The aim of this study was to investigate the biochemical,physiological and morphological responses of sugarcane to iso-osmotic salt and water-deficit stress.Disease-free sugarcane plantlets derived from meristem cuttings were photo-autotrophically grown in MS media and subsequently exposed to -0.23(control),-0.67 or -1.20 MPa iso-osmotic NaCl(salt stress) or mannitol(water-deficit stress).Chlorophyll a(Chl a),chlorophyll b(Chl b),total carotenoids(Cx+c),maximum quantum yield of PSⅡ(Fv/Fm),photon yield of PSⅡ(PSⅡ),stomatal conductance(Gs) and transpiration rate(E) in the stressed plantlets were significantly reduced when compared to those of plantlets of the control group(without mannitol or NaCl),leading to net-photosynthetic rate(Pn) and growth reduction with positive correlation.In addition,physiological changes and growth parameters of plantlets in the salt stress conditions were more sharply reduced than those in water-deficit stress conditions.On the other hand,the proline content and non-photochemical quenching(NPQ) in the leaves of stressed plantlets increased significantly,especially in response to iso-osmotic salt stress.The chlorophyll pigments in iso-osmotic stressed leaves were significantly degraded(r2 = 0.93),related to low water oxidation(r2 = 0.87),low net-photosynthetic rate(r2 = 0.81),and growth reduction(r2 = 0.97).The multivariate biochemical,physiological and growth parameters in the present study should be further used to develop salt,or drought,tolerance indices in sugarcane breeding programs.
