Most bract positions are determined at this stage, as inferred from the bract-specific expression of the PLA1 gene (Miyoshi et al. During this phase, the stem also grows by the supply of cells from the rib zone of the SAM. These numerous data are being integrated in several website databases. However, adult leaves follow a similar developmental course. Male and female gametes fuse, forming a zygote in an ovary of the flower.

Vascular bundles become mature, and sclerenchymatous cells differentiate just outside the vascular bundles (Fig.
At present, Arabidopsis is a major source of information regarding plant development because it offers excellent advantages as a model plant for developmental study (Meyerowitz and Somerville 1994). The ovule inclines to form a hemianatropous one.

During this stage, several events take place for differentiating embryonic organs such as the SAM and radicle.

11D). 2003).

(, Skinner, D.J., Hill, T.A. 7D). 6A). 11J). Rev. The staging systems proposed here can be used in the description of mutant phenotypes and interpretation of gene expression and other biological aspects, as well as in establishing a conceptual framework of rice development. 7E); then the spikelet meristem is transformed to a floret meristem to produce two kinds of glumes (one lemma and one palea) and floral organs (Fig. Stomata are cell complexes that are specialized for gas exchange between the leaf and its environment. Onset of ovule inclination, Second mitotic nuclear division. (F) Onset of primary rachis branch elongation. 2000). 5C). Chromosomes align on the equatorial plate of each daughter cell (Fig. The large vascular bundles cover the total width of the leaf, and xylem and phloem are recognized in the mid-vein.

The generative nucleus successively undergoes a second pollen mitosis. From first cell division to about the 25-cell stage at 1 DAP (Fig. Numerous papilla and two kinds of trichomes are found over the entire leaf surface, except for the adaxial surface of the sheath. Comparison of juvenile and adult characters in rice, Staging of inflorescence development in rice. 4H). Plant Mol. 8B). The formation of the stomatal complex, comprising two narrow guard cells and two large subsidiary cells is completed (Fig. Stage Ov1: Ovule primordium formation. 6C). Chromosomes transiently become a compact sphere and adhere to the nucleolus at early zygotene to form a so-called synizetic knot (Nonomura et al. (2004b), fKatayama (1963), gChao and Hu (1960), hKitada and Omura (1983). (C) Formation of four-layered anther wall through periclinal divisions of PSCs.

8H). The empty glumes grow to some extent, but they are sterile. (L) Tetrad stage. Rice has only three kinds of floral organs: two lodicules, six stamens and one pistil. For detailed descriptions of ovule and pollen development, see below. Then, the ovule starts to incline toward the receptacle side.

At the end of this stage, a phragmoplast, a cytoskeletal structure held by two arrays of microtubule bundles, determines the position of the cytokinetic plate (Nonomura et al. At this stage, fundamental organization of the root is established. Similarly, P–1 can be defined as a stage of cells that will become P0 cells in the next plastochron. Stage Sp4: Formation of palea primordium. This system is a small modification of that by Lopez-Dee et al. These processes have not been examined sufficiently, but are expected to be understood soon. (1994), fZhu et al. 2003a). (C) Differentiation of epidermis–endodermis initial into epidermis and endodermis.

After the two margins of the leaf primordium overlap and enclose the SAM, the shape of the leaf primordium becomes cone-like, and the blade (lamina)–sheath boundary is established (Fig. In rice the L1 layer gives rise to the epidermis and the stomium, which play important roles in anther dehiscence; the L2 layer develops into the archesporial cells, which are the primordial germ cells from which pollen and microsporangium differentiate; and the L3 layer gives rise to the connective cells, vascular bundles and circular cell cluster adjacent to the stomium (Raghavan 1988, Nonomura et al. PSCs mature into PMCs and undergo pre-meiotic S at this stage (Nonomura et al. Each haploid gamete contributes equally to the genome of the diploid zygote. 5H). However, in contrast to Arabidopsis, carpel identity is predominantly regulated by the DL gene (Nagasawa et al. and Kleckner, N. (, Kitada, K., Kurata, N., Satoh, H. and Omura, T. (, Komatsu, M., Chujo, A., Nagato, Y., Shimamoto, K. and Kyozuka, J. Symmetric transverse cell divisions in the stomatal cell row produce numerous cells smaller than those on either side of the row. (H) Down-regulation in the non-specialized epidermal cell (arrow), with strong expression in the GMC (arrowhead). Nipponbare, c ND: not determined. bLopez-Dee et al. (1999). In the 1.6 mm long anthers, tapetal cells have almost degenerated (Fig.
The number of stamens is increased in fon1 and fon2 mutants (Nagasawa et al. Angiosperms are flowering plants with male and female reproductive structures that produce haploid sperm and egg cells via meiosis. When endodermal cells divide periclinally to produce cortex, the expression of OsSCR is down-regulated in the daughter cortex cells (Kamiya et al. 4H). Onset of endothecium and middle layer degradation, Formation of spherical and enlarged microspore. Homologous pairing in early meiosis, which plays important roles in faithful cell division and homologous recombination, is divided into several substages based on the state of synapsis and condensation. (C) Second bract formation.

Small nucleoli appear with condensed chromosomes (Fig. When pollen grains reach the stigma of a flower’s female structures, a pollen grain containing two sperm makes its way into the ovary. The leaf sheath is the proximal region and surrounds the shoot apex and younger leaves to protect them from physical damage. The ovary thickens and ripens into a “fruit” that nourishes growing embryonic seeds. Gymnosperms are vascular, nonflowering plant species dating back to the days of the dinosaur. In addition, small vascular bundles are found between the large vascular bundles, and macrohairs differentiate on the leaf-tip epidermis. 5J). Seed dormancy and germination, and the onset of inflorescence development typically delimit these three phases. This phenotype means that in grasses, early vegetative stages are incorporated into embryos before dormancy takes place. 1999). 1998).

Primary branches are produced in spiral phyllotaxy, but spikelets on the primary branches are arranged in a biased distichous phyllotaxy.

and Upadhyaya, N.M. (, Oxford University Press is a department of the University of Oxford. Abortion of rachis meristem at the end of this period. ra, rachis; prb, primary rachis branches; srb, secondary rachis branches; sp, spikelet; B1, first bract; B2, second bract.

(J) SEM image of early P1 and P2 primordium. (2003b), bInukai et al. 5B). Fig. This stage lasts for several hours. 2nd leaf and 10th leaf) are compared. (A) Longitudinal section of mature semianatropous ovule.

(Received October 27, 2004; Accepted November 11, 2004). 9E). (1999), c Yamaki, S., Ito, M. and Nagato, Y. Degeneration of nucellar cells continues. Stage Sp1: Formation of a pair of rudimentary glume primordia. (B) Histone H4 expression in SAM at second (left) and 10th (right) leaf stages. Overlapping of two margins. Stage Em6: Formation of first leaf primordium. 1999, Satoh et al. The rice spikelet consists of a single floret because the spikelet meristem is converted into a floret meristem after producing two pairs of sterile glumes (rudimentary glumes and empty glumes) (Fig.

(B) SEM image of mature integument. ** aid1foscp1g, rf1h,i. The lamina joint is a whitish region in the base of the blade; it functions in bending the leaf blade toward the abaxial side (Fig. 8K). In this review, anther length is used mainly as a parameter to represent the approximate time course in addition to the floret length because the longitudinal lengths of anthers and floret are correlated roughly with meiotic stages.

One ABA-regulated gene, Rab16A, is expressed after 10 DAP. 2003). 7C).