What are angiosperm plants?

The Angiosperm plants Are those that besides having flowers can be fruit. In addition, angiosperms are also known to consist of several characteristics: the presence of ovules, ovary and a complex pollination carried out by the animals, among others more that will be described later in detail and that conform their exact definition.

The flowers of the angiosperms have common features in both the monocotyledons and the dicotyledons, which are their subdivisions in the taxonomy and classification of these plants.

Angiosperm plants

These particular aspects are what create the differences of gymnosperms, plants that are also phanerogamous (use flowers to reproduce) but do not have the same evolutionary advantages as angiosperms, nor their morphology, that is, their appearance.

The biological cycle of these plants even differs from gymnosperms. The angiosperms, unisexual in some cases and hermaphrodite in others, have the peculiarity of being able to give continuity to their species through methods of pollination that have the assistance of animals.

A practical example of this is usually seen in gardens, where you can see how a bee walks from flower to flower to take its nectar without realizing that it is transporting its gametes.

All this process has allowed angiosperms to multiply in abundance and result in a vast biological diversity that can only be elaborated here.

The truth is that these plants have survived geological eras in which natural selection was in charge of getting them to occupy almost every known corner of the Earth. The result was an overwhelming number of subspecies that are but branches of the same genealogical tree.

Although speaking of angiosperms may not seem easy given the length of the subject, it is nevertheless necessary that you treat it as an introduction. The following pages will serve to instruct initiates in biology about what these plants are, what their characteristics are, how their flowers are made up, how they differ from gymnosperms, how they are classified internally, how they reproduce, what their Evolutionary history and why they are so important to man.

Main features of angiosperms

Angiosperm plants (from Greek Angeion ,"Receptacle", and Sperein ,"Sowing") are plants which, situated within the hierarchical division of the plant kingdom, are phanerogamous; That is to say, they are the ones that have flowers by organs of reproduction, which can be observed without difficulty, to the naked eye.

In this sense, the angiosperms form authentic fruits within which there are seeds that in turn contain the embryos that will perpetuate the species through a determined biological cycle. In their most elementary aspects, angiosperms have these characteristics:

  • Ovules: Located inside a practically closed cavity.
  • Ovary: Contains the eggs and is formed due to the meeting of carpels (leaves that are formed in order to form a pistil or a part of it).
  • Fruit: Results from the maturation of the ovum. It is true because it has in its interior the seeds of the plant that are protected to guarantee its dispersion.
  • Flowers: Have a protective sheath, ie the perianth. They are mostly hermaphrodites and can form a tube for the passage of pollen during the breeding process.
  • Pollination: Even in primitive angiosperms occurs through animals, such as insects and mammals.
  • Other features: There is a complete differentiation of conducting tissues, which have tracheas and sieve tubes in which there are attached cells.

Structure of flowers

The flowers of the angiosperms have different parts that make up their structure. These are the most important.

  • Androecium: Are the stamens which, together, form the male reproductive organs.
  • Gineceo: Formed by one or more carpels, is in itself the group of female reproductive organs.
  • Peduncle: Is the axis, the corner or nipple of the flower or inflorescence.
  • Petals: Are the separated leaves of the flower that in group form the corolla.
  • Sépalos: The separate leaves that when grouped constitute the chalice.
  • Thalamus Is the extreme part of the peduncle where the flower and the rest of its parts are inserted.
  • Tépalos: In monocotyledonous plants, are parts of an envelope that protect the androceo and the gynoecium.

Differences between angiosperms and gymnosperms

Angiosperms and gymnosperms have notable differences in several of their characteristics, which are general.

In botany, however, there are some exceptions and particular cases in these traits that do not necessarily mean the invalidity of the standard or the established taxonomic classifications.

Angiosperms Gymnosperms
Ovum Protected Unprotected
Flower Flamboyant, showy, unisexual, hermaphrodite Rudimentary, unattractive, unisexual
Seeds Hidden within the fruit. With pericarp Exposed. Without pericarp
True fruit Yes Do not
Pollen Less than 1,000,000 per ovule More than 1,000,000 per egg
Pollinating agent Animals Wind

Taxonomic classification

Angiosperms are divided into two main classes: Liliopsides , Better known as monocotyledons, and Magnoliopsides , Or dicotyledons.

Each class has important differences in its morphological characteristics, apart from the numerical ones shown below. For ease of understanding, the following comparative table provides a synthesis of some key features that distinguish both types of plants.

Monocotyledons Dicotyledons
Number of species 65,000 175,000
Root Fascisular Pivotal
Sheet Parallel nerves (paralelinervia) Non-parallel nerves

(In the paralelinervia)

Seed From a cotyledon Of two cotyledons
Increase No growth in thickness Yes there is growth in thickness

Monocotyledons and dicotyledons usually have the following general subclassification:

Class Subclass Most important feature Species of Interest
Monocotyledons Alismátidas Aquatic, humid environments Water lilies, posidonia ( Posidonia oceanica )
Liliidas Some plants have secondary lignification Garlic ( Allium sativum ), Tulip ( Tulip )
Arécidos Leaves can be confused with dicotyledons Palm trees, water lentils ( Lemna )
Dicotyledons Magnólidas Relatively primitive morphology Magnolia Magnolia grandiflora )
Ranunculus They live in temperate regions Buttercups ( Ranunculus )
Cariophilides They are usually hermaphrodite and cyclic flower plants Spinach Spinacia oleracea ), Carnation ( Dianthus )
Hamamelidids Usually with unisex flowers Banana ( Platanus ), Walnut ( Juglans regia )
Rósidas Great diversity of forms Legumes, orange, lemon
Dilénidas Often flowers have free petals Tea ( Thea sinensis ), Drosera ( Drosera )
Lámidas Flowers of various shapes Basil ( Ocimum basilicum ), Mint ( Mentha )
Asterisks Flowers with actinomorphic or cigomorphic symmetry Artichoke ( Cynara scolymus )

In an even more summarized and orderly way, the angiosperms are divided as follows:

1- Monocotyledons

  • Alismátidas
  • Liliidas
    • Orchids
    • Gramineae
  • Arécidos

2- Dicotyledones

  • Magnólidas
  • Ranunculus
  • Cariophilides
  • Hamamelidids
  • Rósidas
    • Legumes
    • Rosacea
    • Routes
  • Dilénidas
    • Crucifers
    • Cucurbitaceae
  • Lámidas
    • Labiadas
    • Solanaceae
  • Asterisks

Note that this classification contains only part of the total division of angiosperms. Therefore, there are not the names of all subclasses, families and species belonging to this class of plants. The references section expands this theme to the fullest.

Biological cycle

The reproduction of the angiosperms fulfills a double function. In the first place, its genetic inventory is diversified, and secondly, the continuation of the species is guaranteed. The biological cycle of these plants has something unique in them, which is the double fertilization, which can be visualized in the following illustration.

The biological cycle of angiosperms includes monocotyledons and dicotyledons, and can be grouped into several numbered stages:

  1. Since there is no way that the pollen grain is in direct contact with the ovum, the flower receives it in the stigma. When this grain of pollen is deposited, the pollen tube that reaches the egg develops.
  2. There is a very small gametophyte that does not form a multicellular protalo and not spermatozoa. The microspore, ie the cell of pollen grain, is divided into two cells: on the one side is the vegetative and on the other the germinative.
  3. This pollen cell is able to disintegrate into two sperm nuclei that are used in the reproduction of the plant; Double fertilization occurs.
  4. Here, the embryonic sac of eight haploid nuclei (of which two correspond to the polar nuclei and three to the ovocells), forms the female gametophyte, but there is not yet the multicellular protalo nor the archegonians.
  5. One of the three ovocells of the embryo sac is fertilized by a spermatic nucleus belonging to the pollen grain. A diploid zygote is formed which later develops and forms an embryo.
  6. The secondary nucleus of the embryonic sac, which is formed by the union of two polar sacs, joins the other spermatic nucleus of this pollen grain. When it develops, the endosperm, ie the triploid reserve tissue, is generated. From there the cycle is repeated and involved in this process both mitosis and meiosis.

To conclude, it can be said that angiosperms increase their chances of reproducing when an animal feeds on seeds by eating the fruit.

If a hummingbird sucks the nectar of the flower does a favor to those plants, that a guacamaya is eaten a guava is better; When flying to another place, it will take the seeds in its digestive system and deposit them as soon as it expels them with the feces.

Also, angiosperms can also leave offspring under extreme conditions, when there are no insects, birds or mammals that transport pollen.

The inflorescences are the most suitable means to make that pollen travel with the wind, as do gymnosperms.

But its morphological features sacrifice the viscosity of flowers in favor of a structure that, although simpler, allows it to follow the cycle of life without interruptions.

Brief evolutionary history

Although the origin of the angiosperms remains unknown, it is clear, however, that the oldest fossil remains date back to the early Tertiary period and that from the dicotyledons the monocotyledons were produced, reason for which it has been considered that The former are more archaic than the latter.

This means, then, that these types of plants have been on Earth for millions of years and still exist on this planet in abundant quantities.

Not surprisingly, the success of angiosperms can be counted on the approximately 235,000 species that comprise them in all their biodiversity.

The colonization of almost all terrestrial and freshwater habitats is an achievement that has been possible thanks to insect pollination, which has resulted in the optimization of effort in reproduction, which has benefited the evolution of both plants As of the animals that fertilize them.

Also, this is proven by the same geographical expansion of this flora. When traveling in different parts of the world, the angiosperms are found with the biological diversity of the insects that inhabit different regions, mainly in the tropics, where their number is greater, which decreases as it ascends to the colder zones, in the caps Polar To this must be added the variety of climatological factors that favor its diffusion in the globe.

Importance

In addition to its inherent relevance to biodiversity and its marked history in the geological eras, the angiosperms stand out for their multiple uses for man. The human race has valued for millennia the advantages of nature, and there is nothing better than these plants to prove it.

In short, humans have used both monocotyledons and dicotyledons for their exploitation and maximum benefit in the economy and in food.

See for example pepper ( Piper nigrum ), Basil ( Ocimum basilicum ), Rosemary ( Rosmarinus officinalis ), Thyme ( Thymus vulgaris ) And mint ( Mentha ). What do these species of angiosperms have, what makes them so special? Simply put, use as a seasoning in the kitchen.

Plants like these were traded at very high prices, so they were coveted in the so-called Age of Discovery, because they were spices that were worth a lot in the Old Continent.

The market also benefits from opium poppy ( Papaver ), the tea ( Thea sinensis ), Chamomile ( Matricaria chamomilla ) And tobacco ( Nicotiana ). While tea and chamomile are used to make infusions, tobacco and poppy occur between opiates, that is, between products that are consumed only for pleasure and therefore have no nutritional and medicinal value (except perhaps , The second floor, which in the past was used as anesthesia).

Wheat ( Triticum ), the oats ( Avena sativa ) And maize ( Zea mays ), Let alone the banana ( Musa paradise ), the potato ( Solanum tuberosum ) Or cassava ( Yucca ).

All belong to the angiosperms and are of inestimable importance for the human being's food, which also means that their economic importance is added to, because of these plants depends the financial sustenance of the farmers who sow the food taken to the table.

References

  1. Allaby, Michael (ed., 1998). A Dictionary of Plant Sciences (3rd ed., 2006). Oxford, United Kingdom. Oxford University Press.
  2. Bailey, Jill (ed., 1999). The Penguin Dictionary of plant sciences . London, United Kingdom. Penguin Books.
  3. Berry, Paul E.; Stevens, Peter Et al (2008, March 8). Angiosperm . Input of the Encyclopaedia Britannica . Digital edition consulted the 15 of January of 2017, in: britannica.com.
  4. Canals, Rosa Maria; Peralta, Javier and Zubiri, Eduardo (2009). Botanical glossary . Navarra, Spain. Public University of Navarra. Digital edition consulted on January 15, 2017, at: unavarra.es.
  5. Gonzalez, Ana María; Aguirre, Marisa and Raisman, Jorge S. (2000). Floral evolution [Website]. Cordoba Argentina. National University of Cordoba, Faculty of Exact, Physical and Natural Sciences. Accessed January 15, 2017, available at: efn.unc.edu.ar.
  6. Math Science Nucleus [Website, no year]. Life Cycle. Diversity in a Balance. Dictionary [Online article]. California, United States. Children's Natural History Museum. Accessed January 15, 2017, available at msnucleus.org.
  7. Science Learning Hub (2012) [Website]. Flowering plant life cycles [Online article]. Hamilton, New Zealand. University of Waikato. Accessed January 15, 2017, at: sciencelearn.org.nz.
  8. Sytsma, Ken (2016). Vascular Flora of Wisconsin. Gymnosperms - Pinophyta [Website]. Wisconsin, United States. University of Wisconsin-Madison, Department of Botany. Consulted the 15 of January of 2017, in: botany.wisc.edu.
  9. Watson, Leslie and Dallwitz, Michael J. (2016). The families of flowering plants: descriptions, illustrations, identification, and information retrieval [Website]. Beijing, China. The Chinese Academy of Sciences, Institute of Botany. Digital edition consulted the 15 of January of the 2016, in: delta-intkey.com.


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