Photosynthetic and Growth Response to Salt Stress in P.euphratica

The experiments were carried out with two year old seedlings of P. euphratica and its Hy brids.Two levels of salt treatments were used to identify their photosynthetic and growth response to salt stress.The measurements on photosynthesis and related parameters indicated that CO₂ compensation point and saturation point increased, while Rubisco activity decreased with the increase of salt stress for two genotypes.Under high salt treatment, the net photosynthesis of P. euphratica recovered from salt stress when soil salt content was about 0.7% NaCl, while that of hybrid only recovered when soil salt content was less than 0.2% NaCl and was unable to when soil salt content was about 0.5% NaCl;chlorophyll a contents and Chl a/b ratio increased, while chlorophyll b and carotenoid contents decreased with increasing salt levels.Fluorescence patterns confirmed that reduction of photosynthesis under high salt treatment was not due to damage of photosynthetic apparatus but due to inhibition of the dark reaction.The measurements on growth parameters of leaves confirmed that P. euphratica could actively adjust growth rate and shed some un-injured leaves in primary stage of salt stress (RGR of leaf length was reduced by 70% by day 1 and leaf shedding was observed by day 3 for P. euphratica under high salt treatment), and could develop phyllode succulence when salt stress was further developed (specific leaf area decreased with salt treatment).