Contrasting In Vitro Flowering Progression Among Three Phalaenopsis Hybrids and Developmental Staging in a Miniature Cultivar

In vitro flowering permits direct observation of reproductive development, but the progression from visible inflorescence emergence to anthesis remains poorly characterized in Phalaenopsis. Here, we compared reproductive development in three commercial hybrids under a standardized culture sequence and developed a preliminary staging scheme for FM1630. Twelve-week-old plantlets were cultured for 12 weeks on modified Vacin and Went medium supplemented with 15 mg L−1 6-benzyladenine (BA), comprising 8 weeks at 20 °C followed by 4 weeks at 25 °C. A BA-free Hyponex No. 1 liquid overlay was then added, and the closed culture vessels were transferred to greenhouse conditions. During the 44-week observation period beginning with the initiation of BA treatment, visible inflorescences emerged in 100% of FM1514, JC2206, and FM1630 plantlets (15/15 for each cultivar). Flower buds formed in 1/15 FM1514, 2/15 JC2206, and 15/15 FM1630 plantlets, whereas anthesis occurred only in FM1630 (2/15; 13.3%). Based on external morphology and 100-µm anatomical sections from independently sampled FM1630 plantlets, we established a preliminary morphological–anatomical staging scheme comprising six major stages (S0–S5). Anatomical observations supported stages S0–S4, whereas S5 was defined by external morphology and subdivided into visible flower-bud expansion (S5a) and anthesis (S5b). The scheme represents a developmental sequence reconstructed from different individuals and provides a provisional reference for sampling comparable developmental stages in FM1630 under the tested culture conditions.