Sexeual Reproduction in Plants
It is the process of fusion of gametes(n) from male and female parents resulting of formation of zygote(2n) which later develop into a new organism.
Typical structure of flower
> Flower is structural unit of sexual reproduction in plants
> The flower is specialized reproductive structure of a plant in which sexual reproduction takes place.
> The function of flower is to produce haploid gametes and to ensure that fertilization will take place.
> Typical flower consists of four different whorls viz. calyx, corolla androecium and gynoecium.
> Androecium and gynoecium are called ‘essential whorls’ because they perform the function of reproduction.
> Whereas calyx and corolla are called as ‘accessory whorls’ because they are responsible for protection of inner whorls .
> Members of calyx are called as ‘sepals’ and they are green colored.
> A flower is called as ‘bisexual’ if both whorls i.e. androecium and gynoecium are present in the same flower. Ex. Hibiscus .
> A flower is called as ‘unisexual’ if any one of the two whorls is present in the flower. If only androecium is present, it is ‘male flower’ and if only gynoecium is present, flower is ‘female flower’. Ex. Papaya
> Many flowers have the stalk for support, called as ‘pedicel’ and such flowers are called as ‘pedicellate’ > whereas flower without stalk is called as ‘sessile’.
> Members of corolla are called as ‘petals’ and they are variously colored.
Androecium
>The male reproductive whorl of flower is called androecium.
> Individual member of androecium, is called stamen .
> Stamen consists of filament, connective and anther.
Gynoecium
>Female reproductive whorls of flower is gynoecium( Pistils).
>Members of gynoecium are called as carpels(megasporophyll) carpels may be separate or unite
>Female reproductive whorls of flower is gynoecium( Pistils).
>Flower with many and free carpels is called apocarpous ex michelia Flower has many carpels fuse together is syncarpous ex brinjal .
>Typical carpels has three parts 1 ovary 2 style 3 stigma
>Ovary contains one or many ovules
>Ovary is present at the basal end of each carpel.
>Stigma is present at the tip of style
>A hollow ‘style’ comes up from the ovary
> Stigma is present at the tip of style .
>Ovary contains one or many ovules.
>Ovary with single ovule is called uniovulate eg wheat, mango
>Ovary with many ovule is called multiovulate eg tomato , ladyfingers.
>Embryo sac is formed in each ovule by meiosis.
> Each embryo sac consists of a haploid egg cell and two haploid polar nuclei.
