Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata)
Citation
Foster, A.J., Aloni, R., Fidanza, M., Gries, R., Gries, G., Mattsson, J. (2016). Foliar phase changes are coupled with changes in storage and biochemistry of monoterpenoids in western redcedar (Thuja plicata). Trees - Structure and Function, [online] 30(4), 1361-1375. http://dx.doi.org/10.1007/s00468-016-1373-x
Plain language summary
The paper is published from a chapter of my PhD work between 2008 and 2011 at Simon Fraser University. Our team examined the development of an economically important tree species, Western Red Cedar, and identified different stages of plant growth had different chemical profiles. From a basic science standpoint, the results presented in this paper are fascinating in that new discoveries relating anatomy to chemical composition were found. In short, the manuscript examines changes in the anatomy and chemical profiles of this tree from seed to sapling, characterizes major changes in chemical storage structures, conducts chemical analysis at each stage and explains why this tree is susceptible to herbivores at the early seedling stages, but resistant at the later sapling and mature stages. Knowledge of these chemical profiles will help tree breeding programs develop new lines with increased herbivore defensive chemical profiles and could lead to the discovery of new biopesticides that may have a role in agriculture.
Abstract
Key message: The monoterpenoid content ofThuja plicataneedles and scales differs both quantitatively and qualitatively. Resin storage structures are associated with anatomical modifications that suggest facilitated exit of monoterpenoids. Abstract: 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 (−)-α-pinene as prevalent monoterpenoids. In contrast, scales contain enclosed resin glands and have a monoterpenoid profile that is markedly different from needles, with α-thujone as the most prevalent monoterpenoid and no detectable levels of (−)-α-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.