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EFFECT OF OSMOTIC STRESS ON PROLINE ACCUMULATION, PHOTOSYNTHETIC ABILITIES AND GROWTH OF SUGARCANE PLANTLETS (SACCHARUM OFFICINARUM L.)

Suriyan Cha-um* and Chalermpol Kirdmanee

Abstract: Disease-free sugarcane plantlets derived from meristem cutting were photoautotrophically grown on the MS medium and subsequently exposed to 0, 100, 200, 300 or 400 mM mannitol for 7 days. Osmotic pressure in the culture medium was increased with increase in mannitol concentration, causing low water use efficiency (WUE) (r² = 0.88) and chlorophyll degradation (r² = 0.92). Chlorophyll a (Chl_a), chlorophyll b (Chl_b) and total carotenoids (C_x+c), concentrations in the osmotic stressed leaves decreased, especially in 400 mM mannitol treatment, degrading 44, 81 and 72%, respectively when compared to control. In contrast, proline content in osmotic stressed plantlets was accumulated and peaked at 2,236.75 mmol g^-1 FW in 300 mM mannitol treatment. The WUE and chlorophyll degradation were correlated with maximum quantum yield of PSII (F_v/F_m) (r² = 0.75) and photon yield of PSII (F_PSII) (r² = 0.83), respectively. The F_v/F_m and F_PSII in drought acclimatized plantlets decreased, when non-photochemical quenching (NPQ) reached. The reduction of F_PSII was positively related to net-photosynthetic rate (NPR) (r² = 0.85) as well as the proline content and NPQ (r² = 0.81). The NPR, stomatal conductance (G_s) and transpiration rate (E) in osmotic stressed plantlets were significantly dropped, leading to growth reduction (r² = 0.95). The basic knowledge of osmotic stressed responses may further be applied as effective indices for drought tolerance in sugarcane breeding program.

National Center for Genetic Engineering and Biotechnology (BIOTEC)

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