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Development of Seeds & Fruits in Angiosperms (Parthenocarpy Fruits…
Development of Seeds
&
Fruits in Angiosperms
Types of Fruit
Multiple Fruit
Developed from cluster of flower
Sorosis
Fruits are derived from catkin, spike and spadix type of inflorescence
Eg: Mulberry, Pineapple, Jackfruit
Syconus
Fruit develops from the hypanthodium type of inflorenscence
Eg: Pineapple, Fig
Aggregate Fruit
Developed from more than one carpel that fuse together to form entire fruit
Strawberry, blackberry, raspberry
Accessory Fruit
False fruit
Develop from ripened ovary but sometimes an from from another ovary of flower
Simple Fruit
Dry Fruits
Pericarp is not distinguished into three layers
Examples
Dehiscent fruits
Pericarp rupture after ripening
Legume: Pea, Silique: Brassica (Mustard), Capsule, Follicle
Indehiscent fruits
Pericarp does not rupture when ripening
Akene: Mirabilis jalapa, Nut: Litchi and Cashew nut Trapa, Caryopsis: Wheat, Maize
Schzocarpic fruits
Ripening divides into one-seeded mericarp
Lomentum: Mimosa, Acacia arabica, Compound samara: Elm (Holoptelea), Maple, Cremocarp: Coriander
Not fleshy
Succulent Fruits
Indehiscent
Seeds are liberated after the decay of the flesh
Pericarp distinguished into epicarp, mesocarp and endocarp
Fleshy
Berry: tomato, grape, cranberry, banana, Pome: apple, pear, Drupe: cherry, plum, peach
Development of Fruits
Different method of plants requires
Pollination & no fertilization
No pollination & no fertilization
Types of fruit development
False fruits/accessory fruits
Derived from floral parts other than ovary
Eg: Peduncle in cashew nuts & thalamus in apple
Parthenocarpic fruits
Seedless fruits formed without fertilization
Eg: Pineapple, banana, cucumber, orange
True fruits
Fruit developed after fertilization
Ripened ovary grows into fruits
Eg: Mango, Maize, Grape
Flowers need to be pollinated and fertilized to create fruit
Development of Seeds
Seed Structure
The Seed Coat
Seed coat (Testa and Tegmen)
In dicots, the seed coat further divided into an outer coat, called testa and inner coat called tegmen
Micropyle
Small pore on the seed coat for water absorbing to begin germination
The micropyle is near the funiculus (seed stalk) in angiosperm seeds
The hilum is the scar left when seed is detached from the funiculus
An Embryo
Hypocotyl
The portion of embryo or seedling that lies between the root and the cotyledons
Upon germination, the hypocotyl pushes the cotyledons above the ground to develop
Radicle
The root of embryo
The shoot of a plant that supports the cotyledons in the seed
Plumule
The first true leaves of the young plant
Consisting of the apical meristem
The Endosperm
Cotyledon
Also known as Scutellum
Serves to absorb nutrients from the endosperm during germination
Absorb food molecules from the endosperm & transfer them to other parts of the embryo
Endosperm constitute a major portion of seed
Examples
Tomato, Pepper (Dicotyledons)
Corn, Wheat (Monocotyledons)
Seed Growth
Angiosperms
After fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue
The second part of this process is the fusion of the polar nuclei with a second sperm cell nucleus, thus forming a primary endosperm
The process of seed development begins with double fertilization & involves the fusion of the egg and sperm nuclei into a zygote
The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant: the inner integument forms the tegmen and the outer forms the testa.
Gymnosperms
The ovules after fertilization develop into the seeds.
The two sperm cells transferred from the pollen do not develop seed by double fertilization, but one sperm nucleus unites with the egg nucleus and the other sperm is not used
The seeds do not develop enclosed within an ovary but are usually born exposed on the surfaces of reproductive structures, such as cones.
Parthenocarpy Fruits
Types of Parthenocarpy
Vegetative parthenocarpy (natural)
Production of seedless fruits without fertilization
e.g. pear and fig
Plants that do not require pollination or other stimulation (hormones) to produce parthenocarpic fruit
Stimulative parthenocarpy (artificial parthenocarpy)
A process where pollination is required but no fertilization takes place
Occurs when
A wasp inserts (pollinator) its ovipositor (a tubular organ through which a female insect) into the ovary of a flower
Stimulated by blowing wind or growth hormones into the unisexual flowers found inside a structure called syconium (flask-shaped structure lined with unisexual flowers)
Diploid pollen grain gives a stimulus to the ovary when self pollinated (due to pollen hormones) e.g. grapes and banana
Pollination alone (not followed by fertilization) E.g. watermelon
Production of seedless fruits by applying various stimulation (hormones: auxin, gibberelin) to stop fertilization
Stenospermocarpy (artificial parthenocarpy
Fertilization is followed by embryo (seed) abortion
Pollination triggers fruit development but ovules or embryos abort without producing mature seeds
Produce seedless fruit but the seeds are actually aborted (premature) while they are still small
E.g. Grapes (sprayed with gibberellin to increase size of the fruit and to make fruit clusters less tightly packed
Artificial parthenocarpy
Plant growth regulators has ability to induce parthenocarpy by plant hormones
Hormones auxins, gibberellins and cytokinin are well known to induce parthenocarpy
Hormone gibberellins- effective in producing seedless grapes and is the active component in preparations used to prevent premature dropping of fruit
Hormone auxin- treatment of young, unpollinated ovaries in certain cultivars of strawberry, tomato, grape, orange
Stimulate with pollen
In certain plants, pollen are present incompatible with female flower
Pollen tube enters into an embryo sac through microphyle, but male gamete are not fertilize the egg cell
Pollen tube disappear, but it can stimulate the fruit
Benefits of Parthenocarpy
Improves crop yield without using organic pesticides
Plant growth regulators are natural and fruits produced is larger
Reduces the complete cost of the cultivation
Provides seedless fruits and improves quality
Parthenogenesis
a component process of apomixis
Diploid parthenogenesis
Develops into embryo (2n) without fertilization
Causes by megaspore mother cell (2n)
E.g. strawberry: embryo develops from nucellus cell (2n) and produce more seed
To produce seed with 2n embryo
Haploid parthenogenesis
To produce seed with haploid embryo
The development of an egg and become haploid embryo without fertilization
Apomixis
No meiotic division and fertilization of the gametes to form a zygote
Seeds can be generated from somatic cells (non-sexual cells/somatic cells)
The production of viable seeds without pollination and fertilization
Integument or nucellus cell undergo mitosis, producing an embryo/embryos (polyembryony)
Defined as asexual formation of seeds from the maternal tissues of the ovule from the mother plant
Eg: Kentucky bluegrass, dandelion, citrus, Alliums
Apomictic seeds can be formed from nucellar tissues, egg mother cell, flower heads/bulbils
Embryos develops from tissue other than zygote
What is Parthenocarpy?
An artificial or natural production of fruits without fertilization
E.g. Pineapple, Banana, Cucumber, Grape, Orange, Grapefruit
The fruit resembles a normally produced fruit but is seedless
The word parthenocarpy comes from Greek, meaning 'virgin fruit'
Development of fruit without fertilization of ovules
Differences between Parthenogenesis and Parthenocarpy
Parthenogenesis
Parthenogenesis is a type of reproduction in which unfertilized egg or ovule is developed into a new organism
Parthenogenesis produces haploid organisms
Parthenogenesis is common in plants and animals
Parthenocarpy
Parthenocarpy is a process in which unfertilized ovule is developed into a seedless fruit
Parthenocarpy always produces seedless fruits
Parthenocarpy is common in flowering plants
Similarities between Parthenocarpy and Apomixis
Similarities
No fertilization involved. Both produce off springs similar to parents
There is no chance of diversity in genes
Used as asexual means or vegetative propagation methods. Both methods are asexual
Still involve the sexual organs of the plant- the ovary and the ovules
Differences
Apomixis produces genetically identical mother cells whereas parthenocarpy produces genetically identical offsprings
Both apomixis and parthenocarpy are asexual modes of reproduction, apomixis is the formation of seeds whereas parthenocarpy is the formation of fruits without fertilization
By: Esther Mira Jackson Jambol
D20182085031
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