Collaborative Research: Developing Methods to Study Age-Related Changes in the Physiology of Forest Trees

0110021迈克尔格林伍德，缅因大学0110142芭芭拉邦德，俄勒冈州州立大学树木的大小和复杂性继续增加，在生命周期可能持续许多世纪，每年生长的地区，他们的芽产生新的叶子和生殖结构。 随着年龄的增长和体积的增大，森林树木似乎生长得更慢，产生更厚的叶子和更多的生殖结构。这些变化很可能与林分生长率随年龄而下降有关，这种下降发生在重要木材品种寿命的中点之前。 虽然类似的模式的年龄和大小相关的变化的形态和生理学的叶子已经描述了许多物种，这些变化的机制几乎是未知的。对这些现象的可能解释包括由于水流阻力增加导致光合作用减少，以及遗传控制的衰老过程减缓了生长和光合作用。 调节成熟、老化和衰老的过程是生物学的基础，其中一些过程可能是大型长寿树木所独有的。更全面地了解这种下降的基础是建立模型和准确预测森林随时间的增长所必需的。不同年龄树木之间的枝条相互嫁接提供了很大的潜力，可以作为区分生长行为变化的解释的工具。在这种方法中，来自老生长树的枝条被嫁接到幼年和半成熟树上，来自幼年和半成熟树的枝条被嫁接到老生长树的树冠上。嫁接枝产生的叶片的生长、形态和生理变化的程度、方向和时间进程将为研究与年龄相关的变化机制提供依据。本研究将尝试在两种长寿树，红云杉和道格拉斯冷杉的相互嫁接。 这些物种都适应了大幅度不同的气候制度，因此，比较研究将提供洞察与年龄相关的树木生长变化的过程的普遍性或可变性。

0110021 Michael Greenwood, University of Maine0110142 Barbara Bond, Oregon State University Trees continue to increase in size and complexity over life spans that may last many centuries, and each year the growing regions of their shoots produce new foliage and reproductive structures. As they grow older and larger, forest trees appear to grow more slowly, produce thicker foliage and more reproductive structures. These changes are likely to be associated with age-related declines in the growth rates of forest stands, which occur before the mid-point of the lifespan of important timber species. Although similar patterns of age- and size-related change in the morphology and physiology of foliage have been described for numerous species, the mechanisms governing these changes are virtually unknown. Possible explanations for these phenomena range from decreased photosynthesis due to increased resistance of water flow to a genetically controlled ageing process that slows growth and photosynthesis. Processes regulating maturation, ageing and senescence are fundamental to biology, and some of these processes are probably unique to large, long-lived trees. A more complete understanding of the basis for this decline is necessary to model and accurately predict the growth of forests over time.Reciprocal grafting of shoots between trees of different ages offers great potential as a tool to distinguish among explanations for changes in growth behavior. In this approach, shoots from old growth trees are grafted onto juvenile and young-mature trees, and shoots from juvenile and young-mature trees are grafted into the crowns of old-growth trees. The extent, direction and time-course of changes in the growth, morphology, and physiology of foliage produced by the grafted shoots will provide insight into the mechanisms governing age-related change. This study will attempt reciprocal grafting on two species of long-lived trees, red spruce and Douglas fir. These species are adapted to substantially different climatic regimes, so a comparative study will provide insights into the universality or variability of processes associated with age-related changes in tree growth.