Development of a dwarf rootstock for Japanese pear.

我们发现，以Quince EMA （Cydonia oblonga）为砧木，对日本梨树‘nijisisiki’和‘Akibae’的生长进行了显著的修饰，该体系似乎是一种实用的梨树矮化砧木。在本研究中，我们还研究了梨树矮化的机理，并与生长型砧木白桦进行了比较。长叶木质部液中苯甲酸含量约为30 μg/ml，氰化物含量约为2μg/ml，而桦木木质部液中未检出氰化物。在以往的研究中，长竹上的‘秋叶’茎部也含有与李属相同水平的苯甲酸。在分别含有0至1000ppm苯甲酸和氰化物的溶液中测定梨叶切片的呼吸速率。500ppm或更高浓度的苯甲酸溶液降低了叶片的呼吸作用，而氰化物即使在1000ppm的最高浓度下也不影响呼吸作用。上述结果表明，杉木砧木产生的苯甲酸抑制了日本梨树的生长，降低了日本梨树的呼吸和光合作用等生理活性。

We found out the tree growth of Japanese pear 'Nijisseiki' and 'Akibae' were redacted remarkably by using Quince EMA (Cydonia oblonga) as a rootstock, and the system seemed to be improved for a practical dwarfing rootstock for pear production. We also investigated the mechanism of the dwarf ness of the pear tree in comparison with vigorating rootstock, P.betulaefolia in this study.The xylem sap from 'Akibae' branch grown on C.oblonga rootstock contained about 3Oμg/ml benzoic acid and a 2μg/ml cyanide, but it did not detected in the sap from the branch on P.betulaefolia rootstock. The shoot of 'Akibae' on C.oblonga also contained benzoic acid as the same level as Prunus species as shown in the previous studies. The respiration rate of a pear leaf sections assayed on a solution containing 0 to 1000 ppm of benzoic acid and cyanide, respectively. The respiration of the leaf sections decreased by a 500ppm or higher benzoic acid solution, while cyanide did not affect to the respiration even in a highest concentration of 1000ppm.These results indicated that benzoic acid generated from Cydonia rootstock reduced the tree growth of Japanese pear with a decrease of physiological activity such as respiration and photosynthesis.