Abstract

Stanleya pinnata has been identified as an indicator plant for seleniferous soils. The apparent limitation of its distribution to seleniferous soils suggests that selenium may play an essential role in this species. This study is a preliminary investigation of the role of selenium to Stanleya pinnata. When fully ripe, seeds germinated readily. Concentrations of selenium of 100 parts per million and 1000 parts per million retarded germination. Seeds germiuated in lower concentrations were not affected which was probably due to the selenium content of the seed itself, being greater than in the germinating media. Stanleya pinnata plants were grown from seeds from which seedlings were transplanted to two-liter Pyrex beakers containing Hoagland's nutrient solution except lacking sulfur. The plants were grown in three lots. Sulfur (as magnesium sulfate) and selenium (as sodium selenate) were varied inversely in lot A as follows: 80 ppm. sulfur and .0001 ppm. selenium; .01 ppm. sulfur and .01 selenium, .001 ppm. sulfur and 10 ppm. selenium; .0001 ppm. sulfur and 25 ppm. selenium. Lot B contained Hoagland's complete nutrient solution with additions of selenium in the following amounts: .0001 ppm.; .01 ppm.; 10 ppm.; 25 ppm. Lot C contained Hoagland's nutrient solution except for a sulfur variation which was identical to lot A. Magnesium chloride was added to pots of lots A and C to replenish the deficiency of magnesium. After eighteen weeks (October 30, 1956 to March 6; 1957) of growing the experimental plants in the greenhouse, the plants were all harvested. Fresh and dry weights were determined for roots and tops. The roots and tops were oven dried and subsequently analyzed for selenium content by spectrophotometry. Results indicate that selenium was stimulating to the growth of the plants which were grown in solutions with a sulfur concentration of 80 ppm. and a selenium concentration of 10 ppm. With a sulfur concentration of .01 ppm. or below and selenium concentration of 10 ppm. and above, selenium considerably inhibited the growth of Stanleya pinnata. The growing time in this investigation was insufficient to allow completion of a life cycle, therefore, determination of the essentiality of selenium for normal growth and development of Stanleza pinnata is not conclusive. It was found that the uptake of selenium by the plant was greater when the concentration of sulfur in the solution media was 80 ppm. and selenium concentration was 10 ppm. This suggests that a further increase in sulfur concentration may allow a greater uptake of selenium.

Degree

College and Department

Life Sciences; Plant and Wildlife Sciences

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