Photosynthesis of Oil Palm (Elaeis guineensis)

Oil Palm (Elaeis guineensis) plantations cover more than 107,000 km(2) in SE-Asia but there is little information on its photosynthetic characteristics. Photosynthesis in seedling, juvenile and adult Oil Palm (6 months, 12 y and >5 y old, respectively) were measured using blue-diode Pulse Amplitude Modulation Fluorometry (PAM). The Absorptance Factor of the leaves (Abt(465nm)) was measured using a Reflectance Absorptance Transmission (RAT) meter to calculate actual, rather than relative Electron Transport Rates (ETR). Midday measurements in juvenile and adult Oil Palm tree were: maximum quantum yield of Photosystem II (Y-max) in juveniles was about 0.63, Optimum irradiance (E-opt) was approximate to 300 mu mol photon m(-2) s(-1). The maximum ETR (ETRmax) of juvenile plants was 24.06 +/- 1.69 mu mol e(-) m(-2) s(-1): based on 4e-/O-2 this is equivalent to a maximum Photosynthetic Oxygen Evolution Rate (POERmax) of 89.21 +/- 6.25 mu mol O-2 mg Chl a(-1) h(-1). Adult Oil Palm plants have a Y-max similar to juveniles but E-opt was approximate to 600 mu mol photon m(-2) s(-1). The ETRmax of adult plants was 58.97 +/- 2.07 mu mol e(-) m(-2) s(-1): or POERmax = 305.3 +/- 10.7 mu mol O-2 mg Chl a(-1) h(-1). Oil Palm is a classic sun plant with high photosynthetic rates at high irradiances. Photosynthetic efficiencies (alpha(0)) were high for C3 sun plants: alpha(0) in adult plants (0.272 +/- 0.018 e(-) photon(-1)) was higher than juvenile plants (0.204 +/- 0.034 e(-) photon(-1)) expressed on a leaf surface area basis and on a Chl a basis (1.406 +/- 0.093 vs. 0.757 +/- 0.124 O-2 photon(-1) m(2) g Chl a(-1)). In juvenile and adult plants E-opt, POERmax and alpha(0) tend to maximize about midday. In seedlings, E-opt and POERmax are highest in the early morning but maximum alpha(0) is at about midday. Oil Palms strategically optimize photosynthesis for high irradiances and manipulate their photosynthesis vs. irradiance characteristics during the course of daylight. (C) 2016 Elsevier B.V. All rights reserved.