Gutjahr Sylvain, Lapointe Line
Département de biologie et Centre d'étude de la forêt, Université Laval, Québec (Québec), Canada G1V 0A6.
Ann Bot. 2008 Nov;102(5):835-43. doi: 10.1093/aob/mcn161. Epub 2008 Aug 28.
Woodland spring ephemerals exhibit a relatively short epigeous growth period prior to canopy closure. However, it has been suggested that leaf senescence is induced by a reduction in the carbohydrate sink demand, rather than by changes in light availability. To ascertain whether a potentially higher net carbon (C) assimilation rate could shorten leaf lifespan due to an accelerated rate of storage, Erythronium americanum plants were grown under ambient (400 ppm) and elevated (1100 ppm) CO2 concentrations.
During this growth-chamber experiment, plant biomass, bulb starch concentration and cell size, leaf phenology, gas exchange rates and nutrient concentrations were monitored.
Plants grown at 1100 ppm CO2 had greater net C assimilation rates than those grown at 400 ppm CO2. However, plant size, final bulb mass, bulb filling rate and timing of leaf senescence did not differ.
Erythronium americanum fixed more C under elevated than under ambient CO2 conditions, but produced plants of similar size. The similar bulb growth rates under both CO2 concentrations suggest that the bulb filling rate is dependant on bulb cell elongation rate, rather than on C availability. Elevated CO2 stimulated leaf and bulb respiratory rates; this might reduce feed-back inhibition of photosynthesis and avoid inducing premature leaf senescence.
林地春季短命植物在树冠郁闭前有相对较短的地上生长时期。然而，有人提出叶片衰老由碳水化合物库需求的减少诱导，而非光照可用性的变化。为确定潜在更高的净碳（C）同化率是否会因储存速率加快而缩短叶片寿命，美洲车前草在环境二氧化碳浓度（400 ppm）和升高的二氧化碳浓度（1100 ppm）下生长。
在这个生长室实验中，监测了植物生物量、鳞茎淀粉浓度和细胞大小、叶片物候、气体交换速率和养分浓度。
在1100 ppm二氧化碳浓度下生长的植物比在400 ppm二氧化碳浓度下生长的植物有更高的净C同化率。然而，植株大小、最终鳞茎质量、鳞茎充实率和叶片衰老时间并无差异。
在升高的二氧化碳条件下，美洲车前草比在环境二氧化碳条件下固定了更多的C，但产生的植株大小相似。两种二氧化碳浓度下相似的鳞茎生长速率表明，鳞茎充实率取决于鳞茎细胞伸长率，而非C的可用性。升高的二氧化碳刺激了叶片和鳞茎的呼吸速率；这可能会减少光合作用的反馈抑制，并避免诱导叶片过早衰老。
