Fruit anatomy

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. In fleshy fruits, the outer layer (which is often edible) is the pericarp, which is the tissue that develops from the ovary wall of the flower and surrounds the seeds.

But in some seemingly pericarp fruits, the edible portion is not derived from the ovary. For example, in the fruit of the ackee tree the edible portion is an aril, and in the pineapple several tissues from the flower and stem are involved.

The outer covering of a seed is tough because the parent plant needs to protect the plant growing

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

Categories of fruits

Fruits are found in three main anatomical categories: simple fruits, aggregate fruits, and multiple 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 fruit 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 were 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 wisteria, which is an extreme case where there is an explosion of the pod, 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.[6] It is known that dry fruits were present before fleshy fruits and fleshy fruits diverged from them.[5] A study looking at the Rubiaceae family found that within the family, fleshy fruits had evolved independently at least 12 times.[7] 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.[8] 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.[7] 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.[7] 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

Drupe fruit diagram-en
Diagram of a typical drupe (peach), showing both fruit and seed
Orange cross section description
A schematic picture of an orange hesperidium
Citrus pulp1
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 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.

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

Pinyol arbequina obert
Olive drupe (left), endocarp (center) and seed (right).

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 stone 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 prior to 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.[9]

See also

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. ^ a b c Evert RF, Eichhorn SE, Raven PH (2012-03-02). Raven Biology of plants (8th ed.). New York. ISBN 9781429219617. OCLC 781446671.
  4. ^ a b c d 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. ^ a b c d e f g 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. ^ 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.
  7. ^ a b c 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.
  8. ^ 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.
  9. ^ 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.

External links

Amaranthaceae

Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus Amaranthus. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making it the most species-rich lineage within its parent order, Caryophyllales.

Anabasis (plant)

Anabasis is a genus of the subfamily Salsoloideae in the family Amaranthaceae. It is distributed in southern Europe, North Africa, and Asia.

Author citation (botany)

In botanical nomenclature, author citation refers to citing the person or group of people who validly published a botanical name, i.e. who first published the name while fulfilling the formal requirements as specified by the International Code of Nomenclature for algae, fungi, and plants (ICN). In cases where a species is no longer in its original generic placement (i.e. a new combination of genus and specific epithet), both the author(s) of the original genus placement and those of the new combination are given (the former in parentheses).

In botany, it is customary (though not obligatory) to abbreviate author names according to a recognised list of standard abbreviations.

There are differences between the botanical code and the normal practice in zoology. In zoology, the publication year is given following the author name(s) and the authorship of a new combination is normally omitted. A small number of more specialized practices also vary between the recommendations of the botanical and zoological codes.

Comparative anatomy

Comparative anatomy is the study of similarities and differences in the anatomy of different species. It is closely related to evolutionary biology and phylogeny (the evolution of species).

The science began in the classical era, continuing in Early Modern times with work by Pierre Belon who noted the similarities of the skeletons of birds and humans.

Comparative anatomy has provided evidence of common descent, and has assisted in the classification of animals.

Corispermoideae

The Corispermoideae are a subfamily of the Amaranthaceae, formerly in family Chenopodiaceae.

Dekopon

Dekopon (デコポン) is a seedless and sweet variety of mandarin orange.

It is a hybrid between Kiyomi and ponkan (Nakano no.3), developed in Japan in 1972.Originally a brand name, 'Dekopon' has become a genericized trademark and it is used to refer to all brands of the fruit; the generic name is shiranuhi or shiranui (不知火). Dekopon is distinctive due to its sweet taste, large size and the large protruding bump on the top of the fruit.

Grex (horticulture)

The term grex (pl. greges or grexes; abbreviation gx), derived from the Latin noun grex, gregis meaning 'flock', has been coined to expand botanical nomenclature to describe hybrids of orchids, based solely on their parentage. Grex names are one of the three categories of plant names governed by the International Code of Nomenclature for Cultivated Plants; within a grex the cultivar group category can be used to refer to plants by their shared characteristics (rather than by their parentage), and individual orchid plants can be selected (and propagated) and named as cultivars.

Hesperidium

A hesperidium (plural hesperidia) is a modified berry with a tough, leathery rind.

International Association for Plant Taxonomy

The International Association for Plant Taxonomy (IAPT) promotes an understanding of plant biodiversity, facilitates international communication of research between botanists, and oversees matters of uniformity and stability in plant names. The IAPT was founded on July 18, 1950 at the Seventh International Botanical Congress in Stockholm, Sweden. Currently, the IAPT headquarters is located in Bratislava, Slovakia. Its current president, since 2017, is Patrick S. Herendeen (Chicago Botanic Garden); vice-president is Gonzalo Nieto Feliner (Real Jardín Botánico, Madrid); and secretary-general is Karol Marhold (Plant Science and Biodiversity Centre, Slovak Academy of Sciences, Bratislava).

Both the taxonomic journal Taxon and the series Regnum Vegetabile are published by the IAPT. The latter series includes the International Code of Nomenclature for algae, fungi, and plants, Index Nominum Genericorum, and Index Herbariorum.

International Code of Nomenclature for Cultivated Plants

The International Code of Nomenclature for Cultivated Plants (ICNCP), also known as the Cultivated Plant Code, is a guide to the rules and regulations for naming cultigens, plants whose origin or selection is primarily due to intentional human activity. Cultigens under the purview of the ICNCP include cultivars, Groups (cultivar groups), and grexes. All organisms traditionally considered to be plants (including algae and fungi) are included. Taxa that receive a name under the ICNCP will also be included within taxa named under the International Code of Nomenclature for algae, fungi, and plants, for example, a cultivar is a member of a species.

Legnephora

Legnephora is a genus of flowering plants, consisting of five climbing species, found in Malesia and Australia. The name comes from ancient Greek, referring to a feature of the fruit anatomy being “border bearing”.

Ovary (botany)

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 (e.g. dicarpel or tricarpel), 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.

Peel (fruit)

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.

A fruit with a thick peel, such as a citrus fruit, is called a hesperidium. In hesperidia, the inner layer (also called albedo or, among non-botanists, pith) is peeled off together with the outer layer (called flavedo), and together they are called the peel. The flavedo and albedo, respectively, are the exocarp and the mesocarp. The juicy layer inside the peel (containing the seeds) is the endocarp.

Pteridophyte

A pteridophyte is a vascular plant (with xylem and phloem) that reproduces using spores. Because pteridophytes produce neither flowers nor seeds, they are also referred to as "cryptogams", meaning that their means of reproduction is hidden. The pteridophytes include the ferns, horsetails, and the lycophytes (clubmosses, spikemosses, and quillworts). These are not a monophyletic group because ferns and horsetails are more closely related to seed plants than to the lycophytes. Therefore, "Pteridophyta" is no longer a widely accepted taxon, although the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, to indicate lycophytes and ferns as an informal grouping, such as the International Association of Pteridologists and the Pteridophyte Phylogeny Group.

Ptilimnium nodosum

Ptilimnium nodosum (synonym=Harperella nodosa), common names piedmont mock bishopweed and harperella, is a plant native to riparian environments in the Southeastern United States, found at sites in West Virginia, Maryland, several Southeastern states such as Alabama and North Carolina, and the Ouachita National Forest in Arkansas and Oklahoma.Ptilimnium nodosum was placed on the United States' Endangered Species List in 1988.

Raceme

A raceme ( or ) is an unbranched, indeterminate type of inflorescence bearing pedicellate flowers (flowers having short floral stalks called pedicels) along its axis. In botany, an axis means a shoot, in this case one bearing the flowers. In indeterminate inflorescence-like racemes, the oldest flowers are borne towards the base and new flowers are produced as the shoot grows, with no predetermined growth limit. A plant that flowers on a showy raceme may have this reflected in its scientific name, e.g. Cimicifuga racemosa. A compound raceme, also called a panicle, has a branching main axis. Examples of racemes occur on mustard (genus Brassica) and radish (genus Raphanus) plants.

Succade

Succade is the candied peel of any of the citrus species, especially from the citron or Citrus medica which is distinct with its extra-thick peel; in addition, the taste of the inner rind of the citron is less bitter than those of the other citrus. However, the term is also occasionally applied to the peel, root, or even entire fruit or vegetable like parsley, fennel and cucurbita which have a bitter taste and are boiled with sugar to get a special "sweet and sour" outcome.Fruits which are commonly candied also include dates, cherries, pineapple, ginger, and the rind of watermelon.

Zest (ingredient)

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

In terms of fruit anatomy, the zest is obtained from the flavedo (exocarp) which is also referred to as zest. The flavedo and white pith (albedo) of a citrus fruit together makes up its peel. The amounts of both flavedo and pith are variable among citrus fruits, and may be adjusted by the manner in which they are prepared. Citrus peel may be used fresh, dried, candied, or pickled in salt.

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