morfologi biji
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Reproduksi
Seksual pd
Angiospermae
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Alat Reproduksi Angiospermae
Stamen / Benang Sari Setiap stamen terdiri atas anthera, yang mengandung
mikrosporangia dan didukung oleh filament
Meiosis pada sel induk mikrospora yang diploid di dalam antera menghasilkan empat mikrospora haploid.
Masing masing mikrospora akan berkembang menjadi serbuk sari dengan dua sel, kedua sel tersebut adalah :
Sel buluh serbuk dan Sel generatif
Karpel Karpel terdiri atas stigma, stylus dan ovarium. Semua bagian ini
membentuk pistilum.
The megasporangia, disebut ovul, berkembang di dalam ovarium. Meiosis pada sel induk megaspora di dalam setiap ovul
menghasilkan 4 sel haploid : 1 sel megaspora yang besar, dan 3 sel kecil yang disintegrasi.
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Development of the megaspore
The nucleus of the megaspore undergoes 3 successive mitotic divisions. The 8 nuclei that result are distributed and partitioned off by cell walls to form the embryo sac. This is the mature female gametophyte generation.
The egg cell will start the new sporophyte generation if it is fertilized.
The large central cell, which in most angiosperms contains two polar nuclei, will after its fertilization develop into the endosperm of the seed.
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Pollinasi
When a pollen grain reaches the stigma, it germinates into a pollen tube. The generative nucleus divides by mitosis forming 2 sperm nuclei. These, along with the tube nucleus, migrate down the pollen tube as it grows through the style and into the ovule chamber. The pollen tube with its contents makes up the mature male gametophyte generation.
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Double Fertilization
The pollen tube enters the ovule through the micropyle and ruptures.
One sperm nucleus fuses with the egg forming the diploid zygote.
The other sperm nucleus fuses with the polar nuclei forming the endosperm nucleus. Most angiosperms have two polar nuclei so the endosperm is triploid (3n).
The tube nucleus disintegrates.
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Ovum (n)
Penyerbukan
Zygota (2n)
:
Antipoda (n)
Inti kandungLembaga skunder (2n)
Inti kandungLembaga skunder (2n)
Sperma II (n)
Sperma I (n)
Embryo (2n)
Buluh serbuk
Serbuk sari
Benang sari
Sel kandung lembaga
Bakal biji
Putik
Bunga
Endosperm (3n)
Gambar 3 : Pembuahan ganda
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Buah (hasil pembuahan) Buah partenokarpi
Bakal biji
Ovum x sperma Ovarium Buah tak berbiji
Zygota Giberelin
(dihasilkan bakal biji yang tak dibuahi)
Embryo
Menghasilkan
Giberelin
Ovarium Buah berbiji
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FISIOLOGI
BIJI
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Biji
Mengandung embrio tumbuhan yang sedang berkembang dalam selubung protektif yang disebut testa
Biji terbentuk dari bakal biji (ovula) yang dibuahi di dalam ovarium
Ovarium dengan biji di dalamnya akan menjadi buah.
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After double fertilization, each ovule develops into a seed, which consists of
a plumule, made up of two embryonic leaves, which will become the first true leaves of the
seedling, and
a terminal (apical) bud. The terminal bud contains the meristem at which later growth of the stem takes place.
One or two cotyledons which store food that will be used by the germinating seedling.
Angiosperms that produce seeds with two cotyledons are called dicots. Examples: beans, squashes, Arabidopsis
Angiosperms whose seeds contain only a single cotyledon are monocots. Examples: corn and other grasses.
The hypocotyl and radicle, which will grow into the part of the stem below the first node ("hypocotyl" = below the cotyledons) and primary root respectively.
A pair of protective seed coats derived from the walls of he ovule.
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The food in the cotyledons is derived from the endosperm which, in turn, received it from the parent sporophyte. In many angiosperms (e.g., beans), when the seeds are mature, the endosperm has been totally consumed and its food transferred to the cotyledons. In others (some dicots and all monocots), the endosperm persists in the mature seed.
The seed is thus a dormant embryo sporophyte with stored food and protective coats. Its two functions are dispersal of the species to new locations (aided in angiosperms
by the fruit)
survival of the species during unfavorable climatic periods (e.g., winter). "Annual" plants (e.g., beans, cereal grains, many weeds) can survive freezing only as seeds. When the parents die in the fall, the seeds remain alive - though dormant- over the winter. When conditions are once more favorable, germination occurs and a new generation of plants develops.
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Seed:
Seed Coat
Embryo
Storage Tissue (Endosperm)
Seed Hormones
CK-CytoKinin
cell division
GA-Gibberellic Acid
cell expansion
AbA-Abscisic Acid
dormancy
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The Three Fundamental Parts
of a Seed
1. Seed Coat
2. Embryo
3. Storage
Tissue
1. Leaf
2. Stem
3. Root
of an Embryo
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Parts of a Seed External seed coat or testa Developing plant embryo Stored food called endosperm Seeds may be in one part (monocot)
or two parts (dicots)
MONOCOT
DICOT
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Parts of a Seed
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Gymnosperm Seed
A single fertilization produces the diploid (2n) embryo
The food source is the haploid megagametophyte
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Dicot vs. monocot seed
Dicot has two cotyledons (like bean)
Endosperm (food) is kept in the cotyledon
Monocot has one cotyledon which
absorbs the endosperm
tissue during
germination (corn)
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Kulit buah bersatu dengan kulit biji
Posisi Endosperm
Posisi embryo
Biji utuh
Kulit biji
mikropil
hilum
Biji utuh
endosperm
endosperm
remains of style
Kulit buah dan kulit biji yg bersatu
coleoptil
plumula
radikula
coleorhiza
A. Irisan membujur
radikula
plumula
kotyledon
A. Irisan membujur
embryo
Gambar 5. Struktur BijiA. Biji jagung
B. Biji kacang kedelai
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Growth of the shoot
Photosynthesis and Storage
Lifting the shoot above the soil
Producing lateral roots
Penetrating the soil
These functions. occur in this part of the embryo
Shoot apex
Cotyledon (leaf)
Hypocotyl (stem)
Radicle (root)
Root apex
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23http://www.biologie.uni-hamburg.de/b-online/ibc99/koning/seedgerm.html
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PENYEBARAN
BIJI
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Fruits serve many functions
in the plant world
Food source for the germinating seedling
Plants need to get around. They do this with their fruits.
Adaptations for dispersal
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Fruit and Seed Dispersal
The main function of the fruit is to disperse the seeds
Dispersal is important because 1. It spreads the progeny in order to
colonize new environments
2. Reduces competition for resources with parents
3. Reduces the chances of predators destroying all of the plants yearly seed production
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Types of Seed Dispersal
Three types of seed dispersal:
1. Self dispersal
Mechanical Ejection of Seeds
2. Physical Carrier Dispersal
Wind dispersal
Water dispersal
3. Biological Carrier Dispersal
Animal dispersal
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A. Self dispersal
Plants disperse their seeds by forceful ejection explosive fruits!
Witch hazel, squirting cucumber (jet propulsion)
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Mechanical
Ejection Geranium fruit
exploding
Legume
(Pea seeds)
A
combination
of ejection
and
attraction
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Mechanical
Ejection
Impatiens Fruit Exploding
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Self dispersal The peanut plant sows
(buries) its own seeds!
Geocarpic: carpel grows inside the earth (soil)
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B. Wind dispersal Small and Lightweight seeds.
Fruit and seeds may have special devices for wind dispersal
Plumes catch wind currents: Dandelion
Trees take advantage of their great heights for wind dispersal. Fruits with wings are used to slow the descent to land: maple, ash fruit
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C. Water Dispersal Fruits and/or seeds use flotation
devices to travel by water (in rivers,
oceans, etc.)
Fruit may have air spaces and corky floats: for example coconut
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Coconuts are Water Dispersed
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D. Animal dispersal Plants have interaction with animals to
accomplish seed dispersal
Many plants depend on animals for seed dispersal; they may offer a nutritional reward
Animals learn to recognize ripened fruit colors
Fleshy fruits eaten and dispersed with feces
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Animal dispersal Some dry fruit attach and cling to
animals
(they hitchhike on the animals)
Some have Velcro-like hooks that cling to animal fur (burdock, cockleburs)
Others have sticky substances that stick to host (mistletoe)
Oils attract ants.
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Animal Dispersal
Long distance dispersal by birds:
fruits and seeds trapped in the mud on their feet
Seeds released in excrement
Animals eat fruit, the seeds pass through the digestive tract.
Scarification by digestive enzymes is necessary for germination
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How Ripened Fruits
Attract Animals
1. Softer, easier to digest
2. More fragrant
3. Brightly colored
4. Increase in sugar content is a source of carbohydrates (reward)
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Further Study on Seed
Dispersal What carries the dandelion seeds for miles?
What feature of trees gives them a particular advantage when dispersing seeds by air?
How does the squirting cucumber disperse its seeds?
Although plants use wind and water, what do most plants use as carriers for their seeds?
Blackberries on a tree do not ripen simultaneously, why?
What plant do elephants help to disperse? How do they do it? What percentage of these seeds
germinate in elephant dung? Why?
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Pithecellobium oblongum fruit shows some of the traits often found in the
fruits of bird-dispersed seeds
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Fruits and Dispersal Fruits remain
distasteful to most animals (including humans) until they are ripe
This ensures that the fruit will not be eaten until the seeds are mature