Département de biologie and Centre d'étude de la forêt, Université Laval, Québec, Québec, G1V0A6, Canada.
J Exp Bot. 2023 Jan 1;74(1):489-505. doi: 10.1093/jxb/erac432.
Growth in most spring ephemerals is decreased under warmer temperatures. Although photosynthetic activities are improved at warmer temperatures, leaves senesce earlier, which prevents the bulb from reaching a larger size. A longer leaf life duration during a warm spring, therefore, may improve bulb mass. We tested this hypothesis by modulating leaf life span of Erythronium americanum through the application of Promalin® (PRO; cytokinins and gibberellins) that prolonged or silver thiosulfate (STS) that reduced leaf duration. Gas exchange and chlorophyll fluorescence were measured along with leaf and bulb carbohydrate concentrations. Plants were also pulse labelled with 13CO2 to monitor sugar transport to the bulb. Lower photosynthetic rates and shorter leaf life span of STS plants reduced the amount of carbon that they assimilated during the season, resulting in a smaller bulb compared with control plants. PRO plants maintained their photosynthetic rates for a longer period than control plants, yet final bulb biomass did not differ between them. We conclude that seasonal growth for E. americanum is not limited by leaf life duration under warm growing conditions, but rather by limited sink growth capacity. Under global warming, spring geophytes might be at risk of being reduced in size and, eventually, reproducing less frequently.
在温暖的温度下，大多数春季短命植物的生长会减少。虽然在温暖的温度下光合作用得到了改善，但叶片会更早衰老，从而阻止鳞茎生长到更大的尺寸。因此，在温暖的春天，叶片寿命的延长可能会提高鳞茎的质量。我们通过施用 Promalin®（PRO；细胞分裂素和赤霉素）延长叶片寿命或施用银硫代硫酸（STS）缩短叶片寿命，从而改变延龄草的叶片寿命，以此来验证这一假设。我们测量了气体交换和叶绿素荧光，以及叶片和鳞茎碳水化合物浓度。我们还用 13CO2 脉冲标记植物，以监测糖向鳞茎的运输。STS 植物较低的光合作用速率和较短的叶片寿命缩短了它们在整个季节中同化的碳量，导致其鳞茎比对照植物小。PRO 植物比对照植物保持更长时间的光合作用速率，但它们的最终鳞茎生物量没有差异。我们的结论是，在温暖的生长条件下，E. americanum 的季节性生长不受叶片寿命的限制，而是受有限的汇生长能力的限制。在全球变暖的情况下，春季球茎植物可能会面临体积缩小的风险，最终繁殖的频率也会降低。
