synergiods of the gives rise to embryo sac on development? hypocotyl suspensor of embryo tegmen non of these........ its urgent ans the ques!!!
Answers
Answer:
Experimental studies
The angiosperm zygote is embedded within the ovule and ovary and thus is not readily accessible for experimental manipulation. The following approaches, however, can yield information on the formation of the plant embryo:
Histological studies of embryos at different stages show how carefully regulated cell division results in the construction of an organism, even without the ability to move cells and tissues to shape the embryo.
Culture experiments using embryos isolated from ovules and embryos developing de novo from cultured sporophytic tissue provide information on the interactions between the embryo and surrounding sporophytic and endosperm tissue.
In vitro fertilization experiments provide information on gamete interactions.
Biochemical analyses of embryos at different stages of development provides information on such things as the stage-specific gene products necessary for patterning and establishing food reserves.
Genetic and molecular analyses of developmental mutants characterized using the above approaches have greatly enhanced our understanding of embryonic development.
Clonal analysis involves marking individual cells and following their fate in development (see Poethig 1987 for details on the methodology). For example, seeds heterozygous for a pigmentation gene may be irradiated so that a certain cell loses the ability to produce pigment. Its descendants will form a colorless sector that can be identified and related to the overall body pattern.
Go to:
Embryogenesis
In plants, the term embryogenesis covers development from the time of fertilization until dormancy occurs. The basic body plan of the sporophyte is established during embryogenesis; however, this plan is reiterated and elaborated after dormancy is broken. The major challenges of embryogenesis are
1.
To establish the basic body plan. Radial patterning produces three tissue systems, and axial patterning establishes the apical-basal (shoot-root) axis.
2.
To set aside meristematic tissue for postembryonic elaboration of the body structure (leaves, roots, flowers, etc.).
3.
To establish an accessible food reserve for the germinating embryo until it becomes autotrophic.
Embryogenesis is similar in all angiosperms in terms of the establishment of the basic body plan (Steeves and Sussex 1989) (see Figure 20.15). There are differences in pattern elaboration, however, including differences in the precision of cell division patterns, the extent of endosperm development, cotyledon development, and the extent of shoot meristem development (Esau 1977; Johri et al. 1992).
Figure 20.15. Angiosperm embryogenesis.
Figure 20.15
Angiosperm embryogenesis. A representative dicot is shown; a monocot would develop only a single cotyledon. While there are basic patterns of embryogenesis in angiosperms, there is tremendous morphological variation among species.
Polarity is established in the first cell division following fertilization. The establishment of polarity has been investigated using brown algae as a model system (Belanger and Quatrano 2000). The zygotes of these plants are independent of other tissues and amenable to manipulation. The initial cell division results in one smaller cell, which will form the rhizoid (root homologue) and anchor the rest of the plant, and one larger cell, which gives rise to the thallus (main body of the sporophyte). The point of sperm entry fixes the position of the rhizoid end of the apical-basal axis. This axis is perpendicular to the plane of the first cell division. F-actin accumulates at the rhizoid pole (Kropf et al. 1999). However, light or gravity can override this fixing of the axis and establish a new position for cell division (Figure 20.13; Alessa and Kropf 1999). Once the apical-basal axis is established, secretory vesicles are targeted to the rhizoid pole of the zygote (Figure 20.14). These vesicles contain material for rhizoid outgrowth, with a cell wall of distinct macromolecular composition. Targeted secretion may also help orient the first plane
The basic body m laid down during embryogenesis also begins with an asymmetrical* cell division, giving rise to a terminal cell and a basal cell (Figure 20.15). The terminal cell gives rise to the embryo proper. The basal cell forms closest to the micropyle and gives rise to the suspensor. The hypophysis is found at the interface between the suspensor and the embryo proper. In many species it gives rise to some of the root cells. (The suspensor cells divide to form a filamentous or spherical organ that degenerates later in embryogenesis.) In both gymnosperms and angiosperms, the suspensor orients the absorptive surface of the embryo toward its food source; in angiosperms, it also appears to
Answer:
In vascular plants embryo formation, or embryogenesis, usually occurs within a few hours after fertilization, with the first cell division that cleaves the zygote, or fertilized egg, into two daughter cells. Thereafter, rapid cell division provides the building blocks of the primary organs of the embryo sporophyte: the first root, first leaves, and the shoot apex. Temporary structures concerned with embryo nutrition—suspensor and foot—may also be produced. These organs originate in a polarization established at the time of zygote cleavage, but the details of their development vary widely among the different groups.
Explanation:
please make me as brainliest.