SEXUAL REPRODUCTION IN FLOWERING PLANTS CHAPTER 1 SEXUAL REPRODUCTION IN FLOWERING PLANTS

flowers are morphological and embryological marvels and the sites of sexual reproduction

PRE-FERTILISATION: STRUCTURES AND EVENTS In the flower the male and female reproductive structures, the androecium and the gynoecium differentiate and develop. the androecium consists of a whorl of stamens representing the male reproductive organ and the gynoecium represents the female reproductive organ.

Stamen, Microsporangium and Pollen Grain typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous four microsporangia

Structure of microsporangium Microsporogenesis The process of formation of microspores from a pollen mother cell through meiosis

pollen grains represent the male gametophytes Pollen grains are rich in nutrients

The gynoecium represents the female reproductive part of the flower. The Pistil, Megasporangium (ovule) and Embryo sac The gynoecium represents the female reproductive part of the flower. multicarpellary monocarpellary

syncarpous). apocarpous

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

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

Autogamy- pollination is achieved in the same flower Chasmogamy- Oxalis Cliestogamy- Oxalis

Xenogamy- between different plants Geitonogamy- pollen from the anther to the stigma of another flower of the same plant. Xenogamy- between different plants

Agents of pollination Abiotic and biotic Wind pollination- pollen grains are light and non-sticky. Well exposed stamens Water pollination- long ribben like, mucilage covering

Animal pollinated Pollen robbers Flowers are large, colorful, fragrant and rich in nectar. Small flowers are clustered into inflorescence Yucca and moth Pollen robbers

Outbreeding devices Continued self pollination result in inbreeding depression. Receptivity is not synchronised Anther and stigma are placed in different positions Self incomactibility Unisexual flowers

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

Artificial hybridisation Emasculation and bagging

Double fertilization syngamy and triple fusion- embryo and edoseprm

Post fertilization changes ’ Endosperm, embryo development, maturation of ovules into seeds and ovary into fruit Free nuclear endosperm Endosperm is completely used up- pea, groundnut Endosperm is not completely used up- coconut, castor

embryo

seed A fertilized ovule Albuminous and non albuminous seeds Remnants of nucellus- perisperm

Fruit A mature ovary Pericarp- walls of fruit from integuments dormancy False fruits Parthenocarpic fruits

Apomixis and Polyembryony