Stronium Mobility in Germinating Seeds and Plants

Abstract

Abstract. The uptake of strontium in the bean plant (Phaseolus vulgaris) was linear for the first 34 hr during continuous exposure to radiostrontium. After 35 hr there was a sharp increase in the rate of uptake to 48 hr. Radioactivity could be detected in the plant as early as 1 hr after addition of radiostrontium to the growth medium.Seventy-five percent of the radiostrontium was located in the seed coat immediately after soaking bean seed in an 59Sr solution. This radioactivity in the seed coat decreased rapidly up to the tenth day, while the proportion of stkontium in the cotyledons increased, after which time the proportion of radiostrontium in the cotyledons began to decrease. The amount of radioactivity of the seedling axis increased constantly, as did the activity of the first and second leaves after their appearance on about the seventh day.The radioactivity in the developing third and fourth leaves of ootton plants (Gossypium hirsutum) increased at the expense of the radioactivity in the first 2 leaves and stems. This represents a movement into certain parts and then a retranslocation out of these parts as other tissue begins to develop.Sources of radioactivity whiclh represent potential internal radiation hazards to animals include fallout following explosions of atomic weapons, or industrial accidents resulting in contamination of feed, plant life or water which is destined for animal consumption.Since strontium meets with no great difficultv in gaining entrance into the plant, the question of transport within the plant becomes important. When once delivered to a particular organ in the plant, calcium becomes largely immobile (1). Strontium also behaves in the same way (2). There are some conditions, however, under which calcium does become mobile in plant tissue (3). For example, during the germination of the bean seed, calcium present in the cotyledons becomes distributed throughout the root, hypocotyl, and primary leaves. During the growth of tulip bulbs, calcium moves from the bulb into the growing leaves (4). The (6). and these data were calculated by the computer method of Creger et al. (7), which extrapolates activity 'to the time of original application of the isotope to the plant.For the first phase of this investigation, the objective was to determine the rate of uptake of strontium bv bean seedlings. Bean seeds were germinated in paper towels and allowed to grow in a liquid culture solution until 10 days old. The plants were then transferred to 10 ml of identical culture solution that contained 1 /Ic 89Sr per ml (no cold Sr was added). At certain time intervals plants were removed, washed twice with 1 % EDTA and once with deionized water, separated into tops and roots, and analyzed for radiostrontium. Five plants were analyzed at each interval up to 48 hr.For the second phase of this investigationi, bean seeds were soaked for 24 hr in a culture solution containing 10 Mc 89Sr per ml. The seeds were then removed from the solution, washed twice with I % EDTA and once with deionized water an...