Abstract
To investigate limiters of photosynthate assimilation in the carbon-source limited crop, oil palm (Elaeis guineensis Jacq.), we measured differential metabolite, gene expression and the gas exchange in leaves in an open field for palms with distinct mesocarp oil content. We observed higher concentrations of glucose 1-phosphate, glucose 6-phosphate, sucrose 6-phosphate, and sucrose in high-oil content palms with the greatest difference being at 11:00 (p-value ≤0.05) immediately after the period of low morning light intensity. Three important photosynthetic genes were identified using differentially expressed gene analysis (DEGs) and were found to be significantly enriched through Gene Ontology (GO) and pathway enrichment: chlorophyll a-b binding protein (CAB-13), photosystem I (PSI), and Ferredoxin-NADP reductase (FNR), particularly for sampling points at non-peak light (11:00 and 19:00), ranging from 3.3-fold (PSI) and 5.6-fold (FNR) to 10.3-fold (CAB-13). Subsequent gas exchange measurements further supported increased carbon assimilation through higher level of internal CO2 concentration (Ci), stomatal conductance (gs) and transpiration rate (E) in high-oil content palms. The selection for higher expression of key photosynthesis genes together with CO2 assimilation under low light is likely to be important for crop improvement, in particular at full maturity and under high density planting regimes where light competition exists between palms.
Highlights
Oil palm (Elaeis guineensis) is the world’s most productive oil crop on a per hectare basis and is, an important source of dietary oils and fats
We investigated metabolite concentrations, gene expression changes and leaf gas exchange in two populations of mature oil palms with differing -mesocarp oil content throughout the diurnal cycle to investigate how dynamic changes in photosynthesis may be related to oil yield
Oil palm leaf samples were collected at five different time points associated with likely boundary points in photosynthetic activity due to light intensity changes throughout the day: 07:00—commencement of photosynthesis; 11:00— near the boundary at the end of the low light morning period; 15:00—at the end of peak light at midday; and 19:00—end of day light intensity minimum before dark
Summary
Oil palm (Elaeis guineensis) is the world’s most productive oil crop on a per hectare basis and is, an important source of dietary oils and fats. Fruit bunch weight and especially mesocarp oil content are reported to be heritable [1,2,3], negative correlations do exist for these traits, suggesting a degree of source limitation. There is a significant gap between potential and actual yield in the field caused by factors such as planting.
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