Comparative Study on Cytological Characteristics of Reproductive Organs and Embryonic Development in Three Forms of the Mycoheterotrophic Orchid Gastrodia elata

Gastrodia elata is a mycoheterotrophic orchid. Three of its forms (G. elata f. glauca, G. elata f. elata, G. elata f. viridis) show distinct reproductive traits, but the cytological basis remains unclear. Using multi-timepoint morphological observation and semi-thin/ultra-thin sectioning, we systematically compared their reproductive processes from gametophyte development to seed maturation. All forms exhibited pollen wall polar differentiation (“well-developed locular side, simplified lateral sides”) following a six-stage program, with f. elata germinating fastest, f. viridis intermediate, and no germination in f. glauca. In the female gametophyte, vesicle clusters and degradation zones suggest the possibility of a two-step “chalazal degradation—micropylar localization” nuclear clearance model. Embryo development rate followed f. elata > f. glauca > f. viridis. Mature seeds stored lipid/protein bodies; f. elata uniquely contained amyloplasts and acicular phytin crystals, with form-specific seed coat traits. This study clarifies cytological differentiation, providing a basis for germplasm identification and conservation.