The most diverse and largest group of plants are seed plants. Over 240,000 different species are known. They include all plants that reproduce via a seed and thus sexually. Another method of reproduction is vegetative asexual propagation, in which a genetically identical image of the mother plant is created through cell division.
Seed Plants – Definition
The Seed plants (Spermatophytina) include all plant species that produce seeds as dispersal organs.
Both Seed plants will be between the gymnosperms (Gymnosperms) and angiosperms (Angiosperms). They always consist of a root, the shoot axis and leaves. The angiosperms also have flowers to cover the ovule.
Seed plants – types and examples
Basically, seed plants can be grown in Gymnosperm and angiosperm organize. All plants that have a flower and where the ovules are enclosed in the ovary are considered angiosperms. Angiosperms can represent woody and herbaceous seed plants.
Woody angiosperms include deciduous trees such as beech and oak. Examples of herbaceous angiosperms are daisy family plants such as sunflowers and cornflowers.
Gymnosperms, on the other hand, include all plants in which the ovules are free. This means that the seeds are lying freely on the seed scales.
Gymnosperms are woody plants such as spruce, larch and ginkgo
Seed plants – characteristics
A key feature of all seed plants is that they reproduce using seeds. However, gymnosperms and angiosperms differ in terms of their characteristics, which is why they must be considered separately. A significant difference lies in the formation of a flower, because only the angiosperms form them for reproduction.
Seed plant profile
The following profile shows you the main characteristics of gymnosperms and angiosperms.
Seed plant structure
All seed plants consist of the three main organs that every plant has: the root, the shoot axis and the leaves or flowers. Each organ takes on different functions so that the plant survives as a unit.
root
Roots are usually found underground because their functions are to give the plant support and absorb minerals and water from the soil. The root often consists of a main root from which several secondary roots branch off. However, roots can look very different. It depends on how big the tree is, how deep the roots have to reach to get water or whether they also need to store nutrients.
sprout axis
The shoot axis is located between the root and the leaves. It connects the other two organs with each other. Their main functions are to transport water and nutrients, to ensure the stability of the plant and to store reserve substances.
Water and nutrient transport takes place via the vascular bundles. They consist of a conductive tissue that is made up of a Wood part (xylem) and or bast part (phloem) composed. The xylem is responsible for water transport, while the phloem ensures nutrient transport.
A stem can be either woody or herbaceous. The gymnosperms, like the woody plants, therefore only have woody shoot axes. In addition, only perennial plants with secondary thickness growth have a woody shoot axis.
Cells of the cambium retain their ability to divide and ensure wood formation in the shoot axis and an increase in diameter. Woody shoot axes can also be referred to as a trunk or branch.
If you would like to find out more about the structure of the sprout axis, please read the explanation of the sprout axis here at !
You can also use the phloem as Sieve part of the vascular bundle, in which evolution occurs between the more original ones Sieve cells and the Sieve tubes with companion cells is differentiated. Sieve cells only occur in gymnosperms and ferns, while sieve tubes are present in angiosperms. Sieve tubes are more efficient than sieve cells.
Sieve cells have pointed ends and connect to the next sieve cell via the oblique cell ends. The exchange of nutrients between the cells takes place via plasmodesmata, which you also call Sieve pores can describe.
In angiosperms, the phloem has developed into a sieve tube system made up of elongated cells with sieve-like perforated walls, the so-called Sieve plates, further developed. The transverse walls are perforated with pores like a sieve.
The vessels that make up the xylem are also Tracheids or tracheas called. In their entirety, the vessels are also called vessel part of the vascular bundle. While tracheids occur in gymnosperms, angiosperms have tracheae. Tracheae are specialized tracheids that have a larger diameter.
leaves
Photosynthesis in plants can take place via the leaves, for which they have a particularly large number of chloroplasts with the green pigment chlorophyll. In addition, the leaf surface is usually large so that it can absorb as much sunlight as possible. When it comes to leaves, a distinction can be made between deciduous and needle leaves.
The angiosperms have deciduous leaves, while gymnosperms have needle leaves. This is because the coniferous trees as well as the deciduous trees have adapted optimally to the conditions of their environment. Conifers are found in colder, dry climates where their small surface area means they have less water to evaporate and do not have to shed their leaves in the winter.
This also affects the pollination strategies of the two species. Angiosperms that live in temperate and tropical climates can rely on being pollinated by insects. Because there are enough of them in these climate zones. In the cold regions where gymnosperms live, there are usually not enough insects. In this case, gymnosperms benefit more from wind pollination.
blossom
Flowers are only present in angiosperms. Flowers develop from a specific part of the shoot axis, which is also called inflorescence or inflorescence referred to as. In the flowers of angiosperms, the ovule is enclosed in the ovary of the carpel. Other parts of a flower are the perianth and stamens. The perianth consists, among other things, of the petals, which are responsible for the bright colors of the flowers. Pollen, which plays an important role in reproduction, is produced in the stamens.
In gymnosperms there is no flower in the strict sense. The flower segments are usually arranged one above the other in a spiral arrangement, creating cone-shaped inflorescences.
You can see how a flower is structured in the following illustration:
Fig. 1 – Structure of a flower
Seed Plants – Reproduction
In principle, plants can reproduce through vegetative reproduction or sexually through pollination and fertilization. All seed plants reproduce through pollination and fertilization. However, gymnosperms and angiosperms differ in how they reproduce. While in angiosperms fruits containing the seeds are produced after fertilization, in gymnosperms the seeds are exposed between the cone scales.
The female and male reproductive organs of conifers (conifers) are called cones. The female cones contain woody seed scales in a screw-shaped arrangement with ovules and covering scales. The male cones, on the other hand, consist of scale-shaped microsporophylls. When ripe they release pollen.
pollination
With the help of pollination, the male pollen in seed plants can reach the female egg cell of the ovule. There are three ways to do this: self-pollination, wind pollination and animal pollination. While gymnosperms rely on the wind for pollination, angiosperms can also either self-pollinate or animal pollinate.
Self-pollination
Plants that pollinate themselves must have hermaphrodite flowers. They use their own pollen to pollinate the stigma. The advantage of self-pollination is that an entire population can develop from plant species of which only one plant is present in an abandoned area.
Wind pollination
During wind pollination, the male pollen can be stirred up by the wind in such a way that it accidentally reaches the female part of a plant via the air. In gymnosperms, the pollen from the male flower can be transported to the female ovule of the cone. In angiosperms, the pollen is swirled around in the air so that it can stick to the stigma of a female flower.
Animal pollination
During animal pollination, male pollen is transported between plants via insects and birds. The advantage here is that, in contrast to wind pollination, under the right conditions there is a higher probability that the pollen will reach other plants. Insects are attracted by the striking colors of the flowers, the nectar and scents.
fertilization
Fertilization is similar for all seed plants. After the male pollen reaches the ovule, fertilization takes place. A tube then grows from the pollen grains. This hose will pollen tube called.
In angiosperms, the pollen tube must arrive in the ovary.
After the male sperm cell can fuse with the egg cell, the fertilized egg cell produces the sperm. The seed contains a seedling of the plant, which can later grow into a complete plant. In gymnosperms, the seeds can spread into the soil as soon as the cone falls off. After fertilization, the angiosperms form a fruit around the seed that protects the seed. Another advantage of the fruit is that animals eat it and then spread the seeds through their feces.
Seed plants – the most important thing
- The seed plants (Spermatophytina) include all plant species that produce seeds as dispersal organs.
- Seed plant species: When it comes to seed plants, the gymnosperms…