Simulation of inflorescence dynamics in oil palm and estimation of environment-sensitive phenological phases: a model based analysis

Abstract

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresFor oil palm, yield variation is in large part due to variation in the number of harvested bunches. Each successively-produced phytomer carries a female (productive), male or aborted inflorescence. Since phytomer development takes 3–4 years and nearly two phytomers are produced per month, many inflorescences develop in parallel but have different phenological stages. Environment-dependent developmental rate, sex and abortion probability determine bunch productivity, which, in turn, affects other phytomers via source–sink relationships. Water deficit, solar radiation, temperature and day length are considered key external factors driving variation. Their impact is difficult to predict because of system complexity. To address this question we built a simple model (ECOPALM) to simulate the variation in number of harvested bunches. In this model, trophic competition among organs, expressed through a plant-scale index (Ic), drives sex determination and inflorescence abortion during specific sensitive phases at phytomer level. As a supplemental hypothesis, we propose that flowering is affected by photoperiod at phytomer level during a sensitive phase, thus, contributing to seasonal production peaks. The model was used to determine by parameter optimisation the influence of Ic and day length on inflorescence development and the stages at which inflorescences are sensitive to these signals. Parameters were estimated against observation of number of harvested bunches in Ivory Coast using a genetic algorithm. The model was then validated with field observations in Benin and Indonesia. The sensitive phases determined by parameter optimisation agreed with independent experimental evidence, and variation of Ic explained both sex and abortion patterns. Sex determination seemed to coincide with floret meristem individualisation and occurred 29–32 months before bunch harvest. The main abortion stage occurred 10 months before harvest – at the beginning of rapid growth of the inflorescence. Simulation results suggest involvement of photoperiod in the determination of bunch growth dynamics. This study demonstrates that simple modelling approaches can help extracting ecophysiological information from simple field observations on complex systems

Using plant growth modeling to analyze C source–sink relations under drought: inter- and intraspecific comparison

“…The model has been already calibrated using previously published results (Dufrêne, 1989; Pallas et al, 2013b), using parameter optimization methods (Combres et al, 2013) and additional experimental data. The model was also validated under non-limiting and water deficit conditions on commonly growth commercial hybrids (Pallas et al, 2013b).…”

“…This experimental approach is combined with modeling approaches provided by Ecomeristem (rice; Luquet et al, 2006) or X-Palm (oil palm; Pallas et al, 2013b). Once presented models’ concepts, a set of simulation experiments for different virtual genotypes (sink or source limited) are presented considering different drought types of particular concern for each species: soil dry-down as observed in rainfed or lowland conditions for rice (Courtois et al, 2000) and in West African plantation for oil palm (Combres et al, 2013). Simulation results are then discussed regarding the role plant modeling can play in: (i) the analysis of C source–sink relations and their optimization with respect to a given constraint, (ii) the exploration of trade-offs between plant survival and agronomic performance.…”

Ecohydrological changes after tropical forest conversion to oil palm

“…Modeling efforts to simulate OP behaviour and development also exist but they are mostly focused on agronomic variables (e.g. carbon allocation, yield, fertilization) and neglect carbon/water relations and surface energy fluxes (van Kraalingen et al 1989, Combres et al 2013, Huth et al 2014, Hoffmann et al 2014, Fan et al 2015, Okoro et al 2017, Pardon et al 2017. Only recently, Meijide et al (2017) employed a land surface model adapted to OP (CLM-Palm (Fan et al 2015)) to simulate water/energy fluxes at two OP plantations but changes with comparison to native forests were disregarded.…”

On yield gaps and better management practices in Indonesian smallholder oil palm plantations

“…The number of ripe bunches available for harvest is determined by 1) the number of inflorescences initiated (which in turn depends on the rate of leaf production; Gerritsma and Soebagyo, 1999); 2) sex ratio (Heel et al, 1987;Corley et al, 1995;Adam et al, 2011); 3) abortion of female inflorescences before anthesis ; and 4) failure of developing bunches between anthesis and bunch ripeness (Combres et al, 2013).…”

“…Bunch failure, the abortion of a bunch before full ripening, occurs 2-4 months after anthesis (Sparnaaij, 1960). Bunch failure may be caused by poor pollination or acute and severe assimilate shortage, usually caused by lack of water or radiation (Combres et al, 2013;Corley and Tinker, 2016: 125). Bunch failure rates between 1.5% (Corley, 1973b) and > 25% (Sparnaaij, 1960;Corley and Tinker, 2016: 124-125) have been observed, but the available data is scarce, and the phenomenon remains poorly described and understood.…”