Peak Flowering Research Articles

Phenological Events along the Elevation Gradient and Effect of Climate Change on Rhododendron arboreum Sm. in Kumaun Himalaya

Phenological events of rhododendron ( Rhododendron arboreum Sm.) were monitored along elevation gradients in distinct ecological settings. The observations were carried out between 1500 and 2500 m elevation in Central Himalaya. The phenological events, i.e. bud formation, bud bursting, leafing, flowering, fruit formation and seed formation were recorded. Phenological duration and synchrony of all these phenophases were determined within site and along the elevation gradient in each study site. Our observations showed high synchrony throughout the elevation gradient, especially for peak flowering. Temperature, rainfall, age of the observed trees and site characteristics were related to initial and peak flowering dates. The circumference varied from 35.0 ± 2.73 to 140.0 ± 2.88 cm; similarly, height varied from 5.0 ± 1.02 to 16.5 v 1.41 m. All the phenological events began early at low elevation and were delayed at higher elevation. R. arboreum had a sharp flowering peak from January to March. Wet season flowering was rare, and seed formation occurred in summer. The climatic conditions affected the phenological characters of R. arboreum .

Understanding of the Interactive Effect of Waterlogging and Shade on Cotton (Gossypium hirsutum L.) Growth and Yield

Under the current climatic variability, extreme weather events with multiple stresses have become more frequent. Cotton, a relatively waterlogging sensitive crop, often experiences significant yield losses under persistent summer rainfall followed by extended cloudy weather. In two years of field experiments, we studied individual and interactive effects of soil waterlogging (WL) and shade on cotton growth and yield, hypothesising that low light conditions would amplify WL damage in cotton. The crop was exposed to WL, shade (50% reduction in photosynthetic photon flux) and WL + shade at peak flowering. Waterlogging was imposed by extending irrigation time from 8h to (96h and 120h, in 2012-13 and 2013-14, respectively), while the plants were shaded for 6 days or 9 days in 2012-13 and 2013-14, respectively. Waterlogging significantly inhibited cotton growth and yield during both seasons, although yield reduction in shaded (9 days) cotton was significant only in 2013-14. Under individual stresses, both WL and shaded plants had similar reductions in lint yield (15% and 18%, respectively), compared with controls (non-waterlogged, non-shaded). The interactive effect of WL and shade was significant only when the effect of WL alone on cotton yield was relatively small, suggesting that shade exacerbated moderate WL but intense WL acted on yield independently of light levels. Yield reductions were the result of lower number of final bolls produced, while boll weight remained unaffected. Increased post-waterlogging fruit abscission of WL and / or shaded cotton restricted the total number of bolls produced. In addition, these stresses (individual or combined) significantly impaired leaf nitrogen acquisition, photosynthesis and the consequent development of new fruiting nodes.

Seed development of arrowleaf, balansa, gland and Persian clover

The development process from floral bud formation to seed maturity of four top flowering annual clovers was quantified from a field experiment across 10 sowing dates at Lincoln University, Canterbury, New Zealand. For each species, a numeric reproductive scale was created as a field guide to document morphological changes as the bud progresses through reproductive development. The duration from bud visible to open flower was 341 °C days for 'Cefalu' arrowleaf, 215 °C days for 'Bolta' balansa, 196 °C days for 'Prima' gland and 186 °C days for 'Mihi' Persian clover. The inflorescence then required a further 274-689 °C days, 185 °C days , 256 °C days and 425 °C days for each respective species to reach physiological maturity. This was indicated when 50% of seeds had turned red/brown for 'Cefalu' arrowleaf, 100% pods turned yellow for 'Bolta' balansa, 100% of seeds were yellow and hard for 'Prima' gland, and pods turned brown with the first sign of colour change in seeds for 'Mihi' Persian clover. These results can be used to facilitate on farm decision making in relation to grazing management or seed set for subsequent regeneration. Keywords: floral development chart, harvest maturity, peak flowering, pollination, seed filling, thermal time, Trifolium vesiculosum, T. michelianum, T. glanduliferum, T. resupinatum

Effect of Nitrogen Application Amounts on Uptake and Utilization of Potassium in Cotton Grown in Improved Coastal Saline Land Regions

A field experiment using transgenic cotton cultivar Xiangzamian 8 with different nitrogen application amounts(0, 150, 300, 375, 450, and 600 kg N ha–1) was carried out in the coastal improved saline land region of Dafeng City in 2010 and 2012. Results showed that the nitrogen application increased potassium uptake of cotton at different growth stages, with the highest increment at the peak flowering-boll opening stage, and the percentages of potassium uptake decreased from seedling to peak flowering stages, but increased from peak flowering to boll maturing stages. In addition, nitrogen application lowered the decreasing speed of potassium concentration in middle and upper fruiting branches at later growth stages, but had less influence on lower fruiting branches. The marginal effect of potassium uptake(promoted amount of potassium uptake due to 1 kg increase of N application) showed an upward-downward trend with the increase of nitrogen application rate. The higher the position of fruiting branches grown, the more the nitrogen amount demanded to meet the highest marginal effect of potassium uptake. Under the nitrogen application of 300–375 kg ha–1, the economic coefficient of biomass and potassium was relatively high, eigenvalues of dynamic model of potassium content and potassium accumulation were relatively coordinate, and the marginal effect of potassium uptake and lint production efficiency of potassium were relatively high in middle and upper fruiting branches. Excessively high nitrogen application resulted in a relatively narrow rise of yield, and the marginal effect of potassium uptake and lint production efficiency of potassium were relatively low; excessively low nitrogen application, however, also resulted in a lower yield, as economic coefficient of biomass and potassium was relatively low.

Physiological responses of tomato (Lycopersicon esculentumMill) cv. Arka Ashish to elevated atmospheric CO2under water limiting conditions

The study was conducted to understand the physiological responses of tomato cv. Arka Ashish to 550 ppm elevated CO2 (EC) and to what extent EC alleviates the adverse effects of water stress at peak flowering stage. The plants grown at EC had significantly higher PN with decreased stomatal conductance (gs) and leaf transpiration rate (E) compared to plants grown at 380 ppm ambient CO2 (AC), irrespective of water supply conditions. Plants grown at EC recorded a lower number of stomata on both adaxial and abaxial surfaces. The plants at EC maintained higher water potential(Ψ w), instantaneous water use efficiency (iWUE) and lower osmotic potential (Ψ s) at irrigated and water stress condition. Higher SOD and GR activity was observed at EC compared to the plants grown at AC. Increased number of fruits and fruit weight per plant were observed at EC both at control and water stress condition.

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

Plant phenological events are some of the most sensitive indicators of how plant species respond to favourable or stressful conditions. The evaluation of the flowering phenology of invasive plant species is particularly relevant, mainly due to its crucial importance in determining plant reproductive success and the outcome of invasion. We studied the phenology of Acacia longifolia, an aggressive, invasive plant species in the Mediterranean basin. We measured its vegetative growth and reproductive traits, specifically flowering phenophases and fruit production, under different climatic conditions (mesic and xeric Mediterranean climates), and in two different habitats (pine forest and open area). All the measured phenological phases began earlier at the xeric site than at the mesic site; this was particularly evident when comparing reproductive phenophases. Flowering dates were significantly associated with air temperature, with early peak flowering dates linked to increases in air temperature. The number of fruiting flowers per inflorescence in A. longifolia trees was higher at the mesic site, mainly in the pine forest plot, and the number of aborted fruits was notably lower than in the xeric plots. The presence of a pine forest at the mesic site strongly influenced the flowering phenology of A. longifolia and resulted in the highest reproductive success and the lowest branch growth rate. Our results demonstrate that a combination of climate and forest structure can cause pronounced differences in phenology and reproductive success of A. longifolia. These data can help to understand the variations in invasive rates of A. longifolia across the Mediterranean basin.

Site-specific factors influence the richness and phenology of snowbed plants in the Pyrenees

Although the timing of snowmelt and growth temperatures appear to be the main factors that influence the species richness and phenology of snowbed plants, site-specific characteristics may also play a role in modifying the effects of the timing of snowmelt and temperature. In this study, the effects of site-specific factors (microtopography and snow origin) on species richness and plant phenology were evaluated in 72 plots in two snowbeds in the Andorran Pyrenees. Snowmelt patterns influenced the spatial distribution of species richness and abundance. Site-specific factors had significant effects on the responses of species (shortening or lengthening the duration of the phenophase) and on the extent to which the timing of snowmelt influenced leaf expansion and flowering. Notably, the highest rates of leaf expansion occurred on late snowmelt isoclines, where, nevertheless, the time taken to reach peak flowering was significantly longer than on the early snowmelt isoclines. The results of this study highlight the fact that, in addition to the effects of interannual variability in climate, site-specific factors have a significant effect on the phenology and reproductive success of the commonest plants in the snowbed communities of the Pyrenees.

Two alien invasive acacias in Italy: Differences and similarities in their flowering and insect visitors

In Italy, alien acacias have been introduced for ornamental and reforestation purposes, and some species became invasive occupying patches of the Mediterranean landscape. On the Island of Elba (Central Italy), Acacia dealbata and A. pycnantha form dense stands at short distance, showing an impressive massive flowering at the end of the winter/early spring. Our aim was to investigate the behaviour of the two species in relation to the flowering features, from phenology to floral characteristics, and their replay to the observed flower visitors. Differences between the two species emerged on all the parameters considered. A. pycnantha peak of flowering occurred later than A. dealbata and showed larger flower heads (FHs), more flowers/head, stamens/flower and polyads. On A. dealbata, we recorded longer racemes and more FHs/raceme, determining a more flower-dense crown. Even if contacts with flower visitors were generally low on both species, A. dealbata showed a more heterogeneous visitor assemblage. Both acacias species interacted with local generalist pollinators, as bumblebees and honey bees. Flower handling and resource collection strategy by the honey bee indicate a long-term relationship between the bee and the acacias, with bees investing longer time on the larger A. pycnantha flower heads.

Detectability of the global weedHypochaeris radicatais influenced by species, environment and observer characteristics

Aims: To determine the detectability of a global weedy perennial weed Hypochaeris radicata and its relationship with five common observer, species and environmental variables. Methods: Trained independent observers conducted time-limited repeat surveys of H. radicata during autumn in an endangered grassy box-gum woodland ecosystem in south-east Australia. Single-species single-season site-occupancy modelling was used to determine if detectability of H. radicata was altered by five covariates, observer, litter height, grazing, maximum plant height and flowering state. Important Findings: Detectability for H. radicata varied significantly with observer, litter height, plant maximum height and flowering state, but not with grazing. Despite significant observer-specific variation, there was a consistent increase in detectability with plant height and when plants are in flower for all observers. Detectability generally decreased as litter height increases. Perfect or constant detection rates cannot be assumed in plant surveys, even for easily recognizable plants in simple survey conditions. Understanding how detectability is influenced by common survey variables can help improve the efficacy of plant monitoring programs by quantifying the extent of uncertainty in inferences made from survey data, or by determining optimal survey conditions to increase the reliability of collected data. For plants with traits similar to H. radicata, surveying when most plants are at maximum height or in flower, increasing search intensity when litter levels are high and minimizing observer-related heterogeneity are potentially simple and effective ways to reduce detection errors. We speculate that detection rates may be lower, more variable and involve additional covariates when surveying during the peak flowering spring season with the presence of more warm season and taller annual species.

Foraging behaviour of honeybees (Apis spp.) (Hymenoptera: Apidae) in hybrid seed production of Indian mustard (Brassica juncea)

Pollination of entomophilous crops by honeybees is considered as one of the effective and inexpensive method for improving the crop yield and its quality. In most of the crops, effective pollination is prerequisite for fruitful fertilisation. Hence, we investigated the differential foraging activity of honeybees in relation to aspects of crop management including sowing time and parental row ratio in the hybrid seed production of the first Indian mustard hybrid NRCHB Apis spp. (half of which being Apis dorsata) was the dominant pollinators in our study. The pollinator abundance was maximum in the forenoon in male line (19.1) and in the afternoon in female line (13.9). Pollen collectors (8.7) outnumbered the nectar collectors (7.2) in male line and the reverse in female line. Pollinator abundance decreased in rows distantly positioned from the male parent row. Air temperature was positively correlated (r = 0.631) and relative humidity negatively correlated (r = –0.736) with honeybee foraging. Warmer weather conditions during flowering period showed higher number of honeybee visiting the hybrid seed production plots. This study would help the seed producers to standardise the planting geometry and date of sowing to promote maximum pollinator abundance at peak flowering period resulting in higher hybrid seed yield.

Are mismatches the norm? Timing of flowering, fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)

The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant‐animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north‐temperate, self‐incompatible, insect‐pollinated, and bird‐dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit‐set and experiments indicated that synchronous peak flowering increased fruit‐set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.

Early Evaluation of Camu-Camu Subsamples in Transition Savanna/Forest Area

Camu-camu (Myrciaria dubia (Kunth) McVaugh) is an indigenous fruit of the floodplain and riparian forests of the Amazon region. In Brazil, Roraima state has appropriate conditions for this fruit production. Cultivation outside the floodplains is an alternative to increase the availability of fruits, since flowering occurs almost all year round, and fruit bearing coincides with the end of the dry season and early rain season. The objective of this study was to evaluate the vegetative development of 6 camu-camu subsamples selected from the Instituto Nacional de Pesquisas da Amazonia- INPA (Amazonas state), in a savanna region near Boa Vista city (Roraima, Brazil). The experiment was conducted at the Serra da Prata Experimental Station of the Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA), with a climate type Am according to Koppen climate classification. Four parameters were evaluated for the growth analysis, the basal stem diameter (mm), the plant height (cm), and numbers of basal and terminal shoots, as well as the numbers of flowers and fruits. Measurements were made at 90 days intervals in order to define the growth curve of each subsample for 30 months Based on the parameters of vegetative growth and early flowering, we recommend the UAT 1096-5 subsample with the best vegetative development for transition forest/Savanna area, presenting moreover higher number of terminal shoots, greater height, and early flowering than the remaining camu-camu subsamples. At 30 months after planting, the UAT 1896-7 and UAT 0796-8 subsamples showed no statistical difference from UAT 1096-5 regarding the number of terminal shoots, but showed slightly lower height, with a statistically significant difference. The UAT 1596-7, UAT 1796-7, and URUBU-2 subsamples showed the lowest number of terminal shoots, although UAT 1596-7 presented greater height than the others. In relation to precocity, peak flowering occurred in January, 30 months after planting, with the UAT 0796-8 and UAT 1096-5 subsamples excelling over others, with 500 and 435 flowers in total, respectively.

Spatio-temporal variation in phenological response of citrus to climate change in Iran: 1960–2010

Recent studies investigating floral and faunal phenological responses to climate change have highlighted the extent to which these relationships are species and location specific. This study investigates temporal responses of citrus peak flowering to climate change in the cities of Kerman, Shiraz and Gorgan, Iran. Phenological data comprise peak flowering dates of five citrus types: orange, tangerine, sweet lemon, sour lemon and sour orange, collected daily from government heritage gardens located within each of the cities over the period 1960–2010. For the same period, daily Tmax, Tmin and rainfall data were acquired from the Iranian Meteorological Organization. Time trend analyses were undertaken for both the phenological and meteorological data, followed by linear regression to determine the nature and extent of relationships between these variables. We find that the mean peak flowering dates, and their long-term trends over the 51-year period, are similar across the five citrus types within each city, but demonstrate significant differences between cities. Flowering date advances of 0.12–0.17d/yr are recorded for Kerman, and more rapid advances of 0.56–0.65d/yr for Shiraz. Notably, progressive delays in flowering dates occur in Gorgan (0.05–0.1d/yr). The peak flowering dates in the former two cities demonstrate strong relationships with mean annual Tmin, ranging from r=0.47–0.61 (p=0.0045; p<0.0001) for Kerman to r=0.53–0.67 (p=0.0386; p<0.0001) for Shiraz, and equate to peak flowering advances of 3.15–3.39d/°C and 4.34–5.47d/°C, respectively. By contrast, the strongest relationships between peak flowering dates and annual climate in Gorgan are with rainfall (r=0.02–0.3, p=0.8874; p=0.0528), indicating a weak phenophase response of 0.01d/mm. For Gorgan, the strongest relationships (r=0.43–075, p=0.0002 to p<0.0001) are between peak flowering date and mean Tmax for May, the month during which peak flowering occurs, with a delay in flowering of 1.26–1.86d/°C cooling. This suggests a relatively more influential climatic role directly preceding peak flowering, which may be associated with anomalous cooling in May. However, Kerman and Shiraz demonstrate more consistent strength in correlation between peak flowering and climate variables across the months of the year, with only slight peaks for the months flanking peak flowering. Our study highlights the importance of considering location-specific phenophase shifts within given regions, as dissimilar trends may occur within a country; this has important implications for future agricultural planning and fruit crop supply to local and international markets.

The Importance of Bees for Eggplant Cultivations (Hymenoptera: Apidae, Andrenidae, Halictidae)

The increasing demand for food and the “Pollination crisis” have emphasized the importance of better understanding the potential of different wild bee species for pollinating crops. The aim of this study was to investigate how dependent Solanum melongena L. is on bees for fruit production and if it is possible to observe any insufficiency of pollination in four (two organic and two conventional) eggplant cultivations. Bee samplings were performed during the eggplant’s peak flowering. Three pollination tests (T1= without insect visitation; T2= free insect visitation; T3= Pollen complementation) were carried out in order to evaluate the importance of bees for fruit setting in S. melongena L. Most of the bee species collected on eggplant flowers were buzz-pollinators – Bombus , Xylocopa , Exomalopsis , Centris , Oxaea and many species of Halictidae, and can promote the eggplant pollination. Trigona sp. and Apis mellifera were also collected on flowers, but they can’t vibrate their anthers, although Apis presented a flying adaptation while visiting the flowers and eventually can pollinate the flowers. Most of the unvisited flowers (T1) failed to form fruits and when it happened, those ones were much lighter and smaller than those formed from flowers of T2 and T3; demonstrating the importance of bees for eggplant pollination. No statistical differences were found between the weight of eggplants in T2 vs. T3 within each area, however, the weight of fruits from T2 tests varied and differed significantly between the four studied areas. Our results indicated no pollen insufficiency in the studied areas, although the use of pesticides may disrupt crop-pollinator interactions, which may cause pollination insufficiency. Furthermore, land management seems to be a factor that determines efficiency of pollination in agricultural landscapes and ensures pollination services in cropped areas.

English

Growth retardants have been proven to prevent excessive stem elongation and reduce internode length in plants by inhibiting the effect of cell division and enlargement of cell in plants. This study was aimed to evaluate the effect of concentrations of daminozide and maleic hydrazide on growth, physiology and flowering of chrysanthemum cultivar Punch under protected condition. The treatments composed of two growth retardants: daminozide at four different concentrations (1000, 1500, 2000 and 2500 ppm) with three frequencies (7, 14 and 21 days after darkening) and maleic hydrazide at three different concentrations (500, 750 and 1000 ppm) with two frequencies (7 and 21 days after darkening) along with control (no spray given). Hence based on the results obtained, it can be concluded that single application of daminozide at 2500 ppm at seven days after darkening reduced the plant height at considerable height (34.33, 83.33 and 103.58 cm) at critical stages and improved total leaf area (1694.55 and 1745.27 cm2) at bud appearance and peak flowering stage and showed earliness in flowering and days to harvest (44.72 and 81.33 day), increased pedicel length (5.87 cm), cut stem girth (3.24 cm), stem fresh weight (68.00 g/stem) and chlorophyll (1.93, 2.53 and 2.80 mg/g) and soluble protein content (65.66, 72.33 and 80.66 mg/g) at critical stages. Increased cut stem yield (77.34 stems/m2) and improved vase life (12.50 day) were also recorded. This may be recommended to improve growth and flower quality of &lsquo;Punch&rsquo; chrysanthemum under greenhouse conditions. &nbsp; Key words: Chrysanthemum, daminozide, maleic hydrazide, growth, flowering.

Correlation Studies in Carnation (Dianthus caryophyllus L.)

Eight genotypes of carnation were evaluated for phenotypic and genotypic correlation coefficient between flower yield and 23 quantitative traits, to understand the association between these characters and their relative contribution to flower yield. The aim was to bring about rational improvement in carnation. Genotypic correlation coefficients were higher than phenotypic correlation coefficients for most of the characters studied. Flower yield per square meter showed highly significant association with number of branches, nodes per stalk and nodes per plant; stem girth, number of leaves, leaf area, total dry matter and duration of flowering. Significant association was found with plant spread, girth of flower and flower length, and, negative correlation was seen with days taken to flower bud initiation, first harvest and peak flowering, at the genotypic level. Whereas the number of nodes per plant and duration of flowering exhibited positive and highly significant correlation with yield, only significant correlation was found with plant spread, number of branches, nodes per stalk; stem girth, number of leaves and vase life, at the phenotypic level. These traits may serve as effective selection parameters for carnation improvement.

Pollen-ovule ratios and flower visitors of day-flowering and night-flowering Conophytum (Aizoaceae) species in South Africa

In desert environments mutualistic relationships between plants and their pollinators are believed to be strongly synchronized by rainfall that triggers flowering periods. However, recent studies have shown that this might not always be the case and that the level of specialization may also play a role. Although spring is the main flowering season in Namaqualand, the winter-rainfall region of southern Africa's Succulent Karoo, a pronounced flowering peak occurs in autumn, outside of the normal winter–spring period. One example is the genus Conophytum where, in contrast to the vast majority of the Aizoaceae, most species flower in autumn before the winter rain. About 25% of the species in the genus are night-flowering, maybe as a consequence of the shift in the seasonal flowering time. We therefore studied flower visitors in 30 Conophytum species in South Africa and, for comparison of pollination systems, analysed pollen-ovule ratios in diurnal and nocturnal conophytums. Pollen wasps of the genus Quartinia (Vespidae: Masarinae) were found to be the main flower visitors in diurnal species, whereas in night-flowering species different moth species were observed. We found no significant differences between pollen-ovule ratios of diurnal and nocturnal Conophytum species, suggesting that diurnal and nocturnal pollinators are equally efficient.

Flowering phenology and floral visitors of &lt;i&gt;Piliostigma reticulatum&lt;/i&gt; in a tropical dry forest, Burkina Faso

Piliostigma reticulatum is a dioecious species that provides food, fodder and the revenues from the sale of its pods constituted an important resource for sahelian population. During the flowering, flowers are abundant but the fruit set remained very low in spite of a large number of insect visitors. The aim of this work was to study flowering phenology, to identify potential pollinators and visitors, to determine the visitation rate and the synchronism between floral phenology and the insect visitors. The natural population studied is located at Budtenga in the North Sudanian area of Burkina Faso. The phenological study was carried out from July 2009 to December 2009 on 500 inflorescences randomly sampled from inflorescences of 40 male and female individuals. Potentials pollinators were determined using their physical ability to carry pollen in their body and the reference based diets. Our results showed that many orders of insects visit the flowers of P. reticulatum. Nymphalidae (Lepidoptera), Syrphidae (Diptera), Apidae (Hymenoptera) and Sphecidae (Hymenoptera) were regarded as main potential pollinators of P. reticulatum. Apidae (Apis mellifera) was the most abundant and frequent visitor. We found that August was the peak flowering period for both male and female individuals and the peak emergence of potential pollinators. Therefore, the emergence of potential pollinators responsible for pollen dispersal might be punctuated by flowering phenology.Keywords: Caesalpinioideae, P. reticulatum, phenology, visitors, Sudanian forest

Peak flowering and fruiting patterns in the endangered orchid

Peak flowering and fruiting patterns in the endangered orchid

Effects of Night-Interrupted Lighting on Growth and Flowering Duration of Herbaceous Perennials Grown Under Nursery Conditions in the Southern United States

Staggered starting dates for night-interrupted lighting (NIL) were evaluated for accelerated sequential flowering of herbaceous perennials with different photoperiod requirements outdoors in a southern nursery setting. Plants evaluated were black-eyed Susan (Rudbeckia fulgida ‘Goldsturm’), an obligate long-day (LD) plant; obedient plant (Physostegia virginiana ‘Miss Manners’), a facultative LD plant; and Stokes' aster (Stokesia laevis ‘Peachie's Pick’), a facultative intermediate-day plant. With all species, the dates of first flower and maximum flower number occurred sooner under LDs from incandescent (INC) and fluorescent (FLU) lamps than under natural photoperiod (NP). Mean and maximum flower numbers were greater under NIL than under NP for black-eyed Susan and Stokes' aster but not for obedient plant. Time in flower increased in Stokes' aster, but either decreased or was not affected by NIL for black-eyed Susan and obedient plant. Flowering periods of black-eyed Susan and obedient plant exposed to different NIL timings overlapped extensively while leaving a gap in flowering between plants exposed to NIL and those under NP. This gap in flowering suggests that the intervals between NIL start dates could be longer to lessen the flowering overlap of plants under NIL, and that the interval between the start of the last NIL treatment and the onset of an inductive photoperiod be reduced to maintain sequential peak flowering until the natural flowering period. With Stokes' aster, flowering overlapped for plants in the different NIL timings and under NP, resulting in continuous sequential blooms from first flowering of plants under NIL until the plants' natural flowering period under NP in late May. Flowering periods of Stokes' aster exposed to NIL beginning on different dates overlapped extensively, suggesting that at least one NIL start date could be omitted and the intervals between the start of NIL increased without sacrificing continuous sequential peak flowering. NIL from INC and FLU lamps promoted growth in plant height compared to that of plants under NP, although the increase in plant height was less under FLU lamps.