Flowers appeared only later, as plants evolved, and they reproduced only by means of spores that they carried on their leaves. The typical example of these primary plants is the fern which still uses this means of reproduction today.
It is only during the Lower Cretaceous, 130 million years before our era, that angiosperms appeared. These plants produce seeds after fertilization of the flower. Some seeds have a survival capacity of several years, the chances of survival are thus multiplied by ten.
Are flowers plants?
The difference between plant and flower is that “plant” is plant while “flower” is the set of organs of sexual reproduction and the envelopes that surround them in angiosperms, also called “flowering plants”.
What is a flower?
A flower is an aerial part of a plant that can take on different shapes, structures, scents and colors to attract pollinating animals. It carries the sexual organs of the plant which will allow its reproduction.
The peduncle or flower stalk, carries the receptacle which generally contains the ovaries which will be transformed into fruits carrying the seeds. This peduncle is surmounted by the often green calyx, with the aspect of leaves which groups the sepals, with a variant in monocotyledonous plants where the sepals alternate with the petals; they are then called “tepals”.
A flower can house both male and female organs in its corolla. The stamens (male organs), which contain the famous pollen, surround the pistil containing the female organs and the ovules. (See our sheet on the structure of a flower)
What are the different parts of a flower?
In the middle of a flower there are one or more carpels that make up the pistil. When the flower fades, the ovary becomes a fruit and the ovules it contains become seeds. The flower is thus the reproductive organ of the plant.
The stamens produce the pollen grains in the anther, which is generally formed of two chambers. To produce a fruit, the ovule must be fertilized by one of these pollen grains. The stigma of the carpel has the role of collecting the pollen which germinates there and pushes a tube in the style to the ovule to fertilize it.
The stamens are the male reproductive organs and the carpels the female reproductive organs, by analogy with what happens in the animals where it is the spermatozoon which leaves to the meeting of the ovule.
The petals are generally colored. They can be more or less welded together. The whole of the petals forms the corolla. Their role is to attract insects that will carry the pollen from one flower to another because self-fertilization is often impossible. The perfumes that the flowers give off have the same function.
The sepals are generally green and have the role of protecting the flower in bud. As the petals, they can be more or less welded between them. All the sepals form the calyx. The whole of the petals and the sepals constitute the perianth of the flower.
The sepals and the petals are sometimes similar, they are then called tepals. The set of tepals is sometimes called perigone.
How flowers work
Many plants can self-pollinate since they carry both male and female organs which, when brought together at the right time by water, wind or pollinating animals, will produce seeds.
However, as nature is well done, cross-pollination diversifies the genetic contribution and gives birth to stronger plants ensuring a better survival of seedlings and an increased resistance of adult plants.
The various structures of the flowers are amazingly ingenious and prove an exceptional adaptation to the environment. The flowers of some trees do not need to wear a formal dress since pollination occurs naturally thanks to the wind. This is particularly true of conifers and oaks, whose pollen spreads visibly during the spring gusts.
In the case of a cross-pollination requiring the intervention of pollinators, the flowers will be very colored, or very scented to attract a specific animal. Sometimes they even take on the appearance of an insect in order to attract a particular species, as in the case of certain orchids which simulate the shape of the female insect in order to attract the male.
Some orchids simulate the shape of the female insect in order to attract the male. Others, such as carallumas or stapelias, develop a foul odor to attract flies, while some cacti, such as Echinopsis mirabilis, unfurl their nocturnal and fragrant flowers to attract bats.
Once this pollination has taken place and the ovules have been fertilized by pollen, the ovary will become a fruit containing one or more seeds with all the genetic material necessary for the formation of as many new plants that will wait for optimal climatic conditions to germinate.