elimination of potyviruses from two commercial iranian garlic populations, hamedan and azar-shahr, through thermotherapy and by meristem tip culture were investigated. the infected bulbs of either one of the populations were initially treated at 30o c for one week and then at 36oc for 5 weeks. the meristems of cloves at two sizes of 0.4-0.6 mm and 0.6-0.8 mm were then cultured on ms medium supp...

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...

Meristems may be determinate or indeterminate. In maize, the indeterminate inflorescence meristem produces three types of determinate meristems: spikelet pair, spikelet and floral meristems. These meristems are defined by their position and their products. We have discovered a gene in maize, indeterminate floral apex1 (ifa1) that regulates meristem determinacy. The defect found in ifa1 mutants ...

The development of higher plants depends on the activity of a shoot apical meristem. Organs are formed on the flanks of the meristem, while pluripotent stem cells are found in a separate domain in the meristem centre. Further domains are distinguished by the expression patterns of genes that control the development of the shoot meristem. Although most plant cells are immobile, their relative po...

The two main tasks of a meristem, self-perpetuation and organ initiation, are separated spatially. Slowly dividing cells in the meristem center act as pluripotent stem cells, and only their derivatives in the meristem periphery specify new organs. Meristem integrity and cellular proliferation are controlled in part by regulatory interactions between genes that are expressed in specific subdomai...

The two main tasks of a meristem, self-perpetuation and organ initiation, are separated spatially. Slowly dividing cells in the meristem center act as pluripotent stem cells, and only their derivatives in the meristem periphery specify new organs. Meristem integrity and cellular proliferation are controlled in part by regulatory interactions between genes that are expressed in specific subdomai...

The control of organ growth by coordinating cell proliferation and differentiation is a fundamental developmental process. In plants, postembryonic root growth is sustained by the root meristem. For maintenance of root meristem size, the rate of cell differentiation must equal the rate of cell division. Cytokinin and auxin interact to affect the cell proliferation and differentiation balance an...

To characterize the SHL2 and SHL1 genes in detail, we analyzed three strains carrying weak alleles of SHL2, shl2-6, shl2-7, and shl2-8, and one weak allele of SHL1, shl1-3. In contrast to strong alleles, which result in lack of shoot meristem, strains bearing these weak alleles formed shoot meristem frequently during embryogenesis. In shl2-6 and shl2-7 mutants, the meristem was lost during seed...

The shoot apical meristem contains a pool of undifferentiated stem cells and controls initiation of all aerial plant organs. In maize (Zea mays), leaves are formed throughout vegetative development; on transition to floral development, the shoot meristem forms the tassel. Due to the regulated balance between stem cell maintenance and organogenesis, the structure and morphology of the shoot meri...