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

迈克尔•格林伍德0110021 Maine0110142芭芭拉·邦德大学,俄勒冈州立大学树木继续增加在规模和复杂性的寿命可能会持续几个世纪,和每年不断增长的地区的芽产生新的叶和生殖结构。随着年龄的增长和树木的生长，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的下降有关，这种下降发生在重要木材树种寿命的中点之前。虽然在许多物种中已经描述了与年龄和大小相关的叶片形态和生理变化的类似模式，但控制这些变化的机制实际上是未知的。对这些现象的可能解释包括：由于水流阻力增加导致的光合作用减少，以及基因控制的衰老过程减缓了生长和光合作用。调节成熟、衰老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特有的。更全面地了解这种减少的基础是建立模型和准确预测森林随时间增长的必要条件。不同树龄的树木之间的枝条相互嫁接提供了巨大的潜力，作为区分生长行为变化的解释的工具。该方法将老树的枝条嫁接到幼树和幼树上，将幼树和幼树的枝条嫁接到老树的树冠上。嫁接枝产生的叶片的生长、形态和生理变化的程度、方向和时间过程将为了解控制年龄相关变化的机制提供见解。本研究将尝试在红杉和花旗松两种长寿树木上进行互惠嫁接。这些树种适应了截然不同的气候制度，因此比较研究将提供对树木生长中与年龄相关的变化相关过程的普遍性或可变性的见解。

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.