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Topic 9 Plant Biology - 9.4 Reproduction in Plants
Nature of science: Paradigm shifts; more than 85% of the world’s 250,000 species of flowering
plants depend on pollinators for reproduction. This knowledge has led to protecting entire
ecosystems rather than individual species.
UNDERSTANDING STATEMENTS


Flowering involves a change in gene expression in the shoot apex.
o Vegetative Structures =
o Plant stays in vegetative phase for weeks, months, or years until a trigger causes
the plant to change into the reproductive phase and produce flowers.
o This happens when meristems in the __________________________________________
_____________________________________________________________________________.
o Flowers are structures that allow for ___________________________________. They
are produced by the shoot apical meristem and are a reproductive shoot.
o ______________________________________ can play a role in changing a leafproducing shoot into a flower-producing shoot, but ___________________________
is the main trigger (__________________________________________)
o Light plays a role in the production of either inhibitors or activators of genes that
control flowering. Ex: In long day plants, the active form of the pigment
phytochrome leads to the transcription of a flowering time (FT gene). The FT
mRNA is then transported in the phloem to the shoot apical meristem where it is
translated into FT protein. The FT protein binds to a transcription factor. This
interaction leads to the activation of many flowering genes which transform the
leaf-producing apical meristem into a reproductive meristem.
The switch to flowering is a response to the length of light and dark periods in many
plants.
o Long-day plants flower in the summer when the nights have become short
enough.
o Short-day plants flower in the autumn, when the nights have become long
enough.
o Experiments have shown that it is the length of ________________________________
that matters (not daylight)
o Plants us a pigment in leaves to measure the length of dark periods. It is called
phytochrome and is unusual as it can switch between two forms PR and PFR
o When PR absorbs red light of wavelength 660 nm, it is converted into PFR
o PR is more stable than PFR, so in darkness PFR very gradually changes into PR
o PFR is the active form of phytochrome and that the receptor proteins are present
in the cytoplasm to which PFR binds, but not PR
o Long day plants 
o
Short day plants 
SKILL: Drawing of half-views of animal-pollinated flowers.
Sepals –
Anthers –
Filaments –
Pollen –
Carpel –
Stigma –
Style –
Ovary –
Ovule –

Most flowering plants use mutualistic relationships with pollinators in sexual reproduction.
o Sexual reproduction in flowering plants depends on the transfer of pollen from the
stamen to the stigma of another plant.
o Pollen is transferred between plants via a number of strategies including wind, and
by animals called pollinators.
o Examples of pollinators: ______________________________________________________
o Mutualism - _____________________________________________________________________

Success in plant reproduction depends on pollination, fertilization, and seed dispersal.
Pollination = ________________________________________________________________
Fertilization = ________________________________________________________________
Seed dispersal = _____________________________________________________________
SKILL: Drawing the internal structure of seeds.
Embryo root –
Embryo shoot –
Cotyledons –
Testa –
Micropyle –
SKILL: Design of experiments to test hypotheses about factors affecting germination.