24 junio, 2024

Parts of plants and their functions

The Parts of a plant best known are the roots, leaves, stems, flowers, fruits and seeds. Plants, as well as animals and other multicellular living beings, have organs or «parts» that work in unison to allow them to fulfill all their vital requirements and functions.

If we do a quick analysis, we can determine that these living beings are made up of two fundamentally different “portions”: one underground (the one that holds them to the ground) and the other aerial (the one we see growing above the ground).

Hundreds of different animal species depend on both the “aerial” and the “underground” portions of different types of plants, not only for food and oxygen, but also for shelter, cure for disease, etc.

In short, much of the life on the biosphere depends, in one way or another, on plants and their organs, for example:

– The decomposition of dead plant tissues on the ground allows its nutritional enrichment, which in turn favors the subsequent development of new plants.

– Plants also contribute to reducing soil erosion, as their roots hold it in place.

– Photosynthesis, one of the most important metabolic routes for plants, implies that they “absorb” carbon dioxide (CO2) from the environment and release oxygen (O2), which terrestrial animals can breathe.

– Man currently uses the stems, roots, leaves, flowers, fruits and seeds of many plants not only for food, but also to extract compounds with different practical uses.

outer part of plants

Estate

The underground portion of plants is represented by the roots. The root is the first vegetal organ that is observed after the germination of a seed. In many species, the root system represents approximately 50% of its fresh weight.

Roots are vital for plants as they not only help them hold on to a substrate, but also function in the absorption of water and mineral nutrients from it.

In addition, some plants have roots that serve as storage sites for food reserves, mainly carbohydrates, which are available when the plant needs them most.

The roots not only participate in the absorption and conduction of water, but also produce hormones and other substances that regulate the growth of plants.

Root characteristics

There are two types of root systems: the axonomorphic root system and the fasciculated root system.

– Axonomorphic root systems are typical of dicotyledonous species and gymnosperms. These consist of a large taproot that “seeks” deep water sources in the soil, and a series of root hairs and lateral roots that function to absorb nutrients.

– Fasciculate root systems are generally observed in monocots and grasses. Instead of having one main root, they have many similar cord roots, each with its own lateral roots and root hairs.

Roots “tip grow”, thanks to the activity of a group of meristematic cells known collectively as the “root apical meristem”, closely associated with undifferentiated cells known as the “quiescent center” cells.

The structure of a root consists of three “zones” (from bottom to top): the growth zone, the elongation zone, and the maturation or differentiation zone. It has an epidermis that covers it in its entirety and a cortex where the vascular system (phloem and xylem) is located.

Aerial part of plants

The aerial portion of plants is everything we see growing above the ground, so it includes the stems, the leaves that arise from the stem nodes, the flowers that are produced in the meristems, and the fruits with their stems. seeds, which are the product of sexual reproduction of flowering plants.

the stem

The stem and leaves form what is known as the stem system. The external structure of the stems varies greatly between species, however, we can point out some characteristics that are common:

– They have an apical meristem and a series of meristems or axillary buds, often located in the region of the nodes where the leaves are formed.

– They have knots, which are the places where the leaves form and join and where the lateral branches “come out” from. The space between each node along a stem is known as the internodal region or “internodal region”.

– Both the new leaves (foliar primordia) and the lateral buds are formed from the apical meristem of the stem.

The stems are also covered by an epidermis and inside they have what we call «vascular tissue», which includes the elements of xylem and phloem, which function in the transport of water and sap.

The stems support the leaves and position them in the direction of the sun’s rays to make better use of the energy coming from it. In addition, they correspond to the transport structures of water and elaborated matter (sap) from the roots to the apices.

Leaves

The leaves, after the roots, are one of the most important organs of plants, since they are the ones that define these organisms as autotrophic beings. These are the main photosynthetic organs and, furthermore, they are essential for the gas exchange between the plant and the environment that surrounds it.

During photosynthesis, the leaves function as «antennas» for the perception of the sun’s rays. In this process, water and carbon dioxide molecules chemically combine in the presence of light energy to produce oxygen and sugars or food storage substances.

The leaves essentially have two parts: the leaf blade (which is the flat and thin part that we see, usually green) and the petiole (which is the «stick» that joins each leaf with the main stem or a branch. side).

The flower

Although not all plants produce flowers, angiosperms are the largest and most abundant group of plants that exist on earth, and these are the flowering plants.

The flowers are, for this group of plants, the reproductive part through which they reproduce sexually, thanks to the help of entities that we know as pollinators. In addition, the fruits and seeds that function in the dispersal of the species are formed from the flowers.

There are many different types of flowers: they can vary not only in colour, shape, size and scent, but also in the position where they form on the stem structure.

A hermaphrodite flower, that is, where the male reproductive “part” and the female reproductive “part” are found in the same structure, has the following “parts”:

– Floral peduncle: the portion of the stem that joins the flower to the plant

– Sepals and petals: modified leaves that protect and nourish the reproductive part and that “attract” pollinators, respectively.

– Stigma, style and ovary: the “female” reproductive part

– Anthers and filaments (stamens): the “male” reproductive part

The fruits

The fruits are the structures that protect the seeds and that are formed after pollination in the place where the flowers were. Many of them have very nutritious external fleshy structures and this usually attracts animals that, when eating them, take the seeds with them, dispersing them.

As is true for flowers, there are many different types of fruit, with very different structures, textures, meatiness, odors, and flavors (sugar and water concentration).

The seeds

The seeds, finally, are the dispersal structures of the plants, of sexual origin. These protect the embryo that has developed after the fusion of the male and female gametes (formation of the zygote) from different plants.

In addition to protecting it, the seeds sustain the life of the embryo when, upon germination, it activates its metabolism and requires food.

References

Nabors, MW (2004). Introduction to botany (No. 580 N117i). Pearson,. Raven, PH, Evert, RF, & Eichhorn, SE (2005). Biology of plants. macmillan. Taiz, L., Zeiger, E., Møller, IM, & Murphy, A. (2015). Plant physiology and development. Strasburger, E. (1921). Strasburger’s Textbook of Botany. macmillan. Lindorf, H., Parisca, L., & Rodríguez, P. (1991). Botany. Central University of Venezuela. Editions of the Library. Caracas. Solomon, E.P., Berg, L.R., & Martin, D.W. (2011). Biology (9th edn). Brooks/Cole, Cengage Learning: USA.

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