PLANTS CAN UTILIZE IRON FROM FE-N,N'-DI-(2-HYDROXYBENZOYL)-ETHYLENEDIAMINE-N,N'-DIACETIC ACID, A FERRIC CHELATE WITH 106 GREATER FORMATION CONSTANT THAN FE-EDDHA
PLANTS CAN UTILIZE IRON FROM FE-N,N'-DI-(2-HYDROXYBENZOYL)-ETHYLENEDIAMINE-N,N'-DIACETIC ACID, A FERRIC CHELATE WITH 106 GREATER FORMATION CONSTANT THAN FE-EDDHA
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DOI：
10.1080/01904168809363867
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发表时间：
1988-01-01
影响因子：
2.1
通讯作者：
CHANEY, RL
中科院分区：
文献类型：
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作者：
CHANEY, RL
HBED[N，N‘-二(2-羟基苯甲酰基)-乙二胺-N，N’-二乙酸乙酯]于1967年合成，但直到最近才有了植物营养研究所需的数量。这种螯合剂是EDDHA的近亲，但它的Fe~(3+)形成或稳定常数(离子强度为μ+0.1时)为39.68，而EDDHA为33.91。甚至HBED的Fe~(3+)选择性(即Fe~(3+)/Ca~(2+)稳定常数比)也大于EDDHA。这些与Fe3+的更高的稳定性似乎是由于HBED对Fe3+更好的空间适配性。大豆、玉米和坚果在含有0 Fe、10μM FeHEDTA、10μM FeEDDHA(1：1和1：3 Fe：EDDHA)或10μM FeHBED的完全Hoagland类型营养液中生长，以控制pH至7.5.大豆和五倍子获得了充足的铁并保持了绿色，而玉米在除FeHEDTA外的所有处理中都严重失绿。结果表明，非禾本科植物根系还原Fe3+络合物和吸收曝气液中的铁的能力极强，在Fe3+络合物还原后，Fe2+不能持续很长时间。与玉米不同，Nutsedge被发现是一个典型的Strategy-1物种，尽管莎草科和Poaceae被一些分类权威机构归类在一起。GEOCHEM是一个计算机程序，设计用于计算土壤溶液中化学物种的平衡，用于营养溶液，以允许将HBED与EDTA、DTPA和EDDHA进行比较。现在看来，以前对EDDHA营养溶液进行物化的尝试对CuEDDHA螯合物种使用了不正确的形成常数。利用已公布的生成常数，地质化学表明，铜将在很大的pH范围内取代铁，但在实际营养液的pH值下，其他元素不会取代铁。HBED对Fe~(3+)的较大选择性阻止了铜取代Fe~(3+)。用化学方法研究了FeEDDHA在pH为5.5时的铜置换反应，结果表明，CuEDCHA的生成常数约为22.3(μ=0.1M)，而不是先前估计的23.9。在正常的营养液pH范围内，铜可以取代EDDHA中的铁。与EDDHA相比，HBED作为营养液的铁络合剂具有几个优点。EDDHA催化Mn2+和Co2+氧化成稳定常数未知的强络合态Mn3+和Co3+，而HBED则不能。因此，对于具有HBED的营养元素，形成常数是可用的，但对于EDDHA是不可用的。在实际营养液中，没有元素可以取代FeHBED中的Fe，但铜可以取代FeEDDHA中的Fe。然而，EDCHA中的Fe比FeHBED中的Fe更容易被植物利用，这可能是因为HBED对Fe2+的螯合作用更强。HBED提供了一种比EDDHA更可预测的试剂来控制营养液中微量营养元素的活性。HBED比EDDHA更昂贵，但这不应干扰HBED在植物营养研究中的使用。
HBED [N,N'‐di‐(2‐hydroxybenzoyl)‐ethylenediamine‐N,N'‐diacetic acid] was synthesized in 1967, but it only recently became available in the quantities needed for plant nutrition research. This chelator is a close relative of EDDHA, but has a Fe3+‐chelate formation or stability constant (at ionic strength, μ+0.1) of 39.68 compared to 33.91 for EDDHA. Even the Fe3+selectivity (i.e. Fe3+/Ca2+stability constant ratios) is greater for HBED than for EDDHA. These greater stabilities with Fe3+appear to result from better steric fit of HBED to Fe3+. FeHBED has Fe3+stability constant and Fe3/Fe2+and Fe3+/Ca2+stability constant ratios much lite the Fe3+selective bacterial siderophores.Soybean, corn, and nutsedge species were grown in complete Hoagland type nutrient solution containing 0 Fe, 10 μM FeHEDTA, 10 μM FeEDDHA (1:1 and 1:3 Fe:EDDHA ratios), or 10 μM FeHBED, and containing CaCO3to control pH at 7.5. Soybean and nutsedge species obtained adequate Fe and remained green, while corn was severely chlorotic on all treatments except FeHEDTA. The results show the extreme ability of non‐graminae plant roots to reduce Fe3+chelates and absorb iron in aerated solutions where Fe2+can not persist long after Fe3+chelates have been reduced. Nutsedge was found to be a typical Strategy‐1 species, unlike corn, even though theCyperaceaeandPoaceaeare placed together in the orderCyperalesby some taxonomic authorities.GEOCHEM, a computer program designed to calculate equilibria for chemical species in soil solutions, was adapted to nutrient solutions to allow comparison of HBED with EDTA, DTPA, and EDDHA. It now appears that previous attempts to speciate EDDHA nutrient solutions used incorrect formation constants for CuEDDHA chelate species. Using published formation constants, GEOCHEM indicated that Cu would displace Fe across a wide pH range, but that other elements do not displace Fe at practical nutrient solution pH. The greater Fe3+selectivity of HBED prevents Cu from displacing Fe from FeHBED. Chemical studies of Cu displacement of Fe from FeEDDHA at pH 5.5 (where the kinetics of Fe3+exchange allow the reaction to be studied) showed that the formation constant for CuEDCHA is about 22.3 (μ = 0.1 M), not 23.9 as previously estimated. Cu can displace Fe from EDDHA within the normal nutrient solution pH range.HBED has several advantages for use as an Fe‐chelator for nutrient solutions compared to EDDHA. EDDHA catalyzes oxidation of Mn2+and Co2+to strongly chelated Mn3+and Co3+species with unknown stability constants, but HBED does not. Thus, formation constants are available for nutrient elements with HBED, but not EDDHA. No element can displace Fe from FeHBED in practical nutrient solutions, but Cu can displace Fe from FeEDDHA. However, Fe in EDCHA is more easily available to plants than is Fe in FeHBED, probably because of stronger chelation of Fe2+by HBED. HBED provides a more predictable reagent to control activities of micronutrient elements in nutrient solutions than does EDDHA. HBED is more expensive than EDDHA, but this should not interfere with use of HBED in plant nutrition research.