Chaffei Chiraz, Gouia Houda, Masclaux Céline, Ghorbel Mohamed Habib
Laboratoire de physiologie végétale, Unité de recherche Nutrition et métabolisme azotés et protéines de stress, Département des sciences biologiques, Université de Tunis El Manar, 1060 Tunis, Tunisie.
C R Biol. 2003 Apr;326(4):401-12. doi: 10.1016/s1631-0691(03)00119-7.
In order to better understand the effects of heavy metals on the growth of plants, we decided to perform recovering experiments by following both chemical and physiological parameters in cadmium pre-stressed tomato seedlings after cadmium had been removed from the nutrient solution. The work shows that cadmium suppression results in resumption of growth activity. The biomass of leaves and stems rose steadily. The increase in root biomass exceeded those of leaves and stems. At the same time, nitrate content was increased to reach the level obtained with unstressed controls. In all the organs studied, the activities of the enzymes involved in the anabolic nitrogen primary assimilation pathways (nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS) soared after that cadmium had been removed. While NAD(+)-dependent glutamate dehydrogenase (GDH-NAD+) activity also rose progressively during the recovering time, the cognate NADH-dependent glutamate dehydrogenase (GDH-NADH) activity decreased. This result allows us to propose that the ammonia produced by the stress-induced protein catabolism is detoxified and re-assimilated by the GDH-NADH isoenzyme. On the basis of these results, we will discuss the ability of the plant to dilute the effects of pollutants during the recovering period. An important outcome of this work is that a transient contamination of the culture medium by pollutants is not necessarily followed by a significant depreciation in product yield or quality.
为了更好地了解重金属对植物生长的影响，我们决定通过跟踪从营养液中去除镉后镉预胁迫番茄幼苗的化学和生理参数来进行恢复实验。这项工作表明，镉抑制导致生长活性恢复。叶和茎的生物量稳步上升。根生物量的增加超过了叶和茎。同时，硝酸盐含量增加到与未受胁迫对照相同的水平。在所有研究的器官中，参与合成代谢氮初级同化途径的酶（硝酸还原酶（NR）、亚硝酸还原酶（NiR）和谷氨酰胺合成酶（GS））的活性在镉被去除后飙升。虽然依赖NAD(+)的谷氨酸脱氢酶（GDH-NAD+）活性在恢复期间也逐渐上升，但同源的依赖NADH的谷氨酸脱氢酶（GDH-NADH）活性下降。这一结果使我们能够提出，应激诱导的蛋白质分解代谢产生的氨被GDH-NADH同工酶解毒并重新同化。基于这些结果，我们将讨论植物在恢复期间稀释污染物影响的能力。这项工作的一个重要成果是，培养基被污染物短暂污染不一定会导致产品产量或质量的显著下降。
