Effects of self-, chase and mixed self/cross-pollinations on pistil longevity and fruit set in Ceiba species (Bombacaceae) with late-acting self-incompatibility

BACKGROUND AND AIMS: Late-acting self-incompatibility (LSI), in which selfed flowers fail to form fruits despite apparently successful growth of the pollen tubes to the ovules, is a contentious and still poorly understood phenomenon. Some studies have indicated pollen tube-pistil interactions, and major gene control. Others favour an early acting inbreeding depression explanation. METHODS: Experimental pollinations, including selfs (in a subsample of which the style was cut before pollen tubes reached the ovary), chase self/cross-pollinations, crosses, and mixed self/cross-pollinations were used to study floral/pistil longevity and effect on fruit set and seed yield in two Ceiba species known to have LSI. RESULTS: Self-pollinations, including those with a cut style, had extended floral longevity compared with unpollinated flowers. Chase pollinations in which cross-pollen was applied up to 3 h after selfing set fruits, but with reduced seed set compared with crosses. Those with cross-pollen applied at 4 and 8 h after self-pollination all failed to set fruits. Flowers subjected to 1 : 1 and 2 : 1 self/cross-pollinations all produced fruits but again with a significantly lower seed set compared with crosses. CONCLUSIONS: Extended floral longevity initiated with self-pollen tubes growing in the style indicates some kind of pollen tube-pistil interaction. Fruit set only in chase pollinations up to 3 h implies that self-pollen tubes either grow more slowly in the style or penetrate ovules more slowly on arrival at the ovary compared with cross-tubes. This agrees with previous observations indicating that the incidence of penetrated ovules is initially lower in selfed compared with crossed pistils. However, the low seed yield from mixed pollinations indicates that self- and cross-pollen tubes arrive at the ovary and penetrate ovules more or less simultaneously. Possible explanations for these discordant results are discussed.     

Carbohydrate analysis of floral nectar using medium infrared

An instrumental method based on a chemometric model of the medium region of the infrared (MIR) was developed to analyse total sugar content and the proportions of glucose, fructose and sucrose. In order to construct the model, a set of 127 standard aqueous solutions of different sugars in the concentration range 0-20% (w/v) were prepared and analysed in the interval 4900-700 cm(-1). The MIR was transformed by normalisation, correction of baseline using the second derivative, and suppression of the signals of water and carbon dioxide. The region between 1150 and 950 cm(-1) showed the highest correlation between signal and concentration. The correlation coefficient for total sugar content was 0.956, whilst those for glucose, fructose and sucrose were 0.982, 0.972 and 0.992, respectively. The method was validated using a set of 28 samples of nectar which had been assayed by chromatographic and refractometric methods. The method shows potential utility for the prediction of nectar sugar components.     

“Stepping-sticks” and “seat-sticks”: New types of tools used by wild chimpanzees (Pan troglodytes) in Sierra Leone

In Tenkere, Sierra Leone, a community of wild chimpanzees (Pan troglodytes verus) spent long hours eating the fruits and flowers of the Kapok (Ceiba pentandra) tree. The branches of this species are covered in sharp thorns which make movement in their high canopies problematic for the chimpanzees. In an apparent attempt to increase their mobility and to ease the discomfort of lengthy bouts of eating in these trees, some of the Tenkere chimpanzees have been observed using stick tools as foot (“stepping-sticks”) and body (“seat-sticks”) protection against the painful thorns. This form of tool-using is culturally unique to the Tenkere chimpanzees, as at other sites where these apes have been observed eating parts of kapok trees, there are no published records of this tool technology. In three of the stepping-stick tool use incidents, the chimpanzee used the tool(s), held between their greater and lesser toes, in locomotion. This form of tool use is the first recorded case of habitually used tools that can be justifiably categorized as being “worn” by any known wild population of Pan troglodytes. Am J Primatol 41:45–52, 1997. © 1997 Wiley-Liss, Inc.     

Root–shoot allometry of tropical forest trees determined in a large-scale aeroponic system

Background and Aims

This study is a first step in a multi-stage project aimed at determining allometric relationships among the tropical tree organs, and carbon fluxes between the various tree parts and their environment. Information on canopy–root interrelationships is needed to improve understanding of above- and below-ground processes and for modelling of the regional and global carbon cycle. Allometric relationships between the sizes of different plant parts will be determined.

Methods

Two tropical forest species were used in this study: Ceiba pentandra (kapok), a fast-growing tree native to South and Central America and to Western Africa, and Khaya anthotheca (African mahogany), a slower-growing tree native to Central and Eastern Africa. Growth and allometric parameters of 12-month-old saplings grown in a large-scale aeroponic system and in 50-L soil containers were compared. The main advantage of growing plants in aeroponics is that their root systems are fully accessible throughout the plant life, and can be fully recovered for harvesting.

Key Results

The expected differences in shoot and root size between the fast-growing C. pentandra and the slower-growing K. anthotheca were evident in both growth systems. Roots were recovered from the aeroponically grown saplings only, and their distribution among various diameter classes followed the patterns expected from the literature. Stem, branch and leaf allometric parameters were similar for saplings of each species grown in the two systems.

Conclusions

The aeroponic tree growth system can be utilized for determining the basic allometric relationships between root and shoot components of these trees, and hence can be used to study carbon allocation and fluxes of whole above- and below-ground tree parts.     

Microsatellite markers for Ceiba pentandra (Bombacaceae), an endangered tree species of the Amazon forest

From a genomic library enriched for AG/TC repeats, eight polymorphic microsatellite markers were developed for Ceiba pentandra, a pan‐tropical forest tree. Polymorphism was evaluated using a panel of 74 adult trees. Using automated fluorescence detection, a total of 112 alleles was detected with an average of 14 alleles per locus. All microsatellite loci showed very high levels of genetic information content, with expected heterozygosity ranging from 0.814 to 0.895. These microsatellite markers represent a powerful tool to investigate refined questions of mating systems, gene flow, family structure and population dynamics in natural populations of C. pentandra.     

Floral scent of bat-pollinated species: West Africa vs. the New World

Floral scent of seven West African bat-pollinated tree species, belonging to six families, was collected in situ from flowering individuals using headspace adsorption. The seven species shared neither any specific compounds nor any other discernible pattern in their floral scent composition. Most of the identified compounds are common in the floral scent of species pollinated by a variety of animals. Adansonia digitata (Bombacaceae) was the only African species found to have a substantial proportion of sulphur compounds in its floral scent. This feature contrasts with the sampled New World bat-pollinated plants, which frequently contain these compounds. The floral scent of Ceiba pentandra (Bombacaceae), native to both South America and Africa, contained no sulphur substances, contradicting a previous study in the New World that identified the major floral compounds as dimethyl disulphide and dimethyl trisulphide. We suggest that the differences in the floral scent of C. pentandra , including the absence of sulphur compounds in the African variety, result from the different selective regimes exerted by the Pteropotidae bats, in Africa, and Phyllostomidae bats, in the New World, that visit their flowers.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 161–168.     

Diversity of Tropical Tree Seedling Responses to Drought

Drought is an important seedling mortality agent in dry and moist tropical forests, and more severe and frequent droughts are predicted in the future. The effect of drought on leaf gas exchange and seedling survival was tested in a dry-down experiment with four tree species from dry and moist forests in Bolivia. Seedlings were droughted and wilting stage and gas exchange were monitored. Drought led to a gradual reduction of photosynthesis and stomatal conductance over time, whereas respiration and photosynthetic water-use efficiency initially increased with drought and then declined. Seedlings gradually went through the different wilting stages, until they eventually died, but the trajectory differed for the four species. The strong relationship between wilting stage and photosynthesis means that simple field observations can provide valuable information on plant physiological performance. Three different drought strategies were identified. Dry forest species Ceiba samauma shed its leaves and survived. The moist forest species Cariniana ianeirensis postponed drought stress by having low rates of transpiration and high water-use efficiency. Dry forest Astronium urundeuva and moist forest Triplaris americana followed an opportunistic strategy; they are early successional species that can quickly grow to maturity but periodic drought can be lethal. Strikingly, dry and moist forest species did not differ clearly in their drought tolerance strategies.     

Antidiabetic properties of aqueous and methanol extracts from the trunk bark of Ceiba pentandra in type 2 diabetic rat

The type 2 diabetes is one of the major global health issues that affects millions of people. This study evaluated the antidiabetic activity of aqueous extracts (AECP) and methanol extracts (MECP) from Ceiba pentandra trunk bark on an experimental model of type 2 diabetes (T2D). This model was induced in rats by the combination of a high-fat diet (HFD) and a single dose of streptozotocin (40 mg/kg, intraperitoneal) at the seventh day of experimentation. Diabetes was confirmed on day 10 by fasting blood glucose more than or equal to 200 mg/dL. Diabetic animals still under HFD were treated orally and twice daily, with MECP and AECP (75 and 150 mg/kg) or metformin (40 mg/kg) for 14 days. During the experiment, blood glucose and animal weights were determined. Oral glucose tolerance test was performed on day 15, followed by animals sacrifice for blood, liver, and pancreas collection. Total cholesterol and triglyceride levels were evaluated in plasma, whereas malondialdehyde (MDA), glutathione (GSH), superoxide dismutase, and catalase were quantified in tissue homogenates. AECP and MECP significantly reduced the hyperglycemia by up to 62% and significantly improved the oral glucose tolerance test. The impaired levels of cholesterol and triglycerides registered in diabetic control were significantly reversed by both extracts at all the doses used. Alterations in diabetic pancreas weight, GSH, and MDA were also significantly reversed by plant extracts. AECP and MECP possess type 2 antidiabetic effects that could result from their ability to improve the peripheral use of glucose, lipid metabolism or from their capacity to reduce oxidative stress. These finding provide a new avenue for better control and management of early or advanced T2D.     

Relationship between specific leaf area,leaf thickness,leaf water content and <Emphasis Type="Italic">SPAD-502</Emphasis> readings in six Amazonian tree species

The aim of this work was to assess the effect of leaf thickness, leaf succulence (L_S), specific leaf area (SLA), specific leaf mass (W_s) and leaf water content (LWC) on chlorophyll (Chl) meter values in six Amazonian tree species (Carapa guianensis, Ceiba pentandra, Cynometra spruceana, Pithecolobium inaequale, Scleronema micranthum and Swietenia macrophylla). We also tested the accuracy of a general calibration equation to convert Minolta Chl meter (SPAD-502) readings into absolute Chl content. On average, SPAD values (x) increased with fresh leaf thickness (FLT [μm] = 153.9 + 0.98 x, r ² = 0.06**), dry leaf thickness (DLT [μm] = 49.50 + 1.28 x, r ² = 0.16**), specific leaf mass (W_s [g (DM) m⁻²] = 6.73 + 1.31 x, r ² = 0.43**), and leaf succulence (L_S [g(FM)] m⁻² = 94.2 + 1.58 x, r ² = 0.19**). However, a negative relationship was found between SPAD values and either specific leaf area [SLA (m² kg⁻¹) = 35.1 − 0.37 x, r ² = 0.38**] or the leaf water content (LWC [%]= 80.0 − 0.42 x, r ² = 0.58**). Leaf Chl contents predicted by the general calibration equation significantly differed (p<0.01) from those estimated by species-specific calibration equations. We conclude that to improve the accuracy of the SPAD-502 leaf thickness and LWC should be taken into account when calibration equations are to be obtained to convert SPAD values into absolute Chl content.