The first leaf of barley seedlings—III. Use as a radiobiological test system after gamma irradiation of caryopses

Abstract

Barley caryopses were exposed to gamma radiation and effects were studied on the ontogenesis and growth of the first leaf in order to examine the conditions in which it can be used as a radiobiological test of the mutagenic effectiveness of seed treatments. The effects on cell elongation were found to be independent of the effects on cell division. The blade, which already exists in the caryopsis, is affected differently from the sheath, which is initiated at germination. The doses (D) resulting in a 50% reduction in the first leaf height do not depend on the growth stage at which the leaf is measured. Above D 50, however, measurements during the growing cycle tend to minimize irradiation effects due to the retarded growth and smaller proportion of sheath. For determining the significance of results and greater ease of observation, it is preferable to measure the first leaf when it has stopped growing. This stage is reached when the second leaf extends beyond the first leaf.