Fruit anatomy

Last updated
Longitudinal section of a female flower of a squash plant (courgette), showing the ovary, ovules, pistil and petals Femalesquash3747.JPG
Longitudinal section of a female flower of a squash plant (courgette), showing the ovary, ovules, pistil and petals

Fruit anatomy is the plant anatomy of the internal structure of fruit. [1] [2] Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits.

Contents

In some fruits, the edible portion is not derived from the ovary, but rather from the aril, such as the mangosteen or pomegranate, and the pineapple from which tissues of the flower and stem provide food.

The grains of grasses are single-seed simple fruits wherein the pericarp and seed coat are fused into one layer. This type of fruit is called a caryopsis. Examples include cereal grains, such as wheat, barley, oats and rice.

Categories of fruits

Fruits are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Aggregate fruits are formed from a single compound flower and contain many ovaries or fruitlets. [3] Examples include raspberries and blackberries. Multiple fruits are formed from the fused ovaries of multiple flowers or inflorescence. [3] An example of multiple fruits are the fig, mulberry, and the pineapple. [3] Simple fruits are formed from a single ovary and may contain one or many seeds. They can be either fleshy or dry. In fleshy fruit, during development, the pericarp and other accessory structures become the fleshy portion of the fruit. [4] The types of fleshy fruits are berries, pomes, and drupes. [5] In berries, the entire pericarp is fleshy but this excludes the exocarp which acts as more as a skin. There are berries that are known as pepo, a type of berry with an inseparable rind, or hesperidium, which has a separable rind. [4] An example of a pepo is the cucumber and a lemon would be an example of a hesperidium. The fleshy portion of the pomes is developed from the floral tube and like the berry most of the pericarp is fleshy but the endocarp is cartilaginous; an apple is an example of a pome. [4] Lastly, drupes are known for being one-seeded with a fleshy mesocarp; an example of this would be the peach. [4] However, there are fruits where the fleshy portion is developed from tissues that are not the ovary, such as in the strawberry. The edible part of the strawberry is formed from the receptacle of the flower. Due to this difference the strawberry is known as a false fruit or an accessory fruit.

There is a shared method of seed dispersal within fleshy fruits. These fruits depend on animals to eat the fruits and disperse the seeds in order for their populations to survive. [5] Dry fruits also develop from the ovary, but unlike the fleshy fruits they do not depend on the mesocarp but the endocarp for seed dispersal. [5] Dry fruits depend more on physical forces, like wind and water. Dry fruits' seeds can also perform pod shattering, which involve the seed being ejected from the seed coat by shattering it. Some dry fruits are able to perform seed pod explosions, such as wisteria, resulting the seed to be dispersed over long distances. Like fleshy fruits, dry fruits can also depend on animals to spread their seeds by adhering to animal's fur and skin, this is known as epizoochory. Types of dry fruits include achenes, capsules, follicles or nuts. Dry fruits can also be separated into dehiscent and indehiscent fruits. Dry dehiscent fruits are described as a fruit where the pod has an increase in internal tension to allow seeds to be released. These include the sweet pea, soybean, alfalfa, milkweed, mustard, cabbage and poppy. [5] Dry indehiscent fruit differ in that they do not have this mechanism and simply depend on physical forces. Examples of species indehiscent fruit are sunflower seeds, nuts, and dandelions. [5]

Evolutionary history

There is a wide variety in the structures of fruit across the different species of plants. Evolution has selected for certain traits in plants that would increase their fitness. This diversity arose through the selection of advantageous methods for seed protection and dispersal in different environments. [5] It is known that dry fruits were present before fleshy fruits and fleshy fruits diverged from them. [5] A study looking at the family Rubiaceae found that within the family, fleshy fruits had evolved independently at least 12 times. [6] This means that fleshy fruits were not passed on to following generations but that this form of fruit was selected for in different species. This may imply that fleshy fruit is a favorable and beneficial trait because not only does it disperse the seeds, but it also protects them. [7] There is also a variety of dispersal methods that are used by different plants. The origins of these modes of dispersal have been found to be a more recent evolutionary change. [6] Of the methods of dispersal, the plants that use animals have not changed in many ways from the original trait. Due to this, it may be assumed that animal dispersal is an efficient form of dispersal, however there has been no evidence that it increases dispersal distances. [6] Therefore, the question remains of what evolutionary mechanism causes such dramatic diversity. It has been found, however, that simple changes within developmental regulatory genes can cause large alterations within the anatomical structure of the fruit. [5] Even without knowing the mechanism involved in the biodiversity of fruit, it is clear that this diversity is important to the continuation of plant populations.

Anatomy of simple fruits

Diagram of a typical drupe (in this case, a peach), showing both fruit and seed Drupe fruit diagram.svg
Diagram of a typical drupe (in this case, a peach), showing both fruit and seed
A schematic picture of an orange hesperidium Orange cross section description.png
A schematic picture of an orange hesperidium
A segment of an orange that has been opened to show the pulp (juice vesicles) of the endocarp Citrus pulp1.JPG
A segment of an orange that has been opened to show the pulp (juice vesicles) of the endocarp

In berries and drupes, the pericarp forms the edible tissue around the seeds. In other fruits such as citrus and stone fruits (Prunus) only some layers of the pericarp are eaten. In accessory fruits, other tissues develop into the edible portion of the fruit instead, for example the receptacle of the flower in strawberries.

Pericarp layers

In fleshy fruits, the pericarp is typically made up of three distinct layers: the epicarp (also known as exocarp), which is the outermost layer; the mesocarp, which is the middle layer; and the endocarp, which is the inner layer surrounding the ovary or the seeds. In a citrus fruit, the epicarp and mesocarp make up the peel. In dry fruits, the layers of the pericarp are not clearly distinguishable.

Epicarp

Epicarp (from Greek : epi-, "on" or "upon" + -carp, "fruit") is a botanical term for the outermost layer of the pericarp (or fruit). The epicarp forms the tough outer skin of the fruit, if there is one. The epicarp is sometimes called the exocarp, or, especially in citrus, the flavedo.

Flavedo

Flavedo is mostly composed of cellulosic material but also contains other components, such as essential oils, paraffin waxes, steroids and triterpenoids, fatty acids, pigments (carotenoids, chlorophylls, flavonoids), bitter principles (limonin), and enzymes.

In citrus fruits, the flavedo constitutes the peripheral surface of the pericarp. It is composed of several cell layers that become progressively thicker in the internal part; the epidermic layer is covered with wax and contains few stomata, which in many cases are closed when the fruit is ripe.

When ripe, the flavedo cells contain carotenoids (mostly xanthophyll) inside chromoplasts, which, in a previous developmental stage, contained chlorophyll. This hormonally controlled progression in development is responsible for the fruit's change of color from green to yellow upon ripening. Citrus flavedo may be scraped off the fruit to create zest.

The internal region of the flavedo is rich in multicellular bodies with spherical or pyriform shapes, which are full of essential oils.

Mesocarp

The mesocarp (from Greek: meso-, "middle" + -carp, "fruit") is the fleshy middle layer of the pericarp of a fruit; it is found between the epicarp and the endocarp. It is usually the part of the fruit that is eaten. For example, the mesocarp makes up most of the edible part of a peach, and a considerable part of a tomato. "Mesocarp" may also refer to any fruit that is fleshy throughout.

In a hesperidium, as is found in citrus fruit, the mesocarp is also referred to as albedo or pith. It is the inner part of the peel and is commonly removed before eating. In citron fruit, where the mesocarp is the most prominent part, it is used to produce succade.

Endocarp

Almond endocarp Almond shell.jpg
Almond endocarp

Endocarp (from Greek: endo-, "inside" + -carp, "fruit") is a botanical term for the inside layer of the pericarp (or fruit), which directly surrounds the seeds. It may be membranous as in citrus where it is the only part consumed, or thick and hard as in the pyrenas of drupe fruits of the family Rosaceae such as peaches, cherries, plums, and apricots.

In nuts, it is the stony layer that surrounds the kernel of pecans, walnuts, etc., and that is removed before consumption.

In citrus fruits, the endocarp is separated into sections, which are called segments. These segments are filled with juice vesicles, which contain the juice of the fruit.

Anatomy of grass fruits

The grains of grasses are single-seed simple fruits wherein the pericarp (ovary wall) and seed coat are fused into one layer. This type of fruit is called a caryopsis. Examples include cereal grains, such as wheat, barley, and rice.

The dead pericarp of dry fruits represents an elaborated layer that is capable of storing active proteins and other substances for increasing survival rate of germinating seeds. [8]

See also

Related Research Articles

<span class="mw-page-title-main">Fruit</span> Seed-bearing part of a flowering plant

In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.

<span class="mw-page-title-main">Berry</span> In the culinary sense, small edible fruit

A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples of berries in the culinary sense are strawberries, raspberries, blueberries, blackberries, red currants, white currants and blackcurrants. In Britain, soft fruit is a horticultural term for such fruits.

<span class="mw-page-title-main">Drupe</span> Fleshy fruit with hard inner layer (endocarp or stone) surrounding the seed

In botany, a drupe is an indehiscent type of fruit in which an outer fleshy part surrounds a single shell of hardened endocarp with a seed (kernel) inside. These fruits usually develop from a single carpel, and mostly from flowers with superior ovaries. Xylem fibres are dead and xylem parenchyma are living

<span class="mw-page-title-main">Accessory fruit</span> Botanical category of fruit

An accessory fruit is a fruit that contains tissue derived from plant parts other than the ovary. In other words, the flesh of the fruit develops not from the floral ovary, but from some adjacent tissue exterior to the carpel. As a general rule, the accessory fruit is a combination of several floral organs, including the ovary. In contrast, true fruit forms exclusively from the ovary of the flower.

<span class="mw-page-title-main">Nut (fruit)</span> In botany, type of dry indehiscent fruit

A nut is a fruit consisting of a hard or tough nutshell protecting a kernel which is usually edible. In general usage and in a culinary sense, a wide variety of dry seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent).

<span class="mw-page-title-main">Achene</span> Class of simple non-opening dry fruits

An achene, also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent. Achenes contain a single seed that nearly fills the pericarp, but does not adhere to it. In many species, what is called the "seed" is an achene, a fruit containing the seed. The seed-like appearance is owed to the hardening of the fruit wall (pericarp), which encloses the solitary seed so closely as to seem like a seed coat.

<span class="mw-page-title-main">Pome</span> Fruit with apple-like features

In botany, a pome is a type of fruit produced by flowering plants in the subtribe Malinae of the family Rosaceae. Pome fruits consist of a central "core" containing multiple small seeds, which is enveloped by a tough membrane and surrounded by an edible layer of flesh. Pome fruit trees are deciduous, and undergo a dormant winter period that requires cold temperatures to break dormancy in spring. Well-known pomes include the apple, pear, and quince.

<span class="mw-page-title-main">Mangosteen</span> Tropical evergreen tree with edible fruit

Mangosteen, also known as the purple mangosteen, is a tropical evergreen tree with edible fruit native to tropical lands surrounding the Indian Ocean. Its origin is uncertain due to widespread prehistoric cultivation. It grows mainly in Southeast Asia, southwest India and other tropical areas such as Colombia and Puerto Rico, where the tree has been introduced.

<span class="mw-page-title-main">Aril</span> Membranous or fleshy appendage that partly or wholly covers a seed

An aril, also called an arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode or false aril is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ovary, an arillode forms from a different point on the seed coat. The term "aril" is sometimes applied to any fleshy appendage of the seed in flowering plants, such as the mace of the nutmeg seed. Arils and arillodes are often edible enticements that encourage animals to transport the seed, thereby assisting in seed dispersal. Pseudarils are aril-like structures commonly found on the pyrenes of Burseraceae species that develop from the mesocarp of the ovary. The fleshy, edible pericarp splits neatly in two halves, then falling away or being eaten to reveal a brightly coloured pseudaril around the black seed.

<i>Sclerocarya birrea</i> Species of tree

Sclerocarya birrea, commonly known as the marula, is a medium-sized deciduous fruit-bearing tree, indigenous to the miombo woodlands of Southern Africa, the Sudano-Sahelian range of West Africa, the savanna woodlands of East Africa and Madagascar.

<i>Mammea americana</i> Species of tree

Mammea americana, commonly known as mammee, mammee apple, mamey, mamey apple, Santo Domingo apricot, tropical apricot, or South American apricot, is an evergreen tree of the family Calophyllaceae, whose fruit is edible. It has also been classified as belonging to the family Guttiferae Juss. (1789), which would make it a relative of the mangosteen.

<span class="mw-page-title-main">Dehiscence (botany)</span> Splitting of a mature plant structure along built-in line of weakness to release contents

Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent. Structures that do not open in this way are called indehiscent, and rely on other mechanisms such as decay or predation to release the contents.

<span class="mw-page-title-main">Ovary (botany)</span> Flowering plant reproductive part

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule(s) and is located above or below or at the point of connection with the base of the petals and sepals. The pistil may be made up of one carpel or of several fused carpels, and therefore the ovary can contain part of one carpel or parts of several fused carpels. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary, and, for each individual pollen grain, to fertilize one individual ovule. Some wind pollinated flowers have much reduced and modified ovaries.

<span class="mw-page-title-main">Berry (botany)</span> Botanical fruit with fleshy pericarp, containing one or many seeds

In botany, a berry is a fleshy fruit without a stone (pit) produced from a single flower containing one ovary. Berries so defined include grapes, currants, and tomatoes, as well as cucumbers, eggplants (aubergines) and bananas, but exclude certain fruits that meet the culinary definition of berries, such as strawberries and raspberries. The berry is the most common type of fleshy fruit in which the entire outer layer of the ovary wall ripens into a potentially edible "pericarp". Berries may be formed from one or more carpels from the same flower. The seeds are usually embedded in the fleshy interior of the ovary, but there are some non-fleshy exceptions, such as Capsicum species, with air rather than pulp around their seeds.

<span class="mw-page-title-main">Zest (ingredient)</span> Scraped skin of citrus fruit

Zest is a food ingredient that is prepared by scraping or cutting from the rind of unwaxed citrus fruits such as lemon, orange, citron, and lime. Zest is used to add flavor to foods.

<span class="mw-page-title-main">Peel (fruit)</span>

Peel, also known as rind or skin, is the outer protective layer of a fruit or vegetable which can be peeled off. The rind is usually the botanical exocarp, but the term exocarp also includes the hard cases of nuts, which are not named peels since they are not peeled off by hand or peeler, but rather shells because of their hardness.

This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.

<i>Prunus rivularis</i> Species of tree

Prunus rivularis, known variously by the common names creek plum, hog plum, or wild-goose plum is a thicket-forming shrub. It prefers calcareous clay soil or limestone-based woodland soils. This deciduous plant belongs to the rose family, Rosaceae, and is found mainly in the central United States. It is a shrub consisting of slender stems with umbel clusters of white blossoms. The fruit is a drupe that resembles a large berry; though it has a bitter taste, it serves as a source of food for birds and other wildlife. "Prunus" is Latin for plum, whereas "rivularis" means being near a stream.

References

  1. Beck CB (22 April 2010). An Introduction to Plant Structure and Development: Plant Anatomy for the Twenty-First Century. Cambridge University Press. ISBN   978-1-139-48636-1.
  2. Pandey SN, Chadha A (1993). A Text Book Ofbotany: Plant Anatomy and Economic Botany. Vikas Publishing House Pvt Ltd. ISBN   978-0-7069-8685-3.
  3. 1 2 3 Evert RF, Eichhorn SE, Raven PH (2012-03-02). Raven Biology of plants (8th ed.). New York. ISBN   9781429219617. OCLC   781446671.{{cite book}}: CS1 maint: location missing publisher (link)
  4. 1 2 3 4 Evert RF, Eichhorn SE, Perry JB, Raven PH (2013). Laboratory topics in botany : to accompany Raven Biology of plants (8th ed.). New York, NY: W.H. Freeman and Co. ISBN   9781464118104. OCLC   820489734.
  5. 1 2 3 4 5 6 7 8 Dardick C, Callahan AM (2014). "Evolution of the fruit endocarp: molecular mechanisms underlying adaptations in seed protection and dispersal strategies". Frontiers in Plant Science. 5: 284. doi: 10.3389/fpls.2014.00284 . PMC   4070412 . PMID   25009543.
  6. 1 2 3 Bremer R, Eriksson O (September 1992). "Evolution of fruit characters and dispersal modes in the tropical family Rubiaceae". Biological Journal of the Linnean Society. 47 (1): 79–95. doi:10.1111/j.1095-8312.1992.tb00657.x. ISSN   0024-4066.
  7. Xiang Y, Huang CH, Hu Y, Wen J, Li S, Yi T, Chen H, Xiang J, Ma H (February 2017). "Evolution of Rosaceae Fruit Types Based on Nuclear Phylogeny in the Context of Geological Times and Genome Duplication". Molecular Biology and Evolution. 34 (2): 262–281. doi:10.1093/molbev/msw242. PMC   5400374 . PMID   27856652.
  8. Godwin J, Raviv B, Grafi G (December 2017). "Dead Pericarps of Dry Fruits Function as Long-Term Storage for Active Hydrolytic Enzymes and Other Substances That Affect Germination and Microbial Growth". Plants. 6 (4): 64. doi: 10.3390/plants6040064 . PMC   5750640 . PMID   29257090.