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OBSERVATIONS ON MEIOSIS IN THREE CYTOTYPES OF BETULA ALBA L.
Author(s) -
BROWN IAN R.,
ALDAWOODY DAWOOD
Publication year - 1979
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1979.tb02311.x
Subject(s) - meiosis , biology , botany , ploidy , chromosomal translocation , chromosome , metaphase , cytogenetics , genetics , gene
S ummary Meiosis was studied in three birch cytotypes; B. pendula 2 n = 28, B. pubescens 2 n = 56 and a type with the intermediate chromosome number 2 n = 42. Meiosis was similar in B. pendula and B. pubescens and a similar range and frequency of abnormalities was found. In relation to both types there was strong circumstantial evidence that x = 7 rather than x = 14, which is commonly accepted. In addition it was also shown that in B. pubescens there exists means of producing aneuploid gametes. Meiosis in 2 n = 42 trees differed greatly from that in 2 n = 28 and 2 n = 56 trees. Many cells contained coalesced masses of chromatin and could not be analysed. Those that were studied showed a much greater frequency of abnormality than that found in the other two cytotypes. Surprisingly, around 50 % of analysable cells showed 21:21 distribution of chromosomes at metaphase II. Although the origin of these trees is unknown it is suggested that they are not triploids but hexaploids, i.e. x = n = 7.