Thermal plasticity of Laminaria digitata - seasonal growth; recruitment; thermal physiology of juvenile sporophytes

We investigated effects of temperature during ontogeny of the kelp Laminaria digitata across haploid gametophyte and diploid sporophyte life cycle stages in 5 distinct genetic lines. We sampled meristematic discs from wild sporophytes on the island of Helgoland (North Sea; 54.1779 N, 7.8926 E) in May 2017, July 2017 and February 2018 and conducted a seasonal growth experiment at 5°C and 15°C over 14 days (experiment 1). Based on meiospores from five individuals (genetic lines) sampled in July 2017, we applied a full-factorial experimental design to generate different temperature histories by applying 5°C and 15°C during meiospore germination, gametogenesis of parental gametophytes and recruitment of offspring sporophytes (19-26 days; recruitment), and juvenile sporophyte rearing (91-122 days). We then tested for thermal plasticity among temperature history treatments at 5°C and 15°C in a final 12-day experiment assessing growth, the storage compound mannitol, carbon and nitrogen contents, and fluorometric responses in 3-4 month old sporophytes (experiment 2).

本研究探究了掌状海带（Laminaria digitata）个体发育过程中的温度效应，涵盖其5个独立遗传品系的单倍体配子体（haploid gametophyte）与二倍体孢子体（diploid sporophyte）的完整生活史阶段。研究团队于2017年5月、2017年7月及2018年2月，从北海黑尔戈兰岛（54.1779°N，7.8926°E）的野生孢子体上采集分生组织盘（meristematic disc），并于5℃与15℃条件下开展为期14天的季节性生长实验（实验1）。基于2017年7月采集的5个个体（对应5个遗传品系）的减数孢子（meiospore），本研究采用全因子实验设计（full-factorial experimental design），通过在减数孢子萌发、亲本配子体配子发生（gametogenesis）、子代孢子体定植（时长19~26天）以及幼孢子体培育（时长91~122天）这三个阶段施加5℃与15℃的温度条件，构建不同的温度经历处理。随后，在为期12天的最终实验（实验2）中，我们以3~4月龄的孢子体为材料，在5℃与15℃条件下检测不同温度经历处理下的热可塑性（thermal plasticity），测定指标包括生长速率、贮藏化合物甘露醇（mannitol）含量、碳氮含量以及荧光响应。