Abstract

The effect of flooding on young grapevine plants grafted onto two rootstocks: Harmony and Freedom was evaluated. Grafted and non-grafted plants were grown in plastic pots under normal and flooding conditions. Flooding condition was obtained by keeping the water three cm above the soil and the oxygen diffusion rate (ODR) was 0.2 mu g O-2 cm(-2) min(-1): In control ODR was 1.7 mu g O-2 cm(-2) min(-1). Net CO2 assimilation and stomata conductance were evaluated in developing and mature leaves. In general, at the beginning of flooding, plants grafted on Harmony showed a rapid reduction in net CO2 assimilation. This reduction reached a minimum after at seven days of flooding treatment. By contrast, the plant grafted on Freedom did not show any reduction on net CO2 assimilation until seven days of flooding. This indicates that this last rootstock confers to the scion a tolerance to hypoxia. On the other hand, the reduction in net CO2 assimilation was well correlated with dry matter production and leaf area in both rootstocks. Harmony grafted plants presented the highest reduction (54%) in dry matter accumulation, while Freedom grafted plants presented 36% of reduction. After the flooding treatment, a significant increase in the accumulation of P was found in plants grafted on Harmony. This raises questions on the role of this element in the plant metabolism under low oxygen conditions. Finally, after the results obtained in dry matter reduction under flooding condition, we conclude that in 'Sultanina' grafted plants, Freedom rootstock induced a better tolerance to hypoxia than Harmony.