Abstract

The aim of the present study is to investigate the biochemical, physiological and morphological responses of oil palm seedlings when exposed to polyethylene glycol (PEG)-induced water deficit. Oil palm seedlings were photo-autotrophically grown in MS media and subsequently exposed to -0.23 (control), -0.42, -0.98 or -2.15 MPa PEG-induced water deficit. Osmotic potential (_s) in root and leaf tissues of oil palm seedlings grown under PEG-induced water deficit was decreased leading to chlorophyll degradation. Chlorophyll a (Chl_a), chlorophyll b (Chl_b), total chlorophyll (TC), total carotenoids (C_x+c), maximum quantum yield of photosystem II (PSII) (F_v/F_m) and photon yield of PSII (F_PSII) in the oil palm seedlings under water deficit conditions dropped significantly in comparison to the control group, leading to a reduction in net-photosynthetic rate (P_n) and growth. A positive correlation between physiological and growth parameters, including osmotic potential, photosynthetic pigments and water oxidation in photosystem II and P_n was demonstrated. These data provide the basis for the establishment of multivariate criteria for water deficit tolerance screening in oil palm breeding programs.

Key words: Chlorophyll fluorescence, net-photosynthetic rate, pigment, water oxidation, water deficit stress.

Abbreviation

PEG, Polyethylene  glycol;  P_n,  net  photosynthetic  rate; RH,relative humidity; PPFD, photosynthetic photon flux density; Chl_a, chlorophyll a;Chl_b, chlorophyll b; TC, total chlorophyll; C_x+c, total carotenoid; F_v, variable fluorescence yield; PSII, photosystem II; F_v/F_m, variable to maximum fluorescence;NPQ, non-photochemical quenching; C_in, carbon IV oxide  inside; C_out, carbon IV oxide  outside; SH, shoot height; RL, root length; LA, leaf area; FW, fresh weight;DW, dry weight; Y_s, osmotic potentials; F_v/F_m, maximum quantum yield of photosystem II; F_PSII, photon yield of photosystem II; qP, quantum efficiency of photosystem II; NPQ, non photochemical quenching.