Rates of Cuticular Penetration of Chelated FeIII: Role of Humidity, Concentration, Adjuvants, Temperature, and Type of Chelate
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- 作者：Jö ; rg Schö ; nherr ; Victoria Ferná ; ndez ; and Lukas Schreiber
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2005
- 出版时间：June 1, 2005
- 年：2005
- 卷：53
- 期：11
- 页码：4484 - 4492
- 全文大小：143K
- 年卷期：v.53,no.11(June 1, 2005)
- ISSN：1520-5118
文摘
Time courses of cuticular penetration of FeCl3 and FeIII complexes of citric acid, EDTA, EDDHA(Sequestrene 138Fe), imidodisuccinic acid (IDHA), and ligninsulfonic acid (Natrel) were studied usingastomatous cuticular membranes (CMs) isolated from Populus x canescens leaves. At 100% relativehumidity, the FeIII chelates disappeared exponentially with time from the surface of the CMs; that is,penetration was a first-order process that can be described using rate constants or half-times ofpenetration (t1/2). Half-times ranged from 20 to 30 h. At 90% humidity, penetration rates wereinsignificant with the exception of Natrel, for which t1/2 amounted to 58 h. Rate constants wereindependent of temperature (15, 25, and 35 
C). Permeability decreased with increasing Fe chelateconcentration (IDHA and EDTA). At 100% humidity, half-times measured with FeIDHA were 11 h (2mmol L-1), 17 h (10 mmol L-1) and 36 h (20 mmol L-1), respectively. In the presence of FeEDTA,penetration of CaCl2 was slowed greatly. Half-times for penetration of CaCl2, which were 1.9 h in theabsence of FeEDTA, rose to 3.12 h in the presence of an equimolar concentration of EDTA and 13.3h when the FeEDTA concentration was doubled. Hence, Fe chelates reduced permeability of CMsto CaCl2 and to the Fe chelates themselves. It is suggested that Fe chelates reduced the size ofaqueous pores. This view is supported by the fact that rate constants for calcium salts were about 5times higher than for Fe chelates with the same molecular weights. Adding Tween 20 (5 g L-1) as ahumectant did not increase permeability to FeIDHA at 90% humidity and below, while addition ofglycine betaine did. Penetration of FeCl3 applied at 5 g L-1 (pH 1.5) was not a first order process asrate constants decreased rapidly with time. Only 2% of the dose penetrated during the first 2 h andless than that in the subsequent 8 h. Recovery was only 70%. This was attributed to the formationof insoluble Fe hydroxide precipitates on CMs. These results explain why in the past foliar applicationof Fe compounds had limited success. Inorganic Fe salts are instable and phytotoxic because of lowpH, while Fe chelates penetrate slowly and 100% humidity is required for significant penetrationrates. Concentrations as low as reasonably possible should be used. These physical facts are expectedto apply to stomatous leaf surfaces as well, but absolute rates probably depend on leaf age andplant species. High humidity in stagnant air layers may favor penetration rates across stomatous leafsurfaces when humidity in bulk air is below 100%.Keywords: Iron chlorosis; foliar nutrition; EDTA; EDDHA; IDHA; Natrel; Sequestrene 138Fe
C). Permeability decreased with increasing Fe chelateconcentration (IDHA and EDTA). At 100% humidity, half-times measured with FeIDHA were 11 h (2mmol L-1), 17 h (10 mmol L-1) and 36 h (20 mmol L-1), respectively. In the presence of FeEDTA,penetration of CaCl2 was slowed greatly. Half-times for penetration of CaCl2, which were 1.9 h in theabsence of FeEDTA, rose to 3.12 h in the presence of an equimolar concentration of EDTA and 13.3h when the FeEDTA concentration was doubled. Hence, Fe chelates reduced permeability of CMsto CaCl2 and to the Fe chelates themselves. It is suggested that Fe chelates reduced the size ofaqueous pores. This view is supported by the fact that rate constants for calcium salts were about 5times higher than for Fe chelates with the same molecular weights. Adding Tween 20 (5 g L-1) as ahumectant did not increase permeability to FeIDHA at 90% humidity and below, while addition ofglycine betaine did. Penetration of FeCl3 applied at 5 g L-1 (pH 1.5) was not a first order process asrate constants decreased rapidly with time. Only 2% of the dose penetrated during the first 2 h andless than that in the subsequent 8 h. Recovery was only 70%. This was attributed to the formationof insoluble Fe hydroxide precipitates on CMs. These results explain why in the past foliar applicationof Fe compounds had limited success. Inorganic Fe salts are instable and phytotoxic because of lowpH, while Fe chelates penetrate slowly and 100% humidity is required for significant penetrationrates. Concentrations as low as reasonably possible should be used. These physical facts are expectedto apply to stomatous leaf surfaces as well, but absolute rates probably depend on leaf age andplant species. High humidity in stagnant air layers may favor penetration rates across stomatous leafsurfaces when humidity in bulk air is below 100%.Keywords: Iron chlorosis; foliar nutrition; EDTA; EDDHA; IDHA; Natrel; Sequestrene 138Fe© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |