ASPECTS OF THE MECHANISM OF COLCHICINE RESPONSE IN ALLIUM CEPA AND LUZULA PURPUREA. I. CYTOLOGY AND 3H-COLCHICINE AUTORADIOGRAPHY

Abstract

Luzula purpurea, a plant with holokinetic chromosomes, has a colchicine response different from that of most plants, typified by Allium cepa. Following short treatments with colchicine concentrations of 10−4 to 10−3M, dividing cells of Luzula continue to higher ploidy levels and do not return to normal mitosis even after 72 hr recovery. This repeated arrest and reversion to interphase with subsequent doubling of chromosome number is opposed to the situation in most plants, which return to normal mitosis, with some tetraploid figures, after several hours in water. Luzula, labeled for short periods with 1.25 × 10−3M 3H-colchicine and placed in water to recover, shows autoradiographically detectable label retained within the cells up to 72 hr after treatment. The silver grains are found over cytoplasm and developing xylem elements. These are areas containing microtubules, the subunit protein of which, in animal systems, has been shown to bind colchicine. Allium treated with 3H-colchicine does not retain label after recovery periods, a result consistent with the observed rapid cytological recovery.