Willows responses to alternate periods of drought and flooding stress

DOFFO GUILLERMO; RODRÍGUEZ MARÍA EMILIA; MONTEOLIVA SILVIA; CERRILLO TERESA; LUQUEZ VIRGINIA MARTHA CRISTINA

Vancouver

Congreso; International Poplar Symposium VI; 2014

In the next years, climate change will increase the occurrence of flash flooding as a consequence of extreme rain events. In certain areas of Argentina, this fact will create alternate periods of drought and flooding during the growing season. To develop willow plantations in these areas, it is necessary to gain a better understanding of the physiology under these particular combinations of stresses. In this work, we explored the responses of two willow clones to different combinations of stress treatments: continuous flooding or drought for 6 weeks, or cyclic treatment of 2 weeks of stress separated by 2 weeks of normal watering. The type of stress and the order of occurrence modified in different ways the growth in height, dry matter partitioning, gas exchange, leaf area dynamics and shoot hydraulic conductivity. Above ground growth was severely reduced by drought in both clones, either in continuous or cyclic treatment. A cycle of drought followed by flooding reduced growth in a lesser extent than the opposite situation. The clones responded to the flooding followed by drought combination in a different way. One clone experienced a marked reduction in shoot hydraulic conductivity that was ten times lower than in control plants, combined with and extensive defoliation. In the other clone, the reduction of hydraulic conductivity was not significant, and it experienced a lesser degree of defoliation. It is likely that the extensive defoliation is a consequence of the inability to maintain an adequate water supply to the leaves because of the occurrence of severe embolism. The higher susceptibility to embolism correlates with the occurrence of fewer vessels with a higher lumen. The two willow clones analyzed in this work had different strategies to cope with the occurrence of drought episodes. One clone experiences an extensive defoliation and a rapid resuming of growth after the end of the stress, while the other maintained the leaf area at the expense of growth