MeSH headings : Animals; Cycadopsida / anatomy & histology; Cycadopsida / chemistry; Cycadopsida / growth & development; Cycadopsida / immunology; Insecta / physiology; Terpenes / chemistry; Terpenes / immunology; Tracheophyta / anatomy & histology; Tracheophyta / chemistry; Tracheophyta / growth & development; Tracheophyta / immunology; Trichomes / anatomy & histology; Trichomes / chemistry; Trichomes / growth & development; Trichomes / immunology

TL;DR: Spruce GTs may provide an early, terpene-based chemical defense system at a developmental stage when young shoots are particularly vulnerable to foliage and shoot feeding insects, and before the resin duct system characteristic of conifers has fully developed. (via Semantic Scholar)