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Asexual and Sexual Reproduction in Plants (Reproductive cycles in Plants…
Asexual and Sexual Reproduction in Plants
Asexual Reproduction
What is It?
Parent plant produced offsprings that are genetically identical to each other
This can be an advantage when the organism is well adapted in the environment.
Natural Vegetative Propagation:
new individuals are grown from stem leaves of an existing plant
Grafting: bud from one plant is joined to another by putting
the vascular cambium tissue together.The graft is then covered to prevent water loss
Purpose: can produce plant with diverse characteristics, prevents water loss, faster maturity rate
Leaf Cutting: Leaf cut off from plant and placed in soil where the meristematic tssue helps form roots and plant base
Purpose: simple and inexpensive way to grow genetically identical plants, versatile to any season and can be used to save leaves
Division/ Splitting: Plant is split into two with both shoot and root system where they are separately replanted and grow independently.
Purpose: Simple, fast and thin out plants with large surface area
Stem cutting
Purpose: Stem from one plant is cut off and put in a growth medium to fully develop
Artificial Propagation
:cloning of a plant from the portion of its roots, stems or leaves
Simple Layering:
Plants with low lying stems are put into theground where they develop individual shoot and root systems
Pros: Large, mature and genetically identical daughter plant is produced faster. Also still has connection to parent plant which can provide it with nutrients
Air Layering:
Strip of outer bark is removed and tighly sealed for mosit envirometn then new root system startes to form and is then planted
Pros:Can be used on woody plants that cannot use other ethods
Root cutting:
root removed from a parent plant and placed horizontally in a bed of soil and organized in rows. This develops small individual plants with separate shoot and root systems.
plants can be grown faster in off seasons simply with minimal costs and offer as an alternative to vegetative propagation
Cell Culturing:
Individual plant cell put in nutrient-rich environment where plantlets form, and then put into soil to form individual plants
Pros: can produce mass amounts of plants( endangered plants)
Pollination Mechanisms
Self Pollination/ Cross Pollination
Self Pollination can lead to lack of genetic variation, common is most angiosperms
Cross pollination: Can receve pollen from other plants= genetic diversity
Animal pollination
brightly coloured with strong scents and nectar, insects and animals carry pollen to different flowers as they search for nectar
Wind Pollination
usually done by plants that lack colour or fragrenc, but carry large volume of pollen
Sexual Reproduction: sporic reproduction
Seed plants
Adapted for reproduction in dry environment, non motile sperm and protected zygote, embryo with dependent gametophyte
male gametophytes= microspores/ female= macrospores
Types
Angiosperm
protected seeds within ovary walls- wind, insects or animal pollination, double fertilization
Flower is the reproductive organ
Stamens- most flowers have several male reproductive organs - Compised of filament and anther (filament stalks supposrtanther during meiosis and mitosis
Pistil: in the center of the flower, usually one or more accompanied by stigma
Stigma: tip of the pistil, where pollination occurs
Style- connects stigma to ovary(contains one or morre ovules)
Ovules: sacs that contain female gametes
Ovary: where female gametophytes develop into egg forms in it
petals: usually colourful structures that attract pollinating insect and provide them with a platform
Sepals:Protect the flower bud, can look like small leaves or flower petals
Gymnosperm
Freeliving plants
unprotected seeds that develop on the upper surface
wind pollination -single fertilization Female= macrospore/ male= microspore
Male gametophytes(pollen grain)=microspores
travels to female gametophytes, then pollination occurs when pollen lands on female reproductive structure (does not requires water transfer of sperm to egg occurs through pollen tube
. - Pollen grain encases cells to prevent sperm from dyring out
Seedless plants
Adapted to reproduction in wet environment, unprotected zygote, embryo and independent gametophyte
Non Vascular: Dominant gametophyte plant
Vascular: Dominant sporophyte plant
Reproductive cycles in Plants
Haploid
Meiosis form spores that undergo cell division which mature into a gametophyte
divides and turns into male and female gamete that combine to form diploid
Diploid sporophyte
Fertilization forms zygote( 2n)
fertilization occurs when sperm units with an egg to form zygote which develops into an embryo (covered by tough layer=sed) -
male+female=sporophyte -sporophyte goes through cell division where reproductive cells develop and the process repeats.
Seed germination
Seed and fruit development
