Plant rooting studies indicate sclerenchyma tissue is not a restricting factor

In many fruit and ornamental plants, uniformity of yield and quality or appearance are achieved only by means of clonal or vegetative propagation-usually by the rooting of stem cuttings. Some varieties are easily rooted, while others are very difficult. There are few explanations to account for such differences in ease-of-rooting, but one long held horticultural hypothesis suggests that stems of shy-rooting plants possess a band of tissue (sclerenchyma) that mechanically blocks protrusion of roots formed to the inside of the sclerenchyma. Results of research reported here show that there is no simple relationship between the density or continuity of the ring of sclerenchyma and ease of rooting in olive, pear, and cherry stem cuttings. Great differences were found in the capacity of stem tissues to form root primordial to the inside of the sclerenchyma ring. Such differences may be related to the ability of cells of the root-initiating tissues to expand and proliferate, and subsequently to organize root primordia.