The effect of excess macronutrients in the root environment on mannitol and sucrose metabolism was investigated in celery (Apium graveolens L. var dulce [Mill.] Pers.). Plant growth was inhibited progressively as macronutrient concentration in the media, as measured by electrical conductivity (E.C.), increased from 1.0 to 11.9 decisiemens m-1. Plants grown for 35 d at higher E.C. had a lower water content but similar dry weight in their roots, leaves, and petioles compared to plants grown at lower E.C. Macronutrient concentrations of leaves, roots, and petioles were not affected by the imposed stress, indicating that the macronutrient stress resulted in a water-deficit stress response rather than a salt-specific response. Mannitol accumulated in sink tissues and was accompanied by a drastic decrease in activity of mannitol-1-oxidoreductase. Sucrose concentration and activities of sucrose-metabolizing enzymes in sink tissues were not affected by the macronutrient stress. Mature leaves exhibited increased concentrations of both mannitol and sucrose, together with increased activity of mannose-6-phosphate reductase and sucrose phosphate synthase, in response to macronutrient stress. Thus, mannitol accumulation in osmotically stressed celery is regulated by diminished catabolism in sink tissues and increased capacity for mannitol biosynthesis in source leaves.
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机译:在芹菜中研究了根系环境中过量的常量营养素对甘露醇和蔗糖代谢的影响(Apiumgravolens L. var dulce [Mill。] Pers。)。随着培养基中大量营养物浓度的升高(通过电导率(E.C.)),植物的生长被逐渐抑制,其电导率从1.0升高到11.9十m-1。与在较低EC下生长的植物相比,在较高EC下生长35 d的植物的水分含量较低,但其根,叶和叶柄的干重相似。叶,根和叶柄的宏观营养素浓度不受施加的胁迫的影响,表明大量营养素胁迫导致缺水胁迫响应,而不是盐分特异性响应。甘露醇在水槽组织中积累,并伴随着甘露醇-1-氧化还原酶活性的急剧下降。大量营养物胁迫不影响水槽组织中的蔗糖浓度和蔗糖代谢酶的活性。响应大量营养素胁迫,成熟的叶片显示出增加的甘露醇和蔗糖浓度,以及增加的6-磷酸磷酸甘露糖还原酶和蔗糖磷酸合酶活性。因此,渗透胁迫下的芹菜中甘露醇的积累是通过减少水槽组织中的分解代谢和增加源叶中甘露醇生物合成的能力来调节的。
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