Bulblet Differentiation after Scale Propagation of Lilium longiflorum

Abstract

External, middle and inner scales in parent bulbs were studied to evaluate bulblet differentiation in Lilium longiflorum Thunb. during scale propagation at 25 °C. A 13-stage developmental process describes different steps including preprimordial, primordial, and bulblet formation. For all scales, preprimordial and primordial stages occurred within the first 4 days. The differentiation process depended on parent scale position. Most bulblets arising from external scales developed three true scales after 30 days while bulblets from middle scales formed four true scales. Homogeneity in the morphology of the parent scales, only shown in the middle ones, was associated with a rapid change in developmental stage for the population of bulblets. Inner scales showed few bulblets with three and four true scales, the rest remaining at earlier developmental stages. Bulblet production decreased from external to internal scales: 2.6, 2.2, and 1.2 bulblets per scale, respectively, and showed a positive correlation with the scale base width. Maximum scale weight and surface area and maximum bulblet fresh and dry weight occurred in the middle scales. We conclude that middle scales are the ideal starting material for experimental uses involving scaling propagation. For production purposes, the external scales, in addition to the middle scales, must also be included for propagation.