Development of an efficient micropropagation system for Tecoma stans (L.) Juss. ex Kunth using thidiazuron and effects on phytochemical constitution

The present study was designed to investigate the stimulatory effects of different doses (0.1 to 2.5 μM) of thidiazuron (TDZ) on in vitro shoot induction and proliferation of mature nodal explants of Tecoma stans. Of the tested concentrations, 2.0 μM TDZ proved to be optimal for maximum regeneration (91%) with a mean shoot number of 5.6 ± 0.67, and length of 2.38 ± 0.08 cm, after 4 wk of incubation. To determine the negative effects of prolonged TDZ exposure, after 4 wk of incubation at optimized level of TDZ, the cultures were transferred to a secondary medium either lacking plant growth regulators or supplemented with benzyladenine (BA) alone, or in combination with different auxins (indole-3-acetic acid, indole-3-butyric acid, or α-naphthalene acetic acid; NAA). Among the tested concentrations, 2.5 μM BA in combination with 0.5 μM NAA yielded the maximum mean shoot number (16.60 ± 0.40), and average shoot length (4.76 ± 0.15 cm) after 4 wk of culture. The best rhizogenesis (93%) was achieved on ½ MS medium containing 1.5 μM NAA, with a mean root number of 7.60 ± 0.40 and length of 4.11 ± 0.23 cm, after 4 wk of incubation. The micropropagated plantlets were successfully acclimatized and hardened off in Soilrite™ with a 90% survival rate. The plantlets grew well with normal growth, flowering and showed, by gas chromatography–mass spectroscopy, an increase in the number of bioactive compounds compared with the donor plant. This is the first report on T. stans in vitro regeneration using TDZ.

     

Biology and host range of the leafminer,Pseudonapomyza sp. (Diptera: Agromyzidae), a potential biological control agent for Tecoma stans (Bignoniaceae) in South Africa

Tecoma stans (Bignoniaceae), is an evergreen shrub that has a wide natural distribution in the tropical and subtropical parts of the western hemisphere. This shrub is native to Mexico and the southern regions of the USA. This weed is widely distributed in South Africa and neighbouring countries. As part of the biological control initiative, a leafmining fly, Pseudonapomyza sp. (Diptera: Agromyzidae), was imported into South Africa, and was subsequently studied as a potential biological control agent for T. stans. During no-choice tests involving 46 plant species in 16 families, Pseudonapomyza sp. only oviposited and developed on T. stans. Neither oviposition nor larval development was recorded on the closely related and indigenous plant species. When six plant species in the Bignoniaceae family were exposed to Pseudonapomyza sp. during multi-choice tests, oviposition and larval development only occurred on T. stans. It was concluded that Pseudonapomyza sp. was sufficiently host-specific to be released against T. stans in South Africa. Pseudonapomyza sp. also displayed very promising biological attributes that could enhance its effectiveness to control T. stans.     

Bee pollination and fruit set of Coffea arabica and C. canephora (Rubiaceae)

Self-sterile Coffea canephora and self-fertile C. arabica are important cash crops in many tropical countries. We examined the relative importance of insect, wind, and spontaneous self-pollination and the degree of self-fertility of these two coffee species in 24 agroforestry coffee fields in Indonesia. In both species, open pollination and cross pollination by hand led to the highest fruit set. Wind pollination (including self-pollination) led to 16% lower fruit set than open pollination in C. canephora and to 12.3% lower fruit set in C. arabica. Self-pollinated flowers and unmanipulated controls achieved an extremely low fruit set of 10% or less in the self-sterile species, and of 60% and 48%, respectively in the self-fertile species. These results constitute experimental evidence that cross pollination by bees causes a significant increase in fruit set of not only the self-sterile, but also the self-fertile coffee species. The practical implication is that coffee yield may be improved by managing fields for increased flower visitation by bees.     

Role of phenolics and boron in reproductive success in seasonally transient sterile Tecoma stans L

Quantitative and qualitative analysis of phenolics and boron in stigma of transient sterile Tecoma stans L. during seedless (May-July), partially seedbearing (August-November, April) and seedbearing periods (December-March) was made. UV absorption profile of stigmatic exudates indicated the presence of simple phenolics. Total phenolics were higher in stigma during seedless period. Thin layer chromatographic analysis of stigmatic extracts exhibited only three principal spots. Mass spectrophotometry showed the presence of derivatives of cinnamic acid, namely, caffeic acid in these spots. Quantity of boron in stigma during seedless period was lowest but the difference with other periods was not significant. It was suggested that the accumulation of higher quantity of caffeic acid in the stigma during seedless period due to high temperature (40 degrees-45 degrees C) could lead to inhibition of pollen germination in vivo, thereby rendering the plants seedless. This was confirmed by inhibition of in vitro pollen germination in the basal medium containing higher quantity of caffeic acid.     

Relationship between floral traits and floral visitors in two coexisting Tecoma species (Bignoniaceae)

In this paper, we studied the floral biology of Tecoma fulva ssp. garrocha and T.?stans in Vaqueros (Salta, Argentina), where both species coexist. We tested the idea that floral traits are associated with the pollinator types that visit them. According to our results, T.?fulva ssp. garrocha presented traits common to bird flowers and were visited by two species of Trochilidae (Colibri serrirostris and Chlorostilbon lucidus). In addition, T.?stans exhibited traits common to hymenoptera flowers and were visited principally by Apis mellifera and Bombus atratus. This study showed that floral traits are predictive of animal visitors.     

Evolution of floral morphology and pollination system in Bignonieae (Bignoniaceae)

The radiation of angiosperms is associated with shifts among pollination modes that are thought to have driven the diversification of floral forms. However, the exact sequence of evolutionary events that led to such great diversity in floral traits is unknown for most plant groups. Here, we characterize the patterns of evolution of individual floral traits and overall floral morphologies in the tribe Bignonieae (Bignoniaceae). We identified 12 discrete traits that are associated with seven floral types previously described for the group and used a penalized likelihood tree of the tribe to reconstruct the ancestral states of those traits at all nodes of the phylogeny of Bignonieae. In addition, evolutionary correlations among traits were conducted using a maximum likelihood approach to test whether the evolution of individual floral traits followed the correlated patterns of evolution expected under the "pollination syndrome" concept. The ancestral Bignonieae flower presented an Anemopaegma-type morphology, which was followed by several parallel shifts in floral morphologies. Those shifts occurred through intermediate stages resulting in mixed floral morphologies as well as directly from the Anemopaegma-type morphology to other floral types. Positive and negative evolutionary correlations among traits fit patterns expected under the pollination syndrome perspective, suggesting that interactions between Bignonieae flowers and pollinators likely played important roles in the diversification of the group as a whole.     

Cytochemistry of pollen development in Campsis radicans (L.) Seem. (Bignoniaceae)

In this study, cytochemical staining methods were used to follow the cytochemical modifications of microspore cytoplasm and sporoderm in Campsis radicans (L.) Seem. from tetrad stage to mature pollen. Flower buds were collected at different stages of development, and the anthers were fixed and embedded in Araldite. To make cytochemical observations under light microscope, semithin sections were cut and stained with different dyes. Cytochemical methods provided the opportunity to localize the reserve material in the microspore and pollen cytoplasm, to distinguish the different layers of the sporoderm, and to determine its chemical structure at different developmental stages. Microspore cytoplasm contains variable amounts of proteins, lipids, and insoluble carbohydrates at different stages of microsporogenesis. Sporoderm formation starts at tetrad stage by the formation of primexine and is completed at vacuolated microspore stage by the addition of sporopollenin from tapetum. During the vacuolization and enlargement of the microspores, the structure and the chemical composition of the exine are modified. The endexine becomes chemically different from the ectexine. The ectexine is composed of sporopollenin and a small amount of protein, whereas the endexine is composed of sporopollenin, proteins, and traces of polysaccharides.     

Comparison of two cacao (Theobroma cacao L.) clones for the effect of pollination intensity on fruit set and seed content

We compared the influence of pollination intensity (PI) on fruit set and seed number per pod in two cacao (Theobroma cacao L.) clones, IFC5 (Forastero Lower-Amazon Amelonado), which is self-compatible and known to produce a high number of seeds per pod under open pollination, and SCA6 (Forastero Upper-Amazon), which is self-incompatible and known to produce a low number of seeds per pod under open pollination. With both clones, PI had a positive effect on fruit set, with the maximum rate requiring more than 150 pollen grains per pod. One-half of the maximum rate of fruit set was reached with 39 pollen grains per pod for SCA6, and 78 for IFC5. With SCA6, a significant positive effect of PI on seed number per pod was also observed, with maximum seed number requiring more than 200 pollen grains per pod. In contrast, seed numbers with IFC5 were approximately equal over the PI range 100–800 pollen grains per pod. Patterns of seed number per pod were compared after: (1) open insect pollination, (2) low-intensity hand pollination and (3) high-intensity hand pollination. The patterns obtained with IFC5 under open pollination showed a peak of 40–50 seeds per pod, whereas the distribution patterns were more even with SCA6. The pattern of seed number under open pollination was similar to that obtained with high-intensity hand pollination for IFC5, and with low-intensity hand pollination for SCA6. We concluded that the high number of seeds per pod observed with IFC5 under natural insect pollination may be explained by a high number of compatible self-pollen grains on the stigma and by a severe drop of low-pollinated flowers eliminating potential lowfilled fruits. With SCA6, however, the number of compatible pollen grains deposited on the stigma was probably low under open pollination, and the flowers required lower pollen quantities to set fruit, which resulted in a high frequency of low seed numbers per fruit. This difference in the capacity to set low-seeded fruits might be considered as an adaptive trait related to the mode of reproduction.     

Effective pollination period in apricot (Prunus armeniaca L.) varieties

A study of the effective pollination period (E.P.P.) of six varieties of apricot has shown that in the warm climate of the South Mediterranean this parameter is extremely short. The percentage of fruit set of emasculated flowers diminishes rapidly with time. Temperature plays an important role in this process and is responsible for the rapid degradation of the stigma, which hinders pollen germination.     

A new mode of ring cleavage of 2,3-dihydroxybenzoic acid in Tecoma stans (L.). Partial purification and properties of 2,3-dihydroxybenzoate 2,3-oxygenase.

2,3-Dihydroxybenzoic acid has been shown to be oxidized via the 3-oxoadipate pathway in the leaves of Tecoma stans. The formation of 2-carboxy-cis,cis-muconic acid, a muconolactone, 3-oxoadipic acid and carbon dioxide during its metabolism has been demonstrated using an extract of Tecoma leaves. The first reaction of the pathway, viz., the conversion of 2,3-dihydroxybenzoate to 2-carboxy-cis,cis-muconic acid has been shown to be catalysed by an enzyme designated as 2,3-dihydroxybenzoate 2,3-oxygenase. The enzyme has been partially purified and a few of its properties studied. The enzyme is very labile with a half-life of 3--4 h. It is maximally active with 2,3-dihydroxybenzoate as the substrate and does not exhibit any activity with catechol, 4-methyl catechol, 3,4-dihydroxybenzoic acid, etc. However, 2,3-dihydroxy-p-toluate and 2,3-dihydroxy-p-cumate are also oxidized by the enzyme by about 38% and 28% respectively, compared to 2,3-dihydroxybenzoate. Sulfhydryl reagents inhibit the enzyme reaction and the inhibition can be prevented by preincubation of the enzyme with the substrate. Substrate also affords protection to the enzyme against thermal inactivation. Sulfhydryl compounds strongly inhibit the reaction and the inhibition cannot be prevented by preincubation of the enzyme with its substrates. Data on the effect of metal ions as well as metal chelating agents suggest that copper is the metal cofactor of the enzyme. Evidence is presented which suggests that iron may not be participating in the overall catalytic mechanism.     

Perfect syncarpy in apple (Malus x domestica 'Summerland McIntosh') and its implications for pollination, seed distribution and fruit production (Rosaceae: Maloideae)

BACKGROUND AND AIMS: The gynoecium of the domestic apple, Malus x domestica, has been assumed to be imperfectly syncarpic, whereby pollination of each stigmatic surface can result in fertilization within only one of the five carpels. Despite its implied effect on fruit quantity and quality, the resulting influence of flower form on seed set and distribution within the apple fruit has seldom been investigated. Instead, poor fruit quality is usually attributed to problems with pollination, such as low bee numbers and/or ineffective pollinators within apple agro-ecosystems. The objective of this study was to determine the true nature of gynoecial structure and its influence on fruit production in the apple cultivar 'Summerland McIntosh'. METHODS: A stigma-excision method was used to determine the effects of uneven pollination among the five stigmas on fruit quantity (as measured by fruit set), and quality (seed number and distribution). In addition, flowers were examined microscopically to determine pollen tube pathways. KEY RESULTS: Fruit set, seed number, seed distribution, and the microscopic examination of flower gynoecial structure reported in this study indicated that the gynoecium of the cultivar Summerland McIntosh is perfectly syncarpic and not imperfectly syncarpic as previously thought. CONCLUSIONS: Pollination levels among the five stigmas need not be uniform to obtain full seed development within Summerland McIntosh fruit; even if one stigmatic surface is adequately pollinated, a full complement of seeds is likely. The importance of perfect syncarpy in recognizing true causes of poor fruit quality in apple is discussed.     

Alternative criteria for assessing nutrient limitation of a wetland macrophyte (Peltandra virginica (L.) Kunth)

Various nutrient incorporation and plant production parameters were measured to assess their relative usefulness in determining possible nutrient limitation of the wetland plant Peltandra virginica (L.) Kunth. From four stations located along a transect in a tidal freshwater marsh, we documented spatial differences in peak standing biomass of plants. Plant biomass was positively correlated with porewater concentrations of both ammonium and phosphate, but not with sediment concentrations of total nitrogen and phosphorus. Tissue nitrogen and phosphorus concentrations decreased significantly over the growing season, but there were no differences among plants from the four stations, and correlations between plant biomass and ratios of carbon to nitrogen and carbon to phosphorus were weak. Because in situ fertilization of plants had no effect on either peak biomass or tissue concentrations of nitrogen and phosphorus, growth of Peltandra was probably not nutrient limited. Other criteria did predict nitrogen or nitrogen and phosphorus limitation, however, demonstrating that application of parameters used by ecologists to support contentions of nutrient limitation can yield conflicting results. Assessment of nutrient limitation of primary producers may be an ambiguous and unnecessary task in some environments where these criteria are utilized.     

Pollination in Jacaranda rugosa (Bignoniaceae): euglossine pollinators, nectar robbers and low fruit set

Nectar robbers access floral nectar in illegitimate flower visits without, in general, performing a pollination service. Nevertheless, their effect on fruit set can be indirectly positive if the nectar removal causes an incremental increase in the frequency of legitimate flower visits of effective pollinators, especially in obligate outcrossers. We studied pollination and the effect of nectar robbers on the reproductive fitness of Jacaranda rugosa , an endemic shrub of the National Park of Catimbau, in the Caatinga of Pernambuco, Brazil. Xenogamous J . rugosa flowers continuously produced nectar during the day at a rate of 1 μl·h⁻¹. Female and male Euglossa melanotricha were the main pollinators. Early morning flower visits substantially contributed to fruit set because stigmas with open lobes were almost absent in the afternoon. Ninety-nine per cent of the flowers showed damage caused by nectar robbers. Artificial addition of sugar water prolonged the duration of flower visits of legitimate flower visitors. Removal of nectar, simulating the impact of nectar robbers, resulted in shorter flower visits of euglossine bees. While flower visits of nectar-robbing carpenter bees ( Xylocopa frontalis , X . grisescens, X . ordinaria) produced only a longitudinal slit in the corolla tube in the region of the nectar chamber, worker bees of Trigona spinipes damaged the gynoecium in 92% of the flowers. This explains the outstandingly low fruit set (1.5%) of J. rugosa in the National Park of Catimbau.     

An experimental study of floral display and fruit set in Chilopsis linearis (Bignoniaceae)

Summary Intact cores from the wet coastal arctic tundra at Barrow, Alaska, were used as microcosms in the measurement of CO₂ fluxes between peat, vegetation, and atmosphere under controlled conditions. Net ecosystem CO₂ uptake was almost twice as high at present summer temperatures (4° C) than at 8°. Lowering the water table from the soil surface to -5 cm also had a pronounced effect in decreasing net ecosystem carbon storage. Warming of the tundra climate could change this ecosystem from a sink for atmospheric CO₂ to a source.     

Production of double haploids in oat (Avena sativa L.) by pollination with maize (Zea mays L.)

The aim of the study was to optimize the method of oat haploid production by pollination with maize. Seventeen oat genotypes were used in the experiment. Various factors influencing the growth and development of ovaries and embryo production were investigated: genotype, time of pollination, growth regulators and time of their application. Emasculated before anthesis, oat florets were pollinated with maize pollen after 0, 1 or 2 days. Next, one of two auxins analogues (2,4-D or dicamba) were applied to oat pistils. These auxins had no significant influence on the number of enlarged ovaries and embryos. The time of application of these growth regulators had a significant influence on embryo production. Haploid embryos were obtained from all used genotypes, although the frequency of enlarged ovaries and obtained embryos did not differ markedly between the genotypes. On average, 85% of ovaries were enlarged and 11.7% of them produced haploid embryos. Depending on the regeneration medium, 24–41% of embryos were germinated, of which 12% had developed into green plants. A strong significant difference in the number of germinating embryos and haploid plants was observed between the kind of regenerating medium used. There were no albino plants and all the obtained plants were haploid.     

Mapping QTLs controlling fruit quality in peach (Prunus persica (L.) Batsch)

 The organoleptic quality of fleshy fruits is in a large part defined by their composition of soluble sugars and organic acids. An F₂ population issuing from a cross between two peach varieties, ‘Ferjalou Jalousia’, a non-acid peach, and ‘Fantasia’, an acid nectarine, was analysed over 2 successive years for agronomic characters and for molecular-marker (isoenzymes, RFLPs, RAPDs, IMAs and AFLPs) segregations. Blooming and maturity dates, as well as productivity, were noted for each tree. Four fruits per tree were analysed at maturity for fresh weight, colour, pH, titratable acidity, soluble-solids content (SSC), acid (malic, citric and quinic acids) and sugar (sucrose, glucose, fructose, sorbitol) contents. QTLs were detected for all fruit components analysed, except for fruit colour. The QTLs for nearly all components were present on two linkage groups. For productivity, fresh weight, pH, quinic acid, sucrose and sorbitol content, all the detected QTLs displayed the same effect as the parental phenotypes. By contrast, for maturity date, titratable acidity, malic and citric acids and fructose, some QTLs displayed the same effect as the parental phenotypes while others displayed the opposite effect. The fraction of the total variation in each trait throughout the population explained by the QTLs was very high and reached more than 90% for some characters. For most of the characters analysed, epistasis was observed between QTLs. Received: 10 October 1997 / Accepted: 18 August 1998     

Fidelity of Hymenoptera and Diptera pollinators in onion (Allium cepa L.) pollination

Onion (Allium cepa L.) is protandrous in nature and requires cross‐pollination to avoid inbreeding. The pollination potential of native bees (Hymenoptera) and true flies (Diptera) was assessed in the perspective of finding the best pollinators for onion cross‐pollination and seed multiplication. The community of pollinators was composed of four bee species and twelve true fly species. Episyrphus balteatus, Eupeodes sp., Musca domestica and Eristalinus aeneus were the most abundant pollinators. The maximum pollinator activity was observed from 12 to 24 days after opening of the flowers. The pollination effectiveness of tested bees (Apis dorsata and Apis florea) was greater than true flies (E. balteatus, Eupeodes sp., M. domestica, E. aeneus and Callihoridae sp.) in terms of Spears values.     

Studies on pollination and fertilization in the field bean (Vicia faba L.)

The percentage of cross-fertilization in the field bean was found to be around 45%, and to be higher on the lower nodes of the plants than on the upper. No differences in the relative pollen tube growth rates of self and foreign pollen were observed. The different lines and genotypes investigated responded differently to open pollination, selfing with manual tripping, and selfing without tripping. Fertilizer application and date of sowing affected the number of flowers produced and the number of seeds set, but did not affect the ratio of seeds to flowers, i.e. the index of self fertility.