Morfo-anatomical insights into the germination and protocorm growth of the endangered Vanilla lindmaniana (Orchidaceae).

Despite their global importance, knowledge of Vanilla plant nutrition and physiology remains limited, particularly regarding germination processes that underpin species ecology, fruit attraction, and seed dispersal. This study elucidates the germination stages of the endangered Vanilla lindmaniana through detailed morpho-anatomical analyses. Mature seeds were disinfected, chemically scarified, and sown on BM1 medium under controlled conditions (30 °C, darkness). Protocorm development was characterized through stages at morphological and anatomical levels, utilizing light microscopy and scanning electron microscopy (SEM). Successful in vitro germination was achieved, with initiation at three months and a germination rate of 61.8%, alongside a protocorm rooting frequency of 93.86%. Germination was triggered by rupture of a specific seed coat layer, resulting in a "clam-like" split, concurrent with starch accumulation. Roots emerged at Stage IV, growing vigorously, while the shoot apex remained short; raphides were occasionally observed in the root cortex. This work presents a novel inoculation and germination procedure for mature V. lindmaniana seeds, highlighting BM1 medium as a suitable formulation for germination and early development. Understanding these mechanisms is vital for conservation efforts and genetic engineering, facilitating species propagation and advancing knowledge of the Vanilla life cycle. Our findings contribute essential insights into the early development stages of this rare species, supporting both its preservation and sustainable cultivation.