Why are plant cells important

Plants: the basis of life

Why are plants indispensable?

Because they produce the oxygen that many living beings on earth depend on and which enables them to exist in the first place. In order to achieve this, plants need light, because that is the prerequisite for being able to build up the substances they need for their growth. This process is called photosynthesis (literally something like "building up from light"). Only green plants can photosynthesize because only their cells contain the green leaf pigment chlorophyll. With its help, high-energy grape sugar (glucose) is produced from water (which is taken from the soil) and carbon dioxide (which gets into the leaf tissue from the air) in the presence of sunlight; this releases oxygen and water. The glucose in turn is converted into other substances, such as starch, which are required for the structure of the plant body and for its vital processes.

Plants are therefore able to produce the organic substances they need for life from inorganic substances; they are therefore also referred to as autotrophic ("self-nourishing"). Animals and humans, on the other hand, have to ingest organic substances, i.e. plants or animals, with their food in order to keep their metabolism going. They are "heterotrophic" ("feeding on others").

When did the plants conquer the land?

Around 400 million years ago. At least from this time - the Devonian - the first real mainland plants are documented by fossils, such as Drepanophycus spinaeformis, an ancestor of today's Bärlappe, which probably grew on flat sandbanks or in the transition zone from the tidal flats to the sandy beach.

The colonization of the mainland made new demands on the plants. So they developed roots with which they could anchor themselves firmly in the ground and absorb water and minerals. Special cells, which formed the so-called strengthening tissue, stabilized the plants and allowed them to grow in height. So that water and nutrients could also be transported into the upper parts of the plant, a system of tubes was formed: the so-called vascular bundles also supply the leaves at the top and, on the other hand, ensure that the products of photosynthesis reach the storage organs, such as the roots , reach. The leaves of the first land plants already had simple stomata that enabled them to exchange gas, i.e. to release water vapor and oxygen and absorb carbon dioxide. And cutin was already embedded in the outer layer of the plant body, which protected against excessive evaporation and the harmful UV radiation from the sun.

Do all plants produce seeds?

No, only the so-called higher plants. The lower plants, i.e. algae, mosses, ferns, horsetail and bear moss plants spread through spores, microscopic, mostly single-celled structures that are only used for reproduction. In doing so, they are absolutely dependent on water.

Flowering or better seed plants, as they are biologically correct, are no longer dependent on water for their reproduction. Instead, they rely on the transmission of pollen by wind or animals. How successful this strategy is is shown by the fact that most of the known plant species today belong to the seed plants. They can be divided into two large groups, the naked and the covered. In the blooms of the Nacktsamer, of which around 800 species are currently known, the ovule lies freely on the open carpels. They only produce seeds, not fruits. The ovules are enclosed in ovaries from which the fruits develop; they contain the seeds.

Why do plants adorn themselves with flowers?

To attract pollinators and thus to ensure reproduction and thus also the spread of the species. Above all, colors and scents are attractive signals to encourage bees, bumblebees and co. To visit. Red-blue anthocyanins, orange-colored carotenoids or yellow flavonoids serve as starting materials for a wide variety of colors. Corrugated surfaces or surfaces covered with wax reflect the light in a wide variety of directions and make many flowers shine particularly intensely. In addition to their basic color, many flowers help the insects to get to the nectar as quickly and accurately as possible with colored paints, colored stripes and dots on the petals. For those who cannot see well but can smell well, the flowers with their fragrances create distinctive channels that bees, flies or wasps perceive with their fine sense of smell even from a great distance, sometimes kilometers away.

As nutritious freebies, pollen provides everything the winged visitor needs. The nectar produced exclusively as a reward for submissive animals is also in great demand; the flowers produce this sweet juice in special glands, the nectaries. Some flowering plants also reward their visitors with nutritious fats that they form in special oil glands.

What controls the development of plants?

The development of plants is controlled by various plant hormones. Comparable to humans, in whom hormones control the ripening from child to adult as well as their aging, the developmental stages in the life of a plant are also controlled by various hormones, starting with germination, through growth, flower formation, fruit ripening and leaf shedding up to aging. These biochemical messenger substances, which are called phytohormones in plants, transmit information from tissue to tissue, from organ to organ and trigger specific effects even in very low concentrations.

One such phytohormone is ethylene - now known as ethene - which plants produce in small quantities during their entire life cycle. The colorless, sweet-smelling gas is of particular importance for aging processes. In the aging leaf, it ultimately determines when the separating tissue on the petiole becomes active and the leaf loosens. Ethylene also promotes fruit ripeness and thus ultimately fruit fall. Last but not least, it serves as an alarm substance for plants. After injuries, for example from pests, ethylene flows out together with other substances and stimulates the formation of defense mechanisms. So increases z. B. the toxin content of the leaves to spoil the appetite of predators. The gas does not only act on directly affected parts of the plant, but also from plant to plant.

Why do plants smell?

This question has not yet been finally resolved, but the reason may be their immobility. Plants cannot move in order to reproduce or to protect themselves from predators. When it comes to reproduction, they either have to rely on wind or water, or they have to get animals to play the messenger of love for them - and they manage this, among other things. with their floral scent. But scents can also protect against predators, such as sage and rosemary, the leaves of which give off a spicy scent. Plants also communicate with the help of their fragrances: Lima beans (Phaseolus lunatus), for example, emit chemical substances when they are attacked by spider mites. On the one hand, the odor signal attracts predatory mites, where spider mites are at the top of the menu. On the other hand, lima bean plants not yet infested in the neighborhood are encouraged to also emit odor signals as a precaution in order to ward off an attack.

Most fragrances belong to the group of essential oils, volatile, oily substances that smell aromatic in a more or less pleasant way. They are mainly found in leaves, flowers or seeds. Depending on the type of plant, they are made up of different components. It takes a lot of energy for the plant to produce these volatile substances. That is why some have specialized in releasing their fragrances in a targeted manner, for example only in the evening.

How do plants conquer new locations?

By spreading their seeds and fruits as widely as possible. Animals and wind help with this. Many seeds and fruits show good flight characteristics and can thus use the wind as a means of transport, such as the seeds of poppies and orchids, which are so light that the wind can carry them away. In the case of elm, maple and linden, they are even provided with wings and can therefore cover longer distances.

Conspicuously colored fruits such as viburnum, elder or mountain ash, on the other hand, are often eaten by birds. The indigestible seeds are excreted with the feces and can then germinate, often far away from the mother plant. Nuts and acorns are spread by squirrels and dormice, who use them as winter supplies. The fruits of the balsam even throw their seeds three to five meters on their own.

Are Plants Smart?

The scholars are still arguing about this. The most common counter-argument is the reference to the non-existent brain in plants. However, it has now been discovered that the plant cell membranes, as the sheaths around the cells are correctly called, have similar functions to the nerve tracts and the brain in animals and humans. In both animal and plant membranes, certain signal molecules (so-called neurotransmitters) ensure that information is passed on and processed within the organism; in addition, signals are processed in these locations and their dissemination coordinated.

It is now also established that plants can see, taste, smell, feel and probably even hear. In 1996, a team of researchers discovered a receptor in the tip of maize seedlings that is similar to the visual protein rhodopsin in the human retina. The British naturalist Charles Darwin (1809–1882) had already proposed that plants have to perceive the light, which is essential for photosynthesis, in some way. How else can we explain that houseplants that stand by the window grow purposefully towards the light?

It seems that plants even have something that acts like a memory: They can have experiences, learn from them and can still remember these experiences months or years later: For example, if you expose the roots of a young plant to a low salt concentration, the would normally harm it or maybe even kill it, the plant learns to tolerate certain amounts of salt. Amazingly, years later, the same plant will still be able to cope with higher amounts of salt. Plants, on the other hand, that did not have the opportunity to have this "experience" at a young age did not tolerate the salt water and died.

Did you know that …

Are trees important climate regulators? A beech forest gives off 3.6 million liters of water annually on an area of ​​one hectare, one hectare of spruce forest even up to 3.9 million liters.

Seeds can weigh up to 20 kilograms? The Seychelles nut palm does this and produces the largest seed on earth.

can plants reproduce asexually? They produce runners, tubers or daughter bulbs from which a new plant grows.

What does a seed contain?

The complete plant in small size that just has to grow. In the case of a bean seed, for example, the bud and the radicle of the seedling or embryo can already be clearly seen. It is protected from damage and drying out by the rather hard seed coat. The seed coat also encloses two cotyledons, which serve to supply the seedling with nutrients such as starch, proteins and fats.

Why do fruits look so different?

Because the ovary, from which all fruits arise, can develop differently. From the outside to the inside, different cell layers can be distinguished, which are called exo-, meso- and endocarp. If they become leathery and coarse, a capsule such as B. that of the poppy (Papaver), they become fleshy and soft like tomatoes (Lycopersicon) or cucumber (Cucumis sativa), then a berry develops, which some animals welcome as food. Often all layers are lignified and then enclose the seed as a hard nut. But there are a few other varieties in which the exo-, meso- and endocarp develop differently. This is how, among other things, Fruits like cherries (Prunus), in which the outer layers remain soft while the inner lignifies and surrounds the seed.

Did you know that …

there are also fruits without seeds? Bananas or citrus fruits produce such sterile fruits; Seedless plants are propagated via cuttings.

there are insects that pollinate only one type of plant? Both partners have adapted to each other so perfectly in physique and behavior that they are completely dependent on each other. This is how beautiful bees pollinate (Euglossinae) only certain types of orchids.