The Meiotic Consequences of Radiation Induced Chromosome Breaks in Lathyrus sativus and Vicia ervilia

Abstract

Mature and dry seeds of L. sativus and V. ervilia were irradiated with 5, 10, 15, 20, 25, 30 and 50 Krad doses of gamma rays (Co⁶⁰) and M₁ and M₂ plants were grown along with the controls. Meiosis of both the generations were studied to detect and explain the types of chromosomal abnormalities produced at different stages of meiosis in the M₁ generation and that were subsequently still present in the meiosis of the M₂ generation. Meiosis in the control flowers of both the species was normal. The various types of abnormalities observed in the different stages of the Ml generation were as follows:
Diakinesis: heavy fragmentation of the nucleolus; metaphase I: univalents, tetravalents, multivalents, fragments, complex interchanges, rings, clumped and unusual configurations and unorientated chromatin material forming a large, round and darkly stained mass when a few of the bivalents aligned at the equatorial plate; anaphase I: abnormal separation of the homologues, single and double bridges with or without fragments, anaphase I with laggards only, unequal numbers of chromosomes going to the poles; anaphase II: single bridges with or without laggards, anaphase II with laggards only, unequal volumes of chromatin material in daughter nuclei, unequal pollen grains, fused or twin pollen grains and very small pollen grains.
In the M₂ generation, very few meiotic aberrations were observed in both the species. They were as follows in the different stages of meiosis; diakinesis: fragmentation of the nucleolus; metaphase I: complex interchanges and configurations, fragments, unorientated chromatin material; anaphase I: lagging chromosomes in anaphase I; anaphase II: laggards in anaphase II, and unequal volume of nuclear material in the daughter nuclei.