plant reproduction system. p lant r eproduction s ystem the reproduction mechanism of a particular...
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Plant Reproduction
System
PLANT BREEDINGAGR 3204
PLANT REPRODUCTION SYSTEM
The reproduction mechanism of a particular plant species or the way it reproduces determines
its genetic characteristicsthe breeding approach.
1. SEXUAL REPRODUCTION
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. SEXUAL REPRODUCTION (CONT.)
POLLINATIONTransfer of pollen from anther
(male organ) to the stigma (female organ).
Two kinds of pollination, Self pollinationCross pollination
Transfer of pollen from anther to stigma of the same flower / plant
SELF POLLINATION
Natural mechanisms that encourages self pollination:
1. Cleistogamy Pollination happens when
flower is still closed. Example: Rice
SELF 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
SELF POLLINATION (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.
SELF POLLINATION (CONT.)
Transfer of pollen from anther to stigma of flower of different plant.
CROSS POLLINATION
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
CROSS POLLINATION(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.
CROSS POLLINATION(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.
CROSS POLLINATION(CONT.)
Protogyne: Potato flower
CROSS POLLINATION(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.
CROSS POLLINATION(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
CROSS POLLINATION(CONT.)
METHODS 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. ASEXUAL REPRODUCTION
Does not involve sex or union of male and female gametes.
Mechanisms:-1. Vegetative reproduction2. Apomixis
VEGETATIVE REPRODUCTIONo Stem/branch/root cuttings e.g.
cassavao Grafting e.g. rubber, rambutan
& duriano Rhizome e.g. tumeric & gingero Stolon e.g. grasso Tuber e.g. potato & sweet
potatoo Tiller e.g. pineapple ,
sugarcane & banana
APOMIXISFormation of seeds without union of gametes, i.e. fertilization.
APOMIXIS (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.
APOMIXIS (CONT.)
1. Obligate apomixis Apomixis reproduction
is the main method of reproduction.
Example: mangosteen
APOMIXIS (CONT.)
2. Facultative apomixis
Both apomixis and sexual reproduction occur.
Example: Guinea grass (Panicum maximum), Citrus sp.
CHARACTERISTICS OF CROSS POLLINATED, SELF POLLINATED AND ASEXUAL PLANTS
Characteristic Cross pollinated Self pollinated Asexual
Population Heterogeneous Homogeneous Homogeneous
Genotype Heterozygous Homozygous Heterozygous
Gamete Different Similar Different
Progeny Different & heterozygous
Similar & homozygous
Similar & heterozygous
Inbreeding depression
Present Absent Present
Incompatibility Present Absent Present