Resumen de Root hydraulic and morphologic traits in vitis sp. Rootstochs and their linkage with ecophysiology of the grafted vitis vinifera cultivar under mediterranean climate
Taking into account the reported negative effects of drought in plant growth and yield, and the predictions for middle term changes in temperature and rainfall distribution in the Mediterranean area, more efforts have to be focused on understanding the drought adaptations of the grapevine system rootstock-cultivar. The objective of this work is to define the hydraulic architecture and the hydraulics of grapevine, considering that the combination rootstock-cultivar is a single individual that should adopt a coherent response at root level and at canopy level to maintain growth and yield under Mediterranean climate. In the first chapter, the objective was to determine if vulnerability to embolism in stems of grapevine cultivars was limiting for plant growth under drought, and if increase in water uptake due to osmoregulation occurred in parallel to increasing vulnerability to embolism. Vulnerability curves, water status and drought tolerance mechanisms at leaf level were assessed in 8 V. vinifera cultivars in field conditions and grafted onto 110R. Embolism did not seem to be limiting for vine development in most of the cultivars. Seasonally osmotic and elastic adjustments were showed in leaves for different cultivars and in none of the cultivars this mechanisms showed any relation with the level of vulnerability to embolism. In the second experiment, the strategy in front of water availability reduction and seasonal drought was studied in potted vines of #Tempranillo# grafted onto 110R and SO4, considering water transport in the whole plant and relating it to water status and growth. Both cultivar-rootstock combinations showed an isohydrodynamic behavior, but some differences in water absorption and transport regulations from roots to leaves existed between 110R-scion and SO4-scion and they were suggested to be responsible for differences in growth under different water availabilities. In the third chapter, the contribution of each fraction in the root-graft-cultivar trunk hydraulic resistance was measured in vines with the same characteristics and experimental conditions than in chapter 2 using an HPFM that permits root resistance measurement in situ. Furthermore, hydraulic resistance in trunk was measured by a low pressure method. 110R showed a more resistant root system than SO4. The grafting point showed to be a bottleneck for water transport to canopy, and its resistance was significantly higher in vines of #Tempranillo# onto SO4 than those onto 110R. In the fourth chapter, the previous experiments tried to be condensed in a field experiment, where 11 year old vines of #Merlot# grafted onto 1103P and 101-14, reported to be differently vigorous and drought resistant, were studied. The root and graft union resistance were measured with a HPFM and the canopy water relations and root proliferation were followed during the season. At harvest, biomass and yield were obtained, and root morphology parameters were measured. Vessel length distribution in root xylem was defined and related to root water conductance. The capability of 1103P for new roots generation during summer explained the differences in root water conductance and its effect on canopy water status and development. From these results it was concluded that any compatible rootstock-cultivar combination will success to drought periods if a coherent strategy at root and leaf levels are coherent. Optimistic behaviors under drought will success if the rootstock develops a deep high conductance root and the grafting point structure is not a bottleneck for water flow.
