Ben Salah Imène, Albacete Alfonso, Martínez Andújar Cristina, Haouala Rabiaa, Labidi Nehla, Zribi Fethia, Martinez Vicente, Pérez-Alfocea Francisco, Abdelly Chedly
Laboratoire d'Adaptation des Plantes aux Stress Abiotiques, CBBC, Hammam-Lif, Tunisia.
J Plant Physiol. 2009 Mar 15;166(5):477-88. doi: 10.1016/j.jplph.2008.06.016. Epub 2008 Sep 18.
The effect of salt stress on nitrogen fixation, in relation to sucrose transport towards nodules and other sink organs and the potential of sucrose breakdown by nodules, was investigated in two lines of Medicago ciliaris. Under salt stress conditions, the two lines showed a decrease of total biomass production, but TNC 1.8 was less affected by salt than TNC 11.9. The chlorophyll content was not changed in TNC 1.8, in contrast to TNC 11.9. Shoot, root, and nodule biomass were also affected in the two lines, but TNC 1.8 exhibited the higher potentialities of biomass production of these organs. Nitrogen fixation also decreased in the two lines, and was more sensitive to salt than growth parameters. TNC 1.8 consistently exhibited the higher values of nitrogen fixation. Unlike nodules, leaves of both lines were well supplied in nutrients with some exceptions. Specifically, the calcium content decreased in the sensitive line leaves, and the nodule magnesium content was not changed in either line. The tolerant line accumulated more sodium in its leaves. The two lines did not show any differences in the nodule sodium content. Sucrose allocation towards nodules was affected by salt in the two lines, but this constraint did not seem to affect the repartition of sucrose between sink organs. Salt stress induced perturbations in nodule sucrolytic activities in the two lines. It inhibited sucrose synthase, but the inhibition was more marked in TNC 11.9; alkaline/neutral activity was not altered in TNC 1.8, whereas it decreased more than half in TNC 11.9. Thus, the relative tolerance of TNC 1.8 to salt stress could be attributed to a better use of these photoassimilates by nodules and a better supply of bacteroids in malate. The hypothesis of a competition for sucrose between nodules and other sink organs under salt stress could not be verified.
在两株睫毛状苜蓿中，研究了盐胁迫对固氮的影响，以及蔗糖向根瘤和其他库器官的运输情况，还有根瘤分解蔗糖的潜力。在盐胁迫条件下，两株苜蓿的总生物量产量均下降，但TNC 1.8受盐胁迫的影响小于TNC 11.9。与TNC 11.9不同，TNC 1.8的叶绿素含量没有变化。两株苜蓿的地上部、根部和根瘤生物量也受到影响，但TNC 1.8在这些器官的生物量生产方面表现出更高的潜力。两株苜蓿的固氮能力也下降了，并且比生长参数对盐更敏感。TNC 1.8始终表现出较高的固氮值。与根瘤不同，两株苜蓿的叶片营养供应充足，但有一些例外。具体来说，敏感株系叶片中的钙含量下降，而两株苜蓿根瘤中的镁含量均未变化。耐盐株系叶片中积累了更多的钠。两株苜蓿根瘤中的钠含量没有差异。盐胁迫影响了两株苜蓿中蔗糖向根瘤的分配，但这种限制似乎并未影响蔗糖在库器官之间的分配。盐胁迫导致两株苜蓿根瘤中的蔗糖分解活性受到干扰。它抑制了蔗糖合酶，但在TNC 11.9中抑制作用更明显；TNC 1.8中的碱性/中性活性没有改变，而在TNC 11.9中下降了一半以上。因此，TNC 1.8对盐胁迫的相对耐受性可能归因于根瘤对这些光合产物的更好利用以及苹果酸中类菌体的更好供应。盐胁迫下根瘤与其他库器官之间对蔗糖的竞争假说无法得到证实。
