Amundson R G, Kohut R J, Laurence J A
Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853, USA.
Tree Physiol. 1995 Mar;15(3):167-74. doi: 10.1093/treephys/15.3.167.
Red spruce (Picea rubens Sarg.) trees growing at high elevation in the northeastern United States have experienced decline in recent years but seedlings have proved to be relatively tolerant of a wide range of environmental stresses in controlled studies. One possible reason for the wide tolerance to stress in seedlings is their inherently large pool of carbohydrate reserves, which is available for maintenance during and regrowth after periods of stress. We tested for the effects of foliar N and exposure to ozone on foliar carbohydrate reserves of 20-year-old naturally regenerated saplings. The trees were maintained in native soil in 360-l containers for 5 years before the experiment. The year before the experiment, trees were fertilized with N,P,K to provide a population of trees from N deficient to N sufficient. As foliar N decreased below 0.9%, length of current-year shoots and specific needle area of current-year needles declined. Foliar N concentration was correlated with foliar sugar and starch concentrations, but relationships varied with time of year. Before bud break, foliar carbohydrates and N, in general, were positively correlated, and date of bud break was delayed in N-deficient trees. During active growth, foliar soluble sugars and N were positively correlated, but starch concentrations were negatively correlated with N. By late September, neither starch nor sugar concentration was correlated with N concentration. Ozone and foliar N concentrations did not interact to change foliar carbohydrate concentrations or shoot and needle growth in this relatively short-term study.
生长在美国东北部高海拔地区的红云杉（Picea rubens Sarg.）近年来出现了衰退现象，但在对照研究中，幼苗已被证明对多种环境胁迫具有相对耐受性。幼苗对胁迫具有广泛耐受性的一个可能原因是它们固有的大量碳水化合物储备，这些储备可用于在胁迫期间维持生长以及在胁迫期过后重新生长。我们测试了叶片氮含量和臭氧暴露对20年生天然更新幼树叶片碳水化合物储备的影响。在实验前，这些树在360升的容器中种植于原生土壤中达5年。在实验前一年，对树木施加氮、磷、钾肥料，以提供从氮缺乏到氮充足的一系列树木。当叶片氮含量降至0.9%以下时，当年新梢长度和当年针叶的比叶面积下降。叶片氮浓度与叶片糖和淀粉浓度相关，但这种关系随一年中的时间而变化。在芽萌发前，叶片碳水化合物和氮总体上呈正相关，氮缺乏的树木芽萌发日期延迟。在生长活跃期，叶片可溶性糖和氮呈正相关，但淀粉浓度与氮呈负相关。到9月下旬，淀粉和糖浓度均与氮浓度无关。在这项相对短期的研究中，臭氧和叶片氮浓度没有相互作用来改变叶片碳水化合物浓度或新梢和针叶生长。
