Removal Of Bracts Research Articles

The conspicuously large bracts influence reproductive success in Thunia alba (Orchidaceae)

Abstract In angiosperms, diverse floral traits are adaptations to various selective pressures and ecological functions. So far, studies on floral traits in orchids have focused primarily on the labellum but never on bracts. A bumblebee-pollinated and rewarding terrestrial or epiphytic herb, Thunia alba (Lindley) H. G. Reichenbach (Orchidaceae), has conspicuously large and curly bracts that enclose the spur and pedicel of flowers. We hypothesized that these large bracts could protect spurs against nectar robbers. To confirm this hypothesis, we experimentally removed the bracts to record the changes in visiting behavior of mutualistic pollinators and antagonistic nectar robbers and evaluated their effects on reproduction success. Our result revealed that Bombus breviceps, the only pollinator of T. alba, shifted to nectar robbery when the bracts were removed, and the proportion of robbed flowers also significantly increased. Thunia alba was found to be pollinator limited regardless of whether in intact treatment or removed bract treatment. Removal of bracts had no effect on the visiting frequency of B. breviceps, but it reduced male and female reproductive success. These findings indicate that, under complex environmental pressures with limited pollination, large bracts can protect against nectar robbers and enhance the fitness of T. alba.

Effects Of Diaspore Bracts And Cations On Germination Of Ceratoides Arborescens (Losinsk.) Tsien Et C.g. Ma Under In Vitro Culture

Ceratoides arborescens (Losinsk.) Tsien et C. G. Ma, a species endemic to China, is widely used in ecological restoration and as fine forage due to its high drought resistance and nutrient content, respectively. Its bracts are often removed from diaspores during planting because their dense hair covering is not conducive to sowing. However, it is not clear whether the removal of bracts is beneficial to C. arborescens seed germination. A seed germination experiment was conducted to measure how bracts influence seed germination. Three diaspore treatments were used: seed bracts removed (BR), bracts removed and recombined with seeds (BRB); and seed bracts not removed (B). To further explore whether bract nutrient content affects seed germination, seeds without bracts (BR) were tested with additions of three different nutrient (Mn, Ca, and Fe) in a culture solution. It was found that BR accelerated average germination time but had no detectable effect on seed germination rate. Further, the BR significantly decreased seed germination potential and germination index. Additionally, seed germination potential and the germination index were improved by BRB, while the seedling vigor index was also enhanced. Moreover, it was found that the elements Ca, Mn, and Fe were higher in bracts than those in seeds. However, nutrient addition manipulation showed that the addition of Mn promoted seed germination. The findings of this experiment suggest that C. arborescens bracts are beneficial during planting, because they contain essential elements for germination. Removing bracts from the diaspore has no potential impact on the reduction of costs and improvement of the seed germination characters of C. arborescens. Bangladesh J. Bot. 51(4): 897-905, 2022 (December) Special

Highly efficient transient gene expression of three tissues in Osmanthus fragrans mediated by Agrobacterium tumefaciens

As one of the 10 most famous flowers, sweet osmanthus (Osmanthus fragrans) is widely utilized in landscaping and food processing in China. Owing to the high complexity and large size of its genome, it is still an enormous challenge to develop transgenic technology for O. fragrans. Therefore, it is necessary to develop an efficient transient expression protocol for the rapid identification of gene functions in O. fragrans. In this study, we selected three different tissues of O. fragrans, including calli, floral buds, and leaves, as explants for transient transformation mediated by Agrobacterium tumefaciens. However, we found that one protocol did not work for all tissues. Calli were induced and proliferated from the immature plumule of O. fragrans on one-half Murashige and Skoog media that contained 0.5 mg·L−1 6-benzylaminopurine and 1 mg·L−1 naphthalene acetic acid. GUS (β-glucuronidase) was used as a reporter gene, where its level of transcription reflected the abundance of Agrobacterium-mediated T-DNA transferred into explants. To obtain the optimal transient expression protocol for each explant, we evaluated the effects of Agrobacterium load, acetosyringone concentration, co-culture duration, bud bract removal, and explant preculture on the transformation efficiency. The use of our transient expression protocols to overexpress a transcriptional repressor of OfXTH14, OfMYB4, in calli, floral buds, and leaves showed that the relative levels of expression of OfXTH14 decreased significantly in all three of our selected tissues. Since the transformed explants exhibited a transient high level of expression of the target gene, affecting the transcription of related genes as well as the synthesis of related metabolites, they can be widely applied to identify gene functions and study the molecular regulatory mechanisms of O. fragrans. Moreover, the critical steps to significantly increase the transformation efficiency varied from tissue to tissue, providing a reference for the development of transient expression protocols in other plant species.

Opportunistic Use of Banana Flower Bracts byGlossophaga soricina

The evolution of cue reception and cue production is well documented. The ability of species to use cues they did not evolve with is important in understanding flexibility in behaviour. We observed Neotropical nectar-feeding bats (Glossophaga soricina) feeding at Old World banana flowers (Musa acuminata) in a Belize garden. The flowers produce a rich source of nectar that is exposed as a bract lifts before dusk. We tested the hypothesis that the bracts serve as beacons to foraging bats and discuss this approach and the use of acoustic information by bats feeding at flowers. We ensonified a bract with cues like those of echolocating G. soricina, which revealed the production of strong echoes from the bract. Additionally, the removal of bracts from the flowers influenced the bats' flower-visiting behaviour. We suggest that the bats use the echoes from the bract opportunistically as a cue to find the nectar source. Our findings provide an example of an interaction between a plant and flower visitor not refle...

Targeting hidden pests: acaricides against the coconut mite Aceria guerreronis

The control of hidden pest species with pesticides depends on the accurate timing of the application to reach the life stages during their only moment of vulnerability, which is when the pests (temporarily) leave their hiding places. A curious case involves the colonization of the coconut perianth, a bract-protected region of the fruit, by the coconut mite Aceria guerreronis. The coconut bracts apparently provide protection against the direct action of acaricides used against the coconut mite. Furthermore, some acaricides target mite eggs and/or immatures in addition to adults, leading to enhanced mortality and/or compromised progeny production, but only if reaching these stages. In this study, we developed methods for assessing the likely protection provided by the coconut bract against the acaricides used for managing the coconut mite. We also assessed the efficacy of the acaricides currently registered for use against this species. Our results support the notion that coconut bracts provide protection to the coconut mite against direct acaricide action. Some acaricides (abamectin and fenpyroximate) were effective only with the removal of the coconut bracts, whereas others (hexythiazox and spirodiclofen) were not effective even with bract removal. Coconut mites sheltered by bracts were protected against the acaricides over time, but the acaricides seemed to induce mite dispersion. In addition, the preventive application of some acaricides reduced the chances of the perianth colonization by the coconut mite. Among the acaricides used, two (hexythiazox and spirodiclofen) are registered as ovicides, but only one (spirodiclofen) acted on eggs, preventing hatching of approximately 40 % of the eggs. The acaricide impacts on coconut mite management are discussed.

The bracts of the alpine ‘glasshouse’ plantRheum alexandrae(Polygonaceae) enhance reproductive fitness of its pollinating seed-consuming mutualist

Environmental conditions are known to affect the reproductive fitness of insects, as do host plants. Although the highly specialized bracts of Himalayan 'glasshouse' plants are thought to be an adaptive morphology that allows the plant to reproduce in harsh alpine environments, little information appears to exist concerning the benefit of these bracts for the pollinating insects. In this study, we examine whether the semi-translucent bracts of Rheum alexandrae, a giant herb endemic to the alpine zone of the Hengduan Mountains in south-western China, enhance the reproductive fitness of its pollinator. Rheum alexandrae depends mainly on mutualistic seed-consuming Bradysia flies for pollination. Bracts increased interior temperature on sunny days, acted as a buffer against fluctuating air humidity, greatly decreased the intensities of ultraviolet B/C radiation and provided shelter from strong winds. Bract removal significantly decreased adult oviposition and offspring performance of pollinators during flowering and fruiting, respectively. Our results indicate that the bracts of R. alexandrae enhance the reproductive fitness of its pollinating seed-consuming mutualist in alpine environments, which may be attributed to the positive effects of the bracts on the interior microenvironment. (C) 2015 The Linnean Society of London.

How do sink and source activities influence the reproduction and vegetative growth of spring ephemeral herbs under different light conditions?

Spring ephemeral herbs inhabiting deciduous forests commonly complete reproduction and vegetative growth before canopy closure in early summer. Effects of shading by early canopy closure on reproductive output and vegetative growth, however, may vary depending on the seasonal allocation patterns of photosynthetic products between current reproduction and storage for future growth in each species. To clarify the effects of sink-source balance on seed production and bulb growth in a spring ephemeral herb, Gagea lutea, we performed a bract removal treatment (source reduction) and a floral-bud removal treatment (sink reduction) under canopy and open conditions. Leaf carbon fixations did not differ between the forest and open sites and among treatments. Bract carbon fixations were also similar between sites but tended to decrease when floral buds were removed. Seed production was higher under open condition but decreased by the bract-removal treatment under both light conditions. In contrast, bulb growth was independent of light conditions and the bract-removal treatment but increased greatly by the bud-removal treatment. Therefore, leaves and bracts acted as specialized source organs for vegetative and reproductive functions, respectively, but photosynthetic products by bracts were flexibly used for bulb growth when plants failed to set fruits. Extension of bright period was advantageous for seed production (i.e., source limited) but not for vegetative growth (i.e., sink limited) in this species.

Multifunctional bracts enhance plant fitness during flowering and seed development in Rheum nobile (Polygonaceae), a giant herb endemic to the high Himalayas

Specialized bracts are thought to be important for the successful reproduction of some plants and are regarded as adaptations to diverse driving forces. However, few empirical studies have quantified the adaptive significance of bracts within a cost-benefit framework. We explored the adaptive significance of large and showy bracts for reproduction in Rheum nobile, a giant herb endemic to the high Himalayas. We examined whether the bracts enhance reproductive success during flowering and seed development. Bracts increased flower and fruit temperature on sunny days, greatly decreased the intensity of ultraviolet-B (UV-B) radiation reaching flowers and fruits, and prevented pollen grains being washed away by rain. Experiments indicated that high temperature could promote pollen germination, while pollen grains exposed to rain and UV-B radiation at ambient levels were seriously damaged. Furthermore, bract removal decreased the number of pollinators visiting flowers. When bracts were removed before or after flowering, fecundity and progeny quality were adversely affected, but seed predation by larvae of pollinators decreased. A cost-benefit analysis demonstrated that the cost of bracts, i.e., increased seed predation, is modest. Our results suggest that the bracts of R. nobile promote pollen germination, protect pollen grains from rain and intense UV-B radiation, enhance pollinator visitation during flowering, and facilitate the development of fertilized ovules during seed development. We conclude that multifunctional bracts of R. nobile are an effective adaptive strategy in alpine environments and might have been selected for because of abiotic environmental conditions as well as for enhancing pollination success.

Regulation of fruit and seed set in Anagyris foetida L. (Fabaceae): The role of intrinsic factors

We investigated the role of resource limitation, ovary reserve, and selective abortion in controlling flower and fruit set in the Mediterranean leguminous shrub Anagyris foetida. The removal of bracts, but not that of leaves, reduced the initiation of fruit with respect to controls. The removal of a large proportion (2/3 of the total) of preanthesic inflorescences increased the reproductive capacity of individuals via two different strategies: (1) maintaining the number of fruit-bearing inflorescences, but increasing the number of fruits per inflorescence and seeds per fruit; and (2) increasing the number of fruit-bearing inflorescences, while maintaining fruits/inflorescence and seeds/fruit ratios unchanged. At the level of the inflorescence, most of the ripe fruits were located on the basalmost whorls of the raceme. Within the legume, fertilization was independent of the position of ovules, although the more basal presented lower rates of fertilization than the more central-stylar. The same was observed for the probability of a fertilized ovule to develop into a mature seed.

The Bracts of Saussurea velutina (Asteraceae) Protect Inflorescences from Fluctuating Weather at High Elevations of the Hengduan Mountains, Southwestern China

Several members of the subgenus Amphilaena (Saussurea; Asteraceae) growing at high elevations in the Himalayan region have semi-translucent bracts covering their inflorescences, the function of which is not fully understood. We investigated the thermal benefits of these bracts in Saussurea velutina in situ in the Hengduan Mountains, SW China, and compared the reflectance spectra and anatomical characters of bracts and rosette leaves in the laboratory. After removal of bracts in the field the average inflorescence daytime temperature was 2.5 °C colder than in control plants with intact bracts. Manually opened treatment inflorescences grew slower and set significantly fewer seeds than control inflorescences with bracts intact. The mesophyll of bracts is a single cell layer with a lower reflectance in the infrared range than rosette leaves. We show that the semi-translucent bracts in S. velutina function to ensure warmer temperatures for floral and seed development at high elevations in the Hengduan Mountains.

Effects of Processing on the Quality of Preserved Quartered Artichokes Hearts

ABSTRACTDifferent methods of processing preserved quartered artichoke hearts were studied. All methods involved blanching of the product and removal of bracts; however, the order of these 2 unitary operations was changed. The main objective was to compare the effects of the different manufacturing methods on the physico‐chemical and sensory characteristics of the artichoke hearts. The traditional method (1st blanching of the fresh artichokes and then removal of bracts) provided quartered artichoke hearts with the best chemical and sensorial properties during storage at room temperature (20 °C ± 2 °C): slight acid taste, high artichoke flavor, white‐yellowish color, and no presence of brown spots.

Physical and chemical treatments for enhancing seed germination of Oldman saltbush (Atriplex nummularia)

This study was conducted to improve the seed germination of Oldman saltbush (Atriplex nummularia), which is an important fodder shrub commonly used for revegetation of degraded rangelands in the West Asia and North Africa regions. Seeds with and without their bracts (fruits) were subjected to physical (scarification, water soaking, gamma radiation) and chemical (potassium nitrate, sulfuric acid and gibberellic acid) treatments. For each treatment, sets of 100 seeds with and without bracts were selected randomly, divided into four equal groups, and incubated in a germinator at 20 ± 1°C. The treatments had a highly significant (P < 0.0001) effect on seed germination. The scarification, potassium nitrate (0.2% concentration), gibberellic acid (100 and 150ppm) and sulfuric acid (25% for 10min, 50% for 10 and 20min) treatments improved seed germination significantly compared to control treatment (4.0%). The different doses of gamma radiation and high concentrations of sulfuric acid (75%) reduced seed germination significantly (P < 0.001). The removal of bracts surrounding the seeds had a highly significant (P < 0.0001) effect on seed germination and averaged 73.5% for washing, 78.0% for scarification, 80.9% and 88.0% for potassium nitrate of 2% and 4% concentration, 88.1% for gibberellic acid of 150ppm, and 70.4% for sulfuric acid of 25% concentration. The results indicate that the inhibiting factors of germination must be located in the bracts. Future work should focus on developing technologies to remove the bracts surrounding the true seed of A. nummularia.

A method to test the pathogenicity of fungi to Aceria guerreronis with particular reference to Hirsutella thompsonii

Abstract A simple method has been devised for testing the pathogenicity of fungal pathogens, especially Hirsutella thompsonii, against the coconut eriophyid mite, Aceria guerreronis. Except one or two bracts of the inner whorl of the perianth, under which an active and healthy population of the mite was thriving, the rest of the five or four bracts were removed from a young nut and a suspension of conidia was injected into the thin space between the nut surface and the inner surface of the bract/s by gently lifting the bract/s but leaving it/them intact. The meristematic region of the nut that got exposed after the removal of bracts as well as the retained bract/s were sheathed with a stretched parafilm up to the green portion of the nut in such a manner that there were no gaps. The treated nuts were incubated under ambient conditions. At the end of 96 h, the parafilm was unwound and the bract/s was/were opened to observe infected mites on the inner surface of the bract/s and/or on the nut surface just be...

Butterfly pollination and high-contrast visual signals in a low-density distylous plant.

In low-density butterfly-pollinated Mussaenda frondosa (Rubiaceae), flowers attract pollinators at short distances while conspicuous, non-rewarding accessory bracts are detectable at long distances by long-ranging pollinators such as the birdwing butterfly Troides minos that did not detect flower-bearing plants in the absence of these bracts. However, even in the absence of flowers, the white, ultraviolet-absorbing bracts attracted butterflies that visited flowerless plants. Although flower visits by short-ranging territorial butterflies declined significantly on removal of bracts, they did not cease completely. Nectar-robbing carpenter bees and birds did not change their behaviour following bract removal. Bract removal caused a significant decline in fruit set, indicating their importance as visual signals to pollinators.

EFFECTS OF STORAGE CONDITIONS AND PRESENCE OF FRUITING BRACTS ON THE GERMINATION OF ATRIPLEX HALIMUS AND SALSOLA VERMICULATA

Two shrub species, Atriplex halimus L. and Salsola vermiculata L., are considered useful for rehabilitation of degraded rangelands in west Asia and north Africa. They can be established from direct seeding and are capable of self-sowing. In this study, seed storage at different temperatures and the influence of fruiting bracts on seed germination were examined for the two species during two seasons. Fruits (utricles) were stored at 20–22°C (room temperature), 0°C or −22°C. Germination tests were carried out after 33, 56, 90, 152, 272 and 397 d in storage in the first season and after 44, 76, 104, 170, 288 and 412 d in the second season. Seeds were germinated in their fruiting bracts or after bract removal. Bract removal significantly improved seed germination of both shrubs regardless of storage temperature. For S. vermiculata the increase in germination was in the range of 1.3- to 14.7-fold compared with values for the intact fruit in Season 1 and 0.5 to 3.8 in Season 2. Similarly the ranges for A. halimus were 0.5- to 4.2-fold and 0.7- to 5.3-fold in the two seasons respectively. The effect of cold storage was greater on Salsola than on Atriplex. The reduction of the storage temperature from 21°C to 0°C and −22°C increased the longevity of S. vermiculata seeds by 2.8–46.6 times in Season 1 and by 2.9–2.6 times in Season 2. There was little or no effect on the longevity of A. halimus. A leachate prepared by soaking fruiting bracts from S. vermiculata significantly depressed germination (p &lt; 0.01), the effect being greater on Salsola seeds (20% reduction) than on Atriplex seeds (8% reduction). A leachate from A. halimus produced a slight but non-significant reduction in germination.

THE ROLE OF COLORED ACCESSORY BRACTS IN THE REPRODUCTIVE BIOLOGY OFLAVANDULA STOECHAS

This study investigates the role played by showy structures in the repro- duction of Lavandula stoechas L. (Lamiaceae), a self-compatible Mediterranean shrub with compact, head-like inflorescences that are terminated by a tuft of conspicuous pink bracts. Pollinator visitation rates to plants with bracts correlated positively with that of paired, treated shrubs with all their bracts removed and, overall, bractless and control plants had equivalent visitation rates. In experimentally split shrubs, however, a strong effect on pollinator choice was evident, and distant visitor approaches were most often to that side keeping the attractive organs. Fecundity was not depressed in plants with reduced visual displays, and neither was the amount of pollen dispersed per flower or the size of stigmatic loads. There were, however, more pollen tubes, on average, at the lowermost part of the style in controls (10.8 tubes/style) than in bractless shrubs (8.3 tubes/style). Small, non- significant declines in average seed size, germinability, and seedling mass were detected following bract removal. Data support the notion that bracts are not essential to seed production in mature, relatively dense Lavandula populations where bee pollinators are often in good supply, but may be all-important if plant density is extremely low, or during population establishment. The role of an amplified display in increasing average pollination distance and progeny quality in this species is discussed.

Pollen development of Rheum nobile Hook.f. &amp; Thomson (Polygonaceae), with reference to its sterility induced by bract removal

Abstract The Himalayan alpine herb, Rheum nobile , terminates in a stout conical compound raceme concealed by large translucent bracts. It bears many fruits even under hostile conditions such as low temperature or persistent cloudy weather. To clarify the role of the bracts, the structure and the development of the pollen grains were examined after removing the bracts to expose the flowers to the open air for 9 days. Half of the individuals with bracts removed showed 0 to 1% of pollen stainability and the pollen grains were variable in shape and size. It was also observed that the bracts of Rheum nobile increased the temperature of inflorescence by about 10°C above ambient daytime temperatures. These results suggest that one of the causes for the inhibition of pollen development was low temperature. The remainder, however, indicated high stainability of 70–100%. It is suggested that the extreme difference of pollen stainability between two groups of R. nobile exposed to the surroundings may be related to the stage of microsporogenesis. Bracts of R. nobile might play an important role in normal reproduction under low temperature at high altitudes.

Defense and carnivory: Dual role of bracts inPassiflora foetida

Members of the genusPassiflora are reported to have evolved modifications which kill insects; they have however never been tested for carnivorous syndrome. The flowers ofPassiflora foetida consists of highly reticulate bracts which cover and grow along with the buds and fruits. Removal of bracts from developing bud and fruit resulted in higher predatory damage compared to those where the bracts were intact. These bracts also possess a large number of minute glands which ooze sticky secretion. A variety of tiny insects were found trapped by the secretion of the bracts. The secretion of these glands show high proteases and acid phosphatase activity, two common digestive enzymes found in traps of true carnivorous plants. A high quantity of aminoacids were released from freshly freeze killed ants when incubated in buffer extract of bracts-[14C] phenylalanine smeared on the glandular surface of bracts was recovered from ovules suggesting potential for absorption of aminoacids. These results suggest a novel role for bracts where primary function is to minimize predatory damage to developing flowers and fruits. The bracts serve as insect traps and also possess the mechanism to digest the trapped insects to obtain free aminoacids.

Carbon integration in Plantago aristata (Plantaginaceae): the reproductive effects of defoliation

Patterns of carbon integration in aclonal species are poorly understood in spite of their potential to influence individual fitness. To provide more information about these patterns, we performed a defoliation experiment with P. aristata. We examined, at the metameric level, the reproductive responses to the removal of the major carbon sources within metamers. Bracts on marked reproductive spikes and leaves subtending these spikes were removed at three stages of reproductive maturity: spike elongation, flowering, and fruiting. Spike dry weight and length, capsule number, seeds per capsule, and seed weight were measured. We tested the hypothesis that seed weight would respond least to defoliation. We also performed a complementary 14C translocation experiment to measure the amount of radioactive carbon moving into the marked spikes from outside the metamer. Defoliation depressed all components of reproduction within marked spikes, and little 14C was translocated from outside the metamer into the reproductive spikes, even those that were defoliated. Both results support the view that reproductive metamers in this species are largely autonomous with respect to their carbon budget. Defoliation during spike elongation most depressed reproduction, and bract removal depressed reproduction more than did leaf removal. The data suggest that bracts compensate for leaf removal by increasing their photosynthetic rate; however, the ability to compensate differs among plant populations. Of all the reproductive components, seed weight was least affected by defoliation. The data show, however, that the time of defoliation relative to reproductive development influences which reproductive components are affected.

Factors Influencing Premature Cyathia Abscission in Poinsettia ‘Annette Hegg Dark Red’

Abstract Low irradiance levels, high temperatures, and water stress all promoted premature cyathia abscission in poinsettia ‘Annette Hegg Dark Red’ (Euphorbia pulcherrima Willd.). Abscission was greater in plants placed under 75% shade at 16°C night temperature (NT) than on plants placed under normal daylight (ND) at 16° or 21° NT. Water stress (0.6 MPa) promoted abscission on plants grown at an 18° NT and ND but did not promote abscission on plants grown at 16° NT and ND or on under 75% shade (13° to 21° NT). As plant density increased, transmission of photosynthetically active radiation (PAR) through the bracts to the leaf canopy decreased while cyathia abscission increased concomitantly. More than 90% of the PAR above the bracts was absorbed or reflected 5 cm below the bracts on 20 cm tall plants spaced at 65 or more plants m-2. Reducing natural irradiation 75% by shading leaves of poinsettia promoted cyathia abscission, whereas removing immature bracts decreased abscission. Leaf removal on plants with intact bracts promoted abscission to a degree that 100% of the cyathia abscised prior to anthesis, whereas bract removal on plants with intact leaves resulted in only 23% abscission of the cyathia 25 days after first anthesis. Measurements of nonsoluble carbohydrate showed a significant increase in leaf carbohydrate on plants with bracts removed while carbohydrate decreased in leaves of plants with bracts intact. Carbohydrate depletion appears to be the primary factor responsible for premature cyathia abscission in poinsettia.