CHAPTER 1 REPRODUCTION IN ORGANISMS

SEXUAL REPRODUCTION INFLOWERING PLANTSCHAPTER 1

flowers are morphological and embryological marvelsand the sites of sexual reproduction

PRE-FERTILISATION: STRUCTURES AND EVENTSIn the flower the male and female reproductivestructures, the androecium and the gynoecium differentiate and develop.the androecium consists of a whorl of stamensrepresenting the male reproductive organ and the gynoecium representsthe female reproductive organ.Stamen, Microsporangium and Pollen Graintypical angiosperm anther is bilobed witheach lobe having two theca, i.e., they are dithecousfour microsporangia

Structure of microsporangiumMicrosporogenesisThe process of formation of microspores from a pollen mothercell through meiosis

pollen grains represent the male gametophytesPollen grainPollen grains are rich in nutrients

The Pistil, Megasporangium (ovule) and Embryo sacThe gynoecium represents the female reproductive part of the flower.monocarpellarymulticarpellarysyncarpous).apocarpous

The Megasporangium (Ovule)The ovule is a smallstructure attached to the placenta by means of a stalk called funicle.

MegasporogenesisThe process of formation of megaspores from the megaspore mother cell is called megasporogenesis

Autogamy- pollination is achieved in the same flowerPollinationChasmogamy- Oxalis

Cliestogamy- Oxalis

Geitonogamy- pollen from the anther to the stigma of another flower of the same plant.Xenogamy- between different plantsAgents of pollinationAbiotic and bioticWind pollination- pollen grains are light and non-sticky. Well exposed stamens

Water pollination- long ribben like, mucilage covering

Animal pollinatedFlowers are large, colorful, fragrant and rich in nectar.Small flowers are clustered into inflorescence

Yucca and moth Pollen robbersContinued self pollination result in inbreeding depression.Anther and stigma are placed in different positionsReceptivity is not synchronisedOutbreeding devicesSelf incomactibilityUnisexual flowers

Pollen pistil interactionIf the pollen is of the right type pistill will allow germintaion- communicate through chemicalsPollen grains are shed at two celled stage

Artificial hybridisationEmasculation and bagging

syngamy and triple fusion- embryo and edoseprmDouble fertilization

Post fertilization changesEndosperm, embryo development, maturation of ovules into seeds and ovary into fruitFree nuclear endospermEndosperm is completely used up- pea, groundnutEndosperm is not completely used up- coconut, castor

embryo

seedA fertilized ovuleAlbuminous and non albuminous seedsRemnants of nucellus- perisperm

FruitA mature ovarydormancyFalse fruits Pericarp- walls of fruit from integumentsParthenocarpic fruits

Apomixis and Polyembryony