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.

shading to favor stem elongation. Seven-day-old plants, with stems 10 to 15 cm long, were grouped in two 15-plant bundles per 10-liter Pyrex jar. The nutrient solution volume, unless specified otherwise, was 8 liters. Mild iron deficiency symptoms appeared in the new growth of the plants on the 17th day. Plants were used ("harvested") on the 18th day of growth.For stem exudate collection, roots were washed briefly with deionized water, and the bundled plant groups were placed individually in 1-liter beakers of aerated nutrient solution. Plant tops were decapitated 10 cm above the roots, and the ends of the cut stems were placed in half-inch Tygon tubing which extended into a calibrated tube in an ice bath. Exudate was collected over a 20-hr period in the dark at 24 C.Cation Isotopes and Assays. In certain experiments, 59Fe (7.3 c/g Fe) or 65Zn (3.94 c/g Zn) was used in nutrient solutions at 10 juc/l as 59FeEDDHA and 65Zn(NO3)2, respectively. Radioassay of 65Zn, in nutrient solution, was made in a gamma scintillation spectrometer. In stem exudate, total iron and zinc were determined spectrophotometrically by the o-phenanthroline method (11), and by atomic absorption analysis, respectively.Expressed root sap was obtained from 10 g of previously frozen roots. A Carver press was used at 844 kg/cm2 pressure to express the sap.Experiments. Preliminary experiments were done with various concentrations of zinc to determine its effect upon the translocation of iron. From these studies, 5 ,UM Zn was selected to be used in these studies.1. Uptake of Zinc with Time. Five micromoles of 65Zn (10 ,uc/l) were added to the nutrient solution 96 hr before plants were 18 days old. At selected times, 1-ml volumes of the 1-liter nutrient solution were analyzed for 65Zn and returned to the solution. Effect of Pretreatment with

Reduction of iron (Fe3+ → Fe2+) at the root of Glycine max. (L.) Merrill var. Hawkeye soybean was studied to identify areas of reduction in the root. Sites of iron reduction were indicated by the formation of a Prussian or Turnbull's blue precipitate. This blue precipitate formed whenever the iron in either FeEDDHA or potassium ferricyanide was reduced by the plant. Where FeEDDHA and potassium ferricyanide were supplied together in the nutrient solution, a blue precipitate appeared in epidermal areas. This precipitate appeared in the endodermal areas of the root when FeEDDHA was supplied to the plant 20 hours before placing them in a ferricyanide solution. Reduction was most pronounced between the regions of root elongation and root maturation at both the epidermis and the endodermis. Reducing capacity was greatest in the young lateral diarch roots indicating that these roots contribute significantly to the ability of the plant to take up iron. A reductant which exuded from the roots of an irondeficient plant was capable of reducing approximately 360 µg of inorganic iron. The ability of some plants to reduce iron may partially explain why they can obtain iron from synthetic chelates and can utilize iron in calcareous soils more effectively than other plants.

Two navy beans (Phaseolus vulgaris L.) varieties, ‘Sanilac’ and ‘Saginaw,’ were grown in soil, solution culture, and split medium. Plant growth and Fe, P, and Zn uptake were compared with differential Zn deficiency in each of the three media. In general, Fe and P aggravated Zn deficiency. Differential absorption of Fe and P by the two varieties appears to be the cause of differential susceptibility to Zn deficiency. Sanilac took up more Fe and P than Saginaw in a growth medium relatively low in Zn.

The influence of UV‐B radiation from filtered or unfiltered fluorescent sunlamps on early seedling growth and translocation of 65Zn from cotyledons to the shoot was examined in two cultivars of cotton, Acala and Gregg. Ten‐day‐old seedlings which had been irradiated in the greenhouse for 6 h continuously each day for 14 days with 0.81 or 1.61 W × m‐2 UV‐B radiation under two unfiltered FS‐40 sunlamps, showed pronounced phytotoxic damage. This was characterized at first by bronzing and glazing of the cotyledons and later by upward curling of the leaves and abscission. Leaf expansion, dry matter accumulation, and mobilization of 65Zn from the cotyledons was severely impaired in the young developing shoot under unfiltered UV‐B radiation. A significant stress response also was observed in seedlings exposed to 0.61 W × m‐2 UV‐B radiation through a polystyrene filter and 0.73 W × m‐2 UV‐B radiation through a cellulose‐acetate filter. This stress response was characterized by the formation of a red pigment in the petioles of the cotyledons, reduced leaf expansion, and reduced transport of 65Zn. Control seedlings exposed to 0.03 W × m‐2 UV‐B radiation through a mylar filter were green, had maximum leaf size and dry‐matter accumulation, and had the greatest percentage of 65Zn translocated from the cotyledons.