Reproduction in Plants Flashcards
What is reproduction?
Reproduction is a biological process by which new organisms are produced to ensure the perpetuation of the species
Define asexual reproduction
Asexual reproduction is the reproductive process which results in the production of genetically identical offspring from one parent
What are examples of asexual reproduction?
Natural: vegetative propagation, growth of new plants from tubers and bulbs
Artificial: tissue culture is the growth in an artificial medium of cells derived from living tissue
What are the characteristics of asexual reproduction?
Requires only 1 parent, no fertilisation involved, offspring are genetically identical to parent cell (no genetic variation)
Definition of sexual reproduction
Sexual reproduction is the reproductive process involving the fusion of nuclei to from a zygote and the production of genetically dissimilar offspring (eg. Fusion of sperm and egg to form the zygote in human reproduction)
What are the characteristics of sexual reproduction?
Requires 2 individuals for reproduction to form a zygote, involves the fusion of gamates (fertilisation), offspring is genetically dissimilar/different from parents
Differences in number of offspring produced for asexual and sexual reproduction
Asexual reproduction produces large number of offspring in a short time
Sexual reproduction produces small number of offspring
Advantages of asexual reproduction
Less time and energy consuming
Does not require a mate
Many offspring can be produced
Beneficial traits from parents are passed onto offspring
Disadvantages of asexual reproduction
Less genetic variety in offspring
More likely for a disease or environmental change to wipe out the whole species
Non-beneficial traits from parents are passed onto offspring
Advantages of sexual reproduction
Genetic variety in offspring
Increased adaptations in offspring
Reduces chances of a disease or environment change from wiping out the whole species
Disadvantages of sexual reproduction
Time and energy consuming
Mate required
Beneficial traits may not always be passed onto offspring
What are the parts of a flower?
Receptacle, sepal, petal
Carpel (female): stigma, style, ovary
Stamen (male): anther, filament
Function of the receptacle
Enlarged end of the flower stalk (pedicel) that attaches flower to part of the stem
Function of the sepal
Usually green, protects the flower when in bud, supports petals when in bloom
Function of the petal
Brightly coloured in insect-pollinated flowers
Attract pollinators like bees, butterflies
Act as a landing platform for insects
Function of the carpel
Stigma: structure with sticky fluid for pollen grains to land on
Style: stalk that holds stigma in position to trap pollen grains
Ovary: may contain one or more ovules that produce a female egg cell, developing into a seed after fertilisation
Function of the stamen
Anther: containing pollen grains (two lobes, with two pollen sacs)
Filament: stalk that holds the anther in position to disperse pollen)
What is the difference between bisexual and uni sexual flowers?
Bisexual flowers have both the carpel (female) and stamen (male), and are able to self-pollinate
Unisex flowers have either the carpel or stamen, and cannot self-pollinate
Define pollination
Pollination is the process in which the pollen is transferred from the anther to the stigma of flowers of the same species
Define self-pollination
The transfer of pollen grains from the anther to the stigma of the same flower or stigmas on flowers of the same plant of the same species
Define cross-pollination
The transfer of pollen grains from the anther to the stigma of the flower of a different plant but same species
Insect/wind pollination
Advantages and disadvantages of self-pollination
Only one parent is required, beneficial genes more likely to be passed on, not dependant on external factors, high probability of pollination due to proximity of anthers and stigma, less pollen wasted
Less genetic variation and adaptation, higher probability of harmful recessive alleles expressed, weaker and smaller offspring less disease-resistant
Advantages and disadvantages of cross-pollination
Beneficial qualities from both parents inherited, increased genetic variation and chances of survival, more likely to be heterozygous without expressing harmful alleles, more viable seeds produced
Two parents required, dependant on external factors, lower probability of this pollination method, more pollen wasted
Characteristics of an insect-pollinated flower
Brightly coloured petals that serve as landing platform for insects
Scent produced to attract pollinator
Nectar produced by nectary, nectar guides present
Compact and not feathery stigma, sugary fluid produced to trap pollen grains and stimulate germination
Anthers are found inside the flower
Pollen produced in moderate amounts, larger with rough surfaces
Characteristics of a wind-pollinated flower
Small and dull petals
No scent
Nectar and nectar guide absent
Large and feathery stigma, larger SA to trap pollen grains
Anthers hang outside flower to be exposed to wind
Long and Pendulous filaments
Pollen produced in extremely large amounts, small with smooth surfaces, light to be blown by wind
Characteristics of the Clitoria flower
5 brightly coloured petals of different shapes and sizes, nectar guides, two wing petals and two small keel petals
Long and compact stigma
Long curved hairy style
Long and narrow ovary, one row of ovules
10 stamens with long filaments, 9 stamens fused along length to form trough, enclosing carpel (female reproductive parts)
Nectar only collected by insect with long tubular mouth like a bee or butterfly
Characteristics of the Ischaemum muticum
Flowers in pairs, upper bisexual lower male
Two long feathery stigmas that project out the bract
3 stamens with long pendulous filaments each
Small and light pollen grains shaken from anthers and dispersed by the wind
What happens after pollination in plants? How do the male gametes reach the ovule?
The pollen grains on stigma will germinate due to sugary fluid (containing enzymes and glucose) secreted by mature stigma
Pollen tube grows from pollen grain. Male gamete in pollen grain travels down inside pollen tube.
Pollen tube grows down the style towards ovary, secreting enzymes to digest stigma and style tissues.
Pollen tube reaches ovule through an opening (micropyle)
Male gamete divides to form 2 (mitosis)
Tip of pollen tube absorbs sap, bursting to release male gamates
After the male gametes reach the ovule, how does double fertilisation occur?
The nucleus of one male gamete fuses with egg cell to form zygote (fertilisation)
The nucleus of second male gamete fuses wit two polar nuclei to form endosperm (3n)
Two fertilisation events are known as double fertilisation
- Male gamate + egg cell —> zygote (2n)
- Male gamate + polar nuclei —> endosperm (3n)
What does each flower part develop into in the fruit?
Ovary to fruit Ovary wall to fruit wall (pericarp) Ovule to seed Integuments (outermost layers of ovule) to seed coat/testa Style and stigma to remains
