铵态氮和硝态氮营养与大豆幼苗的抗氰呼吸作用

在植物体内，NO云还原成NHI是一个耗能很多的生化过程，每还原一个NO。大约要消耗15个ATP分子（Salsac等1987）。植物直接吸收和利用NHi＋，可以减少能量消耗，所节约的能量可用于植物的生长。因此，从理论上讲，供NHI的植株要比供NOt的植株能够获得更高的生物产量。然而，对于大多数植物，供NOS的植株常具有更大的生长量和产量。对于这种现象，过去人们一直在矿物质和有机物积累的差异（Robin和Salsac1985）、根际的酸化程度（Ruftv等1983，Tolley－Henry和Rapen1986）、NHt有害浓度的积累（Haynes和Goh1978）、对光合作用的…

Ammonium and Nitrate Nutrition and Cyanide-resistant Respiration in Soybean Seedling

Soybean seedlings were grownwith N-free (- N ), NH4and NO3nutrient solutions for 20 days, NHkions were less accumulated in leaf androot tissues and a higher organic Ncontent was found in NH4 grownseedlings (Table 1 ). NO3 ions werelargely accumulated in soybean tissuesgrown with NO3 nutrient solution, accompagnied by a higher dry weight(Table l, Fig. 1 ). The oxidative andphosphorylative properties of the mitochondria isolated from roots and leaveswere measured with malate as substrate. NH4 and NO3 supplies stimulated oxidative activities of both cytochrome pathway and cyanideresistant pathway (Fig. 2). Compared withNOs nutrition, NH4 nutrition resultedin a higher cytochrome pathway activity in root mitochondria and a highercyanide-resistant pathway activity inleaf mitochondria (Fig. 2). The assimilation of NH4 into amino acids wascarried out exclusively in roots and thehigher rate of organic N synthesismight need a higher cytochrome P8thway activity to produce more ATP tosupply the energy needed. The involvement of photosynthetic energy innitrogen metabolism in leaves reducedthe utilization of respiratory energy.That resulted in an increased activityof cyanide-resistant pathway in leafmitochondria. In this case, leaf mitochondria appeared to produce more carbon skeletons than ATP for amonoacid synthesis. NO3 reduction was occurred mainly in leaves that needed alarge amount of mitochondrial NADHas reducing power and less NADH wasoxidized by cyanide-resistant pathway.The higher growth of soybean seedlingswith NOs nutrition was probablylinked to a lower cyanide-resistant respiration in leaves to avoid consumingmore carbon sources.