Abstract-Lead, cadmium, arsenic, and zinc were quantified in mine wastes and in soils mixed with mine wastes. Metal concentrations were found to be heterogeneous in the wastes. Iceberg lettuce, Cherry Belle radishes, Roma bush beans, and Better Boy tomatoes were cultivated in mine wastes and in waste-amended soils. Lettuce and radishes had 100% survival in the 100% mine waste treatments compared to 0% and 25% survival for tomatoes and beans, respectively. Metal concentrations were determined in plant tissues to determine uptake and distribution of metals in the edible plant parts. Individual soil samples were collected beneath each plant to assess metal content in the immediate plant environment. This analysis verified heterogeneous metal content of the mine wastes. The four plant species effectively accumulated and translocated lead, cadmium, arsenic, and zinc. Tomato and bean plants contained the four metals mainly in the roots, and little was translocated to the fruits. Radish roots accumulated less metals compared to the leaves, whereas lettuce roots and leaves accumulated similar concentrations of the four metals. Lettuce leaves and radish roots accumulated significantly more metals than bean and tomato fruits. This accumulation pattern suggests that consumption of lettuce leaves or radish roots from plants grown in mine wastes would pose greater risks to humans and wildlife than would consumption of beans or tomatoes grown in the same area. The potential risk may be mitigated somewhat in humans, as vegetables grown in mine wastes exhibited stunted growth and chlorosis.

Summary Diurnal variation in the water balance of 2–3 year Pinus sylvestris in pots has been compared at four levels of soil moisture during 24 hours. The physical component of the soil moisture suction was measured with tensiometers and gravimetric gypsum blocks and estimated as o.1, 0.5, 1–2 and >5 atmospheres for the four levels. Leaf water deficit was expressed as a percentage of the water at turgidity, transpiration as the loss in fresh weight of a leaf sample during 1–11 minutes after cutting, and stomatal opening was measured by infiltration with alcoholic gentian violet. Increase in soil moisture tension caused a progressive increase in leaf water deficit, and a decrease in transpiration and stomatal opening, the latter being reduced both in number of open stomata and in the time for which they remained open during the day. The relative value of these measurements as indices of plant water balance and of soil moisture conditions is discussed together with a brief consideration of the relation between transpiration rate and soil moisture. It is concluded that leaf water deficit, transpiration and stomatal opening all reflect increase in soil moisture suction but that, during the day, they are affected also by other factors which obscure the direct effect of soil moisture. However, in the case of leaf water deficit an equilibrium is attained between plant and soil before sunrise. If measured in the morning, before the onset of stomatal transpiration, leaf water deficit appears to be closely related to the soil moisture conditions experienced by the plant. This measurement is suggested as the best plant index of the soil moisture suction in the vicinity of the roots. The persistence of appreciable deficits in wet, drained soil indicates that factors other than the physical soil moisture tension oppose water uptake.

Summary Experiments were carried out in which pots with 3–5 year old plants of Pinus sylvestris were allowed to dry from field capacity to soil water tensions of 5 atm. or more, while measurements of soil moisture tension, leaf water deficit and transpiration rate were made daily at sunrise and noon. By fitting multiple regressions it was shown that most of the variation in the leaf water deficit could be accounted for by changes in soil moisture tension and transpiration rate. The conclusion reached in earlier work was confirmed by these experiments, namely that the leaf water deficit at sunrise is the best index of the soil moisture conditions experienced by the plant, since effects of transpiration are negligible at this time. The effect of various factors on the relation between soil moisture tension and leaf water deficit was experimentally examined. It was found that the relation was affected by the age of needles used for the determination, by the time of year, by nitrogen nutrition, and by soil moisture conditions prior to the experimental run. The way in which these factors may operate is discussed. Despite the variability in the relation examined, broad conclusions as to the soil moisture tension experienced by young plants of this species may be drawn from measurements of leaf water deficit made on 1‐year old leaves at sunrise. Thus in soils near field capacity, leaf water deficits rarely exceed 8 per cent. Deficits of 12–14 per cent indicate soil moisture tensions in the 1–5 atm. range, and when the deficits rise above 17 per cent, the soil moisture has probably been reduced to the permanent wilting percentage.

No abstract