Andersen C P, Scagel C F
U.S. EPA National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th St., Corvallis, OR 97333, USA.
Tree Physiol. 1997 Jun;17(6):377-87. doi: 10.1093/treephys/17.6.377.
Exposure to ozone (O(3)) and changes in soil fertility influence both the metabolism of plant roots and their interaction with rhizosphere organisms. Because one indication of altered root metabolism is a change in belowground respiratory activity, we used specially designed measurement chambers to assess the effects of O(3) and nutrient availability on belowground respiratory activity of potted three-year-old ponderosa pine (Pinus ponderosa Dougl. ex Laws.). Seedlings were exposed to a factorial combination of three O(3) treatments and three fertilization treatments in open-top O(3) exposure chambers. Ozone exposure decreased and high nutrient supply increased total plant dry weight, but root/shoot ratios were not affected. In general, exposure to O(3) increased rates of belowground O(2) uptake and CO(2) release and the respiratory quotient (RQ, CO(2)/O(2)), although seasonal differences were detected. In October, following the second season of O(3) exposure, rates of belowground O(2) uptake and CO(2) release and RQ were increased in trees in the high-O(3) exposure treatment by 22, 73 and 32%, respectively, over values in control trees in charcoal-filtered air. Increasing nutrient supply resulted in decreasing rates of belowground O(2) uptake and CO(2) release but it had little effect on RQ. In the high-nutrient supply treatment, rates of belowground O(2) uptake and CO(2) release were decreased by 38 and 39%, respectively, compared with rates in the low-nutrient supply treatment. At the end of the second growing season, the high-nutrient supply treatment had decreased lateral root total nonstructural carbohydrates by 22% compared with the low-nutrient supply treatment. Nutrient availability altered the belowground respiratory response to O(3), such that the response to O(3) was greatest in the low-nutrient supply treatment. Significant O(3) effects on belowground respiratory activity were apparent before any reduction in total plant growth was found, suggesting that roots and rhizosphere organisms may be early indicators of physiological dysfunction in stressed seedlings.
暴露于臭氧（O₃）以及土壤肥力的变化会影响植物根系的新陈代谢及其与根际生物的相互作用。由于根系新陈代谢改变的一个迹象是地下呼吸活动的变化，我们使用专门设计的测量室来评估臭氧和养分有效性对盆栽三年生黄松（Pinus ponderosa Dougl. ex Laws.）地下呼吸活动的影响。在开放式臭氧暴露室中，将幼苗暴露于三种臭氧处理和三种施肥处理的析因组合中。臭氧暴露降低了植物总干重，而高养分供应增加了植物总干重，但根冠比不受影响。总体而言，尽管检测到季节差异，但暴露于臭氧会增加地下氧气吸收和二氧化碳释放速率以及呼吸商（RQ，二氧化碳/氧气）。在臭氧暴露的第二个季节后的10月，高臭氧暴露处理的树木地下氧气吸收和二氧化碳释放速率以及RQ分别比木炭过滤空气中对照树木的值增加了22%、73%和32%。增加养分供应导致地下氧气吸收和二氧化碳释放速率降低，但对RQ影响不大。与低养分供应处理相比，高养分供应处理的地下氧气吸收和二氧化碳释放速率分别降低了38%和39%。在第二个生长季节结束时，与低养分供应处理相比，高养分供应处理使侧根总非结构性碳水化合物减少了22%。养分有效性改变了地下对臭氧的呼吸响应，使得在低养分供应处理中对臭氧的响应最大。在发现植物总生长量有任何减少之前，臭氧对地下呼吸活动的显著影响就已显现出来，这表明根系和根际生物可能是受胁迫幼苗生理功能障碍的早期指标。
