Plant Fruit is defined as the developed or matured ovary of the flower that is often formed after fertilization. It harbors the seed and aids their protection and spread. However, some fruits can be developed without fertilization by the process known as parthenocarpy.
Fruits may be classified into three groups, Simple fruits, Aggregate fruits, and Composite fruits.
A. Simple Fruits
Simple fruits are formed from a single ovary of a flower. They are also classified into fleshy fruits (in which the pericarp remains soft and juicy at maturity) and dry fruits (where the pericarp dries up and hardens).
Fleshy Simple Fruits
They possess a soft, fleshy, and edible pericarp.
- Drupe: A one-seeded fruit with a hard stony endocarp, fleshy mesocarp, and thin exocarp. Example: Mango, Coconut, Cherry. In coconut, the mesocarp is fibrous rather than fleshy.
- Berry: The whole pericarp (exocarp, mesocarp, and endocarp) is soft and edible. Example: Tomato, Grape, Brinjal, Banana
- Pome: The edible portion is formed from the parts of the flower (thalamus) rather than the ovary. Example: Apple, Pear
- Hesperidium: A modified berry where the outer part becomes leathery and the mesocarp is spongy. Example: Orange, Lemon
- Pepos: A berry where the outer part is hard and thick. Example: Pumpkin, Cucumber, Watermelon
Dry Simple Fruits
These fruits contain a dry and hard pericarp at the time of maturity. They are again classified as:
Dehiscent Fruits
These fruits split open upon maturity to expel seeds:
- Legume (Pod): Splits open along two sutures (e.g., Pea, Bean).
- Capsule: Splits open in different manners (e.g., Poppy, Cotton).
- Silique: Splits open into two halves with a membrane in between (e.g., Mustard).
Indehiscent Fruits
They do not split open upon maturity and are sub-classified as:
- Achene: Small, single-seeded fruit with a free seed coat (e.g., Sunflower).
- Caryopsis: The seed coat is united with the fruit wall (e.g., Wheat, Maize).
- Nut: The pericarp is hard and woody (e.g., Cashew nut, Acorn).
B. Aggregate Fruits
These fruits result from several ovaries of a single flower, each producing a small fruitlet. The whole structure looks like a cluster of fruits.
Example: Strawberry, Raspberry, Custard Apple.
C. Multiple (Composite) Fruits
These fruits result from a whole inflorescence (collection of flowers). The individual ovaries of various flowers combine to produce one fruit.
- Sorosis: Resulting from spike, spadix, or catkin inflorescences (such as Pineapple or jackfruit).
- Syconus: Resulting from a hypanthodium inflorescence (such as Fig).
Fruit Layers/Parts (Pericarp Structure)
The pericarp is the wall of the fruit that arises from the wall of the ovary. It consists of three layers:
1. Exocarp (Outer Layer)- The outer protective skin of the fruit is called exocarp. It may be soft and thin (e.g., Tomato, Grapes) or leathery and thick (e.g., Mango, Orange).
2. Mesocarp (Middle Layer)-This is the middle layer and is generally a fleshy and edible part of most fruits. It is juicy and thick in mango, watermelon, and citrus fruits.
3. Endocarp (Inner Layer)- The innermost layer that covers the seeds is called endocarp. It is stony and hard in drupes (e.g., Mango, Coconut) but pulpy and soft in berries (e.g., Tomato).
How do Fruits Grow?
Pollination-Pollination is the transfer of pollen from the anther, the male part of a flower, to the stigma, the female part of the flower. This can be through different agents including wind, water, insects, birds, or bats.
Fertilization– After the pollen grains have reached the stigma, they germinate to produce a pollen tube, which grows downward into the style and the ovary. The male gamete unites with the female egg cell within the ovule and forms a zygote. This is known as syngamy.
Ovule Becoming a Seed-The zygote becomes a fertilized egg that grows into an embryo. The ovule becomes a seed. The outer parts of the ovule develop into the seed coat (testa and tegmen).
Development of the Ovary into a Fruit– The ovary grows and develops into a fruit, which covers the seeds. The ovary wall transforms into the pericarp, which can be fleshy (e.g., Mango, Tomato) or dry (e.g., peas, Wheat).
The sepals, petals, and stamens usually dry up, but in a few fruits (e.g., Apple, Strawberry), other parts persist and make contributions to fruit development.
Fruit Ripening- The fruit is modified through biochemical changes such as color change, softening, and synthesis of aromas and sugars to attract dispersal agents. Ethylene, the plant hormone, is involved in fruit ripening.
Exceptions of Fruit Development
Parthenocarpy: Certain fruits form without fertilization, producing seedless fruits (e.g., Banana, Pineapple).
Apomixis: Certain plants form seeds without fertilization, producing genetically similar offspring (e.g., Citrus, Mango).
Functions of Fruits
Fruits are important in the reproductive cycle of plants. They are specialized plant organs that form from the ovary following fertilization and have various functions in the life cycle of the plant.
Seed Protection– The pericarp (wall of the fruit) covers and protects the forming seeds from environmental dangers like predators, desiccation (drying out), and mechanical injury. Hard fruit coats (e.g., Coconut, Nuts) offer robust protection, whereas fleshy fruits (e.g., Mango, Tomato) inhibit seed desiccation.
Seed Dispersal Mechanism- Fruits assist in effective seed dispersal to new sites, avoiding overcrowding and ensuring plant species survival.
Storage of Nutrients– Certain fruits store vitamins, sugars, and starch, which are used to nourish the growing embryo within the seed. Fruits such as Apple, Mango, and Banana serve as energy reservoirs, which benefit both consumers (animals, humans) and the seed.
Attraction of Seed Dispersers– Brightly colored, fragrant, sweet-smelling fleshy fruits contain many attractive chemicals to entice animals to disperse seeds. Birds, mammals, and insects eat the fruit, and the seeds are excreted or dropped at a far-off place, assisting in plant propagation.
Facilitating Germination– Certain fruits supply water and enzymatic stimuli that assist in seed germination. In dehiscent fruits (e.g., Pea, Mustard), the pericarp dries up and opens to discharge seeds at the appropriate time for germination.
Ecological Significance-Fruits preserve biodiversity by facilitating plant migration between various ecosystems. They are a source of food for herbivores and omnivores and are an integral component of food chains and wildlife support.
How do Fruits Assist in Seed Dispersal?
Seed dispersal is necessary for plant reproduction so that new plants can develop in various places away from the parent plant. This avoids competition for resources and enhances plant survival.
Types of Seed Dispersal by Fruits
Dispersal by Wind (Anemochory)- Some fruits form light structures, which are easily carried by wind. Examples: Dandelion (feathery pappus enables seeds to float in the air), Acer (wing-like structures facilitate gliding away from the parent tree), Cotton & Milkweed (hairy seeds facilitate wind dispersal).
Dispersal by Water (Hydrochory)- Fruits that grow in or near water possess buoyant and waterproof adaptations, enabling them to float and be transported by water currents. Examples: Coconut (fibrous, hard husk allows it to float long distances in the sea), Lotus & Water Lily (fruits have air spaces to enable them to float).
Animal Dispersal (Zoochory)- Fleshy, colorful, and sweet fruits attract animals, which eat them and subsequently deposit the seeds at a new site. Certain fruits possess hooks or sticky features to hold onto the fur or feathers of animals for transport. Examples: Mango, Guava, Cherries (consumed by mammals and birds, seeds dispersed via excretion), Xanthium (Cocklebur), Urena (hooked fruits get stuck to animal fur), Peepal, Banyan (consumed by birds and dispersed via droppings).
Dispersal by Explosion (Autochory or Self-Dispersal)- Certain dry fruits build up tension in their pericarp, bursting open when mature to forcefully expel seeds. Examples: Pea, Mustard, Castor (pods dehydrate and explosively split to disperse seeds), Balsam; touch-me-not-(capsules explode on contact).
Human Dispersal (Anthropochory)- Man plants, moves, and sows fruits and seeds for agriculture, horticulture, and food. Examples: Wheat, Rice, Apple, and Tomato (seeds are moved globally for farming).
Plant Fruit Adaptations
Fruits have evolved a variety of adaptations that aid in seed protection, dispersal, and survival. Fruits have evolved hard exterior shells, including coconuts, walnuts, and almonds, to defend the seeds against predators and environmental destruction. Others, including chili peppers and bitter melons, release poisonous or unpleasant substances that discourage animals from eating them until the seeds are mature enough to disperse. These adaptations provide for the survival and germination of seeds to the greatest extent possible.
Fruits also display varying seed dispersal adaptations. Some, for example, dandelions and maples, have light, wing-like parts that enable them to be transported by the wind (anemochory). Others, such as coconuts and lotus fruits, have waterproof, buoyant exteriors, allowing them to float and disperse by water (hydrochory). Most fruits, such as mangoes, apples, and cherries, depend on animals for dispersal (zoochory), enticing them with colors, sweetness, and pulp. Fruits like Xanthium and Urena possess hooked structures that get stuck on animal fur for transportation.
Some plants, like balsam and castor, employ self-dispersal, where their fruits explode when ripe, and forcibly expel seeds.
Environmental factors influencing fruit growth- A number of environmental factors influence the growth and development of fruits. It is important to understand these factors in order to maximize fruit production and achieve healthy fruit growth.
Temperature– Temperature influences all phases of fruit development, including flowering, fruit set, and ripening. Every plant possesses a range of temperatures optimal for proper growth. Low temperatures may inhibit growth, delay ripening, and result in frost damage, while excessive temperatures might lead to premature fruit drop, sunburn, or decrease the quality of the fruit. Tropical fruits like mangoes need warmer conditions, while temperate fruits like apples and cherries are better suited for cooler conditions.
Sunlight– Sunlight is essential for photosynthesis, which is how plants generate energy for growth. Proper sunlight is required for the fruit to achieve good size, shape, and flavor. Inadequate sunlight may result in low-quality fruit, reduced fruit size, and stunted crops. Excessive sunlight in very hot weather, however, may result in sunburn or discoloration of the fruit, which impacts both fruit quality and marketability.
Water Availability– Water is essential for fruit development, as it aids in cell expansion, nutrient transport, and fruit growth. Consistent irrigation ensures healthy fruit development, especially for water-heavy fruits like watermelons and citrus. However, overwatering or heavy rainfall can cause root rot, and fruit cracking, and promote fungal infections, which can damage the fruit. The balance of water supply is crucial for maintaining fruit quality.
Soil Quality and Fertility– The health of the soil has a direct impact on fruit development. Fertile soils with good drainage that is high in the nutrients necessary for healthy growth, including nitrogen, phosphorus, and potassium, support the overall plant health and development. pH in the soil also plays a crucial role in nutrient uptake; various fruits have varying pH requirements. Blueberries, for example, require acidic soil, whereas most other fruits do well in slightly acidic to neutral pH.
Pollination– For the majority of fruit crops, successful pollination is necessary for fruit set and seed production. Pollination is generally performed by insects (bees, butterflies), birds, or wind. When pollination is inadequate, fruits will not develop or yield low-quality fruit. A few plants, like bananas, form fruit without fertilization (parthenocarpy), but cross-pollination produces greater genetic variation and more durable fruit in most.
Pests and Diseases– Insects and diseases are major factors that can influence fruit development. Fruits can be damaged by pests like fruit flies, aphids, and caterpillars either through direct feeding or disease transmission. Bacterial blights and fungal infections are also typical causes of poor fruit development. Pests and disease control are important in maintaining fruit health as well as in having a good harvest.
Common Problems Affecting Plant Fruits
Plant fruits are prone to numerous problems that can affect their growth and lower their yield. These issues may be caused by environmental factors, pests, diseases, or poor care.
Pests and Insects– Pests like fruit flies, aphids, mealybugs, and caterpillars usually consume the fruits or the plant tissues, causing damage to the fruit or making it rotten. These pests can even be vectors for diseases like viruses, inflicting additional damage on the plant. Pest control activities in the form of natural enemies, traps, or organic chemicals are required regularly to keep these threats under control.
Disease Infections– Fungal and bacterial infections are prevalent in fruit crops and can lead to rotting browning, or wilting of fruits. Powdery mildew, anthracnose, and botrytis are some diseases that infect a broad range of fruits such as strawberries, grapes, and peaches. Plant diseases tend to spread quickly in hot and humid conditions, so preventive strategies such as pruning, employing disease-resistant varieties, and crop rotation can reduce risks.
Nutrient Deficiencies– Fruits can be affected by stunted growth or malformations when there are nutrient deficiencies in the soil. Deficiencies of basic nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium can result in issues such as blossom-end rot of the tomatoes or stunted cucumber growth. Soil analysis and prompt fertilization can help counteract nutrient imbalance and enable proper fruit growth.
Inadequate Pollination– Inadequate pollination causes poor fruit sets and, in certain instances, seedless fruits. Lack of pollinators, e.g., bees and butterflies, or adverse weather conditions during the pollination season can cause fruit abortion or lower yields. The incorporation of bee-friendly practices and planting flowers that attract pollinators can enhance pollination and yield a good harvest.
Environmental Stress– Severe weather conditions, such as drought, frost, and strong winds, have the potential to stress fruit crops and impact the development of the fruit. Drought can lead to fruit shriveling or smaller size, whereas frost damage will affect flowers or trigger early fruit drop. Adequate irrigation, frost protection methods, and mulching may reduce the impacts of environmental stress.
Interesting and fun facts about plant fruits
Seedless watermelons: Seedless watermelons are grown by breeding two genetically altered watermelon plants, and the resulting fruit has sterile seeds.
Longest growing fruit: The durian is sometimes called the “king of fruits” and grows for approximately 3-5 years.
Citrus fruits are hybrid fruits: Most citrus fruits, such as oranges and lemons, are hybrids of various species, having been cultivated for their sweet, sour taste.
Apple types: More than 7,500 apple varieties are cultivated across the globe, varying in flavor, size, and color.
Fruits as ancient medicine: Fruits like figs and pomegranates were applied in medicine in ancient times for their medicinal value.
Conclusion
Plant fruits are essential parts of the plant reproductive system and play a multitude of ecological roles, such as seed dispersal, animal nutrition, and maintaining the biodiversity of ecosystems. With their intriguing adaptations and diverse morphologies, fruits supply humans and animals with fundamental sustenance. Fruits develop and grow due to environmental parameters such as temperature, sunlight, water, and soil quality, but issues like pests, disease, and environmental stressors might prevent them from thriving. An understanding of such factors enables us to appreciate fruit crops more and manage them appropriately for their cultivation and sustainability in agriculture. Fruits are not only crucial sources of food but also crucial players in the ecological balance of the planet.
Fruits have also evolved to thrive in harsh environments. In arid environments, fruits such as cacti have thick, water-retaining fruits to survive dry spells. In temperate climates, some fruits, like pinecones and berries, go dormant during winter and germinate during spring. Rainforest fruits, on the other hand, have soft, thin pericarps and are produced in clusters to achieve optimal animal dispersal of seeds. These features enable plants to survive in various environments while perpetuating their species.
References
- Libretexts. (2022, May 4). 2.7.3: Fruits and Dispersal. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Botany/Botany_(Ha_Morrow_and_Algiers)/02%3A_Biodiversity_(Organismal_Groups)/2.07%3A_Angiosperm_Diversity/2.7.03%3A_Fruits_and_Dispersal
- The Editors of Encyclopaedia Britannica. (2025, January 3). Fruit | Definition, Description, Types, Examples, & Facts. Encyclopedia Britannica. https://www.britannica.com/science/fruit-plant-reproductive-body
- Admin. (2021, June 24). Fruits – formation, parts and different types of fruits. BYJUS. https://byjus.com/biology/fruit-formation-parts-types/
- Fruits | Definition, Types & Examples – Lesson | Study.com. (n.d.). study.com. https://study.com/academy/lesson/fruit-definition-types-benefits-examples.html
- Trisha. (2015, August 27). Fruit and It’s Types (Explained With Examples). Biology Discussion. https://www.biologydiscussion.com/plants/fruit-and-its-types-explained-with-examples/6398
- Nakano, M. (2020, September 15). Plant morphology – flowers and fruit. Pressbooks. https://opentextbc.ca/plantidentification/chapter/plant-morphology-flowers-and-fruit/
- Simpson, M. G. (2010). Diversity and classification of flowering plants: Eudicots. In Elsevier eBooks (pp. 275–448). https://doi.org/10.1016/b978-0-12-374380-0.50008-7
- Fruit and Seed Dispersal | Biology for Majors II. (n.d.). https://courses.lumenlearning.com/wm-biology2/chapter/fruit-and-seed-dispersal/
- Seed dispersal. (n.d.). Science Learning Hub. https://www.sciencelearn.org.nz/resources/103-seed-dispersal
- Fruit dispersal. (n.d.). Peda.net. https://peda.net/kenya/css/subjects/biology/form-three/ripaa/fruit-dispersal
- NEETprep. (n.d.). NCERT Ebook for Morphology of Flowering Plants – Morphology of Flowering Plants – Chapter 5 – NCERT Biology – XI. https://www.neetprep.com/ncert/1618-Morphology-Flowering-Plants-Morphology-Flowering-Plants–NCERT-Chapter-PDF
