Cytological studies of sporophytic and gametophytic generation of two bulbaceous species Ledebouria revoluta and Drimiopsis botryoides (Asparagaceae)

摘要

Detailed cytological characteristics of both sporophytic as well as gametophytic generation of two bulbaceous species, Ledebouria revoluta and Drimiopsis botryoides, were studied by investigating together pollen mitosis and root tip mitosis along with meiosis. A comparative study showed there was no significant difference between chromosome characteristics of haploid and diploid plants. The chromosome number of L. revoluta was 2n = 30 (in root tip) and n = 15 (in pollen) and that of D. botryoides was 2n = 66 (in root tip) and n = 33 (in pollen). Both genera have a monomodal chromosome with gradual decreases in size from the longest, 6.79 mu m, to the shortest, 1.50 mu m, in L. revoluta, and 9.65 to 1.55 mu m in D. botryoides. The karyotypic formula of L. revoluta was 20m + 10sm and D. botryoides was 30m + 14sm + 16 st + 6t. All the meiotic events were found to be normal in both genera and a clear 15 and 33 bivalents were observed in L. revoluta and D. botryoides accordingly. Very few meiotic abnormalities were observed in L. revoluta (about 2.4%); a comparatively higher percentage (nearly 7.9%) of abnormalities were observed in D. botryoides in the form of laggard, bridge, chromosome stickiness, early or late anaphasic movement, etc. However, the ultimate product of meiosis, i.e. microspores/pollens, are normal with an expected haploid chromosome number (n = 15 and 33 accordingly). Overall, L. revoluta is karyotypically less asymmetrical with a lower chromosome number than D. botryoides, indicating that D. botryoides is evolutionarily more advanced than L. revoluta.