plants

Biologist

2022

We explain everything about plants, their classification, parts, reproduction and other characteristics. Also, what is photosynthesis.

Plants are essential for the development of life on the entire planet.

What are plants?

Plants are the living beings members of the vegetal kingdom or phylum plant. Is about autotrophic organisms, devoid of the ability to movement, and composed mainly of cellulose. Trees, weeds, grasses, algae, and shrubs are all members of this kingdom of the life.

What we know today as plants are descended from the first eukaryotic and photosynthetic algae that appeared in the Earth about 1.5 billion years ago: Primoplantae (Archaeplastida), product of symbiosis between a protozoon eukaryote and a cyanobacterium.

Out of this ever closer collaboration arose the first chloroplast and the possibility of photosynthesis as an energy process. It was thus that these primitive algae conquered the sea and later they colonized the land, where the evolution made of them ferns, shrubs, trees and the other plant forms that we know today.

Thus, although they originated in water, there are plant species in practically all habitats of the world, as long as it exists Water Y sunlight. Even in deserts warm (such as the Sahara) and frozen deserts (such as Antarctica) can be found plant species adapted to adverse weather conditions.

General characteristics of plants

Three common and fundamental traits characterize plants, shared by all species of the kingdom without distinction:

  • Autotrophic nutrition. Which means that they generate their own food from inorganic matter (water and substances from I usually and the air) and sunlight (ultraviolet radiation). This complex carbohydrate manufacturing process is known as photosynthesis.
  • Absence of locomotion. That is, they are beings unable to move at will (unlike animals). Some of them change habitat at the mercy of the waters (algae and other aquatic plants).
  • Cells endowed with a cell wall. In other words, your cells have a rigid cellulose structure that covers their plasma membrane, giving them hardness, endurance, but making the growth process slower and more complicated.

Plants types

Trees are woody plants, while moss is a non-vascular plant.

In general, it is possible to differentiate plants into two large groups: 1) green algae and 2) terrestrial plants. The first group is evolutionarily much earlier than the other, and for that reason some scholars include them within others. kingdoms of life; But when photosynthesized, they act primarily like plants.

Terrestrial plants, at the same time, are divided into two different categories:

  • Vascular land plants. Known as "higher plants", they have a complete body structure: stems, roots, leaves and internal transport mechanisms (vascular mechanisms) that communicate their organs and travel the distance of their stems. At the same time, the higher plants are divided into:
    • Pteridophytes. Higher seedless plants, commonly known as ferns. They have long, rolled leaves known as fronds, and they can grow to a considerable size.
    • Spermatophytes. Higher seed plants, later than ferns in the evolutionary tree. This group is made up of angiosperms (plants with showy flowers and lots of pollen) and gymnosperms (woody plants), and is the predominant group on the planet.
  • Non-vascular land plants. Plants that do not have internal vascular structures, so they do not have a clear division between stem, root and leaves, nor do they reach a large size. They are a group halfway between ferns and algae, like bryophytes, for example, commonly known as moss.

Parts of a plant

In each species the parts of the plant may or may not be present.

Depending on the type of plant, it may have one or the other structures. But broadly speaking, plants are made up of:

  • Root. The fundamental organ of all types of plants, which serves to absorb water and nutrients from the environment in which they are found, be it liquid or solid. The roots usually do not see the light, and they grow rhizomatically, that is, disorderly. In their structures, in addition, nutrients and emergency substances are usually stored.
  • Stem. The stems are aerial extensions of the plant, which grow in the opposite direction from the root and generally have a system of conducting vessels to transport the sap and nutrients to other organs, such as the leaves. In addition, the stem provides structural support to the organism, since, in the case of trees (there they would no longer be called stems but trunks), the branches are born, which are nothing more than secondary bifurcations of the stem.
  • Leaves. Organs of various shape (round, elongated), color (between green and red) and texture in which photosynthesis takes place. They are born from the stem or on the branches, and depending on the plant species, they can dry out and fall before the arrival of the cold (autumn) to reduce the loss of water from the tree, or not.
  • Flowers. These are the reproductive organs of plants, from which the fruits and seeds are then generated. They are generally composed of stamens (male sex organs) and pistils (female sex organs), although there are plants of a single defined sex. And plants, too, never flower, since their reproduction occurs in another way. The flowers have attractive scents and colors, whose function is to attract animals (such as bees or certain birds), to serve as the transport of pollen from one flower to another, thus allowing insemination and genetic exchange between plants.
  • Seeds. Once the flowers are fertilized, the plants produce seeds, which are embryos ready to produce a new individual. Sometimes these seeds are produced without the need for flowers and fertilization, it all depends on the species. Likewise, some seeds are covered with fleshy flesh known as fruits, while others simply fall to the environment, or they do it wrapped in different forms of protection and transport.
  • Fruits Fleshy or dry coatings of the seeds of a plant, generally nutritious, thus guaranteeing the embryo the fertile sustenance for its germination when it falls or, on the contrary, helping it to move away from the shadow of the parent, when being eaten and then defecated by some animals.

Importance of plants

Plants are essential for the life of the planet as we know it, since they are responsible for the oxygenation of the atmosphere, without which the organisms we breathe would suffocate.

In addition, they are the first link of the Trophic chains both terrestrial and marine (producer organisms), since they feed on inorganic matter and a source of Energy (sunlight), thus feeding the herbivores or primary consumers.

On the other hand, plants fix carbon from the atmosphere in their organisms, since they consume the CO2 atmospheric, which if accumulated would increase the greenhouse effect and the temperature global because they block radiation from the heat out of the planet. Seen this way, plants are the planet's cooling mechanism.

Photosynthesis of plants

Plants manufacture their own sugars or starches, that is, their own carbohydrates necessary to grow and maintain themselves, from the transformation of inorganic material. This is its main metabolic activity and is called photosynthesis.

It consists of taking carbon dioxide (CO2) from the air, water from the ground or other physical media, and the photons from the ultraviolet radiation of sunlight, in order to activate a chemical reaction It generates carbohydrates and byproducts oxygen, expelled back into the atmosphere.

Each year, plants convert about 100,000 million tons of carbon through photosynthesis, returning the oxygen that plants to the air. living beings we require to breathe.

Plant reproduction

Although they have seeds, strawberries often reproduce by stolons.

The plants are reproduce both sexually and asexually, but your exact mechanisms for this generally depend on the species.

Sexual reproduction. It occurs in species that have flowering, since the sexual organs are found in flowers. Some plants are hermaphrodites (They have both sexes) while others have a defined sex.

In both cases, pollination is required: the exchange of pollen grains from male to female organs (from the same plant or from a different plant) to fertilize the ovules within the pistil. This insemination can occur by the action of the wind or animals that feed on flowers, such as bees.

Subsequently, a seed is formed (a fertilized ovule) and around it a fruit of some kind, which contains the embryo ready for a new individual to germinate, when external conditions are favorable.

Asexual reproduction. This mode of reproduction does not require flowers or pollination, but rather uses other parts of the plant. These mechanisms lack genetic variability and produce individuals clones, instead of original individuals. There are various asexual modes of plant reproduction, such as:

  • Stolons. The plant produces horizontal stems, at the end of which a new plant emerges, connected with its parent as by an umbilical cord. When in contact with the ground, the new plant forms its own roots and begins to break the stolon to gain its autonomy.
  • Rhizomes. These are underground stems that the parent creates and that move away from it until a new sprout is allowed, yet keeping all the individuals connected, like a colony. This makes it difficult to distinguish between the first generation of individuals and the second.
  • Tubers Another type of underground stems that the parent generates, sometimes through seeds, and which then thicken, storing nutritious substances, until new individuals germinate that then sprout from the ground.

Plant stratification

Stratification allows various species to coexist at different heights.

In the environment where various plant species proliferate, there is an organization of plant "layers" known as plant strata. This allows the plants to be distributed in different ecosystems within the same environment, allowing trees, shrubs and grasses to coexist without to compete fiercely.

The first stratum is closest to the ground, where grasses and grasses grow to a low height. Higher up are the bushes, in the second layer, already endowed with a firm stem and suspended above the ground. Above them is the third stratum, made up of trees that are several meters above the ground.

Environmental problems

Plants are often faced with various environmental problems caused by humans. For example, monoculture impoverishes soils, the contamination of the latter with chemical elements heavy loads, forest fires or deforestation for industrial purposes (to obtain wood, paper or arable soil).

These are some of the inconveniences that our lifestyle causes them on a daily basis, often causing irreparable damage to the plant community or damage that will take many years to repair, many more than the few moments it took to cause them.

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