What is a Seed?

Our environment will change when we understand the seed, and our world will change when we understand the life cycle of a plant.

The seed is explained as the grain that is formed from the ovule at the end of fertilization in plants and that provides the formation of a new plant (the reproduction of the plant). This small miracle, which is a few millimeters in size (most of the time) and has a basically dysfunctional appearance, contains millions of information, a miracle that can be witnessed. The seeds are usually hard-shelled and surrounded by a membrane. In fact, it can be described as a sleeping creature in this state. This outer area is called the seed coat (testa). After the outermost seed coat in a seed, the nutrient tissue pesiperma, endosperm and embryo parts come inward. The zygote formed by the fertilization of the egg cell in the embryo sac develops and reaches the embryo state. In summary, a seed, a few millimeters in size, that we somehow reach, consists of the outer shell, the nutrient store inside the shell (in some seeds the chin), and the embryo (living outline). This embryo performs its most basic vital activities at a very low level. Therefore, storing the seeds in an airtight way is a wrong practice (I will also mention about the storage of seeds).

Parts of the Seed:

Embryo (living draft) It is the living part of the seed.

The first leaflets in the embryo are called cotyledons. The cotyledons are responsible for storing nutrients and for photosynthesis by rising above the soil after germination. Embryos of plants whose seeds develop in the open and are not covered by fruit leaves (open-seeded) have more than two pods. Example: Pine, spruce, fir, cedar (usually fruitless trees). The flowers of open-seeded plants are called cones. These are called polycotyledonous (Polycotyledonous) plants.

Plants whose seeds are covered by fruit leaves (angiosperm) are divided into monocots (Monocotyledon) and dicotyledons (Dicotyledons). If monosexual flowers with only one of the sex organs are on the same plant, that is, if there are female or male flowers on a plant in different places, these plants are called monocots. Example: Watermelon, melon, pumpkin, hazelnut, walnut, chestnut, onion, mulberry etc. These plants are usually herbaceous, annuals. Other features include having fringe roots, not growing transversely due to lack of cambium tissues, stemless, thin, strip-shaped and parallel veined leaves. If the male and female flowers are on separate plants, these plants are called dioecious (two-pulling) plants. Example: Pistachio, fig, date, papaya, kiwi, apple, spinach, chickpea, asparagus etc. Other features of dioecious plants, which are generally woody plants, are that they are pile-rooted, that they can grow transversely thanks to their cambium tissues, that their transmission pipes are regular, that their leaves are stalked, hairy (mesh) veined, wide and piece-shaped.

Nutrient Tissue (Pesiperma, Endosperma):

It is the feeding place of the plant before it becomes an adult.

Seed Shell (Testa):

It contains substances such as suberin, lignin and cutin in its structure. Thanks to these substances, it has become hard. It has low permeability to water and gases. Thus, protection against excessive water loss and other harmful factors is provided until germination occurs.

Life Cycle in Plants – Life Cycle of Plant:

The existence of a plant begins much earlier than the process in which it can be physically traced and extends far beyond. The accumulation of generations transferred from seed to seed will continue to exist by being transferred from seeds to seeds whenever possible. Think about it, the accumulation of thousands of years ago is waiting somewhere, in a piece of cloth, to meet the soil and breathe the sun with the breath that he takes little by little.

Rosello, J.; Soriano, J.J. – In “The Life Cycle of the Plant”, he describes the process by which the plant can be followed physically as follows:

The physical development of a plant can be interpreted in three phases: youth, maturity and old age.

In youth, rapid development is observed. This phase, which starts with the germination of the seed, ends when the reproductive structures emerge. In the juvenile stage, the shape and size of the leaves may differ from the mature stage. In adulthood, the rate of development of stems, branches and leaves decreases. Flowers are formed, followed by fruit and seeds. The plant is considered mature when it reaches the maximum height and when its limbs reach the stage where they can perform their functions independently of its general condition. In old age, the leaves of the plant degenerate, the plant leaves its seeds to transfer its intergenerational qualities, and the process is completed with the death of the plant.

Vegetable plants can be divided into first-year flowering (annual), second-year flowering (biennial) and multi-flowering (perennial). Annuals flower during the time their seeds germinate (usually in summer), while biennials rest during the winter and flower in the following spring or summer.

Seed and Fruit :

In plants, pollination and fertilization must occur for the formation of fruit and seeding. Pollination can be expressed as the placing of pollen dusts in the male organs (Stamen) of the plant on the stigma, which is one of the female organs (Pistil) of the flower, germinating there and extending the pollen tube to the ovary. Fertilization is the fusion of the pollen tube reaching the ovary with the egg, forming the first draft of a living thing and the zygote, the first stage of the embryo. The formed zygote develops by dividing continuously and forms the embryo. A protective shell forms around the embryo and food is stored inside the shell. Seeds are divided into two parts as nutritive seeds and non-fattening seeds, depending on whether there is a special tissue containing nutrients or not. In the absence of a special nutrient tissue, the nutrient required for the germination of the seed is collected in the embryo, especially in the pods (as in the bean). In nutrient-dense seeds, the embryo, which is usually small, is either embedded in the nutrient tissue or pushed to one side.

Spare nutrients in seeds consist of starch, protein, oil and cellulose accumulated in the cell wall. According to the excess of the nutrient material, the seeds show a grainy, oily or hard horny feature. When the embryo in the seed develops when suitable conditions are found, it comes out of the seed and becomes free to give a plant similar to the mother plant, is called germination. Since the seeds contain little water until they germinate after they mature, their vital activities take place slowly. This process is called dormancy and sometimes they can stay dormant for years depending on the environmental conditions. Each seed has enough carbohydrates, fat, protein and minerals to last through dormancy. Although their basic vital activities take place very slowly, they take moisture from the environment during this period. When nutrients in the endosperm or cotyledon combine with moisture, it becomes essential food for the plant.

Plant seeds such as beans, cowpeas, watermelons, and pumpkins have two first leaves (Cotyledons) that contain nutrients. In other types of seeds, the food source is not the leaf, but the other part of the seed called the endosperm. The endosperm can be flour-like in some seeds, oily in others, and very hard in others, such as grains.

Seed propagation is important for the survival of plants. The influences that play a role in the spread of seeds are wind, water and animals. The seeds of wind-dispersed plants are small, light (1/200 mg), and have air sacs or wings that facilitate flight. Seeds dispersed by animals have organs such as feathers, thorns and hooks in order to be attached to animals and transmitted to distant places. Sometimes, the seeds eaten by animals can be carried far by being excreted in the feces without losing their germination characteristics in the digestive system. People also play an important role in the spread of seeds due to agricultural and economic needs.

Three conditions must be met for the seed to emerge from dormancy and germinate.

suitable temperature,
sufficient humidity,
Sufficient oxygen.

Types of Seed:

Although the general characteristics of the seeds are widely similar, it is quite possible to come across many seeds with differences such as size, shape and hardness. Apart from these differences, there are more common structural similarities. For example, the structure of most seeds consists of two first leaves, stems and roots. Seeds of this type, which cover the majority of plants, are called dicots. Monocots, on the other hand, have only one leaf. The vast majority of grasses, corn, rye and other grains and onions fall into this class.

Some seeds germinate at any given time, while the majority wait for optimal conditions to occur to ensure their development. Among seeds that respond to different conditions, for example, some seeds require cold or freezing temperatures to wake up. In others, a lighted environment is required for this process.

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