Previous investigations showed that the sweet cherry trees on most promising dwarfing, precocious and highly productive rootstocks show water deficiency during the hot and dry summer months, which influence the crop and fruit quality in the subsequent year. No doubt that under extremely dry conditions the maximum productivity and efficiency of water usage in woody heterografts can be achieved at harmonized interaction of factors determining the water relations. Those cherry trees are especially

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... concerned, which are grafted on growth reducing rootstocks, as it became actual practice in intensive sweet cherry orchards. The rootstock research and breeding produced a wide series of dwarfing rootstocks for sweet cherry, but the trees grafted on to most promising of them show water deficiency symptoms under hot and dry summer climate. This is typical to the largest cherry growing countries of the world, like Turkey and Iran, but the conditions are similar in certain sites of Hungary too. Knowledge of hydraulic conductivity, hydraulic architecture and water-usage in case of different woody and herbaceous plant is an increasingly important issue. Because of recently occurred climate changes growing numbers of researchers work on the topic. For easy and fast analysis of plant water regime, water potential of plant parts and hydraulic conductivity of soil-plant-atmosphere, a special, tool (Hydraulic Pressure Flow Meter) was developed. The usage of HPFM is based on pressure-variance in tracheas. During our researches in high-density cherry orchards we found the otherwise promising dwarfing rootstocks (such as Gisela® 5) far the worst drought-tolerant, contrary to trees on Mahaleb. There is no sufficient information about drought-tolerance mechanism and hydraulic architecture of different rootstocks, thus our research purpose is to compare the above mentioned parameters in case of Prunus avium, P. mahaleb, P. cerasus and their hybrids. Our test trees are all multi-component grafts, which complicate the question even more. Not only rootstocks and scions, but graft unit itself influence transport capacity of stem. Anatomical researches have proved that trachea surface by stem cross section in case of strong vigor rootstocks is double, which suppose smaller resistance to sap flow, comparing to dwarfing rootstocks. Anatomical results itself are not enough to fully understand drought-resistance mechanism of plants, therefore our HPFM researches can approve to achieve wider knowledge of this mechanism and hereby to find appropriate dwarfing and semi-dwarfing cherry rootstocks for the Hungarian site conditions.