2300 m) and at an early- and late-thawing subnival site (2650 m) in the Austrian Alps. Marked differences in the timing and progression of reproductive and vegetative development occurred: individuals of the alpine population required a four-month growing season to complete reproductive development and initiate new flower buds, whereas later thawing individuals from the subnival sites attained the same structural and functional state within only two and a half months. Reproductive and vegetative development were not strictly correlated because timing of flowering, seed development, and shoot growth depended mainly on the date of snowmelt, whereas the initiation of flower primordia was evidently controlled by photoperiod. Floral induction occurred during June and July, from which a critical day length for primary floral induction of about 15 h could be inferred. Preformed flower buds overwinter in a pre-meiotic state and meiosis starts immediately after snowmelt in spring. Vegetative short-stem shoots performed a full leaf turnover within a growing season: 16 (+/-0.8 SE) new leaves per shoot developed in alpine and early-thawing subnival individuals and 12 (+/-1.2 SE) leaves in late-thawing subnival individuals. New leaf primordia emerged continuously from snowmelt until late autumn, even when plants were temporarily covered with snow. Differences in the developmental dynamics between the alpine and subnival population were independent of site temperatures, and are probably the result of ecotypic adaptation to differences in growing season length.     

Ethylene- and dark-induced flower abscission in potted Plectranthus: Sensitivity,prevention by 1-MCP,and expression of ethylene biosynthetic genes

Prevention of ethylene- and shipping-induced flower abscission is necessary to maintain the quality of both cut flowers and potted plants during handling, transport and retail display. The aims of the present work were to determine the sensitivity of Plectranthus cultivars to applied ethylene, to alleviate ethylene- and shipping-induced flower abscission in intact potted plants using 1-methylcyclopropene (1-MCP), and to investigate the possible causes of dark-induced flower abscission. All cultivars were sensitive to ethylene in a concentration-dependent manner, and complete abscission occurred within 24 h with 1 and 2 μl l^− 1 ethylene. Unopened buds were more sensitive to applied ethylene, and exhibited greater abscission than open flowers. Ethylene synthesis remained below detection limits at all time points under control and continuous dark conditions. Dark treatment significantly increased flower abscission in Plectranthus cultivars, and like ethylene-induced flower abscission, this could be prevented by continuous 1-MCP treatment. Gene expression of ethylene biosynthetic enzymes ACS and ACO was examined as possible causes for the accelerated flower abscission observed in plants kept in continuous darkness. Expression patterns of ACS and ACO varied between different cultivars of Plectranthus. In some cases, increased expression of ACS and ACO led to increased flower abscission. Gene expression was higher in open flowers when compared to unopened flowers suggesting a cause for the observed preferential shedding of open flowers in some cultivars. Although the cause of dark-induced abscission in Plectranthus remains elusive, it can be effectively controlled by treatment with 1-MCP.     

Preformation and distribution of staminate and pistillate flowers in growth units of Nothofagus alpina and N. obliqua (Nothofagaceae)

Background and Aims

The distribution and differentiation times of flowers in monoecious wind-pollinated plants are fundamental for the understanding of their mating patterns and evolution. Two closely related South American Nothofagus species were compared with regard to the differentiation times and positions of staminate and pistillate flowers along their parent growth units (GUs) by quantitative means.

Methods

Two samples of GUs that had extended in the 2004–2005 growing season were taken in 2005 and 2006 from trees in the Lanín National Park, Patagonia, Argentina. For the first sample, axillary buds of the parent GUs were dissected and the leaf, bud and flower primordia of these buds were identified. The second sample included all branches derived from the parent GUs in the 2005–2006 growing season.

Key Results

Both species developed flowering GUs with staminate and/or pistillate flowers; GUs with both flower types were the most common. The position of staminate flowers along GUs was similar between species and close to the proximal end of the GUs. Pistillate flowers were developed more distally along the GUs in N. alpina than in N. obliqua. In N. alpina, the nodes bearing staminate and pistillate flowers were separated by one to several nodes with axillary buds, something not observed in N. obliqua. Markovian models supported this between-species difference. Flowering GUs, including all of their leaves and flowers were entirely preformed in the winter buds.

Conclusions

Staminate and pistillate flowers of N. alpina and N. obliqua are differentiated at precise locations on GUs in the growing season preceding that of their antheses. The differences between N. alpina and N. obliqua (and other South American Nothofagus species) regarding flower distribution might relate to the time of anthesis of each flower type and, in turn, to the probabilities of self-pollination at the GU level.Key words: Branch, bud, growth unit, Markovian models, Nothofagus alpina, N. obliqua, Patagonian forests, pistillate flower, preformation, staminate flower     

Flower model traps reduced thrips infestations on a pepper crop in field

A flower model trap developed by modifying an artificial yellow chrysanthemum flower was more attractive to flower thrips than commercial yellow sticky traps. Installation of these flower model traps (20 traps per 50 m² plot) was reported to reduce seasonal populations of Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) on strawberry flowers in greenhouses. In this study, we sought to determine if the installation of such flower model traps would reduce thrips populations in a pepper field. The traps were installed at the bottom of the plant canopy at varying densities (0, 5, 10, and 20 traps) in 20 plots (each 3 × 5 m²) using a completely randomized design. Thrips populations on pepper flowers were sampled from 1 to 29 July in 2009. All thrips sampled on the flowers were identified as F. intonsa. A significant effect of treatment and sampling date was found from repeated-measure analysis of variance. The highest density (20 traps per 15 m²) of traps significantly reduced the female and male F. intonsa population compared to the control by 61 and 49%, respectively. However, no difference in immature thrips numbers was found among the treatments. These results indicate that this flower model trap can be a useful tool for the management of flower thrips on field-grown peppers.     

Tillage effects on carbon footprint and ecosystem services of climate regulation in a winter wheat–summer maize cropping system of the North China Plain

Inappropriate farm practices can increase greenhouse gases (GHGs) emissions and reduce soil organic carbon (SOC) sequestration, thereby increasing carbon footprints (CFs), jeopardizing ecosystem services, and affecting climate change. Therefore, the objectives of this study were to assess the effects of different tillage systems on CFs, GHGs emissions, and ecosystem service (ES) values of climate regulation and to identify climate-resilient tillage practices for a winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) cropping system in the North China Plain (NCP). The experiment was established in 2008 involving no-till with residue retention (NT), rotary tillage with residue incorporation (RT), sub-soiling with residue incorporation (ST), and plow tillage with residue incorporation (PT). The results showed that GHGs emissions from agricultural inputs were 6432.3–6527.3 kg CO₂-eq ha⁻¹ yr⁻¹ during the entire growing season, respectively. The GHGs emission from chemical fertilizers and irrigation accounted for >80% of that from agricultural inputs during the entire growing season. The GHGs emission from agricultural inputs were >2.3 times larger in winter wheat than that in the summer maize season. The CFs at yield-scale during the entire growing season were 0.431, 0.425, 0.427, and 0.427 without and 0.286, 0.364, 0.360, and 0.334 kg CO₂-eq kg⁻¹ yr⁻¹ with SOC sequestration under NT, RT, ST, and PT, respectively. Regardless of SOC sequestration, the CFs of winter wheat was larger than that of summer maize. Agricultural inputs and SOC change contributed mainly to the component of CFs of winter wheat and summer maize. The ES value of climate regulation under NT was ¥159.2, 515.6, and 478.1 ha⁻¹ yr⁻¹ higher than that under RT, ST, and PT during the entire growing season. Therefore, NT could be a preferred “Climate-resilient” technology for lowering CFs and enhancing ecosystem services of climate regulation for the winter wheat–summer maize system in the NCP.     

Diversity of fungal endophytes in shrubby medicinal plants of Malnad region,Western Ghats,Southern India

A total of 6125 fungal endophytes were isolated from 9000 leaf segments of 15 medicinal shrubs growing in Malnad region of Western Ghats, Southern India, during winter, monsoon, and summer seasons. These fungal isolates belonged to Ascomycota (8.6 %), Coelomycetes (26.0 %), Hyphomycetes (28.0 %), Mucoromycotina (0.3 %) and sterile forms (4.9 %). Alternaria, Chaetomium, Fusarium, Colletotrichum, Cladosporium, Penicillium, Phyllosticta and Xylaria were the most frequently isolated. Significantly more isolates were obtained during the winter season than monsoon and summer seasons.     

Sea buckthorn (Hippophae rhamnoides L.) vegetative parts as an unconventional source of lipophilic antioxidants

The profile of lipophilic antioxidants in different vegetative parts (leaves, shoots, buds and berries) was studied in sea buckthorn (Hippophae rhamnoides L.) male and female plants collected in the end of spring. Five lipophilic compounds, i.e. three tocopherol homologues (α, β and γ), plastochromanol-8 and β-carotene, were identified in each vegetative part of male and female sea buckthorn plants at the following concentrations: 7.25–35.41, 0.21–2.43, 0.41–1.51, 0.19–1.79 and 4.43–24.57 mg/100 g dry weight basis. Additionally, significant amounts of α-tocotrienol (1.99 mg/100 g dry weight basis) were detected in buds. The α-tocopherol and β-carotene were predominant lipophilic antioxidants in each vegetative part, accounting for 78.3–97.0% of identified compounds. The greatest amounts of lipophilic antioxidants were found in leaves, especially of female plants. Nevertheless, apart from leaves, also shoots of plants of both sexes seem to be a good source of α-tocopherol and β-carotene.     

Herbivory,foliar survival and shoot growth in fragmented populations of Aristotelia chilensis

Habitat fragmentation may modify ecological interactions such as herbivory, and these changes can impinge upon plant fitness. Through a natural experiment, we evaluated if herbivory, foliar survival and shoot growth of the evergreen tree Aristotelia chilensis differ between a continuous forest (600 ha) and small fragments (∼3 ha) of the Maulino forest. From September 2002, we monthly recorded leaf emergence, area lost to herbivores and survival in four cohorts of leaves. Although herbivory of A. chilensis was low overall (foliar area loss <12%), herbivory was higher in the continuous forest than in small fragments. Nevertheless, differences in herbivory hold only for the first cohort of leaves, which were the largest ones. At the end of the growing season, herbivory rates in the continuous forest and fragments converge for all cohorts. Except for the first cohort of leaves, whose survival was higher in the fragments than in the continuous forest, foliar survival and shoot growth was similar in the continuous forest and fragments, and there was no correlation between herbivory and foliar survival or shoot growth. Although Maulino forest fragmentation negatively affects the intensity of herbivory, this effect is only transient, affecting only leaves that emerge early in the season, and might not affect the vegetative fitness of A. chilensis adults. The consequences of changes in ecological interactions triggered by forest fragmentation ought to be assessed rather than inferred from variations in patterns of resource use.     

Identification and characterization of flowering genes in kiwifruit: sequence conservation and role in kiwifruit flower development

Background  

Flower development in kiwifruit (Actinidia spp.) is initiated in the first growing season, when undifferentiated primordia are established in latent shoot buds. These primordia can differentiate into flowers in the second growing season, after the winter dormancy period and upon accumulation of adequate winter chilling. Kiwifruit is an important horticultural crop, yet little is known about the molecular regulation of flower development.     

Estimating seasonal aboveground biomass of a riparian pioneer plant community: An exploratory analysis by canopy structural data

The aboveground biomass (AGB) of vegetation is of central importance for ecosystem services by providing a measure of productivity. Models have been developed for estimating AGB via canopy structural variables in both fundamental and applied ecological studies. However, the potential of canopy structural variables for describing AGB dynamics throughout a growing season are still unclear. This study focuses on the AGB seasonal dynamics of a pioneer community, Cynodon dactylon (L.) Pers. (Bermuda grass), in a newly-formed riparian habitat at China’s Three Gorges Reservoir. The objectives are (1) to determine the most important structural variable for estimating AGB at different growing stages during the season, and (2) to develop a model that can estimate AGB at the different growing stages and using multiple structural variables. We sampled the C. dactylon community six times during the growing season from May to September 2016. Six variables were engaged in the analysis, including five canopy structural variables, i.e., canopy height (H), canopy cover (CC), leaf area index (LAI), the volume related variables V_LAI (H × LAI) and V_CC (H × CC), and one seasonal growth effect variable (SV). We conducted univariate linear regression analysis to determine the most important estimator of AGB and the best subset regression analysis were used to develop the AGB estimation model. The detected most important AGB estimator changed with different growing stages throughout a season. Canopy structural characteristics of the community are key factors for determining such changes. Cover was the most important variable for AGB estimation during the early growing season and V_LAI was the most important variable in the mid and end of the growing season. The developed best multivariate models explained an additional 11% in AGB variance on average for the different growing stages compared with the univariate models using the most important estimators. SV was found to be useful in developing an acceptance general AGB estimation model appropriate for the entire growing season. The findings of this study are expected to provide knowledge for guiding sampling work and to assist with modeling AGB and understanding the AGB seasonal dynamics in the future.     

Snow cover and extreme winter warming events control flower abundance of some,but not all species in high arctic Svalbard

The High Arctic winter is expected to be altered through ongoing and future climate change. Winter precipitation and snow depth are projected to increase and melt out dates change accordingly. Also, snow cover and depth will play an important role in protecting plant canopy from increasingly more frequent extreme winter warming events. Flower production of many Arctic plants is dependent on melt out timing, since season length determines resource availability for flower preformation. We erected snow fences to increase snow depth and shorten growing season, and counted flowers of six species over 5 years, during which we experienced two extreme winter warming events. Most species were resistant to snow cover increase, but two species reduced flower abundance due to shortened growing seasons. Cassiope tetragona responded strongly with fewer flowers in deep snow regimes during years without extreme events, while Stellaria crassipes responded partly. Snow pack thickness determined whether winter warming events had an effect on flower abundance of some species. Warming events clearly reduced flower abundance in shallow but not in deep snow regimes of Cassiope tetragona, but only marginally for Dryas octopetala. However, the affected species were resilient and individuals did not experience any long term effects. In the case of short or cold summers, a subset of species suffered reduced reproductive success, which may affect future plant composition through possible cascading competition effects. Extreme winter warming events were shown to expose the canopy to cold winter air. The following summer most of the overwintering flower buds could not produce flowers. Thus reproductive success is reduced if this occurs in subsequent years. We conclude that snow depth influences flower abundance by altering season length and by protecting or exposing flower buds to cold winter air, but most species studied are resistant to changes.     

Evaluation of several holding solutions for prolonging vase-life and keeping quality of cut sweet pea flowers (Lathyrus odoratus L.)

Cut spikes of sweet pea (Lathyrus odoratus L.) were kept in 2% sucrose, 200 ppm 8-hydroxyquinoline sulfate (8-HQS), pulsing treatment with 200 ppm 8-HQS in combination with 2% sucrose for 12 h, pulsing the spikes with 0.2 mM silver thiosulfate (STS) for 1 h and pulsing with 0.2 mM STS for 1 h followed by 2% sucrose solution. Therefore, this study aimed to see their effects on keeping quality and vase-life of the cut flowers. A control (deionized water) and a standard preservative were also included in the experiment. The results showed that all treatments had improved the keeping quality and vase-life of the cut flowers comparing to control ones. Among all these treatments, the 8-HQS combined with 2% sucrose showed the best water uptake, water balance, percentage of maximum increase in fresh weight of the cut flower stems and vase-life which was extended up to 17 days. Moreover, this keeping solution retarded the chlorophyll as well as carbohydrate degradation. However, anthocyanin concentrations were increased by treatments with sucrose alone or STS followed by sucrose during the postharvest life. It has been concluded that 200 ppm 8-HQS combined with 2% sucrose solution has the potential to be used as a commercial cut flower preservative solution to delay flower senescence, enhance post harvest quality and prolong the vase-life of sweet pea cut flowers.     

Survival and expansion of Pistia stratiotes L. in a thermal stream in Slovenia

We report about successful winter survival of a tropical plant Pistia stratiotes in a natural thermal stream Topla in Slovenia in temperate climate zone in central Europe. Only 2 years after its first occurrence in 2001 P. stratiotes managed to cover most of the water body where the thermal springs cause an elevated temperature (>17 °C year round). Enhanced biomass production of this invasive species took place in spring and summer and new stolons were formed at the end of the vegetation season. Over the winter older rosettes decayed and only small rosettes survived besides new rosettes formed from stolons. Plants developed flowers in April through August. Observations in December revealed viable seed production and seed presence in the sediment.     

Effects of lambing season,sex and birth type on growth performance in Norduz lambs

The aim of this study was to evaluate effects of two production systems (spring and winter), sex and birth type on growth performance in Norduz lambs. Data were collected using 103 and 140 lambs born during the winter and spring, respectively. Lambs born in the winter were heavier (P < 0.01) than those born in the spring at birth, 90 and 180 days of age by 0.5, 1.6 and 1.7 kg, respectively. Ram lambs were heavier (P < 0.01) than ewe lambs at birth, 90 and 180 days of age by 0.5, 1.0 and 2.3 kg, respectively, while lambs born as singles were heavier (P < 0.01) than lambs born as twins at birth, 90 and 180 days of age by 0.9, 1.6 and 2.3 kg, respectively. Lambs born in the winter recorded a higher (P < 0.01) pre-weaning ADG (15 g/day) than spring-born lambs, while ram lambs recorded a higher (P < 0.01) pre-weaning ADG (11 g/day) than ewe lambs. The effect of birth type was not significant on pre-weaning ADG. The influence of lambing season and sex were also not significant on post-weaning ADG. Lambs born as singles recorded a higher (P < 0.01) post-weaning ADG (16 g/day) than lambs born as twins. Results suggest the winter season to give rise to heavier lambs at weaning and post-weaning and suggest lambs born in different seasons to have distinctly different growth patterns. The data also confirm that the influence of sex and type of birth on growth to be very important and to be take into account sheep production.     

Interference between the macroalga Caulerpa prolifera and the seagrass Halodule wrightii

A field experiment was conducted to examine interactions between the seagrass Halodule wrightii and the macroalga Caulerpa prolifera in the Indian River Lagoon, FL, USA, and further if the outcome of the interactions between the two species was influenced by water depth. The experiment involved the manipulation of neighbor presence in plots established at the shallowest (50 cm) and deepest (80 cm) depths at which the two species co-existed at adequate densities to perform removal experiments. Shoot and frond densities were measured at the beginning (April), middle (July) and end (October) of the 6-month growing season, and above- and below-ground biomass values were determined at the end of the experiment (October). In the middle of the growing season H. wrightii had higher shoot densities and greater biomass in plots where C. prolifera had been removed at both water depths. This same pattern in shoot density and biomass for H. wrightii also occurred at the end of the growing season at the 80 cm depth. C. prolifera occurred at higher densities and greater biomass in the 80 cm depth range, but was generally unaffected by the presence of H. wrightii at either depth.     

Mitochondrial response in the apical and lateral flower buds of the Hanfu apple to cold stress during the dormancy stage

In order to study the different physiological bases of cold tolerance in the apical flower buds (AFB) and the lateral flower buds (LFB) of the Hanfu apple (Malus domestica Borkh), we used 4-year-old grafted Hanfu plants as material and evaluated the physiological characteristics of mitochondria in the flower buds, such as electron transport chains (cytochrome pathway and alternative pathway), H₂O₂ content, mitochondrial membrane permeability transition (mPT), and MDA content. AFBs and LFBs showed different changes in total respiratory rate (V_t) during low-temperature stress, except that both reached the lowest V_ts at ?30 °C. The AFB V_t increased to a peak at ?25 °C and decreased sharply to its minimal value at ?30 °C, and then remained relatively low. In contrast, the LFB V_t decreased to its minimal value at ?30 °C and increased sharply to a peak at ?35 °C and then decreased again. In both AFBs and LFBs, the cytochrome pathway was still the main electron transport chain throughout the whole process, and the contributions of the cytochrome pathway (ρV_cyt/V_t) and of the alternative pathway (ρV_alt/V_t) showed similar tendencies to those of V_t as temperature changed. Changes in the AFB mPT were different from those of AFB V_t. LFB mPT zigzagged from peaks at ?25 °C and 35 °C. The H₂O₂ content of the LFBs increased from ?10 °C to ?30 °C, then decreased slightly from ?30 °C to ?35 °C, and then increased again. H₂O₂ content in AFBs went up steadily throughout the whole process. During the early stage of low-temperature treatment, before temperatures reached ?35 °C, LFB MDA content remained relatively low and later increased. MDA content in AFBs began to increase from the beginning of treatment. It can be concluded that the higher cold tolerance of LFBs relative to AFBs could be closely related to their higher V_t and ρV_alt/V_t, which may aid adaptations to stress by supplying energy and metabolic substrates under low-temperature stress conditions.     

Relationship between seasonal progression of floral meristem development and <Emphasis Type="Italic">FLOWERING LOCUS T</Emphasis> expression in the deciduous tree <Emphasis Type="Italic">Fagus crenata</Emphasis>

Estimating the timing of flower bud formation in plants is essential to identify environmental factors that regulate floral transition. The presence of winter dormancy between the initiation of flowers and anthesis, characteristic of most trees in the temperate forests, hampers accurate estimation of the timing of floral transition. To overcome this difficulty, expression levels of flowering-time genes could be used as indicators of the timing of floral transition. Here, we evaluated the usefulness of molecular markers in estimating the timing of floral transition in Fagus crenata, a deciduous tree that shows intermittent and synchronized flowering at the population level. We selected FLOWERING LOCUS T (FT) as a candidate molecular marker and quantified the expression levels of its ortholog in F. crenata (FcFT). Subsequently, we analyzed the relationship between morphogenetic changes that occur between the vegetative state of the buds and the initiation of floral organs, and compared the FcFT expression levels in reproductive and vegetative buds, collected from spring to autumn. FcFT expression in leaves peaked at least two weeks before the morphological changes associated with flowering were visible in the buds in late July. FcFT expression levels were significantly higher in the reproductive buds than in the vegetative buds in July. These results suggest that the FcFT expression in July is a reliable indicator of the timing and occurrence of floral transition. This study highlights the utility of molecular tools in unraveling reproductive dynamics in plants, in combination with ecological and physiological approaches.     

A simulation study of subterranean termites' territory formation

The process through which the Formosan subterranean termite, Coptotermes formosanus Shiraki, establishes territory was simulated using a lattice model in order to understand how such territories are formed from their seeds-founding pairs that fall to the ground every year. The model incorporated, summer–winter cycles, and fourteen years were simulated. Simulated pairs fell to random sites within the lattice space at the beginning of every summer, and their territories grew during the summer season, and shrunk during the winter season. Fourteen years were sufficient for territory size and shape to become stable over time. The simulation revealed that only pairs introduced at t = 0 had established large territories by the end of the simulation (t = 14). Pairs that were introduced later expanded their territory a little at first, but ultimately shrunk back into a single-cell-sized or small-sized territory. This means that stable-state territory size is mostly determined by when that territory was initially established.     

Evaluating the level of agreement between human and time-lapse camera observations of understory plant phenology at multiple scales

The growing popularity of digital-repeat photography in field research is seeing traditional field efforts being assisted and even replaced by low-cost cameras. The efficiency of using cameras is obvious, but there is an assumption that they capture the same information as observations made by humans. This paper aims to determine the level of agreement between these two methods of interpreting understory vegetation phenology. We compared daily phenological observations made by low-cost cameras with those made by personnel during field visits every 10 days. Phenophases were defined as the non-spectral, physical developmental stages of Canadian buffaloberry (Shepherdia canadensis) and alpine sweetvetch (Hedysarum alpinum). The relationship between observation methods was quantified using a weighted kappa statistic at three spatial scales ranging from individual plants to areas up to 6 ha. Agreement between the camera observations and those made by field personnel was nearly perfect (Kappa > 0.9) for both the vegetative and reproductive phenology of both study species at all spatial scales. The level of agreement was found to be more variable early in the season when plant growth is more rapid. Overall there was a slight bias in the image interpretations to underestimate the rate of development. Time-lapse photography was found to be an analogous replacement for field visits; however, some plant species are more suitable for observation by camera than others. Spatially, it was determined that observations of a single plant are all that is required to capture the phenology of the surrounding region in excess of 6 ha. This analysis was carried out over a single growing season in the in the Rocky Mountains of western Alberta, Canada.