Скачать или смотреть 🌻⁵☆•¹ Corona in Apocynaceae (Dogbane Family)

▪︎ Corona in Apocynaceae (Dogbane Family)

Corona is an elaborate set of extra floral appendages located between Petals & Stamens. It plays a critical role in specialized pollination by attracting insects, providing rewards (nectar) & positioning pollinators for efficient pollen transfer.

♤ Types of Coronas
Coronas in this family are classified based on where they originate during flower's development:

♠︎¹ Corolline Corona (Cc): Arises from Petals or Corolla tube. It often appears as hairy outgrowths or scales in sinuses between Petal lobes.
♠︎² Gynostegial Corona: These structures are fused with reproductive organs (Gynostegium). They are subdivided into:
● Staminal Corona (Cs): Attached to back of Stamens.
● Interstaminal Corona (Cis): Originates at base of filament tube between Stamens.
♠︎³ Annular Corona (Ca): A continuous ring-shaped structure situated at base of Gynostegium or Corolla tube.

◇ Biological Significance
◆ Pollination Mechanism: In subfamilies like Asclepiadoideae (Milkweeds), Corona often forms complex 'hoods' that store nectar. These hoods guide legs or proboscis of insects into 'guide rails' ensuring that pollen packets (pollinia) stick to pollinator.
◆ Taxonomic Diagnostic: Because Corona shapes such as anchor-shaped, sagittate or filiform are highly specific to different Genera, they are primary tool used by botanists for classifying species within Family.
◆ Evolutionary Diversity: Corona is considered a key innovation that evolved multiple times within family, showing extreme diversification from simple hairs to massive, colorful 'crowns' seen in Stapelia or Hoya.
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♠︎¹ Corolline Corona (Cc) is a specific type of floral structure, essentially fleshy ridges or outgrowths from Petals (Corolla) of a flower, often found in Apocynaceae (Dogbane Family) like Calotropis (Madar) or Nerium (Oleander), serving to attract pollinators & guide insects for pollination. It's an important taxonomic feature, differing from a Staminal Corona (which arises from Stamens) & representing an early evolutionary form of Corona in flowering plants, sometimes appearing alongside or replacing Staminal Coronas. Develops from fused edges or sinuses (indentations) of Petals, from base of Corolla tube upwards. In simple terms, it's a 'Petal-derived crown' within flower, distinguishing it from other corona types.
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♠︎² Gynostegial Corona: Gynostegium is a, complex central column in Apocynaceae (Milkweed) flowers formed by fusion of Stamens with Stigma. It commonly features a surrounding coronal structure (Corona) with inner & outer lobes, often acting as a specialized structure to assist in pollination by insects.
A fusion product where Stamens adhere to stigmatic surface to form a central column. Serves as a structure for insect pollination, often holding pollinia (pollen masses).
• Corona Components: Corona, which is often derived from Androecium, is usually attached to or part of this structure, featuring inner (horn) & outer (hood) lobes. Common in: Asclepiadoideae, such as Calotropis & Hoya.
Components
¹ Gynostegium: Central column of fused Androecium & Gynoecium.
² Corona: Often divided into an outer (corona hood) & an inner (corona horn) part, which are generally fused at base.
³ Anther Wings: Form a double-guide rail system for pollinators.
⁴ Pollinia: Coherent pollen masses found within structure.
Structure is highly modified for entomophily (pollination by insects), where Corona helps guide insects to pollinia.
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♠︎³ Annular Corona: Refers to a ring-shaped outgrowth of tissue within a flower that is situated below or surrounds Gynostegium. It is a specific type of floral corona a specialized structure used for attracting pollinators or managing nectar access.

It forms a continuous, circular 'ring' or 'annulus'. It can be Corolline (arising from Petals) or Staminal (arising from Stamen tube).
• Function: It often serves as an outward border for nectaries or as a guiding structure for pollinators. While common in certain groups like Gonolobinae & Ceropegieae, it is relatively rare in others, such as Marsdenieae.
▪︎ Petalostelma: Characterized by a rotate corolla & a gynostegial corona often accompanied by an annular corolline corona.
▪︎ Hoya: Some species like (Hoya multiflora) & (Hoya curtisii) possess an annular corona beneath Gynostegium.
▪︎ Pergularia: Features a double Corona, where outer part is annular & membranous.
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🌻⁵☆ Order Gentianales • 23963, 1163, T¹⁰⁶

•¹ Family Apocynaceae • 6887, 415, T²⁶ - Milkweed, Dogbane
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•¹ Family Apocynaceae • 6,710, 382 - Dogbane Family

◇¹ Subfamily Apocynoideae • 910, 78
◇² Subfamily Asclepiadoideae • 4413, 183
◇³ Subfamily Periplocoideae • 200, 33
◇⁴ Subfamily Rauvolfioideae • 985, 81
◇⁵ Subfamily Secamonoideae • 202, 7
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