An overview of the life of an orchid protocorm – 
a developmental perspective

The orchid protocorm is a unique structure formed as a seed germinates. It is designed to house and regulate the growth of its mycorrhizal symbiont. This structure is also responsible for the formation of the shoot apical meristem, enabling plantlet development. The protocorm has remarkable physiological properties - it can limit the growth of fungal hyphae to basal protocorm cells. The protocorm cells are capable of digesting pelotons, allowing the extraction of nutrients from fungal hyphae. During the establishment of a symbiotic association, the meristematic cells at the apical end are well-protected from the fungal hyphae. The smaller apical cells maintain active mitotic activity and are responsible for the formation of the shoot apical meristem, without which a plant will not develop. Adventitious root primordia are subsequently initiated endogenously near the base of the shoot apical meristem. It is envisaged that there is cross-talk among the protocorm cells, leading to the observed morphogenetic changes. Although protocorms have remarkable biological capabilities, protocorms must content with several challenges in nature as they endure various biotic and abiotic stresses and factors to develop into adult plants.