ABSTRACT
This chapter discusses the influences of origin, anatomy and physiology. The origin of the rootstock can have influences on performance and contribute towards advantageous or disadvantageous characteristics. Rootstocks normally originate from one of the following: these are Seedling origin, Clonal origin, Root portion and unrooted stem. Seed raised plants constitute by far the most commonly used rootstocks for ornamental species, where the visual appearance of the scion is of major importance. Rootstocks produced by intensive techniques, such as plug production of seedlings under protection, exhibit juvenile characteristics for a longer period than those produced conventionally in open-ground seed beds. The serious disadvantage of seedling rootstocks is their genetic variability and consequently their indeterminate influence on the scion. Clonal rootstocks propagated vegetatively have the advantage of a fixed and constant genetic make-up. Adventitious roots must be induced to form on the unrooted stem in tandem with the formation of a viable graft union.
