Nutrient Availability Has a Greater Influence than Pot Host on Seedling Development of Hemiparasitic Hawaiian Sandalwood (Santalum paniculatum Hook. and Arn.)

Abstract

Sandalwood (Santalum spp.) has been overharvested throughout its range, including the Hawaiian Islands, where 6 of the 19 species Santalum spp. are endemic. As hemiparasitic plant species, Hawaiian sandalwoods require a host plant for optimal forest establishment, yet the importance of a host during seedling development is unclear. Furthermore, understanding interactions between pot hosts and nutrient availability on sandalwood seedling development during nursery culture will help to promote the production of high-quality sandalwood seedlings for restoration and commercial purposes. We evaluated the effects of controlled-release fertilizer (CRF), chelated Fe treatments, and two pot host species (Acacia koa and Dodonaea viscosa) on the seedling development of Hawaiian sandalwood (Santalum paniculatum). Increased nutrient availability (CRF) led to increased dry mass, root collar diameter, shoot height, chlorophyll index, and nutrient status values, confirming that the hemiparasitic S. paniculatum can be successfully grown in early stages of cultivation by providing adequate mineral fertilizers. There was a significant interaction between the nutrient availability and chelated iron treatments associated with increased height, root collar diameter, dry mass, chlorophyll index, Fe concentration, and Fe content when chelated Fe was applied (vs. not) in a nutrient-limiting environment. The pot host treatment did not affect any growth metrics, but it did affect the total count of haustoria, with A. koa-hosted seedlings developing 60.3% more haustoria than D. viscosa-hosted and control seedlings. Our results demonstrate that high-quality S. paniculatum seedlings can be grown in containers by providing adequate nutrition and that S. paniculatum in a nutrient-limiting growing environment may benefit from chelated iron fertilizers.