Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata)
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| Authors: | Foster, AJ; Aloni, R; Fidanza, M; Gries, R; Gries, G; Mattsson, J |
| Year: | 2016 |
| Journal: | Trees-Structure and Function 30: 1361-1375 Article Link (DOI) |
| Title: | Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata) |
| Abstract: | The monoterpenoid content of Thuja plicata needles and scales differs both quantitatively and qualitatively. Resin storage structures are associated with anatomical modifications that suggest facilitated exit of monoterpenoids. Western redcedar (Thuja plicata) is a highly valued source of lumber. T. plicata trees planted in reforestations efforts are often heavily damaged by extensive ungulate browsing. Research has shown that high foliar content of monoterpenoids deters browsing, providing an avenue for resistance selection in young plants. T. plicata foliage undergoes, however, extensive phase changes during early growth. Currently it is unknown whether the anatomical basis of monoterpenoid storage and release, and the content and composition of stored monoterpenoids, also change at the same time. Here, we studied these aspects of T. plicata seedling biology. Cotyledons lack storage structures for terpenoids. Needles contain a single longitudinal terpenoid duct with (+)-sabinene and (-)-alpha-pinene as prevalent monoterpenoids. In contrast, scales contain enclosed resin glands and have a monoterpenoid profile that is markedly different from needles, with alpha-thujone as the most prevalent monoterpenoid and no detectable levels of (-)-alpha-pinene. Both ducts and glands are close to the epidermis and vascular tissues, frequently companioned by gaps in the sub-epidermal fiber layer, suggesting paths of facilitated diffusion of monoterpenoids out of tissues. We conclude that foliar phase changes are coupled with equally significant changes in resin storage structure anatomy, monoterpenoid levels and composition. Our findings provide a framework for reproducible sampling and selection not only for high levels of monoterpenoids but also for anatomical markers that may affect release of these compounds. |
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