作 者 ：Hong De-Yuan
期 刊 ：植物分类学报 1984年 4期
Keywords:Medicago,
Abstract:
Meiosis and/or mitosis of six species of Fabaceae (Leguminosae) from
Baoxing County, Sichuan, China, were investigated. The voucher specimens are con-
served in PE. Eight pairs (n=8) and 10 chiasmata in meiosis of pollen mother cells
have been observed in Medicago lupulina L. (Pl. 1, A-C). Meiotic observation on
pollen mother cells in Lotus tenuis W. et K. shows 6 bivalents (n=6) in MI and 9 chias-
mata in diakinesis (Pl. 1, D-E). In this species 12 somatic chromosomes (2n=12) in
anther wall cells have also been observed. The chromosomal formula may be expressed
as 2n=12=8m+2sm+2smSAT (Pl. 1, F-G). In pollen mother cells of Vicia tetrasperma
(L.) Schreb., 7 bivalents in MI and 7 chromosomes in A II have been observed (Pl. 2,
A-B). From A II (Pl. 2, B, the inset on the right) the chromosomal formula, n=7=
2m+2sm+lstSAT+2t, may be constructed. Only three chromosomes in this karyotype may
be found to have counterparts in the one reported by Srivastava (1963), which shows
striking differences between these two karyotypes. Meiotic MI shows 7 pairs (n=7)
in Vicia hirsuta (L.) S. F. Gray. Vicia sativa L. is very variable in its chromosomes.
Our observation shows 6 pairs (n=6) in MI and in diakinesis in pollen mother cells.
In Vicia villosa Roth, all the previous chromosome reports are 2n=14 or n=7, but the
result of our work shows that somatic chromosomes are 2n=12 in anther wall cells
(Pl. 3, D, E). The karyotype in our material (Pl. 3, E) is that the longest pair of chro-
mosomes are metacentric, the pairs 2-4 are terminal, 5 are metacentric and last pair
are submetacentric, differing vastly from the idiogram (Pl. 3, F) presented by Yama-
moto (1973). Therefore both the chromosome number and structure in our material
are greatly different from those in all the previous reports.
The evolutionary trends of chromosomes in the genus Vicia is discussed in the
work. Srivastava (1963) holds that the primitive basic number of chromosome in the
genus is 6 and thus both 5 and 7 are derived. The present author would propose ano-
ther possibility that 7 is the original basic number and the other numbers are derived
ones. First, as shown in Table 1, x=7 occurs in 47 per cent of species in the genus,
but 6 only in 28 per cent. Secondly, x=7 is predominant in the perennial and primitive
section Cracca. Thirdly, in genera related to the genus under consideration, such as
Lens, Pisum and Lathyrus, x=7 is also the predominant basic number. Fourthly, ac-
cording to Raven (1975) 7 is the primitive basic number in the angiosperms and x=
7, 8 and 9 are the predominant in the angiosperms.