A Cytogenetic Study of Clarkia unguiculata. II. Supernumerary Chromosomes

Aneuploidy inBothriochloaHybrids

“…With respect to size, morphology and heterochromacity, extra chromosomes, in most cases are easily identified, morphologically from the chromosomes of the normal complement. HAKANssoN (1949), VASEK (1956), andMOORING (1960) however, discussed aneuploid plants where these chromosomes do not differ in size from those of the normal set. ln polyploid species, aneuploid plants with one or a few chromosomes missing, or present in excess, usually do not show any significant gross morphological variations from the normal plants.…”

“…BosEMARK (1956,1957) suggests a correlation between aneuploid plants of some grasses and edaphic factors. MOORING (1960) speculates that aneuploids in Clarkia unguiculata are related to ecological and marginal populations and help the species to tolerate extremes of environmental conditions. In Old World species of Bothriochloa the reason for the rare incidence of aneuploids appears to be in their apomictic mode of reproduction.…”

Occurrence and Meiotic Behaviour of B Chromosomes in <i>Digitaria</i>

“…Muntzing (1948) in Poa alpina andBosemark (1956) in Festuca pratensis have discussed in detail the significance of B chromosomes in the adaptive mechanism of the plants. Mooring (1960) has reported in Clerkia highest frequencies of supernumeraries in ecologically marginal populations which would allow the extremes of various environmental factors. Shambulingappa (1965) has suggested the possibility of a similar occurrence in the genus Clematis.…”

“…B chromosomes are generally smaller than the smallest chromo some of the regular complement (Shambulingappa 1965). However, there are cases as in Clerkia (Mooring 1960) The vegetative samples of these accessions were obtained from the U. S. D. A., about 3-4 years ago, and have been maintained in pots. The spikes for cytological investigations were fixed for 24 hours or more in 3 parts of alcohol and 1 part of propionic acid, the latter having been previously saturated with ferric acetate (Swaminathan et al 1954).…”

Supernumerary Chromosomes in some Grasses

“…Few other instances of association of supernumerary chromosomes with inherited characteristics have also been published recently: JACKSON (1960) and JACKSON and NEWMARK (1960) have found pigment production in the achene walls of Haplopappus gracilis to be dependent on the number (1 to 4) of supernumerary present;and MooRING (1960) has suggested that supernumerary chromosomes of Clarkia unguiculata are " components of polygenic systems which increase tolerance to environmental extremes ».…”