LIFE CYCLE OF THE ANGIOSPERMS Pollen lands on stigma, grows down style to ovule inside carpel

1. LIFE CYCLE OF THE ANGIOSPERMS • Pollen lands on stigma, grows down style to ovule inside carpel • Double fertilization • Nutritive tissue of seed develops after fertilization • Nutritive tissue is triploid endosperm rather than haploid female tissue

2. Sporophytic VS Gamatophytic

3. Apomixis – Seed Development Without Meiosis and Fertilization Apomeiosis – Formation of an unreduced female gamete (egg). Parthenogenesis – Development of the egg cell into an embryo without fertilization by sperm. Apomixis Apomixis, or the production of viable seeds without pollination, is the botanical version of what in animals is called parthenocarpy. These seeds are produced from flowers, just as regular seeds are, but no pollen is involved. The plants grown from such seeds are perfect clones of the original plant. The initial discovery of apomixis in higher plants is attributed to the observation that a solitary female plant of Alchorneailicifolia(syn. Caelebogyneilicifolia) from Australia continued to form seeds when planted at Kew Gardens in England

4. Apomixis: Asexual Seed Formation Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development.

5. Asexual Reproduction in Animals: Parthenogenesis

6. Potential for Apomixis in Plant Breeding: • *Fixation of genotype (hybrid vigour): fixation of genetic character in successive generations • * Reduced cost of hybrid seed production • * Successive progagation of hybrids • * Accelerated breeding • * Encourage “risk” in breeding practice • * Avoidance of complications associated with sexual reproduction, such as pollinators and cross compatibility; and the avoidance of viral transfer in plants that are typically propagated vegetatively, such as potatoes.

7. Types of Apomixis Sporophyticapomixis (adventitious forms directly from an unreduced sporophytic cell. Gametophyticapomixis, which involves the formation of an unreduced embryo sac (female gametophyte). Comparison of sexual and apomictic pathways in angiosperm ovules, with an emphasis on the differences between the two gametophytic pathways, apospory and diplospory, and the sporophytic pathway.

8. Scheme of Sexual and ApomicticReproduction.Reduced stages of the life cycle are shown in shaded ovals, and unreduced stages are shown in rectangular boxes.

9. Mechanism of Apomixis Apomixis share three developmental components: 1. The generation of a cell capable of forming an embryo without prior meiosis (apomeiosis). 2.The spontaneous, fertilization-independent development of the embryo (parthenogenesis). 3.The capacity to either produce endosperm.