Gnan Sebastian, Marsh Tom, Kover Paula X
Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Claverton Down, United Kingdom.
PLoS One. 2017 Oct 3;12(10):e0185835. doi: 10.1371/journal.pone.0185835. eCollection 2017.
Leaves are thought to be the primary carbon source for reproduction in plants, so a positive relationship between vegetative size and reproductive output is expected, establishing a trade-off between time to reproduction and reproductive output. A common response to higher temperatures due to climate changes is the induction of earlier transition into reproduction. Thus, in annual plants, earlier transition into flowering can potentially constrain plant size and reduce seed production. However, trade-offs between early reproduction and fitness are not always observed, suggesting mechanisms to escape the constraints of early flowering do exist. Here, we test whether inflorescence photosynthesis contribution to the reproductive output of Arabidopsis thaliana can offset the cost of early reproduction. We followed the development, growth rate and fitness of 15 accessions, and removed all rosette leaves at flowering (prior to the completion of inflorescence development or any fruit production) in half of the plants to determine the ability of inflorescences to maintain fitness in the absence of leaves. Although leaf removal significantly reduced fruit number, seed weight and plant height, even the most severely impacted accessions maintained 35% of their fitness with the inflorescence as the sole photosynthetic organ; and some accessions experienced no reduction in fitness. Differences between accessions in their ability to maintain fitness after leaf removal is best explained by earlier flowering time and the ability to maintain as many or more branches after leaf removal as in the control treatment. Although earlier flowering does constrain plant vegetative size, we found that inflorescence photosynthesis can significantly contribute to seed production, explaining why early flowering plants can maintain high fitness despite a reduction in vegetative size. Thus, plants can be released from the usually assumed trade-offs associated with earlier reproduction, and selection on inflorescence traits can mediate the impact of climate change on phenology.
叶片被认为是植物繁殖的主要碳源，因此营养体大小与繁殖输出之间预期存在正相关关系，从而在繁殖时间和繁殖输出之间形成一种权衡。气候变化导致温度升高的一个常见反应是诱导植物更早进入繁殖阶段。因此，在一年生植物中，更早进入花期可能会限制植株大小并减少种子产量。然而，早期繁殖与适合度之间的权衡并非总是能观察到，这表明确实存在逃避早花限制的机制。在这里，我们测试拟南芥花序光合作用对其繁殖输出的贡献是否能够抵消早期繁殖的代价。我们追踪了15个生态型的发育、生长速率和适合度，并在一半植株开花时（在花序发育完成或任何果实产生之前）摘除所有莲座叶，以确定花序在没有叶片的情况下维持适合度的能力。尽管摘除叶片显著减少了果实数量、种子重量和株高，但即使是受影响最严重的生态型，以花序作为唯一光合器官时仍能维持其35%的适合度；而且有些生态型的适合度没有降低。摘除叶片后各生态型维持适合度能力的差异，最好用更早的开花时间以及摘除叶片后维持与对照处理相同数量或更多分枝的能力来解释。尽管早花确实会限制植物营养体大小，但我们发现花序光合作用对种子生产有显著贡献，这解释了为什么早花植物尽管营养体大小减小仍能维持较高适合度。因此，植物可以摆脱通常认为的与早期繁殖相关的权衡，对花序性状的选择可以调节气候变化对物候的影响。
