Plant Sexual Reproduction PDF

DEPARTMENT OF FORESTRY PLANT SEXUAL REPRODUCT ION FBS 417 (FOREST GENET ICS AND TREE IMPROVEMENT) Aileen Mikkabelle O.Demandante WHAT IS PLANT SEXUAL REPRODUCTION? In sexual reproduction, two parents are involved i...

DEPARTMENT OF FORESTRY PLANT SEXUAL REPRODUCT ION FBS 417 (FOREST GENET ICS AND TREE IMPROVEMENT) Aileen Mikkabelle O.Demandante WHAT IS PLANT SEXUAL REPRODUCTION? In sexual reproduction, two parents are involved in producing a new individual. Offspring is produced by the fusion of gametes (sex cells) from each parents. Animals like dog, cats, lions, giraffe, humans, etc, all reproduce sexually. PROCESS OF SEXUAL REPRODUCTION Once pollen gets transferred to the stigma the male gametes from pollen grains release and fuse with the egg in the ovule to form a zygote. This process of fusion of gametes is called fertilization. The zygote thus formed, divides and develops into an embryo, and later into a seed. The ovary develops into a fruit. FEATURE OF SEXUAL REPRODUCTION - Two parents are involved (both male and a female). - Gamete formation and fertilization take place - The whole process is slow and lengthy - The variation occurs; offspring are different from parents, genetic and physically Reproduction of plants takes place sexually and asexually as well. But majority of the flowering plants reproduce sexually. The flower is the reproductive part of a plant i.e., both male and female gametes are produced by flowers. Sexual reproduction in plants takes place in flower. The complete flower typically consist of four (4) parts: -PETALS -SEPALS -STAMEN (male reproductive part) -PISTIL/CARPEL (female reproductive part) POLLINATION AND FERTILIZATION In order to form a zygote, male gametes in pollen grains have to fuse with egg in the ovule. This is achieved by the process called pollination. Pollination is the process of transferring the pollen grains from the anther- male part of a flower, to the stigma-female part of a flower. Depending on the pollen landing, pollination can be classified into two types. SELF- POLLINATION AND CROSS-POLLINATION Pollination is the process of transferring the pollen grains from the anther- male part of a flower, to the stigma-female part of a flower. Self-pollination occurs when the pollen from the anther is deposit from stigma (same flower, or another flower from the same plant). Cross-pollination is the transfer of pollen from the anther of one flower to the stigma where the stamen or carpel mature at the same time and are positioned so that the pollen can land on the flower’s stigma. METHOD OF POLLINATION Pollination by Insects - bees, wasp, butterfly, moths, and etc. Pollination by Bats Pollination by Birds Pollination by Winds Pollination by Deception DOUBLE FERTILIZATION After pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule. The microspores, or the pollen, contain two cells: the pollen tube cell and the generative cell. The pollen tube cell grows into a pollen tube through which the generative cell travels. The germination of the pollen tube requires water, oxygen, and certain chemical signals. As it travels through the style to reach the embryo sac, the pollen tube’s growth is supported by the tissues of the style. After fertilization, embryonic development begins. The zygote divides to form two cells: the upper cell (terminal cell) and the lower cell (basal cell). The division of the basal cell gives rise to the suspensor, which eventually makes connection with the maternal tissue. The suspensor provides a route for nutrition to be transported from the mother plant to the growing embryo. DEVELOPMENT OF A SEED The mature ovule develops into the seed. A typical seed contains a seed coat, cotyledons, endosperm, and a single embryo. SEED GERMINATION Many mature seeds enter a period of inactivity, or extremely low metabolic activity: a process known as dormancy, which may last for months, years or even centuries. Dormancy helps keep seeds viable during unfavorable conditions. Upon a return to favorable conditions, seed germination takes place. Favorable conditions could be as diverse as moisture, light, cold, fire, or chemical treatments. After heavy rains, many new seedlings emerge. Forest fires also lead to the emergence of new seedlings. DEVELOPMENT OF FRUIT AND FRUIT TYPES The fruit has a single purpose: seed dispersal. Seeds contained within fruits need to be dispersed far from the mother plant, so they may find favorable and less competitive conditions in which to germinate and grow. Some fruit have built-in mechanisms so they can disperse by themselves, whereas others require the help of agents like wind, water, and animals Fruits and seeds are dispersed by various means. (a) Dandelion seeds are dispersed by wind, the (b) coconut seed is dispersed by water, and the (c) acorn is dispersed by animals that cache and then forget it. (credit a: modification of work by “Rosendahl”/Flickr; credit b: modification of work by Shine Oa; credit c: modification of work by Paolo Neo) POLLEN GRAINS The matured pollen grain contains two cells: a generative cell and a pollen tube cell. The generative cell is present within the larger pollen tube cell. The tube cells form the pollen tube on germination. The generative cell migrates into the ovary through the pollen tube. Inside the pollen tube, the generative cell divides into two gametes or sperms. The anther matures and releases the pollen grains. GYNOECIUM The female regenerative part of the flower is the Gynoecium. It comprises of pistil. Gynoecium is termed in many ways: Monocarpellary: Gynoecium comprises of single pistil (e.g Pea, Bean) Multicarpellary: Gynoecium comprises of more than one pistil. Syncarpous: Gynoecium with combined pistil (e.g Tomato, Cucumber) Apocarpous: Gynoecium with free pistil (e.g Lotus Vinca) PISTIL Each pistil has three sections: the Stigma, Style and Ovary Stigma: At the tip of pistil that provides a landing stage for dust grains Style: Is the lengthened slender part underneath the stigma Ovary: The basal lump part of the pistil POLLINATION Transfer of dust grains to the stigma of a pistil is called Pollination TYPE OF POLLINATION Autogamy: transfer of dust grains from the anther to the stigma of a similar flower. Geitonogamy: transfer of dust grains from the anther to the stigma of the diverse flower but of the similar plant. Xenogamy: transfer of dust grains from anther to the stigma of an alternate plant but of the same species AGENTS OF POLLINATION Plants utilize only two abiotic (Wind and Water) and one biotic (Animals) operators to accomplish pollination. Majority utilize biotic operators for pollinations. Anemophily: Wind Hydrophily: Water Zoophily: Impacts of Creature On the basis of various sorts of creatures involved pollination, they are group into: Entamophily: Insects Ornithophily: Birds Chirapterophily: Bats YUCCA PLANT IS POLLINATED BY MOTH The moth and yucca can’t finish their existence without each other. The moth drills an opening in the ovary to lay its eggs. At that point it gathers dust grains from a few flowers and pushes in the honor end of stigma. INBREEDING The fertilization that happens within the single plant. OUTBREEDING The fertilization between two unique plants of the same species. SELF-STERILITY OR INCOMPATIBILITY In this dust of the flower has no fertilizing impact on stigma of a similar flower. For example: Pas-siflora, Potato Dichogamy: In this male and female sex organ develops at various types (e.g. China rose, Lady’s finger, Jasmine, Custard apple. Herkogamy: The anther and the stigma are put at various positions so that the pollens are not able to achieve of same flower. ARTIFICIAL HYBRIDIZATION Pollinating the dust grains of one flower to the next flower of various plants of the same species. FERTILIZATION The fertilization in angiosperms is named as Double Fertilization and Triple Fusion. As the pollen grains develops as a rule it contains One Vegetative Cell and Two Generative Cells that form into male gamete. In a few plants dust grain sheds as two cell condition. In this, generative cells partitions into two male gametes as pollen tube shapes. As the dust grain arrives on stigma, it begins to germinate. The pollen tube create leaves germ pore. It develops through the tissue of stigma, style and infiltrates the ovule. The section of pollen tube into ovule is from a distinct place and is distinguished into: Porogamy: It is the passage of dust tube through micropyle. Chalazogamy: It is the passage of dust tube through chalaza. Misogamy: It is the section of dust tube through integument or funicle. POST-FERTILIZATION STAGES It is the series of occasions that happens after double fertilization. It includes: Endosperm development Embryo development Development of ovule into seed Development of ovary into fruit. THANK YOU!