BACKGROUND AND AIMS The gametophytes of most homosporous ferns are cordate-thalloid in shape. Some are strap- or ribbon-shaped and have been assumed to have evolved from terrestrial cordate shapes as an adaptation to epiphytic habitats. The aim of the present study was to clarify the morphological evolution of the strap-shaped gametophyte of microsoroids (Polypodiaceae) by precise analysis of t...

The maintenance of meristems throughout plant ontogeny allows the development of a diversity of structural forms from the same genetic base. Examination of the common and contrasting features of these meristems leads to the outline of common regulatory themes in meristem development. In particular, by including comparisons with embryogenesis research, we see that hormones and factors that are g...

Self perpetuation of the shoot meristem is essential for the repetitive initiation of shoot structures during plant development. In Arabidopsis shoot meristem maintenance is disrupted by recessive mutations in the WUSCHEL (WUS) gene. The defect is evident at all developmental stages and is restricted to shoot and floral meristems, whereas the root meristem is not affected. wus mutants fail to p...

A novel protocol for production of multiple shoot tip clumps of Keelar nelli (Phyllanthus amarus Schum. & Thom.) were developed in vitro from shoot tip explants cultured on Murashige and Skoog (MS) medium containing only BAP or BAP with NAA, 3% sucrose and 0.8% agar. The addition of the following combination of growth substances 0.1mgLBAP and 0.05mgLNAA, caused an extensive proliferation of mul...

Almost all aerial parts of plants are continuously generated at the shoot apical meristem (SAM). To maintain a steady pool of undifferentiated cells in the SAM while continuously generating new organs, it is necessary to balance the rate of cell division with the rate of entrance into differentiation pathways. In the Arabidopsis meristem, SHOOT MERISTEMLESS (STM) and WUSCHEL (WUS) are necessary...

sunflower (helictnthur annuus l. cvs mehr shafagh) seedlings were grown in nutrient solutions containing 20.5 to 70.4 mm nacl and 0 as the control. the effects of salinity on developmental changes occurring in the shoot apices of plants were studied. at 20.5 mm naci concentration, the leaf emergence rate and plastochron index of shafagh increased significantly, but this phenomenon was not obser...

Sunflower (Helictnthur annuus L. cvs Mehr Shafagh) seedlings were grown in nutrient solutions containing 20.5 to 70.4 mM NaCl and 0 as the control. The effects of salinity on developmental changes occurring in the shoot apices of plants were studied. At 20.5 mM NaCI concentration, the leaf emergence rate and plastochron index of Shafagh increased significantly, but this phenomenon was not o...