What are plants?

What Does plants Mean

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 that are members of the plant kingdom or phylum plantae . They are autotrophic organisms , devoid of movement capacity , and composed mainly of cellulose. Trees, brush, grass, algae, and shrubs are all members of this realm of life .

What we know today as plants descend from the first eukaryotic and photosynthetic algae that appeared on Earth approximately 1500 million years ago : Primoplantae ( Archaeplastida ), the product of the symbiosis between a eukaryotic protozoan and a cyanobacterium.

From this increasingly close collaboration emerged the first chloroplast and the possibility of photosynthesis as an energy process. This is how these primitive algae conquered the sea and later colonized the land, where evolution made ferns, shrubs, trees and other plant forms that we know today.

Thus, although they originated in water, there are plant species in practically all habitats in the world, as long as there is water and sunlight . Even in hot deserts (such as the Sahara) and frozen deserts (such as Antarctica), plant species adapted to adverse climatic conditions can be found.

See also: Plant cell

General characteristics of plants

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

  • Autotrophic nutrition. Which means that they generate their own food from inorganic matter (water and substances from the soil and air ) and sunlight (ultraviolet radiation). This complex process of making carbohydrates is known as photosynthesis.
  • Absence of locomotion. That is, they are beings unable to move at will (unlike animals). Some of them change their habitat at the mercy of the waters (algae and other aquatic plants).
  • Cells endowed with a cell wall. In other words, its cells have a rigid cellulose structure that covers their plasma membrane , giving them toughness and resistance , 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 other kingdoms of life ; but when photosynthesizing, they act primarily like plants.

Land 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, whether liquid or solid . Generally the roots do not usually 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 the other organs, such as the leaves. In addition, the stem provides structural support to the organism, since from it, in the case of trees (there they would no longer be called stems but trunks), the branches, which are nothing more than secondary bifurcations of the stem.
  • Sheets. 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 smells and colors , whose function is to attract animals (such as bees or certain birds), so that they 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 meatiness known as fruits, while others simply fall into the environment , or do so 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 in both terrestrial and marine trophic chains ( producer organisms ), since they feed on inorganic matter and a source of energy (sunlight), thus feeding herbivores or primary consumers.

On the other hand, plants fix the carbon from the atmosphere in their organisms , since they consume atmospheric CO 2 , which, if accumulated, would increase the greenhouse effect and global temperature because they block the radiation of heat outside the planet. Seen this way, plants are the planet's cooling mechanism .

Photosynthesis of plants

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

Consiste en tomar dióxido de carbono (CO 2 ) del aire, el agua del suelo o de otros medios físicos, y los fotones provenientes de la radiación ultravioleta de la luz solar, para así activar una reacción química que genera carbohidratos y subproduce oxígeno , expulsado de vuelta a la atmósfera.

Cada año las plantas convierten unos 100.000 millones de toneladas de carbono mediante la fotosíntesis, devolviendo al aire el oxígeno que los seres vivos requerimos para respirar.

Más en: Fotosíntesis

Reproducción de las plantas

Aunque tienen semillas, las fresas suelen reproducirse por estolones.

Las plantas se reproducen tanto sexual como asexualmente, pero sus mecanismos exactos para ello dependen generalmente de la especie.

Reproducción sexual . Se da en las especies que poseen floración, dado que en las flores se hallan los órganos sexuales. Algunas plantas son hermafroditas (poseen ambos sexos) mientras que otras poseen un sexo definido.

En ambos casos se requiere de la polinización: el intercambio de granos de polen desde los órganos masculinos a los femeninos (de la misma planta o de otra distinta) para fecundar los óvulos dentro del pistilo. Esta inseminación puede ocurrir por acción del viento o de animales que se alimentan de las flores, como las abejas.

Posteriormente se forma una semilla (un óvulo fecundado) y a su alrededor una fruta de algún tipo, que contiene al embrión listo para que germine un nuevo individuo, cuando las condiciones externas le sean favorables.

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 clonal individuals, rather than 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.

Follow in: Plant reproduction

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 plants to be distributed in different ecosystems within the same environment, allowing trees, shrubs and grasses to coexist without competing 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 layer, made up of trees that are several meters above the ground.

Environmental problems

Plants often face various human-caused environmental problems. For example, monoculture impoverishes soils , contamination of the latter with heavy chemicals, 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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