Genes regulating ovule development

Type :

Presentation

Pages :

5 pages

Format :

.doc

Published date :

11/11/2008

Category :

Science & technology

Sub category :

Biology

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Summary :

Introduction.
Ovule evolution.
1. The nucellus derived from a mega sporangium.
2. A single integument found in gymnosperms.
Molecular evolution.
1. Research on the morphogenesis of ovules and the molecular genetic model of ovule progress.
2. Strubellig (sub) mutant ovules.
3. Genetic and molecular analyses.
Ovule development.
1. The diversity of fruit shape in the angiosperms.
2. Ovule formations on sepals.
3. Integument initiation and growth.
Hormonal regulation of ovule development.
Conclusion.

Abstract

Ovules are the precursors of seeds. More specifically, they are sporophyticstructures and the site of megagametogenesis or female gamete shape that culminates in the formation of the haploid embryo sac. The prototypical angiosperm ovule consists of three parts: (1) the nucellus, where megasporogenesis occurs; (2) one or two integuments, which cover and nourish the megagametophyte; and (3) the funiculus, a supporting stalk that connects the ovule to the placenta. The presence and morphogenesis of these structures are species reliant and result in the range of dissimilar ovule shapes observed in seed plants. Once fertilized, sporophytes play important roles during seed development: (i) the integumentary tapetum nourishes the developing embryo and endosperm; (ii) the integuments differentiate into the seed coat, which can regulate dormancy and seed germination; and (iii) the funiculus may contribute to the retention of the seed until dissemination of the progeny is required. Seeds are needed for the propagation of most plant species, but they have also become, through crop cultivation, a food source for humans and livestock.