Plant reproduction
A plant cannot move to look for a mate or carry its offspring somewhere else. And yet it manages: it hands over the transport of its pollen to the wind or to an insect, and that of its seeds to a fruit that flies, floats or travels in an animal's stomach. The flower is the centrepiece of this strategy.
The flower: the reproductive structure
If you carefully open a rock-rose or poppy flower, you will see that its parts are arranged in well-defined concentric rings: protective coverings on the outside and reproductive filaments loaded with powdery dust in the centre. How are these parts structured and coordinated to ensure reproduction?
Name the four whorls of a complete flower (calyx, corolla, androecium, and gynoecium) and state the parts and function of each one.
Name the four whorls of a complete flower (calyx, corolla, androecium, and gynoecium) and state the parts and function of each one.
Distinguish between a flower and an inflorescence, and give an example of an inflorescence (the capitulum of the sunflower, the spike of wheat, the umbel of the carrot),…
Distinguish between a flower and an inflorescence, and give an example of an inflorescence (the capitulum of the sunflower, the spike of wheat, the umbel of the carrot), explaining what advantage grouping many small flowers can have.
Explain what hermaphrodite flowers and unisexual flowers are, and what monoecious and dioecious plants are, with an example of each case (maize; kiwi or holly).
Explain what hermaphrodite flowers and unisexual flowers are, and what monoecious and dioecious plants are, with an example of each case (maize; kiwi or holly).
Pollination
Differentiate between pollination and fertilisation, indicating what travels in each process, through where, and which floral structures are involved.
Differentiate between pollination and fertilisation, indicating what travels in each process, through where, and which floral structures are involved.
What is nectar and which floral structures produce it (nectaries)? Explain the "contract" it establishes between the plant and the pollinator (food in exchange for…
What is nectar and which floral structures produce it (nectaries)? Explain the "contract" it establishes between the plant and the pollinator (food in exchange for pollen transport).
Compare the floral adaptations of anemophilous plants (wind-pollinated, such as grasses) and entomophilous plants (insect-pollinated): flowers, pollen, nectar, and…
Compare the floral adaptations of anemophilous plants (wind-pollinated, such as grasses) and entomophilous plants (insect-pollinated): flowers, pollen, nectar, and efficiency of the process.
Fertilisation, fruit and seed
When the petals of a cherry tree fall in spring, the withered base of the flower does not drop off but begins to swell until it becomes a juicy cherry with a hard stone at its heart. What microscopic and tissue changes take place from the moment the pollen touches the stigma until the fruit forms?
Which floral structure does the fruit develop from, and which does the seed develop from? Give an example of a fleshy fruit and a dry fruit, indicating which part we eat…
Which floral structure does the fruit develop from, and which does the seed develop from? Give an example of a fleshy fruit and a dry fruit, indicating which part we eat in each case.
Name the parts of the pericarp of a fleshy fruit (exocarp, mesocarp and endocarp) using the cherry as an example, and explain the difference between a true fruit and a…
Name the parts of the pericarp of a fleshy fruit (exocarp, mesocarp and endocarp) using the cherry as an example, and explain the difference between a true fruit and a false one (a pseudofruit: the apple, the strawberry).
Describe the reproductive cycle of an angiosperm from when a pollen grain reaches the stigma until the seed is formed: pollen germination, pollen tube, and double…
Describe the reproductive cycle of an angiosperm from when a pollen grain reaches the stigma until the seed is formed: pollen germination, pollen tube, and double fertilisation (in a simplified way).
Dispersal and germination
Explain what germination is and which three external conditions a seed needs (water, oxygen and a suitable temperature), discussing why seeds kept in a dry jar do not…
Explain what germination is and which three external conditions a seed needs (water, oxygen and a suitable temperature), discussing why seeds kept in a dry jar do not germinate.
Relate the structure of each diaspore to its disperser: the pappus of the dandelion and the wings of the maple fruit with the wind, and the coconut with water. Explain…
Relate the structure of each diaspore to its disperser: the pappus of the dandelion and the wings of the maple fruit with the wind, and the coconut with water. Explain which traits (lightness, surface, buoyancy) each medium selects and why dispersing far from the mother reduces competition.
Dormancy synchronises germination with the favourable season. Explain three mechanisms that maintain it (a hard impermeable coat, chemical inhibitors, the need for a…
Dormancy synchronises germination with the favourable season. Explain three mechanisms that maintain it (a hard impermeable coat, chemical inhibitors, the need for a cold period — stratification) and which signal breaks each one, giving an example of a plant for each mechanism.
Asexual reproduction and alternation of generations
Plants can reproduce asexually by means of stolons, rhizomes, tubers or the propagation of fragments. The offspring come from mitosis and are usually clones, barring genetic changes; there is no fusion of gametes. This kind of reproduction allows rapid colonisation, but provides fewer new combinations than sexual reproduction.