Raymond Handley

Translocation of 85Sr, 137Cs, and 106Ru in crop plants

The distribution of 85 Sr, 137 Cs, and 106 Ru between the root, the old growth and the new growth of bean, tomato, and corn was determined after incorporation of the isotopes into the plants via the roots. The results are compared with those obtained earlier in similar experiments using the xerophytic shrubs, Ceanothus and Adenostoma . As in the latter plants, almost all of the 106 Ru taken up by the crop plants was retained by the roots. Root retention of 85 Sr and 137 Cs was, however, much less in the crop plants. With respect to movement within the shoot (from old growth to new growth), 137 Cs was found in the crop plants as in the shrubs to be more mobile than 85 Sr. The difference in mobility was more pronounced in the crop plants. It is suggested that the relatively high mobility of foliarly applied 85 Sr found in the xerophytic shrubs may be related to their low transpiration rates. The low mobility of foliarly applied 137 Cs in these plants is ascribed to adsorption on or within the leaf cuticle.

Divalent cations and the permeability to Na of the root meristem ofZea Mays

SummaryCa and Sr markedly inhibit the non-metabolic uptake of Na by the nonvacuolated tissue of maize root tips. Loss of previously absorbed Na is also reduced greatly in the presence of these ions. The results obtained suggest that in the absence of metabolically mediated ion transport the plasmalemma, stabilized by Ca-ions, is normally almost impermeable to Na and perhaps other ions. Ca appears to be slightly more effective than Sr in this regard.

Sodium Chloride, Calcium Chloride, and the Respiration of Maize Root Sections

The effects of sodium chloride and calcium chloride at concentrations of 0.005N and 0.010N upon the respiration of vacuolated and nonvacuolated portions of the root tip of maize have been investigated. In both sections CaCl2 produced marked stimulation, while NaCl had no effect. In this tissue stimulation of respiration does not appear to be directly related to metabolic ion accumulation.

Translocation of carrier-free 85Sr, 137Cs, and 106Ru in woody plants.

Abstract Carrier-free solutions of 137 Cs and 106 Ru were applied to the foliage of three genera of woody shrubs ( Ceanothus, Adenostoma and Quercus ) and subsequent translocation into untreated portions of the plants was measured. In all cases the bulk of the retained dose remained with the directly treated material. The results indicate that in these genera foliarly applied 137 Cs is no more mobile than Sr while 106 Ru is considerably less mobile than either. In another series of experiments the distribution of 85 Sr, 137 Gs and 106 Ru between the root, the old growth and the new growth was determined after incorporation of the isotopes into Ceanothus and Adenostoma via their root systems. 137 Cs and especially 106 Ru were largely retained in the root. A relatively large fraction of the retained dose of 85 Sr was found in the shoot. In both series of experiments a preferential movement of 137 Cs into new growth was observed.

Translocation of carrier-free 85Sr applied to the foliage of woody plants*

Abstract Carrier-free 85Sr was applied to the foliage of three genera of woody forage plants (Ceanothus, Adenostoma and Quercus) and subsequent translocation into untreated portions of the plants was measured. Experiments were conducted in the field and in the greenhouse. In all cases the bulk of the retained dose remained with the directly treated material. However, substantial concentrations of 85Sr were found in the new growth arising on previously treated branches of Ceanothus and Adenostoma. The amounts translocated under field conditions under which plants were subject to periodic wetting and drying were greater than those translocated by plants in the greenhouse.

Uptake and translocation of Sr by Zea mays

The uptake of Sr by maize-root segments representing the whole root system is strongly temperature dependent but a large non-metabolic component apparently involving adsorption within the cell membranes is indicated. About 60 per cent of the Sr taken up under conditions permitting metabolism is resistant to elution. K in the ambient solution at a concentration amounting to 20 per cent of the Sr concentration essentially abolishes metabolic uptake. Non-metabolic Sr uptake is little affected by this K concentration. The inhibitory effect of Ca on Sr uptake is less than that of K and largely exerted on the non-metabolic phase. This inhibitory effect is countered to some degree by the ability of Ca to hinder the entry of Sr into the xylem and so its loss via the cut ends of the root segments. In whole-plant experiments K depressed root concentrations of Sr more than shoot concentrations indicating that the inhibition is exerted mainly at the tonoplasts of cortical cells. Ca had a smaller effect than K which was mainly evident in greater root retention of Sr.

Hardness of Maraglas as affected by solvent-monomer interaction.

Acetone and propene oxide were mixed with equal volumes of Maraglas epoxy embedding medium. Retention of these solvents in the resin after cure at 60 C was measured. The retention of propene oxide was greater than that of acetone and appeared to be due to a chemical interaction with the monomer. The reaction was catalysed by benzyldimethylamine. Although 3-4% of added acetone was retained, no evidence that this resulted from a chemical interaction was obtained. Vacuum evacuation of added solvents prior to cure did not materially affect their retention. Retention of both solvents resulted in softer cured resins.