Anatomy and Histochemistry of the Root System of the Kiwifruit Vine, Actinidia deliciosa var. deliciosa.

The kiwifruit vine is a species which has been newly introduced into cultivation and little is known of its comparative physiology and anatomy. In this study we found that fibrous, 'magnolioid' roots, which have undergone secondary vascular development but which retain the cortex and develop a suberized epidermis, comprise the greater part of the root system (95% of total length). Newly initiated roots with primary development conform to norms established in other woody plant species. However, the structural roots, like the fibrous roots, also retain a cortex and phelloderm which is initiated by hypodermal cells within the cortex and not by the pericycle which is the common progenitor tissue in other species. This phellogen produces new cells centrifugally only. The cortex is a relatively small component of the structural root and the bulk of the tissue is vascular in origin, as in the roots of other plant species. The endodermis is retained and continues to divide periclinally to accommodate the increase in circumference with growth.