Manipulation of growth light environment for storage of seedlings of shade-tolerant forest tree species in nursery

Many tropical forest trees produce seeds of immediate germination, and this group includes recalcitrant-seeded species. Forest trees are classified as light-demanders and shade-tolerators based on their responses to light. Pioneers are light-demanders, while non-pioneers or climax species are shade-tolerators. Many recalcitrant-seeded species are non-pioneers. Seedlings of non-pioneers have the capacity to acclimate to dense shade where they grow very slowly. This shade-acclimation potential could be utilised for storage of seedlings, instead of short-term storage of recalcitrant seeds, over periods of several months to years. Two factors are important: the slow growth during storage period and the potential of the stored seedlings to resume growth on return to normal growth light environment after the storage period. Photosynthetic attributes and shade-acclimation potential of non-pioneers are discussed. High-light acclimation potential of shade-grown seedlings is also considered. Research needs to focus on shade-acclimation potential of recalcitrant-seeded species so as to manipulate growth light environment during storage of seedlings in nursery.