Mature Palm Research Articles

New mechanized system for circle spraying of oil palms seedling emergence

A new machine system has been designed, developed and evaluated for extensive circle spraying of oil palms (Elaeis guineensis Jacq.) in an effort to overcome the inefficient spraying problem with the conventional spraying system. The machine system consists of a four-wheeled drive 4WD prime mover with front mounted machine attachments for the circle spraying operation. The configuration of the circle spraying attachment consists of a hexagonal curved spray boom, lifting arm, opening-tilting mechanism unit, storage tank, spray pump, solid cone nozzles, and associate hydraulic system. Field performance tests on the machine system showed an average effective field capacity of 7.89 ha per man per day and when compared to the earlier reported effective field capacity of the walking spray-operated equipment using Serena LT16 knapsack sprayer; a difference of 1.97 time for circle spraying of mature palms grove. Reduction in the human energy expenditure of 101.28 kJ man-1 h-1 or 10.68 % but an increase in the spraying cost of 1.53 USD ha-1 or 24.9 % were obtained with the machine system against the walking spraying-operated equipment using Serena LT16 knapsack sprayer. Justification for machine system to be cost effective could be satisfied if the present effective field capacity is increased to 1.263 time with good skilled operator or if the current R&D cost is reduced to 0.41 time. This is because the improved field capacity of new machine system could not rationalize its current R&D cost. Admittedly, the machine system has great potential to overcome the limitations with the current employed machine/equipment in the circle spraying operation of oil palms in the plantation.

Performance assessment of surface and subsurface drip irrigation system for date palm fruit trees

Surface and subsurface drip irrigation methods can play a significant role in overcoming the scarcity of water mostly in water shortage areas. A field study was conducted to know the effectiveness of surface and subsurface drip irrigation systems under different plasticity pipes, in terms of both water use requirement and yield of date palms at Al-Qassim, Saudi Arabia. Mature palm trees of different varieties with 10 m spacing for both row to row and tree to tree were selected. Three types of pipes (low, medium and high flexible that is, with wall thickness of 1.14, 0.38 and 0.41 mm, respectively) were used in both surface and subsurface drip irrigation systems. Irrigation scheduling was done through a soil moisture sensing device as well as crop water requirement guidelines for Kingdom of Saudi Arabia to ensure enough soil water levels in the soil. Considerable effects of pipe stiffness were observed on water consumption and yield for both surface and subsurface drip irrigation systems. It was found that irrigation water reduced to 36 and 56% for drip pipes of low flexibility under surface drip irrigation system while it was 49 and 53% under subsurface drip irrigation system due to better physical and hydraulic characteristic of pipe as compared to that for medium and high flexibility pipes, respectively. The yield of date palms was increased by 45 and 48% more in case of low flexibility pipe compared to that for other two types under both drip irrigation systems. Date palm response by using low flexible pipe under both surface and subsurface drip irrigation was found relatively good in respect of water consumption, yield and irrigation system itself. Key words: Surface drip irrigation, subsurface drip irrigation, date palm, arid region, pipe flexibility.

Estimating aboveground biomass in forest and oil palm plantation in Sabah, Malaysian Borneo using ALOS PALSAR data

Conversion of tropical forests to oil palm plantations in Malaysia and Indonesia has resulted in large-scale environmental degradation, loss of biodiversity and significant carbon emissions. For both countries to participate in the United Nation’s REDD (Reduced Emission from Deforestation and Degradation) mechanism, assessment of forest carbon stocks, including the estimated loss in carbon from conversion to plantation, is needed. In this study, we use a combination of field and remote sensing data to quantify both the magnitude and the geographical distribution of carbon stock in forests and timber plantations, in Sabah, Malaysia, which has been the site of significant expansion of oil palm cultivation over the last two decades. Forest structure data from 129 ha of research and inventory plots were used at different spatial scales to discriminate forest biomass across degradation levels. Field data was integrated with ALOS PALSAR (Advanced Land-Observing Satellite Phased Array L-band Synthetic Aperture Radar) imagery to both discriminate oil palm plantation from forest stands, with an accuracy of 97.0% ( κ = 0.64) and predict AGB using regression analysis of HV-polarized PALSAR data ( R 2 = 0.63, p < .001). Direct estimation of AGB from simple regression models was sensitive to both environmental conditions and forest structure. Precipitation effect on the backscatter data changed the HV prediction of AGB significantly ( R 2 = 0.21, p < .001), and scattering from large leaves of mature palm trees significantly impeded the use of a single HV-based model for predicting AGB in palm oil plantations. Multi-temporal SAR data and algorithms based on forest types are suggested to improve the ability of a sensor similar to ALOS PALSAR for accurately mapping and monitoring forest biomass, now that the ALOS PALSAR sensor is no longer operational.

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF OIL PALM (ELAEIS GUINEENSIS): A REVIEW

SUMMARYThe results of research on the water relations and irrigation need of oil palm are collated and summarized in an attempt to link fundamental studies on crop physiology to drought mitigation and irrigation practices. Background information is given on the centres of origin (West Africa) and of production of oil palm (Malaysia and Indonesia), but the crop is now moving into drier regions. The effects of water stress on the development processes of the crop are summarized followed by reviews of its water relations, water use and water productivity. The majority of the recent research published in the international literature has been conducted in Malaysia and in Francophone West Africa. The unique vegetative structure of the palm (stem and leaves) together with the long interval between flower initiation and the harvesting of the mature fruit (ca. three years) means that causal links between environmental factors (especially water) and yield are difficult to establish. The majority of roots are found in the 0–0.6 m soil horizons, but roots can reach depths greater than 5 m and spread laterally up to 25 m from the trunk. The stomata are a sensitive indicator of plant water status and play an important role in controlling water loss. Stomatal conductance and photosynthesis are negatively correlated with the saturation deficit of the air. It is not easy to measure the actual water use of oil palm, the best estimates for mature palms suggesting crop evapotranspiration (ETc) rates of 4–5 mm d−1in the monsoon months (equivalent to 280–350 l palm−1d−1). For well-watered mature palms, crop coefficient (Kc) values are in the range 0.8–1.0. Although the susceptibility of oil palm to drought is well recognized, there is a limited amount of reliable data on actual yield responses to irrigation. The best estimates are 20–25 kg fresh fruit bunches ha−1mm−1(or a yield loss of about 10% for every 100 mm increase in the soil water deficit). These increases are only realized in the third and subsequent years after the introduction of irrigation and follow an increase in the number of fruit bunches as a result of an improvement in the sex ratio (female/total inflorescence production) and a reduction in the abortion of immature inflorescences. There is no agreement on the allowable depletion of the available soil water, or on the associated optimum irrigation interval. Drip irrigation has been used successfully on oil palm.

Damage Pattern and Nesting Characteristic of &lt;i&gt;Coptotermes curvignathus&lt;/i&gt; (Isoptera: Rhinotermitidae) in Oil Palm on Peat

The oil palm industry of Malaysia has expanded into peat area in Sarawak. Problem statement: The subterranean termite Coptotermes curvignathus was a serious pest of oil palm on peat. Control of this termite has resorted to heavy usage of chemicals which was deemed uneconomical and hostile to the environment. Baiting system has inconsistent success due to the limited knowledge of the behavior of the pest. Approach: This study was to investigate damage and nesting characteristic of the pest. Infested palm in the peat area was dissected using a chainsaw and observation was made on the endoecie and damage. Microclimate inside the palm was recorded using a data logger and acid insoluble lignin from 3 different infested palms was determined. Results: Dissection of infested palm revealed that termite generally attacked the palm from the spear in immature palm or basal region in mature palm due to the energy requirement and level of water table. Spear region infestation was possible because of the moist environment provided by the proximity of the fronds and leaf sheaths. The high lignin content (42-45%) in the thin laminae indicated the concentration of lignin or incorporation of peat in nest construction. Wood stump residues remained in the plantation was one of the main reasons of termite infestation. The stability and protection of the wood stump encouraged termite breeding. A C. curvignathus queen was discovered in the endoecie under the wood stump and was seen mobile. Conclusion: The pest was generally available in area where wood stumps and moisture were available. Manipulation of water table for certain period after spraying of chemical may help reduce infestation by the termite.

Isolation and characterization of an oil palm constitutive promoter derived from a translationally control tumor protein (TCTP) gene

We have characterized an oil palm (Elaeis guineensis Jacq.) constitutive promoter that is derived from a translationally control tumor protein (TCTP) gene. The TCTP promoter was fused transcriptionally with the gusA reporter gene and transferred to monocot and dicot systems in order to study its regulatory role in a transient expression study. It was found that the 5' region of TCTP was capable of driving the gusA expression in all the oil palm tissues tested, including immature embryo, embryogenic callus, embryoid, young leaflet from mature palm, green leaf, mesocarp and stem. It could also be used in dicot systems as it was also capable of driving gusA expression in tobacco leaves. The results indicate that the TCTP promoter could be used for the production of recombinant proteins that require constitutive expression in the plant system.

Mechanised Weed Control Applicator for Mature Oil Palm

A new machine system has been designed, developed and evaluated for extensive weed control around mature oil palm. The machine system consists of a 4WD prime mover with the front mounted machine attachments for circle spraying operation. The configuration of the circle spraying attachment consists of the hexagonal curved spray boom, lifting arm, opening-tilting mechanism unit, storage tank, spray pump, solid cone nozzles, and associate hydraulic system. Field performance tests on the machine system showed an average effective field capacity of 7.89 ha per manday and when compared against the earlier reported effective field capacity of the walking spray-operated equipment using rechargeable battery powered knapsack sprayer, there was a difference of 1.97 times for circle spraying of mature palms grove. A reduction in the human energy expenditure of 24.19 kcal per manhour or 10.68 per cent but an increase in the spraying cost per hectare of USDl.53 per hectare (RM4.66/ha) or 24.9 per cent were obtained with the machine system against the walking spraying-operated equipment using rechargeable battery powered knapsack sprayer. Justification for machine system to be cost effective could be satisfied if the present effective field capacity is increased to 26.3 per cent with a good skilled operator or if the current R&amp;D cost is reduced to 0.41 times. This is because the improved field capacity of the new machine system could not rationalise its current R&amp;D cost. Admittedly, the machine system has great potential to overcome the limitations with the currently employed machine/equipment in the circle spraying operation of oil palm in the plantation. Keywords: Circle spraying, oil palm cultivation, agricultural machinery, mechanisation.

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF COCONUT (Cocos nucifera): A REVIEW

SUMMARYThe results of research on the water relations and irrigation needs of coconut are collated and summarized in an attempt to link fundamental studies on crop physiology to drought mitigation and irrigation practices. Background information on the centres of origin and production of coconut and on crop development processes is followed by reviews of plant water relations, crop water use and water productivity, including drought mitigation. The majority of the recent research published in the international literature has been conducted in Brazil, Kerala (South India) and Sri Lanka, and by CIRAD (France) in association with local research organizations in a number of countries, including the Ivory Coast. The unique vegetative structure of the palm (stem and leaves) together with the long interval between flower initiation and the harvesting of the mature fruit (44 months) mean that causal links between environmental factors (especially water) are difficult to establish. The stomata play an important role in controlling water loss, whilst the leaf water potential is a sensitive indicator of plant water status. Both stomatal conductance and leaf water potential are negatively correlated with the saturation deficit of the air. Although roots extend to depths &gt;2 m and laterally &gt;3 m, the density of roots is greatest in the top 0–1.0 m soil, and laterally within 1.0–1.5 m of the trunk. In general, dwarf cultivars are more susceptible to drought than tall ones. Methods of screening for drought tolerance based on physiological traits have been proposed. The best estimates of the actual water use (ETc) of mature palms indicate representative rates of about 3 mm d−1. Reported values for the crop coefficient (Kc) are variable but suggest that 0.7 is a reasonable estimate. Although the sensitivity of coconut to drought is well recognized, there is a limited amount of reliable data on actual yield responses to irrigation although annual yield increases (50%) of 20–40 nuts palm−1 (4–12 kg copra, cultivar dependent) have been reported. These are only realized in the third and subsequent years after the introduction of irrigation applied at a rate equivalent to about 2 mm d−1 (or 100 l palm−1 d−1) at intervals of up to one week. Irrigation increases female flower production and reduces premature nut fall. Basin irrigation, micro-sprinklers and drip irrigation are all suitable methods of applying water. Recommended methods of drought mitigation include the burial of husks in trenches adjacent to the plant, mulching and the application of common salt (chloride ions). An international approach to addressing the need for more information on water productivity is recommended.

Measurement of Oil Palm LAI by Manual and LAI-2000 Method*

In this study, accurate Leaf Area Index (LAI) of different palm age groups were determined by manual (direct) method. Optical methods for quantifying variation in LAI of different palm ages were evaluated using LAI-2000 Plant Canopy Analyser (PCA) as an indirect method. In the manual method, LAI values obtained were 0.69, 1.11, 2.38, 2.49, 3.41, 3.83, 4.05 and in the indirect method LAI values obtained were 1.75, 1.4, 1.14, 1.42, 2.87, 1.89, 3.05 for 2, 3, 6, 7, 9, 12 and 16 year old palms, respectively. Results showed that the PCA LAI values were overestimated for immature palms but underestimated for mature palms. The PCA LAI values were overestimated by 30.8-153% for 2 to 3-year old palms and underestimated by 24-52% for beyond 6-year old palms as compared to manual measurement. The relationship between palm age and LAI was also established in this study. A strong linear relationship between direct LAI and palm age was observed with a correlation coefficient, R = 0.90. However, the relationship between PCA LAI and palm age was weak and not significant. A relationship was observed between PCA LAI and direct LAI with a correlation coefficient of R = 0.57. The study shows that it was possible to rapidly determine LAI using the LAI-2000 Plant Canopy Analyser. This rapid and non-destructive method saves labour when compared to manual measurements. However, this instrument gave inconsistent of LAI values in respect to oil palm age.

Isolation and characterization of oil palm constitutive promoter derived from ubiquitin extension protein ( uep1) gene

The ubiquitin extension protein (uep1) gene was identified as a constitutively expressed gene in oil palm. We have isolated and characterized the 5' region of the oil palm uep1 gene, which contains an 828 bp sequence upstream of the uep1 translational start site. Construction of a pUEP1 transformation vector, which contains gusA reporter gene under the control of uep1 promoter, was carried out for functional analysis of the promoter through transient expression studies. It was found that the 5' region of uep1 functions as a constitutive promoter in oil palm and could drive GUS expression in all tissues tested, including embryogenic calli, embryoid, immature embryo, young leaflet from mature palm, green leaf, mesocarp and meristematic tissues (shoot tip). This promoter could also be used in dicot systems as it was demonstrated to be capable of driving gusA gene expression in tobacco.

Termite Attack on Oil Palm Grown on Peat Soil: Identification of Pest Species and Factors Contributing to the Problem

Oil palm grown on peat soil has been reported to be severely attacked by subterranean termites, and this has been thought to be due to the harbouring of the termites in abundant timber residues left behind after the clearing of logged-over peat swamp forests for oil palm cultivation. In this study, oil palm trees and plant residues in plantations established on peat and mineral soils were examined for the presence of termites. The primary termite species capable of killing oil palm trees was Coptotermes curvignathus (Rhinotermitidae). Immature palms were killed as a result of feeding damage to the apical meristem at the base of the spear, while mature palms were killed as a result of damage to the trunk, in which the termite sometimes nested. C. curvignathus was rarely encountered in timber residues or frond heaps on the plantation floor, suggesting that removal of timber residues would not significantly reduce termite attack on oil palm on peat soils. Tivo other species of Coptotermesfound in oil palm trees grown on peat soils were able to form small nests in the trunks of mature palms but did not cause death. Together with Schedorhinotermes spp., they primarily infested plant and wood residues. The results also showed that there was a change in the composition of termite species across different soil types. Termitids were dominant in mineral soil sites, while Rhinotermitids dominated deep peat sites. A high population of C. curvignathus in the original peat swamp habitat is, therefore, likely to be a major factor contributing to the high incidence oftennite attack on oil palm grown on peat soils. Keywords: Coptotermes curvignathus, Isoptera, Rhinotermitidae, termites, peat soil, mineral soil, wood residues, Malaysia.

Paysandisia archon

Paysandisia archon

High levels of genetic variability and inbreeding in two Neotropical dioecious palms with contrasting life histories

We characterized the population genetics of two Neotropical dioecious palm species of Chamaedorea with contrasting life strategies from the region that is both the northernmost extent and most species rich of the genus. Chamaedorea tepejilote is a common, wind-pollinated arboreal understory palm. Although most adult plants reproduce each year, only a few individuals produce the majority of flowers and seeds. Chamaedorea elatior, conversely, is an uncommon climbing subcanopy palm with entomophilous flowers (insect-pollinated characteristics). Most of the mature palms do not reproduce in consecutive years and fruiting is episodic. Isozymes with a total of 107 alleles for 27 loci of 17 enzymes from six populations were assessed. For both species, co-occurrence of high levels of genetic variation and homozygosity was observed (C. tepejilote: He: 0.385-0.442, f: 0.431-0.486; C. elatior: He: 0.278-0.342, f: 0.466-0.535). Genetic differentiation of C. elatior was much lower (theta=0.0315) than that for C. tepejilote (theta=0.152). The contrast in differentiation may be influenced by differences in the spatial scale of the genetic neighborhoods of the two species. The simultaneous maintenance of inbreeding and of a large number of alleles within the populations is attributable to the low and variable number of mating pairs. Demographic studies indicate that this pattern could be explained by low reproductive frequency among individuals and over years in C. elatior and by reproductive dominance in C. tepejilote.

Reproductive developmental complexity in the African oil palm (Elaeis guineensis, Arecaceae)

Species of the palm family (Arecaceae) are remarkably diverse in their inflorescence and floral morphologies, which make them a particularly interesting group for studies of reproductive development and its evolution. Using light and scanning electron microscopy, we describe inflorescence and flower development in the African oil palm Elaeis guineensis from the initiation of the inflorescence meristem to flower maturity. In mature palms, the inflorescence develops over 2-3 years and is characterized by individual stages within which differentiation may be either relatively slow, as in the case of early inflorescence meristem development, or rapid, as in the case of flower organogenesis. The female inflorescence bears floral triads composed of single pistillate flowers flanked by two abortive staminate flowers, whereas the male inflorescence contains single functional staminate flowers. This suggests a possible evolutionary movement from an ancestral hermaphrodite inflorescence form containing fully functional floral triads to the situation of temporal dioecy observed at present. Wild type flowers are compared to those bearing an epigenetic homeotic abnormality, known as mantled, involving an alteration of the identity of the organs in the fertile and sterile androecium.

Copper Toxicity in Oil Palms on Peat and Its Effect on Palm Growth and FFB Production

This paper documents a case of copper toxicity observed on young mature palms in a fertiliser trial evaluating the comparative efficacy of applying three micro nutrients (copper, zinc, iron) via four application techniques (soil, foliar spray, root infusion and trunk injection) in peat soil. Oil palms were more sensitive to copper than either zinc or iron, as toxicity was only induced by the former although the latter two micro-nutrients were applied at much higher rates. With copper, applying a dosage as low as only 3.0 g CuSO4 per palm via root infusion or trunk injection was more toxic than applying the same fertiliser to peat soil (soil application) at rates 166 times higher. Copper toxicity, manifested as scorching or “burn” of lower and middle level fronds, had no negative effect on palm growth, but significantly lowered fresh fruit bunch (FFB) production by as much as 3.0 tonnes per hectare per annum. A drop in yield was consistently recorded 9 to 10 months after each annual application of copper and was caused by a significant reduction in the number of bunches harvested. The latter was attributed to an increase in the rate of female inflorescence abortion, four to five months prior to anthesis or 9 to 10 months before harvest. Lowering of the inflorescence sex-ratio could be another contributing factor. Keywords: Copper, micro-nutrients, oil palm, peat, toxicity.

Palm Pulverisation in Sustainable Oil Palm Replanting

Malaysia has banned open burning of old oil palm biomass at replanting. The most widely adopted zero burn techniques of replanting oil palms in Malaysia currently are the “chipped and windrow” and “under-planting” methods. These methods resulted in very high breeding of Oryctes rhinoceros beetle, which has become the most serious pest in immature and young mature palms in Malaysia currently. Three new no-burn methods of clearing old oil palms for replanting whereby almost the entire palms are pulverized into fine pieces of less than 0.1g dry weight each and spread widely over the entire field and the root mass dug up at felling are reported. More than 50% of the pulverized palm biomass decomposed by 24 weeks after pulverization, which increased to 80% by the 56th week. All the three methods have good potential in reducing the breeding of Oryctes rhinoceros. They also have good potential in reducing the rat and Ganoderma boninense disease problems. In addition, the new clearing methods reduced the fallow period, facilitated replanting and the subsequent field upkeep work, and improved the utilisation of nutrients released by the decomposing palm biomass by the newly replanted palms. The methods of clearing old oil palms for replanting are environmentally less polluting and also improve the sustainability of oil palm plantations.

Slow decline: a new disease of mature date palms in North Africa associated with a phytoplasma

Slow Decline (SD) or El Arkish is an established lethal disease of uncertain aetiology that affects mature date palms (Phoenix dactylifera L.) in Northern Sudan. It is common along the Nile between Dongola and Merowe–Karema, where it causes steady annual losses estimated at 6%. Palm mortality occurs between 12 and 24 months after the first appearance of symptoms. SD symptoms include a yellowing of the lower canopy starting with the outermost (oldest) fronds and progressing towards the young central fronds and emerging spear leaf. All fronds dry white to light-brown and are then shed, leaving an erect dry tuft of young leaves at the top of the trunk which may break off to leave the trunk standing alone. In some case, the white dry spear leaves on palms can be seen from the ground prior to the appearance of any foliar yellowing. Young offshoots of SD-affected palms also show frond yellowing and white spear necrosis as the crown dies. Occasionally, the spear can be pulled out to reveal rotten, foul-smelling basal tissues. Although mature palms were too tall to observe any inflorescence or fruit symptoms, there was no evidence of fruit drop. Using a nested polymerase chain reaction together with general phytoplasma primers which amplify the 16S/23S rDNA (Cronje et al., 1998), phytoplasma-specific products, 1250-bp in size, were amplified from four of six SD-affected palms (one trunk and three of five petiole samples) but not from symptomless palms from the same area. The sequence of the SD phytoplasma 16S/23S rDNA intergenic spacer (GenBank Accession number AF268000) showed a very high (99%) homology with comparable sequences of phytoplasmas associated with White tip die-back, a newly reported disease of young date palms (Cronjéet al. 2000), and Bermuda grass white leaf (BGWL) disease from Sudan (Genbank Accession numbers AF100411, AF100412).

Symptoms and Population Dynamics of Rhynchophorus cruentatus (Coleoptera: Curculionidae) in Canary Island Date Palms

We documented the decline of a 2-hectare Canary Island date palm (Phoenix canariensis) nursery caused by the palmetto weevil (Rhynchophorus cruentatus) in Dade County, FL. External palm symptoms were defined, divided into nine categories, and representative palms were destructively harvested to assess internal weevil associations. Apparently healthy palms declined and died in a mean of 49 days. At the beginning of the study, 42% of 950 palms appeared healthy but within seven months only 3% were alive. Economic losses were estimated at $285,000-$380,000 for the nursery studied. Palm decline was patchily distributed in the field. The mean palm weevil counts ranged from 0.3 to 223.3 weevils per palm, for healthy to collapsing palms, respectively. Twenty-four weevil grubs were sufficient to kill one mature palm. External symptoms did not allow preventative diagnosis and treatment of internal R. cruentatus infestations. By the time that external symptoms were unambiguous, the mean total weevil counts per palm were over 100 with more than 65% as larvae and more than one quarter of these were >2.5 cm in length. Palms in these categories were dying because of irreparable damage to their apical meristems and attempts to save them would have been ineffectual. Thus, phytosanitation (palm removal and destruction) for management of R. cruentatus in Canary Island date palms should be implemented as soon as host leaves droop and weevil frass is observed. Growers and buyers of P. canariensis in regions where R. cruentatus exists should be aware of the potential lethal risk that it poses for this non-native palm. The costs of aggressive phytosanitation at the first symptoms of R. cruentatus infestation and prophylactic pesticide treatment at times of pruning, stress, or transplanting should be factored into the predicted cost of production and maintenance of Canary Island date palms in Florida.

Evaluation of five promoters for use in transformation of oil palm (Elaeis guineensis Jacq.).

The efficiency of GUS (β-Glucuronidase) gene expression in embryogenic callus and young leaflets of mature and seedling palm after microprojectile bombardment with five constructs (pEmuGN, pAHC25, pAct1-F4, pGH24 and pBARGUS) was evaluated to identify the most suitable promoter(s) to use in transformation attempts in oil palm. Expression of the GUS gene driven by theEmu, Ubi1, Act1 35S orAdh1 was assayed, both histochemically and fluorometrically, from a total of 200 plates of tissues in eight independent experiments two days after bombardment. A completely randomized experimental design was used for each experiment, and the data analysed by ANOVA and Duncan's Multiple Range Test. The expression level of GUS driven by theEmu orUbi1 promoters was significantly higher than that of the Act], 35S and Adhl promoters in many experiments, and that of theAdhl was significantly lower than those of the other four promoters. Both histochemical and fluorometric data indicate that in embryogenic callus, the expression of theEmu promoter was higher than that of theUbi1 whereas in young leaflets from mature palm the Ubi1 expression was stronger. The performances of the five promoters were also tested in tobacco callus using a fluorometric GUS assay. The activity of the 35S promoter was highest, and significantly different from that of all the other promoters except theEmu, and that of theAct1 promoter was lowest. These results indicate that either theUbil orEmu promoter should facilitate the expression of desired genes in oil palm and aid in development of an efficient stable transformation system.

The impact of utilization of palm products on the population structure of the vegetable ivory palm (Hyphaene petersiana, arecaceae) in North-Central Namibia

Indigenous trees fulfil many subsistence and economic needs in north-central Namibia.Hyphaene petersiana provides a range of products which contribute to most aspects of people’s livelihoods. Of particular importance is its income-generating capacity through the use of palm leaves for basket production and the sale of liquor distilled from the fruits. This study investigates the population structure ofHyphaene petersiana in two areas of different human and livestock densities. Data were recorded for height class distribution, basal diameter of mature, stemmed individuals and sex ratios. These parameters of population structure indicate a reduction in the recruitment of mature palms and an increase in single-stemmed, vegetatively reproduced palm suckers of the smallest size class (0.5 m). This trend is more pronounced in the site with greater human and livestock population densities. It appears to be related to high recorded levels of browsing by livestock of juvenile, unstemmed palms, despite the unpalatability of palm leaves. This acts to prevent recruitment into larger size classes and increase the compensatory growth of palm suckers, the latter being enhanced due to reduced competition through the prior removal by grazing animals of grasses and other herbaceous species. Accompanying this heavy pressure on juvenile palms are destructive uses of mature, stemmed palms, including their felling for construction purposes and tapping for palm wine. With regional human population increase, exacerbated by a recent trend to privatise land and raise pressure on remaining communal resources, it is possible that these destructive uses of mature palms will increase to unsustainable levels. Concern is thus expressed in this study regarding the long-term viability ofHyphaene petersiana populatiops in this area.