Reproductive Cycle of Flower - Botany PDF

GENERAL BOTANY FINALS LECTURE CHAPTER 10: REPRODUCTIVE CYCLE OF FLOWER REPRODUCTIVE CYCLE refers to the series of important sequential events by which an organism gives rise to another of its own kind. PLANT LIFE CYCLE Diploid phase or Diplophase –...

GENERAL BOTANY FINALS LECTURE CHAPTER 10: REPRODUCTIVE CYCLE OF FLOWER REPRODUCTIVE CYCLE refers to the series of important sequential events by which an organism gives rise to another of its own kind. PLANT LIFE CYCLE Diploid phase or Diplophase – have the diploid (2n) DEVELOPMENT OF THE EMBRYO SAC number of chromosomes in all cells 1. Megasporocyte Formation: Inside a developing ovule, a o Sporophyte – the plant in the diplophase, which large diploid megasporocyte (megaspore mother cell) is produces spores. surrounded by the nucellus and integuments, with a Haploid phase or Haplophase – have the haploid (n) micropyle leading to it. number of chromosomes in all cells. 2. Meiosis: The megasporocyte undergoes meiosis to produce o Gametophyte – the plant in the haplophase, which four haploid megaspores; three of which will degenerate, produces gametes. leaving one functional megaspore. REPRODUCTIVE CYCLE OF FLOWERING PLANTS 3. Mitosis: The functional megaspore undergoes three DEVELOPMENT OF THE POLLEN GRAINS successive mitotic divisions, forming the female 1. Microsporocyte Formation: Within the anther of the stamen, gametophyte or embryo sac. diploid microsporocytes (microspore mother cells) are 4. Embryo Sac Structure: The embryo sac typically consists formed through mitosis. of: 2. Meiosis: Each microsporocyte undergoes meiosis, resulting Two synergids and one egg cell at the micropylar in four haploid microspores. end, 3. Mitosis: Each microspore undergoes mitosis to produce a Two polar nuclei in the center (which may fuse to generative cell and a tube nucleus. The generative cell is form a diploid fusion nucleus), initially a naked cell without a cell wall. Three antipodal cells at the opposite end. 4. Sperm Cell Formation: The generative cell undergoes GERMINATION OF POLLEN GRAIN another mitotic division to form two sperm cells within the 1. Pollen Tube Formation: Upon landing on a receptive stigma, tube cell. the pollen grain germinates by forming a pollen tube. 5. Pollen Grain Structure: This results in a pollen grain, which 2. Pollen Tube Growth: The elongating pollen tube penetrates may contain either two or three cells (the tube nucleus and through stigma and style tissues, reaching the micropyle of two sperm cells). the ovule while carrying both sperm cells and the tube nucleus. 3. Sperm Cell Release: Once it reaches the embryo sac, the tip of the pollen tube ruptures, releasing the two sperm cells into the embryo sac. LICEO DE CAGAYAN UNIVERSITY BACHELOR OF SCIENCE IN BIOLOGY GENERAL BOTANY FINALS LECTURE FERTILIZATION AND SEED DEVELOPMENT Cross Pollination – the transfer of pollen grains from Double Fertilization the anther of a flower of one plant to the stigma of the 1. Pollination: After pollination occurs, one sperm cell from flower of another plant. the pollen grain unites with the egg cell to form a diploid AGENTS OF POLLINATION zygote. a. Insects – Insect pollinated flower or entomophilous 2. Endosperm Formation: The other sperm cell fuses with the flowers. two polar nuclei or diploid fusion nucleus, resulting in a b. Wind – Wind pollinated flower or anemophilous flowers. triploid primary endosperm cell. c. Animal – Animal pollinated flowers or zoophilous flowers. 3. Degeneration of Accessory Cells: Following fertilization, the d. Water – Water pollinated flowers or hydrophilous flowers. synergids and antipodal cells degenerate. GERMINATION AND SPOROPHYTE DEVELOPMENT SEED STRUCTURE Once the seed has been dispersed in a favorable environment, 1. Embryo Development: The zygote undergoes repeated the embryo resumes its growth and develops into a mature mitotic divisions to develop into an embryo, which becomes sporophyte. part of the seed. Germination – the resumption of growth of the embryo. 2. Seed Composition: A seed consists of: Epigean Germination – the cotyledons are lifted above The embryo, the soil level when the embryo resumes its growth. Remnants of the ovule (such as integuments), Hypogean Germination – the cotyledon remains Stored food, which may be located in cotyledons underground. (within the embryo) or as endosperm (outside the embryo). 3. Endosperm Development: The primary endosperm cell also undergoes mitotic divisions to form nutritive tissue called endosperm, which may or may not be consumed during embryonic development. POLLINATION Pollination – transfer of pollen grains from the anther to a receptive stigma. Self-pollination – the transfer of pollen grains from the anther to the stigma of the same flower, from the anther of one flower to the stigma of another flower of the same individual. LICEO DE CAGAYAN UNIVERSITY BACHELOR OF SCIENCE IN BIOLOGY