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An extensive geographical survey was carried out to obtain information on the sodium and potassium content of topdressed grass-clover pastures in New Zealand. Results indicate that in many areas, especially away from the influence of sea spray, herbage sodium levels are below those estimated to be required by grazing animals. The associated potassium contents of these pastures, particulady in the North Island. are well in excess of animal needs and generally are more than adequate for plant nutrition. The possible effects on animal health of a low dietary intake of sodium coupled with excessive amounts of potassium are discussed. The importance of sources other than the plant in supplying sodium for animal needs is also pointed out. It is emphasised that there is an urgent need to assess fertiliser policy more in terms of the requirements of both plants and animals, by a plant analysis and balance sheet approach.

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The ability of the more important pasture and fodder plants grown in New Zealand to translocate sodium from their root systems into their leaf tissue was examined in a glasshouse pot experiment. Plants were classified into two distinct types: natrophilic plants, which have the capacity to accumulate large amounts of sodium in their shoots where adequate quilntities of sodium are present in the growth medium, but have low concentrations in their roots~ and natrophobic plants for which the converse is generally true. A further subdivision was made within both types, depending on the concentration of sodium in the lower stem or stubble tissue. The importance of this classification is discussed in relation to a nutritional problem which arises where natrophobic plants form a substantial part of the diet of grazing animals.

The effect of increasing concentrations of sodium chloride in the root zone on growth, chemical composition and nitrate reductase activity of perennial ryegrass and timothy was investigated in a glasshouse pot experiment. For ryegrass, a natrophile, sodium chloride had little effect on growth, whereas for timothy, a natrophobe, growth was severely depressed by comparatively low concentrations of salt. The result also indicate that translocation of sodium into the leaves of timothy took place readily only after the accumulation sites in the roots and lower stems had been saturated with this element. This means that relatively large quantities of sodium chloride were needed to produce concentrations of sodium in the leaves of timothy as high as those normally found in the leaves of ryegrass. Sodium chloride increased the uptake of total and nitrate‐nitrogen but, in contrast, depressed the uptake of potassium by ryegrass and timothy It was therefore concluded that the marked stimulation by sodium chloride of nitrate reductase activity in both species was more the result of the increased uptake of nitrates than a specific effect of this salt on the enzyme. The practical implications of these results are discussed.

Two independent cases of suspected occupational allergic contact dermatitis from tobacco are reported to illustrate the difficulties inherent in the accurate diagnosis of this condition. An investigatory procedure is outlined whereby the comparatively rare cases of genuine contact sensitivity to tobacco can be distinguished from other commoner dermatoses.

A study of transpiration rates, and of uptake and translocation of sodium and potassium, has supported a previous classification made for certain pasture and fodder species. The plants termed natrophiles were found to have relatively high transpiration rates and to translocate relatively large amounts of absorbed sodium from root systems into leaves. Plants termed natrophobes had lower transpiration rates and translocated less sodium from roots to leaves. In contrast, potassium was readily translocated by both natrophiles and natrophobes; consequently, compared with natrophobes, natrophiles had low K/Na ratios in their leaves. In general, transpiration rate was less associated with absorption of sodium by roots than with translocation of sodium from roots to aerial parts. The practical and ecological implications of these results are discussed.