plant reproduction Flashcards
what is an angiosperm?
a flowering plant
what are the two types of angiosperm?
dicotyledons and monocotyledons
what is a monocotyledon?
a seed that has one cotyledon
- the vascular bundles within the stem are scattered
what is a dicotyledon?
a seed that has 2 cotyledons
- vascular bundles in stem are in circular arrangement
what is a cotyledon?
embryonic/seed leaves
what do insect pollinated flowers look like?
bright colours and a scent
what do wind pollinated flowers look like?
tend to be green and no scent e.g. grass
receptacle
the top of the flower stalk from which the different parts of the flower develop
calyx
- the first set of modified leaves called the sepals
- protect flower while forming and before flower bud opens
corolla
this is the layer of modified leaves called petals - often large and coloured to attract insects
what is the filament?
a stalk that supports the anther and carries water and nutrients to the anther in the vascular bundle
Stamen
made up of the filament and anther
- male reproductive organ of a flower (site of meiosis/mitosis for male gametes)
carpel
- female reproductive organ
- composed of ovary, style and stigma
- site of meiosis for female gametes
where are the female gametes contained?
within the ovules
function of the style?
supports the stigma, a sticky surface that pollen grains land on during pollination
what is the function of the nectaries?
they secrete nectar (a sweet substance) to attract insects that carry the pollen from one flower to another
what is the structure of wind pollinated plants?
- petals are dull in colour/absent
- no scent
- nectaries absent
- anthers and stigma hang outside the flower
- pollen is small and light
- large quantities of pollen produced
where are male gametes of the flower?
in the pollen grain within the anther
thrum vs pin eyed structure of flowers
stigmas of thrums are lower than the anthers, vice versa for pin eyed
what are the ovules also referred to as?
megaspores
how are pollen grains formed?
microsporocytes form by mitosis and undergoes meiosis to form 2 then 4 genet. diff. haploid nuclei. A cell wall forms around each nuclei to make a tetrad of microspores. These then seperate to form pollen grain. miosis of single haploid nucleus results in 2 genet. identical nuclei. One of these is the male gamete and divides to become 2
role of the tapetum in pollen grain development?
important for the nutrition and development of pollen grains
formation of the ovule?
megaspore cells formed by meiosis in embryo sac which develops within the nucellus. 4 haploid cells produced but 3 degenerate. Single haploid nucleus undergoes mitosis 3 times to form 8 genet. identical nuclei.
what are the structures in a mature ovule?
funicle, integuments, micropyle, embryo sac, female gamete, 2 synergids, 2 polar nuclei and 2 anti-podal cells
development of the pollen grain tube
Pollen grain germinates on stigma, the pollen tube grows into style by secretion of hydrolase enzymes. As the pollen tube grows, the 2 nuclei move down the tube behind the pollen tube nucleus. Pollen tube then penetrates micropyle.
how does double fertilisation take place?
One m gamete enters the embryo sac and fuses with the f gamete to produce a diploid zygote. The 2nd male gamete fuses w/ the 2 polar nuclei to form a triploid endosperm nucleus.
what is the primary endosperm nucleus?
the food source for the growing embryo
what forms the testa/seed coat
integuments
what forms the fruit wall?
the ovary wall
what forms the seeds?
the ovules
requirements for germination
- optimum temp. for enzymes
- water for mobilisation of enzymes
- oxygen for aerobic respiration
what happens to the diploid zygote after double fertilisation?
divides by mitosis to form the diploid embryo
what happens to the triploid endosperm nucleus after double fertilisation?
divides by mitosis to form endosperm tissue (food storage for embryo)
what happens to the micropyle after double fertilisation?
remains as a pore in the testa
how are seeds dispersed?
- wind
- water
- attached to animals fur
- animals eat and egest seeds
how do seeds germinate?
water absorbed by seed means tissues swell and enzymes mobilised. Testa ruptures, radicle pushes through first downwards then plumule upwards.
what is gibberellic acid?
plant growth regulator
what happens when gibberellin diffuses into the aleurone layer?
causes transcription of mRNA which is then translated into hydrolytic enzymes. Amino acids in aleurone layer released through the hydrolysis of these proteins. Amylase and maltase are produced and hydrolyse starch to maltose then glucose. Glucose diffuses to the embryo where the radicle and plumule use the glucose for respiration.
what is the food store for monocotyledons such as grains?
the endosperm
where is the food store for dicotyledons?
the cotyledon
which types of seeds is gibberellin involved in the process of germination?
endospermic
