Introduction to Fruits: Definition, Importance and Diversity
The fruits They constitute one of the most fascinating and diverse organs in the plant world. In botany, the fruit is the organ derived primarily from the ovary of the flower, which transforms and matures after fertilization, enveloping and protecting the seeds until they are ready for dispersal. However, in many cases, other organs may participate in their formation, such as the receptacle, the calyx, and even the bracts.
Beyond their reproductive role, fruits have been key to the evolution and adaptation of plants, allowing them to conquer and diversify their habitats. This adaptation has given rise to a surprising variety of fruit shapes, sizes, colors, textures, and flavors, which in turn has decisively influenced the human diet, agriculture, the global economy, and planetary biodiversity.
In everyday life, many plant species have historically been cultivated for their fruits, as these are usually edible, fragrant, juicy, and nutritious, forming the basis of nutrition in different cultures. This is where the common distinction between fruits (usually fleshy and sweet fruits) and nuts, although both have a similar origin and function.
The morphological diversity of fruits is vast: they can be spherical, elliptical, pear-shaped, spiral, winged, or cylindrical, with different surface characteristics such as smooth, rough, spiny, pubescent, or pruinose. Furthermore, their size varies greatly between species, from tiny fruits less than a millimeter in size to giants like certain pumpkins or legumes that exceed a meter in length.
Formation and Anatomy of Fruits
The origin of the fruit is closely related to the process of sexual reproduction in flowering plants (angiosperms). After pollination and ovary fertilization, the ovary begins to undergo physiological and structural changes, developing into a fruit. In certain cases, additional parts of the flower, such as the receptacle or calyx, participate in the formation of the so-called accessory fruit.
In anatomical terms, the basic structure of the ripe fruit is composed of a wall called pericarp, which thickens during development and has the main function of protect the seedsThe pericarp is classically divided into three distinct layers:
- Exocarp (or epicarp): is the outermost layer, which can vary from smooth and thin to thick and rough; it often represents the visible skin of the fruit.
- Mesocarp: This is the middle layer, generally fleshy in fleshy fruits and with varying degrees of hydration. It is usually the edible and tasty part in most fruits.
- Endocarp: is the inner layer that directly surrounds the seed or seeds. In some fruits, such as drupes (such as peaches), it transforms into a bony layer, forming the so-called pit, stone, or pyrene.
The development of these layers and the degree of differentiation between them varies significantly depending on the type of fruit, which contributes to its morphological and functional diversity.
Fruit Classification: Botanical Criteria
Fruits can be classified according to various criteria, primarily according to their structural origin, texture, seed dispersal, and the number of carpels involved in their development. The main classification criteria and resulting subgroups are explained below:
By consistency of the pericarp: Dry and fleshy fruits
- Nuts: They have a dry, hard pericarp when ripe and are generally not succulent. They are more abundant in the world's flora and have multiple subtypes depending on how they split open to release the seeds. To learn more about the different types, visit types of nuts.
- fleshy fruits: Its pericarp remains hydrated and fleshy at maturity, is generally edible and constitutes the most appreciated part of many fruits.
By the form of opening: Dehiscent and indehiscent
- Dehiscent: They split open spontaneously at maturity to release the seeds. Typical examples are the capsule, follicle, legume, and siliqua.
- Indehiscent: They do not open when ripe; the seed remains enclosed until the fruit decomposes or is ingested by animals.
By the number of carpels involved
- Simple fruits: they develop from one or more fused carpels of a single flower.
- Aggregate fruits (etheriums): arise from a single flower with distinct free pistils; they give rise to a cluster of small fruits on the same receptacle, as occurs in the strawberry.
- Multiple fruits (collective or compound): they originate from the fusion of several gynoecium of different flowers of an inflorescence, as in the pineapple.
By the dispersing agent
- Anemochores: dispersed by the wind; they are usually light and may have wings or hairs (e.g., maple samaras).
- Zoocoros: dispersed by animals, either externally attached (epizoochory) or after being ingested (endozoochory). For examples of animal dispersal, see garden plants.
- Hydrochores: dispersed by water (e.g., coconut).
- Autochoirs: They have their own seed expulsion mechanisms.
- Policoros: they have a combination of dispersal mechanisms.
Nuts: Types and Characteristics
The nuts These are those whose pericarp hardens completely upon maturity, lacks juicy pulp, and serves as a protective function for the seed. They are found in both wild and cultivated species and come in a variety of shapes and opening or dispersal mechanisms. Their main types are detailed below, enriching the information with new insights into ecology, taxonomy, and nutritional and cultural uses.
Indehiscent Nuts
These fruits do not split open spontaneously when ripe. The seeds remain trapped inside until the fruit degrades, is cracked by animal action, or is subjected to physical processes.
- Achene: a dry fruit with a single seed; the pericarp is not attached to the seed. Example: sunflower, dandelion.
- Samara: winged achene, ideal for wind dispersal. Example: maple, ash.
- Caryopsis (or caryopse): characteristic of grasses (wheat, rice, corn), the pericarp is welded to the seed.
- Nut: a fruit with a hard, woody pericarp and a single, large seed. Examples: hazelnut, chestnut, common walnut, acorn.
- Nutella: small nut, often with additional covering (example: oak fruit).
Dehiscent Nuts
They open through defined slits or pores to release the seeds around them or allow for assisted dispersal. For examples of fruits that open, see types of nuts.
- Follicle: opens by a single suture; typical of oleander and lily.
- Legume: opens by two sutures; characteristic of legumes (beans, peas, carob).
- Capsule: fruit with several carpels, variable aperture (pores, valves, teeth). Example: poppy, lily, cotton.
- Siliqua and silicle: elongated capsules (silíqua) or short capsules (silicula) typical of the Brassicaceae family, which open into two valves.
- Pixidio: capsule that opens transversely.
Schizocarpic Nuts
They correspond to those that, when mature, fragment into portions known as mericarps, each containing a seed, but they do not open spontaneously. The schizocarp is typical of families such as Umbelliferae. To learn more about their structures, review deciduous forest.
- Cremocarpus: fruit of umbelliferae, divided into two hanging mericarps.
- Jailer: it is fragmented into four parts, frequent in Labiates and Boraginaceae.
- Regma: It is divided into as many mericarps as carpels, typical of Euphorbiaceae.
Nuts: Uses and Nutritional Benefits
In the human diet, many nuts play a fundamental role due to their energy content, proteins, healthy fats, fiber, minerals, and vitamins. The most notable ones are nuts, almonds, hazelnuts, pistachios, pinions, peanuts (botanically a legume), Cashews, macadamia and other lesser-known varieties such as sacha inchi, pili nuts, cola nuts, and tiger nuts. For more information on their cultivation, visit types of rice.
- AlmondsRich in vitamin E, calcium, and fiber, varieties such as Marcona and Llargueta are appreciated in baked goods and dairy products.
- Nuts: High in omega 3 fatty acids and antioxidants, with varieties such as common, pecan and macadamia.
- PistachiosHigh in vitamin B6 and fiber, varieties such as Kerman and Siirt are used in snacks and haute cuisine.
- Cashew nuts: Rich in iron, magnesium and healthy fats, they are ideal for vegan sauces and pastries.
- Pinions: Delicate flavor, present in Mediterranean and Asian cuisine, Mediterranean and Chinese varieties.
Other lesser-known fruits, such as cedar nuts, acorns, ginkgo nuts, and egusi nuts, are notable for their ancestral and medicinal value, or for their use in traditional cuisines in Asia, Africa, and the Americas.
Fleshy Fruits: Types and Examples
The fleshy fruits They are characterized by a partially or completely succulent, juicy, and generally edible pericarp. They are key to the human diet, but also to ecology by attracting dispersing animals that aid in plant reproduction. For more information on varieties, check out rare succulent plants.
- Baya: a fruit with completely fleshy walls and seeds immersed in the pulp. Example: tomato, grape, banana, guava.
- Drupe: contains a single seed surrounded by a hard endocarp (stone) and a fleshy mesocarp. Example: cherry, olive, peach, mango.
- Knob: The floral receptacle forms the majority of the fruit; typical of apples and pears.
- Hesperidium: characteristic of citrus fruits, it has an outer covering with aromatic glands and juicy sacs inside. Examples: orange, lemon, tangerine.
- Peponide: fleshy fruit of cucurbits, with a hardened shell and juicy pulp; example: pumpkin, cucumber, melon, watermelon.
Other fleshy fruits include the rose hip, which has a mixed characteristic, and fruits with complex or multiple development, such as those found in pineapple and fig.
Aggregate and Multiple Fruits: Structural Complexity
- Aggregate fruit (etherium): the result of a single flower with several free pistils, each developing into a small fruit. For example, strawberries (polyachenes) and raspberries (polydrupes). To grow them and learn more, visit espalier.
- Multiple or collective fruit: formed from the fusion of multiple gynoeciums of several flowers in an inflorescence. For example, the pineapple (sorosis) and the fig (syconium).
Its interest lies in the participation of additional floral organs in the final constitution of the fruit, which increases structural diversity and ecological adaptability.
Evolution, Ecology and Fruit Dispersal Strategies
The evolution of fruits is closely linked to the coevolution of dispersal agents (wind, water, animals) and the ecological conditions of their environment. Plants have developed sophisticated strategies to ensure efficient seed dispersal, which is vital for reducing competition between nearby individuals and promoting the colonization of new habitats.
- Anemochoric dispersal: Light fruits (such as samaras) have wings or hairs that facilitate their transport by the wind.
- Zoochoric dispersal: involves the participation of animals. Fruits may adhere to fur or plumage (epizoochory) or be ingested and expelled without harm (endozoochory); they often have bright colors, intense aromas, or appealing flavors. To learn more about animal dispersers, check out types of chickpeas.
- Hydrochoric dispersion: fruits that can float, such as coconuts.
- Self-dispersion: active expulsion of seeds through mechanisms specific to the fruit, such as twisting or bursting of the pericarp in some legumes.
In addition, there are species with heterocarpy, that is, they produce fruits of different morphologies and dispersal strategies on the same plant, which increases adaptability to environmental changes.
Histological Structure and Physiology of the Fruit
Histologically, the fruit shows well-differentiated layers. The pericarp includes reserve tissues, protective tissues, and often tissues adapted to attract dispersers (pigmented cells, essence- or sugar-forming cells). Fruit ripening is regulated by complex hormonal mechanisms, where phytohormones such as auxins, gibberellins, cytokinins and ethylene play a fundamental role.
Ripening involves changes in texture, color, chemical composition, and aroma. In fleshy fruits, the degradation of chlorophyll and the increase in carotenoids and anthocyanins give them the vibrant colors of ripe fruits. This process coincides with the synthesis of sugars and the accumulation of essential nutrients.
Climacteric and Non-Climateric Fruits: Ripening and Postharvest
Fruits are classified as climacteric or non-climacteric depending on how they regulate and complete ripening after harvest, which is essential for the food industry and the design of preservation and transportation systems. To learn about best practices, you can visit flower branches.
- Climacteric fruits: They significantly increase ethylene production and the respiratory rate during ripening (e.g., tomato, banana, apple, avocado).
- Non-climacteric fruits: They do not experience this ethylene peak, their ripening occurs more slowly and gradually (e.g., citrus fruits, grapes, strawberries).
Post-harvest handling, storage in controlled atmospheres, and the use of hormone regulators have revolutionized the way fresh fruit is distributed and consumed globally.
Fruits in Gymnosperms and Pseudocarps
In flowerless plants, such as gymnosperms, there are no true fruits since there are no closed ovaries; however, similar structures called pseudocarps o strobili, whose purpose is to protect and aid in seed dispersal. For more information on the species, see amazon plants.
- Strobila: typical of cypresses, pines and firs; it can be woody or fleshy (in junipers and savins).
- Aril: a fleshy outgrowth surrounding the seed, as in the yew, with the appearance of a red fruit.
Although these structures can be confused with fruits in the botanical sense, their origin and formation is different from that of the true fruits of angiosperms.
Economic, Ecological and Nutritional Importance of Fruits
The diversity of fruits has an immense impact on the global economy, food security, human health, and ecosystem maintenance. Many fruits form the basis of agriculture, serving as a primary source of vitamins, minerals, antioxidants, fiber, and energy in the diet. For more details on specific species, see .
In different agricultural and cultural systems, fruits are essential, both fresh and in processed products. Some, such as cocoa and coffee, have spawned entire industries and shaped civilizations. Others, such as nuts, have played a leading role in nutrition due to their energy density and long-term preservation.
Furthermore, the fruits fulfill ecological functions: they are food for thousands of animal species, they help regenerate forests, they influence the water cycle, soil fertility, and the maintenance of biodiversity.
Main Varieties and Species of Fruits of Human Interest
- Fleshy edible fruits: apples, pears, bananas, grapes, oranges, watermelons, peaches, cherries, mangoes, papayas, pomegranates, tomatoes, avocados.
- Dried fruits for consumption: almonds, walnuts, hazelnuts, pistachios, pine nuts, peanuts, cashews, macadamia nuts, tiger nuts.
- Accessory fruits: apple, strawberry, pineapple.
- Exotic fruits: sacha inchi, pili nuts, ginkgo nut, cola nut, egusi nut, acorns (with traditional uses).
Each of these types presents enormous varieties adapted to different regions and climates, with particular characteristics of flavor, texture, color, and nutritional value.
Nutritional Properties and Health Benefits
Fruits, especially sweet and juicy ones, are rich in natural sugars, fiber, antioxidant vitamins (such as vitamins C and A), essential minerals (potassium, magnesium, calcium, iron), and phytonutrients that prevent disease and promote overall well-being. Nuts, meanwhile, are notable for their healthy fats, proteins, and their beneficial effects on cardiovascular and metabolic health.
Regular consumption of a wide variety of fruits contributes to a balanced diet, prevents chronic diseases, promotes longevity, and improves quality of life.
Fruits and Culture: Traditional and Current Uses
Throughout history, fruits have been symbols of fertility, abundance, and life in numerous cultures. Beyond their nutritional value, they have had medicinal, religious, artistic, and social uses, playing a central role in mythologies, festivals, and ancestral practices. To learn more about their history, read this article.
Today, global gastronomy values the diversity of fruits, integrating native and foreign species into innovative preparations, pastries, juices, oils, jams, alcoholic beverages, and more. Preserving local and wild varieties is essential to maintaining resilience and genetic diversity in times of climate change and growing food needs.
The bet for a diet rich in various fruits, both fresh and dried, is a widespread recommendation among nutrition and public health experts, given its relationship with disease prevention and the promotion of overall health.
