Edwards Brianne, Burghardt Liana T, Kovach Katherine E, Donohue Kathleen
Biology Department, Duke University, Box 90338, Durham, NC 27708, USA.
Integr Comp Biol. 2017 Nov 1;57(5):1021-1039. doi: 10.1093/icb/icx065.
Variation in the developmental timing in one life stage may ramify within and across generations to disrupt optimal phenology of other life stages. By focusing on a common mechanism of developmental arrest in plants-seed dormancy-we investigated how variation in flowering time influenced seed germination behavior and identified potential processes that can lead to canalized germination behavior despite variation in reproductive timing. We quantified effects of reproductive timing on dormancy cycling by experimentally manipulating the temperature during seed maturation and the seasonal timing of seed dispersal/burial, and by assessing temperature-dependent germination of un-earthed seeds over a seasonal cycle. We found that reproductive timing, via both seed-maturation temperature and the timing of dispersal, strongly influenced germination behavior in the weeks immediately following seed burial. However, buried seeds subsequently canalized their germination behavior, after losing primary dormancy and experiencing natural temperature and moisture conditions in the field. After the complete loss of primary dormancy, germination behavior was similar across seed-maturation and dispersal treatments, even when secondary dormancy was induced. Maternal effects themselves may contribute to the canalization of germination: first, by inducing stronger dormancy in autumn-matured seeds, and second by modifying the responses of those seeds to their ambient environment. Genotypes differed in dormancy cycling, with functional alleles of known dormancy genes necessary for the suppression of germination at warm temperatures in autumn through spring across multiple years. Loss of function of dormancy genes abolished almost all dormancy cycling. In summary, effects of reproductive phenology on dormancy cycling of buried seeds were apparent only as long as seeds retained primary dormancy, and a combination of genetically imposed seed dormancy, maternally induced seed dormancy, and secondary dormancy can mitigate variation in germination behavior imposed by variation in reproductive phenology.
一个生命阶段发育时间的变化可能在代内和代际间产生连锁反应，从而扰乱其他生命阶段的最佳物候。通过聚焦植物发育停滞的一种常见机制——种子休眠，我们研究了开花时间的变化如何影响种子萌发行为，并确定了尽管繁殖时间存在变化但仍能导致萌发行为趋于稳定的潜在过程。我们通过实验控制种子成熟期间的温度以及种子传播/埋藏的季节时间，并评估在一个季节周期内未出土种子的温度依赖性萌发，来量化繁殖时间对休眠循环的影响。我们发现，繁殖时间通过种子成熟温度和传播时间，强烈影响种子埋藏后立即几周内的萌发行为。然而，埋藏的种子在失去初级休眠并经历田间自然温度和湿度条件后，随后使其萌发行为趋于稳定。在完全失去初级休眠后，即使诱导了次级休眠，种子成熟和传播处理下的萌发行为仍相似。母体效应本身可能有助于萌发的趋同：首先，通过在秋季成熟的种子中诱导更强的休眠，其次通过改变这些种子对其周围环境的反应。不同基因型在休眠循环方面存在差异，已知休眠基因的功能等位基因对于在多年的秋季至春季温暖温度下抑制种子萌发是必需的。休眠基因功能的丧失几乎消除了所有的休眠循环。总之，繁殖物候对埋藏种子休眠循环的影响仅在种子保留初级休眠时才明显，并且遗传施加的种子休眠、母体诱导的种子休眠和次级休眠的组合可以减轻繁殖物候变化所带来的萌发行为变化。
