Physiological Study On Loqaut Trees (Eriobotrya Japonica Lindl.) Under Elevated Atmospheric CO₂ Concentration

Loqaut Trees (Eriobotrya japonica Lindl.) grown in two open-top growth chambers with CO2 concentrations of 400 mol . mol-1 and 700 mol . mol-1 were used to study the effects of elevated atmospheric CO2 concentration on photosynthesis, the parameters of chlorophy fluorescence of leaves, carbohydrate contents & yield et al. and the effects of elevated atmospheric CO2 concentration & water stress on photosynthesis, chlorophy fluorescence and antioxidative enzymes et al. in leaves. The results showed as follows:1. During the treatment, elevated atmospheric CO2 concentration (700umol.mol-1) obviously enhanced the photosynthetic rate (Pn), and that didn't occur down-regulation. High CO2 condition raised stomatal resistance and water use efficiency (WUE) increased by 2.5, whereas decreased stomatal conductance (Gs) & transpiration rate (Tr).2. Elevated atmospheric CO2 concentration enhanced the contents of Chl., Chl.a, Car, moreover decreased the content of Chl.b, raised the value of Chl.a/b ,but the value of Chl./Car was significantly weaker. Furthermore, under high CO2 condition, the values of Fv , Fv/Fm and PS are obviously higher than under atmospheric CO2, but the value of Fo was not significant.3. Elevated atmospheric CO2 concentration enhanced carbohydrate contents in Loqaut Leaves, the contents of sucrose & total sugar were obviously higher, but there was no significant different in the content of fructose .4. Elevated atmospheric CO2 concentration could obviously enhance the yield, the increase of leaves weight was the most obvious, the root and stem were no significant difference, but the value of R/S obviously reduced.5. During water stress treatment, the value of RWC obviously failed, the effect of CO2 was no distinctness. The different water stress decreased Pn, whereas elevated atmospheric CO2 concentration (700umol.mol-1) obviously reduced the scope, high CO2&water stress markedly raised stomatal resistance and reduced stomatal conductance (Gs) & transpiration rate (Tr).Under water stress, there was no variety in WUE, but high CO2&water stress WUE could be obviously increased.6. Water stress obviously decreased the values of Fm , Fv/Fm, Fv/Fm and PS II ,wherase enhanced the value of Fo. But under high CO2 condition, the range was significantly lower. Furthermore, water stress could decrease the value of Qp, and that enhanced the value of Qn.7. Water stress decreased the contents of Cli.(Chi.a, Chl.b), Car, and the ratio of Chl.a/b raised. Under light water-stress & moderate water-stress, the ratio Chl./Car was almost changed, but under atmospheric CO2&severe water-stress condition, it was significantly weaker.8. Water stress could obviously enhanced the activities of SOD, POD and CAT, but under elevated atmospheric CO2 concentration, the scopes of the activity increase of SOD, POD and CAT induced by water deficit were significantly lower than under atmospheric CO2. Simultaneously, the content of MDA also had less increase. The results indicate that high CO2 concentration may have amelioration effect on drought-induced oxidative damage.