Rootstock influence on tree architecture may be seen in a variety of expressions. Above ground effects include canopy volume and shape, crotch angles, branch display angles, relative distribution of long shoots and spurs, internode length, relative distribution of fruit buds and spurs, and trunk taper. Below the graft union, effects include relative distribution of fine vs. coarse roots, total root mass, and numbers, nature and distribution of burrknots. Many of these phenomena are indirect effects that stare from induction of fruiting by the rootstock, e.g., early fruit production induced by the rootstock will result in reduced canopy volume, reduced aboveground total mass, flatter branch display angles, and reduced root mass. The rootstock also plays a major role in the duration of shoot extension growth; by influencing the production of growth regulators in the shoot tip, the rootstock indirectly influences the inhibit ion of lateral buds and therefore the production of feathers.
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