On the Systematic Significance of Floral Organogenesis in Saururaceae

Liang Han-xing

Received:1900-01-01 Revised:1900-01-01 Online:1994-09-18 Published:1994-09-18

Abstract:

The sequence of organ initiation and the change in number and position of sta-

mens and carpels are compared among the four genera in the Saururaceae in this paper. Sev-

eral evolutionary trends of organogenesis are revealed and summarized as follows:

The first trend is that the first appearance of stamens and carpels converts from the me-

dian sagittal ones to the lateral ones. In Saururus the median sagittal stamens and carpels all

appear first, while in Gymnotheca the median posterior stamen arises first, the lateral pair

second, the median anterior one third, and the lateral carpels appear first. In Anemopsis and

Houttuynia the lateral stamens have changed to arising first. The second trend is the conver-

sion of initiation of stamens and carpels from the median sagittal ones in pair as in Saururus

to singular, acompanied by delayed development in Gymnotheca and to final degeneration of

the anterior stamen and carpel in Anemopsis and Houttuynia. The latter two genera have a

pair or only one stamen at the posterior position, but during early development there is a gap

as a trace of degenerating stamen at the anterior position. Moreover, in Gymnotheca with

four carpels, a gap exists at the anterior position, which is the place of the delayed anterior

carpel; in the genera with three carpels, a gap is present at the anterior position in Anemop-

sis, but absent in Houttuynia. The other trends involve the change of the two lateral stamens

from separate initiation in Saururus to initiation from a common primordium in Gymnotheca

and Anemopsis and to reduction of one stamen in Houttuynia; the conversion of single poste-

rior stamen to a pair from a common primordium in Anemopsis; the change of initiation of

three carpels from separate primordia in Anemopsis to from a ring primordium in Houttuyni-

a. The facts seem to show that the genus Houttuynia is more advansed than Anemopsis. The

evolutionary trends of flowers in the Saururaceae can be explaned as the results of fusion, re-

duction and multiplication. The systematic relationships among the four genera were inferred

in a diagram.

Key words: Saururaceae, floral organogenesis, systematic significance

Liang Han-xing. On the Systematic Significance of Floral Organogenesis in Saururaceae[J]. .

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