ABSTRACT
The transportation load of oil palm (Elaeis guineensis Jacq.) seedlings from the nursery to planting sites is a crucial problem facing the extension of smallholder plantations in Cameroon. This load can be considerably reduced by removing soil from the roots, which in turn exposes the plants to water and nutrients stresses. A greenhouse pot experiment was carried out to evaluate the recovery performance of such soil-stripped seedlings as a function of watering frequency and soil texture. Plant recovery potential was monitored on 360 nursery seedlings aged 4 months, under two soil types (sandy clay soil with 46% fine particles and sandy loam soil with 19% fine particles) and two watering frequencies (daily and two-days). Three monthly measurements were taken on morphological plant growth parameters including Plant height, Foliar surface, Collar diameter, Root length and Plant weight. Within and between groups analyses of variance and means separation showed the greatest variability for collar diameter, foliar surface and plant weight. All the parameters showed a greater variability and an almost-constant growth from one month to another, except for plant weight that did show a highly significant (p = 0.000) increase between the first measurement and the second. Soil type, watering and their interaction explained 97-99.5% of the variations of all parameters. Except for root length, all other parameters were more sensitive to the effect of soil texture, explaining 83-95% of the total variation. Only plant weight and root length showed slightly greater values under daily watering, other parameters did not show any sensibility to the two watering frequencies proposed in this experiment. Our results showed a low response of plant growth recovery on the low clay sandy loam soil, revealing that a careful selection of a soil texture is crucial for the survival of seedlings and further establishment of the plants following drought stress. It is therefore strongly recommended to many tropical countries where oil palm is an economically important crop, to take this into account during the selection of soil type for oil palm seedlings nursery.
ABSTRACT
Oil palm can accumulate up to 90% oil in its mesocarp, the highest level observed in the plant kingdom. In contrast, the closely related date palm accumulates almost exclusively sugars. To gain insight into the mechanisms that lead to such an extreme difference in carbon partitioning, the transcriptome and metabolite content of oil palm and date palm were compared during mesocarp development. Compared with date palm, the high oil content in oil palm was associated with much higher transcript levels for all fatty acid synthesis enzymes, specific plastid transporters, and key enzymes of plastidial carbon metabolism, including phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase. Transcripts representing an ortholog of the WRI1 transcription factor were 57-fold higher in oil palm relative to date palm and displayed a temporal pattern similar to its target genes. Unexpectedly, despite more than a 100-fold difference in flux to lipids, most enzymes of triacylglycerol assembly were expressed at similar levels in oil palm and date palm. Similarly, transcript levels for all but one cytosolic enzyme of glycolysis were comparable in both species. Together, these data point to synthesis of fatty acids and supply of pyruvate in the plastid, rather than acyl assembly into triacylglycerol, as a major control over the storage of oil in the mesocarp of oil palm. In addition to greatly increasing molecular resources devoted to oil palm and date palm, the combination of temporal and comparative studies illustrates how deep sequencing can provide insights into gene expression patterns of two species that lack genome sequence information.
