Grade 12 Reproduction in Flowering plants Part 2 - Flowers as Reproductive Organs Flashcards
What is angiosperm reproduction?
Plants with FLOWERS which produce their OVULES ENCLOSED IN AN OVARY.
Not naked in a cone scale, as in GYMNOSPERMS (e.g. pines)
Angiosperms grows in nearly every habitat (except ocean - where algae is found) - Unlike mosses and ferns which grows in damp habitat
Explain what a flower is:
-An organ of sexual reproduction.
-Contains reproductive organs - often will attract pollinators.
-Many flowers make both male and female gametes - Hermaphrodite / bisexual.
-Male gamates - found inside the pollen grains produced by ANTHERS
-Female gamates - found inside the OVULES which are found enclosed by OVARY.
What is the structure of a flower:
All flowers have certain basic futures:
A series of modified leaves arranged in four whorls of circles - the CALYX (often green), the COROLLA (often coloured), the STAMENS (male whorl) and CARPELS (female whorl).
Many variations, colour / size / shape - diversity probably related to way pollen is transferred.
List the four parts of a flower:
CALYX
COROLLA
STAMEN
CARPEL
What makes up the female part (CARPEL) of the flower? (See textbook page 61 for short summary)
Stigma - sticky surface to which pollen adheres
Style - slender section joining stigma to ovary
Ovary - female organ where ovules are formed. After fertilisation - matures into FRUIT - CONTAINS the Ovule - contains female gamete. After derivation forms a SEED
What makes up the male part (STAMEN) of a flower?
Anther - male organ where pollen grains are formed
FILAMENT - flexible stalk
What is the PERIANTH?
Corolla and Calyx combined
What are petals and their function?
Whorl of modified leaves - attracts pollinators
What are sepals and their function?
Whorl of modified leaves - Calyx protects unopened bud
What is the function of the receptacle?
Supports the floral parts
What is the difference between pollination and fertilisation?
**Pollination: **
* Transfer of pollen from an ANTHER to a STIGMA - thereby enabling fertilisation and reproduction.
* When anther is mature it splits open and discharges POLLEN
* Pollen then carried to the STIGMA by various natural means - e.g. wind, insects
* In plant breeding - human controlled
Fertilisation:
* The joining of two HAPLOID cells - the male gamete and female gamete, to form a DIPLOID ZYGOTE.
* Zygote develops into adult plant through MITOSIS
* In flowering plants fertilisation takes place AFTER pollination.
* After pollen grain lands on the stigma, it develops a pollen tube which grows along the STYLE and into the OVULE
* The pollen tube carries the male gamete
* Once gamete enters the ovule - FERTILISATION occurs
After fertilisation the development of embryo and seed begins
Distinguish between cross-pollination and self-pollination:
Cross pollination:
* Pollen is transferred from the ANTHER of a flower of ONE PLANT to the STIGMA of a flower of ANOTHER PLANT of the same species.
* Genetic variation
Self-pollination:
* Pollen is transferred from the ANTHER to the STIGMA of the same flower or to ANOTHER FLOWER of the SAME PLANT
* No genetic variation in offspring.
How can self-pollination be prevented?
**In nature: **
-Bisexual plants the anthers and stigmas of the same plant ripen at DIFFERENT TIMES. ANTHERS ripen first.
-Flowers are unisexual - they cannot self-pollinate
-Stigma is positioned above the anthers
Plant-breeders:
-Will remove anthers to prevent self-pollination
Explain in detail how a seed is formed:
**After fertilisation. **
1) ZYGOTE divides numerous times by MITOSIS and develops into an embryo consisting of:
-cotyledon or seed leaves - take food from parent plant for storage
-radical (embryonic root)
-Plumule (embryonic shoot)
2) The **rest of ovule develops into ENDOSPERM TISSUE **- stored food e.g. starch, protein, oil
3) The outer covering of the ovule thickens and hardens, forming the seed coat or TESTA. Why? saves the seed from damage and prevents entry of bacteria and fungi
Explain how a FRUIT is formed:
- While seed is being formed, the ovary is also growing.
- This is called FRUIT
- Happens in different ways in different plants
Label the flower re sexual reproduction:
Label the structure of the petunia plant - name the parts and where they should go
