A kinematic analysis of tepal growth in Lilium longiflorum.

Time-lapse marking experiments indicate that the growth of tepals in Lilium longiforum Thunb. from 3.7 mm to maturity is triphasic. Phase I (tepal lengths 3.7-10 mm) is characterized by spatial and temporal variation in growth rate and, in the epidermis, a random distribution of mitoses with an acropetal increase in cell area. During phase II (10-90 mm) cell elongation and (later) cell division is restricted largely to basal regions. Cell division ceases when tepals are less than one-third of their mature length of 155 mm. Phase III (90-155 mm) is characterized by the gradual transition from basal to apical growth, and a modification of epidermal cell shape. A sharp peak in growth at the extreme tip of the tepal coincides with anthesis.