An Fe‐inefficient tomato mutant, T3238fe (Lycopersicon esculentum) was identified by growing the plants in solution cultures containing different concentrations of FeHEDTA. Approach grafts of T3238Fe (Fe‐efficient) top on T3238fe rootstock and vice versa, located the cause of Fe inefficiency in T3238fe roots. The T3238Fe tomato takes up more Fe than T3238fe and it responds favorably to Fe‐stress by releasing hydrogen ions from its roots, increasing reduction of Fe3+ to Fe2+ at its roots, and increasing the citrate concentration in its roots. T3238fe showed very little response to Fe stress; it was unable to absorb and transport adequate Fe from PeEDDHA to support growth.

T3238fer (Fe-inefficient) and T3238FER (Fe-efficient) tomato plants differ in their ability to utilize Fe and therefore can be used as test genotypes to locate sites of Fe uptake or to characterize changes that occur in roots in response to Fe stress (Fe deficiency). T3238fer does not respond to Fe stress. Release of hydrogen ions and reduction of Fe^+ to Fe^+ are two primary responses of T3238FER roots to Fe stress. Fe reduction sites were predominately in the young lateral roots, and between the regions of root elongation and maturation of the primary root. The use of BDPS (bathophenanthrolinedisulfonate) to trap Fe^+ did not affect the release of H+ ions or reduction by T3238FER roots. BPDS did not decrease Fe uptake until it exceeded the Fe concentration in the nutrient solution. A sevenfold increase in BPDS caused a threefold decrease in Fe taken up by the plant. Fe^+ is reduced to Fe^+ at root sites accessible to BPDS. Adding Zn decreased the response to Fe stress.Iron stress initiates the development of lateral roots, and we propose that most Fe enters the plant through these roots. The iron moves through protoxylem into the metaxylem of the primary root and then to the top of the plant as Fe citrate. Root environmental factors that are competitive or inhibit Fe-stress response, or genotypes that fail to respond to Fe stress, contribute to the development of Fe deficiency in plants.

SummaryThe effects of the newly available biotechnology product, recombinant desulphatohirudin (CGP 39393) have been investigated in rats. This highly potent and selective thrombin inhibitor exhibited marked anticoagulant properties with controllable titration of anticoagulant effect, as measured by activated partial thromboplastin time (APTT), up to nearly four times control values. Furthermore, CGP 39393 exhibited impressive antithrombotic activity in vivo. In an arteriovenous shunt model of thrombus formation on a cotton-thread, the compound was capable of complete inhibition of thrombus development (ED50 = 0.3 mg/kg i.v. and 1.0 mg/kg s.c.). Venous stasis thrombosis was also highly susceptible to inhibition by CGP 39393 (ED50 = 0.01 mg/kg i.v. and 0.45 mg/kg s.c.). Comparison of the anticoagulant and antithrombotic activities of the compound shows that potent antithrombotic effects (83-97% inhibition in the rat shunt model) are achieved within the generally acceptable range of anticoagulation. These results suggest a clear potential for this new agent in the clinical treatment of thrombotic disease.

Iron‐stressed (deficient) ‘Hawkeye’ (HA) releases more “reductant” into nutrient solutions than PI‐54619‐5‐1 (PI) soybean [Glycine max (L.) Merrill] roots. These two plants differ in their response to Fe stress and their susceptibility to Fe chlorosis. The objective of this study was to characterize the “reductant” and to determine its role in the uptake of Fe by HA and PI soybeans. Reducing capacity of the ‘reductant’ was determined by its ability to reduce ferric to ferrous iron. Fe2+ was measured using 2,4,6,‐tripyrldyl‐s‐triazine (TPTZ) to form the color complex Fe2+(TPTZ)2. The reductant compounds were separated using paper chromatography (BAW‐4:1:5) and located on the paper as prussian blue spots after the papers were placed in ferricyanide‐ferrichloride solutions. Reductant from 16 HA reduced 90 μmoles (Fe3+ to Fe2+) compared to 5 μmoles for PI soybeans. The chelating agents HEDTA and DTPA (3 μmoles) decreased the reducing capacity from 1.8 μumoles Fe2+/ml concentrated reductant to 0.2 μmoles/ml. Adding more reductant partially overcome the interfering effects of the chelating agents. Adding the concentrated reductant to nutrient solutions increased the amount of Fe~+ iron in solution, but it did not increase the uptake of Fe by the plant. Something other than reductant in nutrient solution appears to be the controlling factor in the uptake of Fe by PI and HA soybeans. We believe the reductant can aid in releasing Fe from chelating agents to the root and that it can maintain Fe2+ in the reduced state in the root. The latter may be its more important role in Fe nutrition.