In the plant kingdom, the cotyledons They play an essential role in the development and reproduction of plants. Like animals, flowering plants arise from an embryo that develops in precise stages. The first leaf that emerges from the plant embryo, during the initial development of the plant, is called a cotyledon.
In this article, we will explore in depth all the characteristics, functions and importance of cotyledons, expanding on existing information and detailing their relevance in the life cycle of plants.
What are cotyledons
The term cotyledon comes from the Greek word “kotylḗ”, meaning “cavity” or “hollow” and refers to the shape of primitive leaves. In botany, the cotyledon refers to the first leaf mobilized by the embryo of flowering plants, the phanerogams, when the seed begins to germinate. This primordial leaf not only has the function of being the first to emerge, but also plays a crucial role in providing essential nutrients for the initial growth of the plant.
The number of cotyledons in a plant is one of the botanical keys used for its classification. Thus, plants can be monocotyledonous (they have only one cotyledon) or dicotyledonous (they develop two cotyledons). This parameter is essential to effectively identify plant species within the Plantae kingdom.
Origin of cotyledons and their development
The cotyledon develops during the bud phase. embryogenesis, a process that gives rise to the plant embryo. During this phase, various structures of the embryo, such as cotyledons, roots, and shoots, begin to form before the seed germinates. These structures are critical to the initial growth of the plant once the seed begins to absorb water and other nutrients from the environment.
The cotyledon, in particular, plays a vital role in the nutrition of the young plant. Not only does it provide stored nutrients during the seed stage, but it also becomes a photosynthetic structure, absorbing sunlight to convert it into energy through the process of photosynthesis.
Main characteristics of cotyledons
The cotyledon is notable for being the first leaf to emerge from the plant embryo. These leaves, particularly in dicotyledonous plants, are larger than the leaves that will appear later. For this reason, size is a key differentiating factor that allows cotyledons to be identified during the early stages of the plant's life.
Another notable feature of cotyledons is that, in some plants, these structures have the ability to digest albumen, a tissue that surrounds the embryo and acts as its main food. This process is essential to ensure that the cotyledon, and therefore the plant, have the nutrients necessary for its early development.
Apart from their initial nutritional function, cotyledons do not usually have a very long life. As the plant continues to develop and its true leaves begin to fulfill the photosynthetic function, the cotyledons lose their usefulness and eventually wither and fall off.
Functions of cotyledons
One of the most important roles of cotyledons is to serve as the first food source for the developing plant. Cotyledons contain reserves of nutrients, such as oils, starch, and proteins, which are essential for the young plant to begin growing before its true leaves are fully formed and can carry out photosynthesis.
In addition, the cotyledons allow the seed to germinate effectively by providing the energy needed to break through the seed coat and begin root and stem growth. Once the first true leaves emerge, the cotyledons continue to play an important role in providing energy until the plant can support itself through photosynthesis.
Another key function is photosynthesis Early. Although cotyledons do not have the sophisticated structure of mature leaves, some of them contain chloroplasts, which allow them to carry out photosynthesis in the early stages. This process is essential for energy production in the young plant.
Monocotyledonous and dicotyledonous plants
Monocotyledonous
Monocotyledonous plants are characterized by having a single cotyledon, an embryonic leaf that emerges when the seed germinates. These plants do not develop a true secondary growth, which means that they do not generate a trunk-like structure. In addition, they do not have the ability to form wood, and their growth occurs through the elongation of the internodes.
Among the best-known monocotyledonous plants are the grasses, which includes many cereals such as corn, wheat, and sugar cane. Other monocotyledonous plants include lilies, palm trees, tulips, onions, and orchids.
Dicot
Dicotyledonous plants, on the other hand, develop two cotyledons when germinating. They are the largest group of flowering plants and their germination is marked by the appearance of two embryonic leaves, which also have a nutritional function before the young plant develops its first true leaves.
The leaves of dicotyledonous plants vary significantly in shape and size, and may be heart-shaped, ribbon-shaped, or have compound forms. These plants typically develop growth rings which allow them to grow in height and width, often producing wood or firewood. Among the most important groups of dicotyledonous plants are the Rosaceae, Legumes and Rutaceas.
Some examples of dicotyledons are sunflowers, daisies, coffee, avocado, cherries and leguminous plants such as beans, peas and chickpeas.
Evolutionary importance of cotyledons
Cotyledons have played a key role in plant evolution. Differences in their structure and function, especially between monocots and dicots, reflect adaptations that have allowed different species to thrive in diverse ecological environments. For example, monocots, with only one cotyledon, have adapted to certain resource economies that make them more efficient in certain ecosystems, while dicots, with two cotyledons, have greater variability in growth and form.
Studying cotyledons also allows botanists to gain valuable insights into the evolution of plant species. This knowledge is not only important from a scientific perspective but also from a practical one, as it can contribute to improvements in agricultural techniques and cultivation methods, helping to optimize both food production and the sustainability of agricultural ecosystems.
Life cycle of cotyledons
The life cycle of cotyledons is relatively short but essential. They are the first structures to emerge in the germination process, providing initial support until the plant develops roots and true leaves. In some species, such as cannabis plants, cotyledons can last for several days or even weeks, until the true leaves are large and functional enough to take over photosynthesis and biomass production.
Once the true leaves emerge and begin to function, the cotyledons lose their importance. They wither and fall off, having fulfilled their role as the initial source of nutrients and energy for the plant.
Ultimately, cotyledons are a crucial part of the plant life cycle, providing the resources that seeds need to transform the energy stored in the embryo and begin their growth process towards a mature plant. Although their lifespan is short, their impact on the early development of plant species cannot be underestimated.
With this information, we have been able to observe the importance of cotyledons not only in terms of their biological function, but also as a key element in the adaptation and evolution of plants in the plant world. Their study continues to be a valuable source of knowledge, both in scientific disciplines and in agriculture and biotechnology.