SAROJ ASIF (PGT BIO)

  CHAPTER 2 – SEXUAL REPRODUCTION INFLOWERING PLANTS   FLOWERS  v Site of sexual Reproduction.  v Male and female reproductive organs are borne on flowers.  PARTS OF A FLOWER :  Four WHORLS – CALYX (sepals), COROLLA (petals), ANDROECIUM (Male reproductive organ), GYNOECIUM (Female reproductive organs).  Male Reproductive Organ  v Androecium consists of Stamens.  v Stamen consists of anther, filament & connective (when anther is bilobed) v Anther bilobedhas 4 Microsporangia.  Refer fig. 2.1 of NCERT (L.S. OF A FLOWER WITH DIFFERENT PARTS)  MICROSPOROGENESIS :  Microspore mother cell (2n)  Meiosis  Microspore (n)  Mitosis  Pollen grains (n)  Pollen grains have two outer walls; i) Exine ii) Intine  v Exine is made of sporopollenin (HARDESTNATURAL SUBSTANCE)  v Mature pollen grains have two cells – big vegetative cell & small generative cell. v Generative cell forms two male gametes bymitotic division.  v Pollen grains shed in 2-celled