Survival of Native Indonesian Orchid Seeds in Conventional Seed Banking and Its Relationship with Micro-Morphometry

Abstract

Maintaining orchid seed viability during conventional seed bank storage is essential for ex situ conservation, yet it remains unclear whether seed micro-morphometric characteristics can predict seed longevity. This study evaluated the relationship between seed micro-morphometry and storage longevity in 13 Indonesian orchid species stored at −20 °C for up to nine years. Seed area (SA), embryo area (EA), and seed air space (SAS) were measured from 30 seeds per species using light microscopy and image analysis. Germination tests were conducted periodically throughout storage using asymbiotic culture media, and the data were analyzed using one-way ANOVA, Kruskal–Wallis tests, principal component analysis (PCA), and Spearman's correlation. Significant interspecific differences were observed in all micro-morphometric traits. Dendrobium antennatum had the largest seed and embryo areas, whereas Phalaenopsis amabilis had the smallest. Phaius tankervilleae exhibited the highest SAS, while Vanda tricolor had the lowest. PCA explained 87.8% of the total variation and separated the 13 species into three distinct groups according to their seed morphology. Seed area showed strong positive correlations with both embryo area (r = 0.885) and SAS (r = 0.861), indicating coordinated allocation of seed structural components. However, storage duration was only weakly correlated with SA, EA, and SAS, suggesting that seed size and internal morphology alone are poor predictors of longevity. The longest viability was recorded in Vandopsis lissochiloides, which retained 98.2% germination after nine years of storage, whereas D. lineale lost viability within one year. These findings demonstrate that orchid seed longevity under conventional storage is species-specific and cannot be reliably predicted solely from seed micro-morphometry. Additional physiological and biochemical factors should be investigated to improve predictions of seed longevity and optimize ex situ conservation strategies for orchids.