02748nas a2200313 4500008004100000245008200041210006900123300001200192490000700204520181600211653001302027653002202040653001902062653002802081653001802109653001802127653001302145653001902158653001502177100001802192700002302210700002202233700001702255700001302272700002302285700002202308700001702330856008702347 2006 eng d00aPerianth development in the basal monocot Triglochin maritima (Juncaginaceae)0 aPerianth development in the basal monocot Triglochin maritima Ju a107-1250 v223 a

Basal monocots exhibit considerable variation in inflorescence and floral structure. In some cases, such as Triglochin maritima, it is not clear whether the lateral and terminal structures of the inflorescence are flowers or pseudanthia, or where the limits between flowers and inflorescence lie. To address these questions, morphological studies were carried out, and the results show that in T. maritima both terminal and lateral structures are flowers, not pseudanthia. The terminal flower of T. maritima develops from the apical inflorescence meristem, suggesting that the apical meristem identity changes from ‘‘inflorescence’’ to ‘‘flower’’ during inflorescence development. In addition, distal flowers of T. maritima are reduced, and there is no distinct flower-subtending bract; instead, the perianth develops unidirectionally, resulting in an abaxial-median bract-like tepal and bilaterally symmetrical flowers, similar to those of other basal monocots, such as Aponogeton and Acorus. It is possible that the leaf primordium changes its positional homology from ‘‘flower-subtending bract’’ to ‘‘tepal.’’ Therefore, in some basal angiosperms with abbreviated development of lateral flowers the demarcation of the flower vs. the inflorescence is ontogenetically ambiguous. In situ hybridization experiments show that a putative ortholog of the B-class gene APETALA3 / DEFICIENS is expressed in developing stamens and carpels, and may also be expressed in the shoot axis of the very young inflorescence. This expression pattern seems to be consistent with the gradual transition between inflorescence and flower that was observed morphologically.

10aAPETALA310abasal angiosperms10afading borders10agene expression pattern10aJuncaginaceae10aMADS-box gene10amonocots10aorgan identity10aTriglochin1 aBuzgo, Matyas1 aSoltis, Douglas, E1 aSoltis, Pamela, S1 aKim, Sangtae1 aMa, Hong1 aHauser, Bernard, A1 aLeebens-Mack, Jim1 aJohansen, Bo uhttp://curis.ku.dk/ws/files/13860089/PERIANTH_DEVELOPMENT_IN_THE_BASAL_MONOCOT.pdf