Instituto de Agrobiotecnología (IdAB), Universidad Pública de Navarra-CSIC-Gobierno de Navarra, ES-31192, Mutilva Baja, Spain; Unitat de Fisologia Vegetal, Facultat de Biologia, Universitat de Barcelona, ES-08028, Barcelona, Spain.
Physiol Plant. 2015 Jan;153(1):91-104. doi: 10.1111/ppl.12222. Epub 2014 Jun 25.
The contribution of carbon and nitrogen reserves to regrowth following shoot removal has been studied in the past. However, important gaps remain in understanding the effect of shoot cutting on nodule performance and its relevance during regrowth. In this study, isotopic labelling was conducted at root and canopy levels with both (15) N2 and (13) C-depleted CO2 on exclusively nitrogen-fixing alfalfa plants. As expected, our results indicate that the roots were the main sink organs before shoots were removed. Seven days after regrowth the carbon and nitrogen stored in the roots was invested in shoot biomass formation and partitioned to the nodules. The large depletion in nodule carbohydrate availability suggests that root-derived carbon compounds were delivered towards nodules in order to sustain respiratory activity. In addition to the limited carbohydrate availability, the upregulation of nodule peroxidases showed that oxidative stress was also involved during poor nodule performance. Fourteen days after cutting, and as a consequence of the stimulated photosynthetic and N2 -fixing machinery, availability of Cnew and Nnew strongly diminished in the plants due to their replacement by C and N assimilated during the post-labelling period. In summary, our study indicated that during the first week of regrowth, root-derived C and N remobilization did not overcome C- and N-limitation in nodules and leaves. However, 14 days after cutting, leaf and nodule performance were re-established.
过去已经研究了碳和氮储备对去除枝条后再生的贡献。然而，在理解枝条切割对根瘤性能的影响及其在再生过程中的相关性方面，仍然存在重要的差距。在这项研究中，对仅固氮紫花苜蓿植物的根部和冠层水平进行了（15）N2 和（13）C depleted CO2 的同位素标记。正如预期的那样，我们的结果表明，在去除枝条之前，根部是主要的汇器官。在再生后 7 天，根中储存的碳和氮被投资于枝条生物量的形成，并分配到根瘤中。根瘤碳水化合物可用性的大量减少表明，为了维持呼吸活性，根源碳化合物被输送到根瘤。除了碳水化合物可用性有限之外，根瘤过氧化物酶的上调表明，在根瘤性能较差期间，氧化应激也参与其中。在切割后 14 天，由于光合作用和固氮机器的刺激，由于在标记后期间被同化的 C 和 N 取代，新 Cnew 和 Nnew 的可用性在植物中大大减少。总之，我们的研究表明，在再生的第一周，根源 C 和 N 的再动员并没有克服根瘤和叶片中的 C 和 N 限制。然而，在切割后 14 天，叶片和根瘤的性能得到了恢复。
