Larmure Annabelle, Munier-Jolain Nathalie G
Agroécologie, AgroSup Dijon, INRA, Univ. Bourgogne Franche-Comté, Dijon, France.
Front Plant Sci. 2019 Dec 20;10:1608. doi: 10.3389/fpls.2019.01608. eCollection 2019.
Higher temperatures induced by the on-going climate change are a major cause of yield reduction in legumes. Pea ( L.) is an important annual legume crop grown in temperate regions for its high seed nitrogen (N) concentration. In addition to yield, seed N amount at harvest is a crucial characteristic because pea seeds are a source of protein in animal and human nutrition. However, there is little knowledge on the impacts of high temperatures on plant N partitioning determining seed N amount. Therefore, this study investigates the response of seed dry matter and N fluxes at the whole-plant level (plant N uptake, partitioning in vegetative organs, remobilization, and accumulation in seeds) to a range of air temperature (from 18.4 to 33.2°C) during the seed-filling-period. As pea is a legume crop, plants relying on two different N nutrition pathways were grown in glasshouse: N-fixing plants or NO -assimilating plants. Labeled nitrate (NO ) and intra-plant N budgets were used to quantify N fluxes. High temperatures decreased seed-filling duration (by 0.8 day per °C), seed dry-matter and N accumulation rates (respectively by 0.8 and 0.032 mg seed day per °C), and N remobilization from vegetative organs to seeds (by 0.053 mg seed day per °C). Plant N-fixation decreased with temperatures, while plant NO assimilation increased. However, the additional plant N uptake in NO -assimilating plants was never allocated to seeds and a significant quantity of N was still available at maturity in vegetative organs, whatever the plant N nutrition pathway. Thus, we concluded that seed N accumulation under high temperatures is sink limited related to a shorter seed-filling duration and a reduced seed dry-matter accumulation rate. Consequently, sustaining seed sink demand and preserving photosynthetic capacity of stressed plants during the seed-filling period should be promising strategies to promote N allocation to seeds from vegetative parts and thus to maintain crop N production under exacerbated abiotic constraints in field due to the on-going climate change.
持续的气候变化所导致的温度升高是豆类作物减产的主要原因。豌豆（L.）是一种重要的一年生豆类作物，因其种子氮（N）含量高而种植于温带地区。除产量外，收获时种子的氮含量是一个关键特征，因为豌豆种子是动物和人类营养中的蛋白质来源。然而，关于高温对决定种子氮含量的植物氮分配的影响，人们了解甚少。因此，本研究调查了在灌浆期，一系列气温（从18.4到33.2°C）对全株水平上种子干物质和氮通量（植物氮吸收、在营养器官中的分配、再转运以及在种子中的积累）的响应。由于豌豆是豆类作物，在温室中种植了依赖两种不同氮营养途径的植株：固氮植株或硝酸根同化植株。使用标记硝酸盐（NO）和植株内氮预算来量化氮通量。高温缩短了灌浆持续时间（每升高1°C减少0.8天），降低了种子干物质和氮积累速率（分别为每升高1°C减少0.8毫克种子/天和0.032毫克种子/天），以及从营养器官向种子的氮再转运（每升高1°C减少0.053毫克种子/天）。植物固氮随着温度升高而降低，而植物硝酸根同化增加。然而，无论植物的氮营养途径如何，硝酸根同化植株额外吸收的植物氮从未分配到种子中，并且在成熟时营养器官中仍有大量氮可用。因此，我们得出结论，高温下种子氮积累受库限制，这与较短的灌浆持续时间和降低的种子干物质积累速率有关。因此，在灌浆期维持种子库需求并保持受胁迫植株的光合能力，应该是在田间因持续气候变化导致非生物胁迫加剧的情况下，促进氮从营养部分分配到种子从而维持作物氮产量的有前景的策略。
