Peak Flowering Period Research Articles

The impact of different cutting regimes on population density of Jacobaea aquatica (Hill) G. Gaertn., B. Mey. & Scherb. and grassland vegetation

Jacobaea aquatica is a monocarpic Asteraceae growing in wet grasslands of low management intensity. It is considered a noxious weed because it contains pyrrolizidine alkaloids, which cause health problems to livestock. The aim of this study was to develop management options to reduce the population density of J. aquatica in meadows of high nature conservation value without negative impacts on plant species diversity. The study site is located at the Hercynian part of Lower Austria near the city of Gmünd. The effect of five different cutting regimes on population density and seed production of J. aquatica as well as on species richness of the surrounding vegetation was tested on permanent plots from 2007 to 2012. One cut in October diminished J. aquatica but species richness decreased. Two cuts during the peak flowering period (July and August) and October reduced the population density of J. aquatica by c. 70% without obvious loss of species richness. Traditionally practiced two cuts in June and September lead to a rapid population growth of J. aquatica. According to our results, a first cut in June providing non-toxic fodder and two additional cuts during peak flowering are appropriate to reduce J. aquatica and to maintain biodiversity.

Reproductive Biology of <I>Elaeocarpus blascoi</I> Weibel, an Endemic and Endangered Tree Species of Palni Hills, Western Ghats, India

Elaeocarpus blascoi Weibel is a lesser known endemic tree species growing in the Vattakanal shola forest of Palni Hills, Western Ghats, India. A study on reproductive biology of the species was conducted in the natural habitat to study its phenology, floral biology, pollen biology, fruit set and seed germination. Flowers are bisexual, anther dehisces 2-3 hours after anthesis and stigma becomes receptive on the day of anthesis and extends up to 6 days. Breeding experiments confirmed that the species permits autogamy and geitonogamy. Six different pollinators were observed during peak flowering period and Apis dorsata (honey bee) was found to be an effective pollinator and it takes 55 ± 15 sec per flower. Percentage of fruit set observed in the natural habitat was 78% and seed germination rate was found to be less than 5% in the natural habitat. Tests showed that more than 70% of seeds lost their viability after a year and most of the seeds were infested with Fusarium sp., Lasiodiplodia sp. and Penicillium sp. Further, the natural habitat of the species is altered by commercial plantations, tourism and urbanization in the Palni Hills, which leads to their reduction.

Synchrony in Leafing, Flowering, and Fruiting Phenology ofSenegalia senegalwithin Lake Baringo Woodland, Kenya: Implication for Conservation and Tree Improvement

Leafing, flowering, and fruiting patterns ofSenegalia senegalwere studied over a period of 24 months from January 2014 to December 2015. The phenological events of the species are bimodal and follow the rainfall patterns. The leafing phase starts during the onset of rains and lasts for 18 weeks. New leaves continued to appear on the new shoots while old leaves persisted to the leaf fall period. Flowering event takes 12 weeks and is concentrated in the months of high relative humidity (April and October) with one-month peak flowering period. Fruiting phase starts at the peak of the rainy seasons (May and November) and peaks in June and December. This phase lasted for 14 weeks. The fruits mature towards the end of the rainy season (January/February and July/August). The fruits open for dispersal mainly in February/March and September during the peak dry season. High synchrony index (SI) was found in leafing (SI: 0.87), flowering (SI: 0.75), and fruiting (SI: 0.85) events among the populations. Temperature, precipitation, and soil moisture content were significantly correlated with the phenological events. Significant variations in floral morphology and fruits traits were also evident. Seed collections should be undertaken in the months of January/February and July/August.

The Utility of AISA Eagle Hyperspectral Data and Random Forest Classifier for Flower Mapping

Knowledge of the floral cycle and the spatial distribution and abundance of flowering plants is important for bee health studies to understand the relationship between landscape and bee hive productivity and honey flow. The key objective of this study was to show how AISA Eagle hyperspectral data and random forest (RF) can be optimally utilized to produce flowering and spatially explicit land use/land cover (LULC) maps for a study site in Kenya. AISA Eagle imagery was captured at the early flowering period (January 2014) and at the peak flowering season (February 2013). Data on white and yellow flowering trees as well as LULC classes in the study area were collected and used as ground-truth points. We utilized all 64 AISA Eagle bands and also used variable importance in RF to identify the most important bands in both AISA Eagle data sets. The results showed that flowering was most accurately mapped using the AISA Eagle data from the peak flowering period (85.71%–88.15% overall accuracy for the peak flowering season imagery versus 80.82%–83.67% for the early flowering season). The variable optimization (i.e., variable selection) analysis showed that less than half of the AISA bands (n = 26 for the February 2013 data and n = 21 for the January 2014 data) were important to attain relatively reliable classification accuracies. Our study is an important first step towards the development of operational flower mapping routines and for understanding the relationship between flowering and bees’ foraging behavior.

EDITOR'S CHOICE: Enhancing gardens as habitats for flower‐visiting aerial insects (pollinators): should we plant native or exotic species?

Summary Domestic gardens typically consist of a mixture of native and non‐native plants which support biodiversity and provide valuable ecosystem services, particularly in urban environments. Many gardeners wish to encourage biodiversity by choosing appropriate plant taxa. The value of native and non‐native plants in supporting animal biodiversity is, however, largely unknown. The relative value of native and non‐native garden plants to invertebrates was investigated in a replicated field experiment. Plots (deliberately akin to garden borders) were planted with one of three treatments, representing assemblages of plants based on origin (native, near‐native and exotic). Invertebrates and resource measurements were recorded over four years. This paper reports the abundance of flower‐visiting aerial insects (‘pollinators’) associated with the three plant assemblages. For all pollinator groups on all treatments, greater floral resource resulted in an increase in visits. There was, however, a greater abundance of total pollinators recorded on native and near‐native treatments compared with the exotic plots. Short‐tongued bumblebees followed the same pattern whilst more hoverflies were recorded on the native treatment than the other treatments, and more honeybees on the near‐native treatment. There was no difference between treatments in abundance of long‐tongued bumblebees or solitary bees. The lack of difference in solitary bee abundance between treatments was probably due to a third of individuals from this group being recorded on one exotic plant species. The number of flower visitors corresponded to the peak flowering period of the treatments, that is there were fewer flower visitors to the exotic treatment compared with the other treatments in early summer but relatively more later in the season. Synthesis and applications. This experiment has demonstrated that utilizing plants from only a single region of origin (i.e. nativeness) may not be an optimal strategy for resource provision for pollinating insects in gardens. Gardens can be enhanced as a habitat by planting a variety of flowering plants, biased towards native and near‐native species but with a selection of exotics to extend the flowering season and potentially provide resources for specialist groups.

Absence of sex differential plasticity to light availability during seed maturation in Geranium sylvaticum.

Sex-differential plasticity (SDP) hypothesis suggests that since hermaphrodites gain fitness through both pollen and seed production they may have evolved a higher degree of plasticity in their reproductive strategy compared to females which achieve fitness only through seed production. SDP may explain the difference in seed production observed between sexes in gynodioecious species in response to resource (nutrients or water) availability. In harsh environments, hermaphrodites decrease seed production whereas females keep it relatively similar regardless of the environmental conditions. Light availability can be also a limiting resource and thus could theoretically affect differently female and hermaphrodite seed output even though this ecological factor has been largely overlooked. We tested whether the two sexes in the gynodioecious species Geranium sylvaticum differ in their tolerance to light limitation during seed maturation in the field. We used a fully factorial block experiment exposing female and hermaphrodite plants to two different light environments (control and shade) after their peak flowering period. Specifically, we measured fruit and seed production in response to decreased light availability and compared it between the sexes. Shading reduced the number of fruits and seeds produced, but the decrease was similar between the sexes. Furthermore, shading delayed seed production by three days in both sexes, but did not affect seed mass, seed P content, or the probability of re-flowering the following year. Our results give no evidence for reproductive SDP in response to light during seed maturation.

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.

Flowering phenology and floral visitors of <i>Piliostigma reticulatum</i> 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

Phenology and pollen studies of some species of Annonaceae in Nigeria

Phenology and pollen studies were investigated in some species of Annonaceae in Nigeria to help in providing pollen data and record of flowering patterns of the species studied. Phenological data for flowering and fruiting were tracked once a week for both rainy and dry seasons. Pollen grains from fresh anthers of the different species of Annonaceae were collected for pollen grain stainability and morphological studies. The peak flowering period in all the species studied was between March and April. Flower production took place before flushing of leaves in M. tenuifolia , however, in A. reticulata and A. squamosa , flowering and flushing of leaves occurred at the same time. All the species have predictable annual fruiting periods; the harvesting of their fruits and seeds, and sustainable management is bound to be relatively easy. The percentage pollen stainability was higher than percentage pollen germination in the species studied. Low fertility was observed in A. reticulata and C. patens . Tetrad pollen observed in Annona, Monodora and Xylopia is an advanced character in Annonaceae and could have an advantage over the monad. The genus Cleistopholis now appears to be one of those genera which have retained the largest number of the characteristics of a primitive member of Annonaceae. The evolutionary development is from Cleistopholis (monad) to Xylopia (tetrad) to Monodora (tetrad) to Annona (tetrad). Keywords : Phenology, Pollen, Annonaceae, Evolution, Monad, Tetrad.

Sex dependent risk management in face of perceived danger of socially foraging Bee-eaters (Merops apiaster) during migration

The proximal reasons and ultimal consequences of decisions made during foraging by breeding individuals are widely studied in numerous avian systems. However, the effects of these decisions are more pronounced in migratory birds because they spend more time and energy foraging than on the actual journey itself. The peak flowering and pollination period of crops in southern Israel, when large numbers of hives are transported to the region, coincide with the peak migration of Bee-eaters. We hypothesized that Bee-eaters cue on conspecifics while foraging at a stopover site, react to perceived danger at a given foraging patch, and that the degree of risk taken by an individual was a function of body condition and sex. Bee-eaters were caught on 44 different mornings in spring 2004, 2005, and 2009. A sex-dependent trapping was noted and significantly more females were caught in the first bout. The sex ratio remained significantly male biased in bouts 3–8. Birds caught in the first bout were heavier in comparison to those caught in the second bout, and there was a significant interaction between sex and bouts. From the second bout onwards both sexes showed a significant increase in body mass, by 1.05g/bout on average (±0.6 SD), however wing lengths remained similar for both sexes. We conclude that migrant Bee-eaters cue on conspecifics to evaluate predation risks when socially foraging at a localized food patch and males, who we assume to be time-minimizers, are more likely to forage at a novel site and once danger of foraging is perceived only high energy demand individuals will attempt to hunt.

First report of flower chafer beetle, Oxycetonia versicolor, on pigeonpea and mungbean from Punjab, India

The occurrence of flower chafer beetle, Oxycetonia versicolor (Fabricius) (Scarabaeidae: Coleoptera) damaging the flowers of important grain legumes such as pigeonpea (Cajanus cajan (L.) Millsp.) and mungbean (Vigna radiata (L.) Wilczek) is reported for the first time from Punjab, India. Heavy infestation of these flower beetles at flowering may cause considerable damage to these crops. A mild to moderate level of infestation of 15–17 beetles per ten plants was recorded at the time of peak flowering period on both the grain legumes. Adult beetles devour the flowers and buds, thereby greatly reducing the number of pods that are set. Information on important taxonomic characters of the beetle is highlighted in this report. Careful monitoring and timely reporting on this chafer beetle is necessary to avoid any future outbreak.

Floral phenology and morphology of colchicine-induced tetraploid Acacia mangium compared with diploid A. mangium and A. auriculiformis: implications for interploidy pollination

Floral phenology and morphology of colchicine-induced auto-tetraploid trees of Acacia mangium Willd. (AM-4x) growing in Vietnam were compared with adjacent diploid A. mangium (AM-2x) and A. auriculiformis A.Cunn. ex Benth (AA-2x). Flowering lasted for several months with a slightly later peak flowering period for A. auriculiformis (December–January), than for A. mangium (November–December). Flower spikes of AM-4x were shorter and had fewer flowers per spike than those of AM-2x, but were longer and had more flowers than AA-2x. Percentages of male to hermaphrodite flowers were less than 23% for all three species/ploidy combinations. Flowers of AM-4x had slightly shorter styles than did AM-2x, but AM-4x stigma and polyad diameters were greater. For all polyad-stigma combinations among species/ploidy levels, at least one polyad could be accommodated. AM-4x had fewer (13) ovules per ovary, compared with AM-2x and AA-2x (14–16). AM-4x set fewer (less than 3) seeds per pod than did AM-2x and AA-2x (7–8 and 5–6, respectively). Foraging behaviour of the main insect pollinators (honeybees) and examination of polyads collected from them suggested interspecific and interploidy pollination would occur. There appeared to be no phenophase or flower structure barriers to interploidy pollination.

Reproductive isolation and pollination success of rewarding Galearis diantha and non-rewarding Ponerorchis chusua (Orchidaceae)

Increasing evidence challenges the conventional perception that orchids are the most distinct example of floral diversification due to floral or prezygotic isolation. Regarding the relationship between co-flowering plants, rewarding and non-rewarding orchids in particular, few studies have investigated whether non-rewarding plants affect the pollination success of rewarding plants. Here, floral isolation and mutual effects between the rewarding orchid Galearis diantha and the non-rewarding orchid Ponerorchis chusua were investigated. Flowering phenological traits were monitored by noting the opening and wilting dates of the chosen individual plants. The pollinator pool and pollinator behaviour were assessed from field observations. Key morphological traits of the flowers and pollinators were measured directly in the field. Pollinator limitation and interspecific compatibility were evaluated by hand-pollination experiments. Fruit set was surveyed in monospecific and heterospecific plots. The species had overlapping peak flowering periods. Pollinators of both species displayed a certain degree of constancy in visiting each species, but they also visited other flowers before landing on the focal orchids. A substantial difference in spur size between the species resulted in the deposition of pollen on different regions of the body of the shared pollinator. Hand-pollination experiments revealed that fruit set was strongly pollinator-limited in both species. No significant difference in fruit set was found between monospecific plots and heterospecific plots. A combination of mechanical isolation and incomplete ethological isolation eliminates the possibility of pollen transfer between the species. These results do not support either the facilitation or competition hypothesis regarding the effect of nearby rewarding flowers on non-rewarding plants. The absence of a significant effect of non-rewarding P. chusua on rewarding G. diantha can be ascribed to low levels of overlap between the pollinator pools of two species.

Effect of Nitrogen Fertilizer Application on Development of Boll and Fi-ber Quality in High Fiber Quality Cotton

The objective of this study was to investigate the extent of the yield increase and fiber quality improvement with nitrogen fertilizer application at different developing periods for high fiber quality cotton. Two cultivars of high quality cotton, hybrid Kemian 1, and conventional Kemian 4, were used to study the effect of nitrogen application on boll weight, boll volume and fiber quality. The five experiments were conducted on the farm of Jiangsu Provincial Key Laboratory of Crops Genetics and Physiology of Yangzhou University from 2003 to 2005, the first experiment was the ratio of nitrogen fertilizer at transplanting, flowering and boll setting, peak boll setting period of 20:60:20, 10:60:30, 25:65:10 for Kemian 1, and 20:60:20, 15:70:15, 10:75:15 for Kemian 4, the second was the basic nitrogen fertilizer at transplanting of 10%, 20%, 30% for Kemian 1, and 10%, 15%, 20% for Kemian 4, the third was 0, 20%, 30%, 40% of the nitrogen fertilizer at early flowering period for both cultivars, the fourth was the nitrogen fertilizer applied at 17, 19, 21 leaf age on main stem, and the fifth was the nitrogen fertilizer at peak boll setting period of 10%, 20%, 25% for Kemian 1, and 10%, 15%, 20% for Kemian 4. The results showed that bigger boll and better fiber quality were gotten under the application of 208.5 to 243.0 kg nitrogen per hectare, and the treatment of nitrogen fertilizer 20%, 60%, 20% for Kemian 1, and 15%, 70%, 15% for Kemian 4, respectively in the first experiment. 30% of nitrogen fertilizer applied at early flowering was optimal for the development of bigger boll and better fiber quality, 15–20% of nitrogen fertilizer applied at the peak boll setting period was best for development of the late boll in autumn. The nitrogen fertilizer application at peak flowering period was earlier at 17 leaf age, later at 21 leaf age, and optimal at 19 to 20 leaf age on the main stem. The correlation analysis indicated further that there were positive correlation between boll size, boll weight and yield, fiber quality. The nitrogen fertilizer application at the early flowering period was beneficial to develop bigger boll, higher yield and better fiber quality. These results suggest that the key of the high lint yield and good fiber quality is to develop big boll for the high fiber quality cotton.

Pollination ecology of Justicia rusbyi (Acanthaceae), a common understory plant in a tropical mountain forest in eastern Bolivia

AbstractThe present study reports the species composition, behavior and ecology of floral visitors to a common understory herb, Justicia rusbyi (Acanthaceae), in a tropical mountain forest. Although the analyses were made during the peak flowering period, floral visitors were rare. In total, 22 species were observed visiting. The most frequent visitors were a small species of stingless bee (Meliponinae) and a skipper (Hesperiidae). Approximately three‐quarters of all floral visitors visited only one flower during a stay. Most visitors were observed at noon and in direct sunlight, and there was a positive correlation between the number of J. rusbyi flowers displayed and the number of visitors. The nectar was found to be rich in hexose, which is unusual in bee‐pollinated plants.

Physiological activities and expression of insecticidal protein in Bacillus thuringiensis transgenic cotton leaves subjected to high and low temperatures

This research was to investigate physiological activities and the expression of insecticidal protein in cotton leaves of Kemian 1, a widely grown cotton cultivar in the lower reaches of the Yangtze River, treated under high (40°C and 35°C) and low (25°C and 20°C) temperatures for 48 h. The main results indicated that the contents of free amino acid and malondialdehyde (MDA) increased during the heat and cold stress with the biggest increments in the first 12 h; and the content of soluble protein, activities of superoxide dismutase (SOD), and glutamic-pyruvic transaminase (GPT) decreased during the stress with the biggest decrements also in the first 12 h; the activity of nitrate reductase (NR) decreased in the first 24 h, and during the remaining 24 h its activity followed a gradual uptrend. The content of insecticidal protein in cotton leaves followed a downtrend during the stress, and the biggest decrements occurred in the first 12 h, suggesting that the expression of insecticidal protein was immediately inhibited during the process of stress. The results also indicated that physiological activities and the expression of insecticidal protein in cotton leaves were closely related. Compared with other stress temperatures, 40°C produced more immediate effects on the physiological activities and insecticidal protein content. In contrast to the peak flowering period, the physiological activities and insecticidal protein expression at the peak boll-setting period were more susceptible to heat and cold stress.

Indoor and outdoor pollen concentrations in private and public spaces during the Betula pollen season

Although the number of studies of pollen concentrations inside and outside buildings is increasing, little is known about the efficiency of penetration of pollen from outdoor to indoor air, and further. We studied indoor and outdoor pollen concentrations in the town of Lappeenranta and in the municipality of Rautjarvi in SE Finland from May 3–23, 2004, i.e. throughout the Betula pollen season, and assessed the risk of exposure to pollen grains. Pollen concentrations were measured inside and outside a block of flats, a detached house, and the regional central hospital, using rotorod-type samplers; in the town of Joutseno data were compared with Burkard counts. Outdoor concentrations of Betula pollen grains ranged between low and abundant (0–855 grains m−3). The corresponding indoor concentrations near the main front doors varied from low to moderate (0–17 grains m−3) in the central hospital and were low (<10 grains m−3) in both residential buildings. Indoor concentrations further from the main front door were low (<10 grains m−3) at all study sites. The concentrations of Betula pollen decreased substantially from outdoors to indoors, and further toward the centre of the building, probably indicating relatively poor penetrating properties of the pollen grains and/or the short-lived presence of pollen grains in indoor air. The concentrations of Betula pollen inside the buildings during the peak flowering period were mostly at a level barely inducing reactions even in the most sensitive persons.

Landscape Performance, Flowering, and Seed Viability of 15 Japanese Silver Grass Cultivars Grown in Northern and Southern Florida

Japanese silver grass (Miscanthus sinensis) and 14 cultivars were transplanted in northern and southern Florida and evaluated for landscape performance, flowering, growth, and seed viability. All plants survived the 84-week study at both locations with the exception of `Morning Light', where 22% to 33% of the plants died. In northern and southern Florida, `Arabesque', `Adagio', `Cosmopolitan', and `Gracillimus' received the highest visual quality ratings on average throughout the entire study, yet other cultivars such as `Central Park' and `Silberfeder' performed well but had much narrower windows of peak performance. Cultivars such as `Little Kitten' and `Sarabande' performed far better in southern Florida than in northern Florida. Regardless of location, `Morning Light' and `Puenktchen' generally did not perform as well as other cultivars. In northern Florida, four consecutive months of very good to excellent flowering (75% to 100% canopy coverage) were observed for `Adagio', `Arabesque', `Cosmopolitan', `Gracillimus', `Little Kitten', `Sarabande', `Silberfeder', and `Zebrinus'. However, in southern Florida, peak flowering periods for these cultivars were delayed and generally only lasted for 1 to 2 months. On average, plants in northern Florida were larger and produced 2.8 times more flowers than plants in southern Florida. All cultivars produced viable seed with germination of viable seed ranging from 53.6% (`Cabaret') to 100% (`Gracillimus') in southern Florida, and from 49.8% (`Arabesque') to 100% (`Adagio', `Little Kitten', `Sarabande', and `Variegatus') in northern Florida.

Xylem and Phloem Derived Polyamines during Flowering in Two Diverse Rose Species

Polyamine contents in xylem (root) and phloem (leaf) exudates in two diverse species of rose, viz. Rosa damascena Mill and Rosa bourboniana Desport, were analyzed before, during, and after flowering in the main flowering season, that is, April–May. Only free putrescine (Put) was detected in the xylem and phloem exudates at these time points, and it was high during the peak flowering period. In phloem, Put content was significantly higher in R. bourboniana than in R. damascena at all three stages; whereas in the xylem exudate it was relatively higher in R. damascena at the peak flowering period. A spray of α-difluoromethylornithine (DFMO), an irreversible inhibitor of the putrescine biosynthetic inhibitor ornithine decarboxylase (ODC), markedly decreased the flowering. This effect was reversed by application of Put alone or in combination with DFMO. The significance of this finding is discussed in light of polyamine translocation during flowering.

Four Levels of Soil Water Depletion Minimally Affect Carambola Phenological Cycles

Phenological cycles were determined for carambola (Averrhoa carambola) trees in a gravelly loam soil at four different soil water depletion (SWD) levels in containers and in an orchard in southern Florida. The phenological cycles of young trees grown in containers were not as well defined as those of mature trees in an orchard. Shoot extension of trees in the orchard and containers was observed from the first week of March until the third week of December. Two peak flowering periods occurred during the first week of March, and from mid-September to mid-October. The major fruit harvest periods were August and December. Shoot flushing, extension shoot growth, flowering, and fruiting showed little response to irrigation at four SWD levels. This lack of response was likely caused by sufficient soil water due to precipitation and capillary rise from the high water table located about 1–2 m below the soil surface. Regardless of the lack of SWD effects on phenological cycles of carambola, the periodicity of shoot flushing, extension shoot growth, flowering, and fruiting and the intensity of these phenological events elucidated in this study should provide useful guidelines for carambola orchard management in southern Florida.