Presentation on theme: "Plant Reproduction System. P LANT R EPRODUCTION S YSTEM The reproduction mechanism of a particular plant species or the way it reproduces determines its."— Presentation transcript:
Plant Reproduction System
P LANT R EPRODUCTION S YSTEM The reproduction mechanism of a particular plant species or the way it reproduces determines its genetic characteristics the breeding approach.
1. S EXUAL R EPRODUCTION Using sex organs to form next generation / to produce seeds.
Important steps: 1. Production of gametes (gametogenesis) 2. Pollination – Transfer of pollen from anther (male organ) to the stigma (female organ). 3. Fertilization – The union of male and female gametes to produce new genotypes. 1. S EXUAL REPRODUCTION ( CONT.)
POLLINATION Transfer of pollen from anther (male organ) to the stigma (female organ). Two kinds of pollination, Self pollination Cross pollination
Transfer of pollen from anther to stigma of the same flower / plant S ELF P OLLINATION
Natural mechanisms that encourages self pollination: 1. Cleistogamy Pollination happens when flower is still closed. Example: Rice S ELF POLLINATION
2. Stigma protected by anther Anthesis and pollination occur instantaneously once the flower blooms. Many pollen are produced, covering the stigma, hence preventing pollination by pollen from outside. Example: lime, tomato and chilli S ELF P OLLINATION ( CONT.) Chilli flower
3.Stigma and anther protected by other parts of flower. Male (stamen) and female (pistil) organs covered by keel, i.e. two fused petals. Example: Leguminosae family, sub-family Papilionoideae. S ELF POLLINATION ( CONT.)
Transfer of pollen from anther to stigma of flower of different plant. C ROSS P OLLINATION
Natural mechanisms to promote cross pollination: 1. Dieocious Male and female flowers are formed on different plants. Have male and female plants. Example: Papaya, salak C ROSS P OLLINATION ( CONT.) Male salak flower Female salak flower
2. Monoecious Male and female flowers are in separate positions on the same plant but mature at slightly different times. Example: Oil palm, corn and rubber. C ROSS P OLLINATION ( CONT.)
3. Dichogamy Anther and stigma from hemaphrodite flower or flower of monoecious plant mature at different times. Protogyne Stigma (female flower) matures before anther (male flower). Example: Potato, cassava and cashew. C ROSS P OLLINATION ( CONT.) Protogyne: Potato flower
C ROSS P OLLINATION ( CONT.) 3. Dichogamy (cont.) Protandry Anther (male flower) matures before stigma (female flower). Example: Starfruit and rubber. Protandry: Starfruit flower
4. Self-incompatibility Pollens are unable to fertilize ovule (female gamete) of the same flower/plant due to genetic factor (self incompatibility gene) Example: Potato, passion fruit and starfruit. C ROSS P OLLINATION ( CONT.)
In some species, there are more than one mechanism to promote cross pollination: 1. Rubber and corn: monoecious and protandry. 2. Potato, Sweet potato: Self- incompatibility and protogyne 3. Starfruit & passion fruit: Self- incompatibility and protandry C ROSS POLLINATION ( CONT.)
M ETHODS TO DETERMINE MODES OF POLLINATION 1. Identify flower formation system. 2. Isolate plants. No fruit/seed cross pollinated Fruit set/seed set self pollinated and possibly cross pollinated 3. Selfing. To observe the effects of inbreeding. Present cross pollinated. Absent / minimal self pollinated.
2. A SEXUAL R EPRODUCTION Does not involve sex or union of male and female gametes. Mechanisms:- 1. Vegetative reproduction 2. Apomixis
V EGETATIVE R EPRODUCTION o Stem/branch/root cuttings e.g. cassava o Grafting e.g. rubber, rambutan & durian o Rhizome e.g. tumeric & ginger o Stolon e.g. grass o Tuber e.g. potato & sweet potato o Tiller e.g. pineapple, sugarcane & banana
APOMIXIS Formation of seeds without union of gametes, i.e. fertilization.
A POMIXIS ( CONT.) Apogamy – Embryo formation from synergids or antipodals
Apospory Embryo develops from somatic cell such as nucellus and integument. Diplospory Embryo develops from megasporocyte. Adventitious embryo Embryo develops directly from nucellus and integument cells without involving embryo sac cells. Parthenogenesis Embryo develops from unfertilized eggs. A POMIXIS ( CONT.)
1. Obligate apomixis Apomixis reproduction is the main method of reproduction. Example: mangosteen A POMIXIS ( CONT.)
2.Facultative apomixis Both apomixis and sexual reproduction occur. Example: Guinea grass (Panicum maximum), Citrus sp.
C HARACTERISTICS OF CROSS POLLINATED, SELF POLLINATED AND ASEXUAL PLANTS CharacteristicCross pollinated Self pollinatedAsexual PopulationHeterogeneousHomogeneous GenotypeHeterozygousHomozygousHeterozygous GameteDifferentSimilarDifferent ProgenyDifferent & heterozygous Similar & homozygous Similar & heterozygous Inbreeding depression PresentAbsentPresent IncompatibilityPresentAbsentPresent