Calyx

Jai Ganesh · Yesterday 17:49:51

Calyx

Gist

What Is a Calyx? In flowering plants (also called angiosperms), the part of the flower that surrounds the growing bud, often found at the base of the bloom, is called the calyx. The calyx is composed of one or more leaf-like structures called sepals.

Are sepals called calyx?

Collectively, the sepals are called the calyx (plural: calyces), the outermost whorl of parts that form a flower. The word calyx was adopted from the Latin calyx, not to be confused with calix 'cup, goblet'.

Summary

Calyx is the usually green outer whorl of a flower consisting of separate or fused sepals. The calyx serves primarily to protect the developing flower bud and, in some cases, to support the flower once it has bloomed. In some species, the calyx persists even when the fruit matures, as seen in persimmon, eggplant, strawberry, and tomato. Given that it is not directly involved in reproduction, the calyx is considered an accessory part of the flower.

There are commonly four distinct whorls of flower parts: (1) an outer calyx consisting of sepals; (2) the corolla, within the calyx and consisting of petals; (3) the male androecium, comprising the pollen-bearing stamens; and (4) the female gynoecium, at the center and consisting of the pistils, which hold ovules and one or more ovaries. A flower’s calyx and corolla (e.g., all the sepals and petals together) form the perianth, which serves to protect the reproductive organs and attract pollinators. The arrangement of floral organs, including the calyx, is typically in concentric whorls, with the sepals forming the outermost layer, though not every flower has every whorl. The numbers and arrangements of flower parts—including the number and degree of fusion of the sepals of the calyx—are key characteristics botanists use to identify flowering plant species.

The calyx exhibits a wide range of morphological diversity across different angiosperm species. In some flowers, the sepals are free and distinct, a condition known as aposepalous or polysepalous. In other species, the sepals are fused together, forming a tubular structure with lobes or teeth at the end, a condition referred to as synsepalous. The number of sepals in a calyx often corresponds to the number of petals, either directly (e.g., five sepals and five petals) or in multiples (e.g., four sepals and eight petals). In some species, the sepals are brightly colored and function as petals—for example, Clematis and Bougainvillea. In others, the petals and sepals are both present but are similar in color and appearance, as in the tulip tree (Liriodendron tulipifera) and Easter lily (Lilium longiflorum); in such cases, they are known as tepals.

Details

A sepal is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom. Collectively, the sepals are called the calyx.

Description

Sepals are usually green. The term tepal is usually applied when the parts of the perianth are difficult to distinguish, e.g. the petals and sepals share the same color or the petals are absent and the sepals are colorful. When the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly colored tepals. Since they include Liliales, an alternative name is lilioid monocots. Examples of plants in which the term tepal is appropriate include genera such as Aloe and Tulipa. In contrast, genera such as Rosa and Phaseolus have well-distinguished sepals and petals.[citation needed]

The number of sepals in a flower is its merosity. Flower merosity is indicative of a plant's classification. The merosity of a eudicot flower is typically four or five. The merosity of a monocot or palaeodicot flower is three, or a multiple of three.

The development and form of the sepals vary considerably among flowering plants. They may be free (polysepalous) or fused together (gamosepalous). Often, the sepals are much reduced, appearing somewhat awn-like, or as scales, teeth, or ridges. Most often such structures protrude until the fruit is mature and falls off.

Examples of flowers with much-reduced perianths are found among the grasses.

In some flowers, the sepals are fused towards the base, forming a calyx tube (as in the families Lythraceae and Fabaceae). In other families (e.g. Rosaceae and Myrtaceae), a hypanthium includes the bases of sepals, petals, and the attachment points of the stamens.

Mechanical cues may be responsible for sepal growth and there is a strong evidence suggesting that microtubules are present and determine the tensile strength and direction of growth at a molecular level.

Morphology

Morphologically, both sepals and petals are modified leaves. The calyx (the sepals) and the corolla (the petals) are the outer sterile whorls of the flower, which together form the perianth. In some plants, such as Aristolochia, the calyx is the primary whorl, forming a flower up to 50 cm (20 in) wide, with one sepal growing to a slender ribbon with a length of up to 4 m (13 ft) in Aristolochia grandiflora, the largest of all calyces.

Function

Sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom.

Similarly to ordinary leaves, sepals are capable of performing photosynthesis. However, photosynthesis in sepals occurs at a slower rate than in ordinary leaves due to sepals having a lower stomatal density which limits the spaces for gas exchange.

After flowering, most plants have no more use for the calyx, which withers or becomes vestigial, although in a few plants such as Lodoicea and Solanum melongena (aubergine, brinjal) the calyx grows along with the fruit, possibly to protect the attachment point. Some plants retain a thorny calyx, either dried or live, as protection for the fruit or seeds. Examples include species of Acaena, some of the Solanaceae (for example the tomatillo Physalis philadelphica), and the water caltrop, Trapa natans. In some species, the calyx not only persists after flowering but instead of withering, begins to grow until it forms a bladder-like enclosure around the fruit. This is an effective protection against some kinds of birds and insects, for example in Hibiscus trionum and in Physalis species. In some other plants, the calyx grows into an accessory fruit.

Additional Information:

Calyx Meaning

The outermost whorl of the flower is referred to as the calyx. Sepals are the functional units of the calyx, meaning that the calyx is a collection of sepals. The sepals are mostly green in colour and protect the inner structures of the flower from breakage, mechanical injury and desiccation. It supports the other internal structures of flowers such as the corolla, gynoecium and androecium. Corolla is the collection of petals, androecium is the male reproductive whorl and gynoecium is the female reproductive whorl of the flower.

The calyx is found just below the corolla. In some plants, the calyx and corolla are indistinguishable and are termed as perianth. Once the flower has bloomed, the calyx goes on to support the development of fruit. Sometimes, an additional whorl is found externally to the calyx that consists of a whorl of bracts that arise by the union of sepal appendages.

Forms of Calyx

* Polysepalous: When the calyx consists of sepals that are free from each other, it is referred to as polysepalous. E.g., Rose, Cassia
* Gamosepalous: When the sepals are fused in the calyx, it is referred to as gamosepalous. E.g., Datura
* Caducous: When the sepals of a flower wither or drop off, it is referred to as caducous. E.g., Poppy
* Petalloid: In petalloid conditions, the sepals of the flowers are coloured. E.g., Delphinium
* Persistent: In this form, the sepals do not wither and are persistent even in the fruits. E.g., Brinjal.

Functions of Calyx in Plants

The calyx serves several essential functions in the life cycle of a plant. These are:

* Protection: Primarily, the calyx is a protective covering for the developing flower bud, shielding it from physical damage, desiccation, and predation.
* Support: The calyx also provides structural support to the flower, holding its various components in place as it grows and develops. This support is crucial, especially in windy conditions, as it prevents the flower from dislodging or damaging.
* Regulation of Pollination: The sepals of the calyx can also play a role in attracting pollinators to the flower. In some plant species, the sepals' color, shape, and texture may aid in pollinator attraction, ultimately facilitating the transfer of pollen and ensuring successful fertilization, like in Petalloid Calyx.
* Water Regulation: The calyx also helps regulate the uptake and retention of water within the flower bud. The calyx prevents excessive water loss through transpiration and maintains optimal flower hydration.

The different types of calyx are:

* Polysepalous Calyx: This type of Calyx has sepals that are free and separate from each other. Polysepalous calyx examples are found in flowers like Hibiscus and Camellia, where individual sepals encircle the base of the flower, forming a protective shield around the developing bud.
* Gamosepalous Calyx: The sepals in this type are fused or united, forming a single structure. The Petunia is a classic example of a plant having a gamosepalous calyx.
* Caducous Calyx: Caducous Calyx is a calyx where the sepals eventually wither or fall off after the flower blooms. This can be seen in trees like the Maple, where the calyx serves its protective purpose during the bud's development and sheds away once the flower matures.
* Petalloid Calyx: Here, the sepals transform remarkably, adopting colors akin to petals. This phenomenon can be seen in plants like the Poinsettia, where the calyx protects and contributes to the flower's reproductive success by attracting pollinators like bright-colored petals.
* Persistent Calyx: The sepals remain even after the flower has bloomed. Instead of withering away, they stay attached to the developing fruit, offering continued support and protection. A notable example of this can be found in the Tomato plant, where the calyx persists even as the fruit ripens.

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#1 Yesterday 17:49:51

Calyx

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