抄録
Most of tea trees are propagated by cuttings, and the adventitious roots play an important role throughout the growth of tea trees in the fields. Adventitious roots grows in the soil by forming highly branched and bent root system (Matsuo, Root Research 13:157-158). However, they grow as a beautifully organized root system with apical dominance in the mist culture (Homma & Saba 2002; Matsuo, Root Research 14:15-16). In the hydroponics, they grow intermediate form between soil and mist. To understand the ageing process of adventicious root cells in the apical region of the roots, we examined fundamental cytology and mechanical properties of cell walls, and then examined these data if affected or regulated by gibberellin (GA). The inhibitor of GA biosynthesis caused expansion of cortical cells and suppressed elongation. Cell wall extensibility decreased towards the base and the gradient from tip to the base was steeper than those of pea roots. Soil grown tea roots showed steeper gradient towards the base than that of hydroponics-grown roots. Suberin deposition in exodermis proceeded more apically in the roots treated with the inhibitor of GA-biosynthesis. Tea tree is a week short-day plant but 100% flower buds were induced by the inhibitor of GA-biosynthesis even under continuous light. This effect of the inhibitor may be useful for the efficient breeding of tea trees.
