STOCK-SCION CHEMISTRY AND THE FRUITING RELATIONSHIPS IN APPLE TREES

Abstract

Mailing Nine or true Paradise apple stock has been vegetatively propagated for centuries as a rootstock for use in the production of dwarf apple trees. Mailing Nine is said to be native to parts of southern Russia (3), and is presumably a type that has adapted itself to semi-arid conditions. stock itself is a low branching shrub, rather than a tree. As to the physiological effects in dwarfing the scions (11) of apple varieties grafted or budded upon it, very little is known. Blackman (1) states: The influence of stock on scion is one which has puzzled plant physiologists for decades. No progress has been made as to the mechanism of the action of a dwarfing stock. ' ' Mailing Twelve stock used in this work is one of extreme vigor among the vegetatively propagated stocks (8), closely approaching the vigor of the free-growing or seedling crab stocks in common use by American nurserymen for the production of standard budded or grafted apple trees. two stocks, Mailing Nine and Mailing Twelve, represent very nearly the extremes in growth habit, vigor, age of fruiting, etc., found in the Pyrus makes species. Of the scion varieties used, is a very low N tree, slowing up in growth at an early age, while Snow is an extremely high N variety, very vigorous in growth. A chemical study of the trees grown on the two stocks just mentioned should reveal something of the chemistry involved in growth extremes in apple, and possibly something of the fruiting relationships as they occur in dwarf and in standard apple trees of different varieties. All apple scion varieties are not affected in the same way by these two Mailing stocks, according to Roberts 's (14) work. Of the varieties studied here, Wealthy is only moderately dwarfed by the Mailing Nine stock, but is fruiting heavily (at the age of 6 years) on a biennial schedule. Mclntosh on Nine is decidedly dwarfed, with characteristically open top, and fruits heavily. Spy, Winesap, and Whitney are severely dwarfed, and are fruitful. All of these varieties as grown on Mailing Twelve stock are as yet entirely unfruitful (with the exception of Wealthy which fruits lightly) and are very vigorous growers. Snow on Nine is not appreciably dwarfed, however, while Snow on Twelve makes a fair growth but does not show the extreme vigor that might be expected from this combination of root and scion. York in