Types of flower
Unisexual flowers (Dioecious)
Bisexual flowers (Monoecious)
Both male and female parts are presnt in flower
Parts of flower
Pedicel
Flower Stalk
Sessile flowers are flowers without a pdeicel
Receptacle
Enlarged end of flower
holds other parts of plant
Sepal
Outermost layer of modififed leaves
Protect flower in bud stage
Makes up calyx
Petal
Most obvious part of flower
Makes up corolla
See pollination methods
Stamen Male Repro Organ
Anther
Produces pollen grain
Pollen grains has a hapliod set of chromosomes
Has two nuclei
Vegetative nucleus
Generative nucleus
Filament
Carpel Female Repro Organ all carpel is pistil
Stigma
Secretes sugary fluid to sitmulate germination of pollen grains
Swollen structure that receives pollen grains
Style
Connects stigma to ovary
Holds stigma in a suitable position to trap pollen grains
Ovary
Contains one or more ovules
Ovules contain ovum and the definitive nucleus
Attached to the placenta by a stalk called funicle
Growth of pollen tube
Types of pollination
Self-pollination
Characteristics
Bisexual (Monoecious)
Stigma directly below anther
Anther and Stigma mature at the same time
Pros
Beneficial quanlities passed down
Pollination more likely to take place since stigma is close to anther
Less pollen wasted
Not dependent on external factors for pollination
Only one parent required
Cons
lesser genetic variation
fewer varities of offspring
Defn: transfer of pollen grains from A to S of the same flower / same flower on plant
Cross-pollination
Characterstics
Unisexual (Dioecious)
Only male or female repro parts present
Bisexual (Monoecious)
Stigma situated at a distance away from anthers
Chemical incompatibility
Anther and stigma mature at different times
Pros
more varieties in offspring
greater genetic variation
Cons
dependent on external factors for pollination
two different plants of same species are needed
pollination less likely to occur
More pollen wasted
Methods
Wind-pollinated
Petals
Stigma
Protudes out of flower
Large and feathery
Stamen
Long, pendulous
Pollen
More abundant
Tiny and light with dry and smooth surfaces so they don’t stick to each other
Insect-pollinated
Petals
Large, brightly coloured petals
Attract insects for pollination
Provide landing platform for insects
Stigma
Small, compact and sticky
Allow insects to brush against it
Found inside plant
Stamen
Filament and not pendulous
Pollen
Larger with sticky/rough surfaces to cling onto insects’ bodies
Fairly abundant
Fragrant and sweet smelling
Necter guides
Defn: transfer of peollen grains to the flower of another plant from the same species