Sunflower scientifically known as Helianthus annuus. It is a member of the Asteraceae family. Sunflowers are mainly grown for their properties. They are grown in gardens for decoration and their seeds are also roasted and eaten. Oil is also extracted from sunflowers which is used in cooking food. In this article, we will learn about the position of leaves, flowers, and fruits of Sunflower.
Scientific Name: Helianthus annuus
Some Basic Information about Sunflower (Helianthus annuus)
Habit – An annual, tall, erect herb, often reaching heights of 1.5–3 meters.
Root – Tap root system, strong and deep-penetrating.
Stem – Erect, branched (rare), solid, cylindrical, hairy (pubescent), green turning brown with age.
Leaf – Simple, petiolate, alternate (lower ones opposite), ovate to heart-shaped, entire or serrate margin, unicostate reticulate venation, rough and hairy texture.
Inflorescence – Capitulum (head), large, terminal, solitary, surrounded by an involucre of bracts; the head contains two types of florets:
Ray florets – sterile, zygomorphic, yellow, outermost.
Disc florets – fertile, actinomorphic, tubular, brownish to yellow, central.
Flower – Bracteate, sessile, complete, heterogamous (different types of florets), epigynous, actinomorphic (disc), zygomorphic (ray).
Calyx – Represented by pappus, usually reduced or absent in sunflower.
Corolla –
Ray florets: Ligulate (strap-shaped), yellow, gamopetalous.
Disc florets: Tubular, gamopetalous, 5 lobes, valvate aestivation.
Androecium – (In disc florets only) 5 stamens, epipetalous, syngenesious (anthers fused into a tube), dithecous, basifixed, introrse.
Gynoecium – Bicarpellary, syncarpous, inferior ovary, unilocular, with basal placentation, style bifid, stigma linear.
Fruit – Cypsela (a dry, one-seeded, indehiscent fruit), often with remains of pappus.
Floral Formula
Disc Floret: Br ⚥ ⊕ K(pappus) C(5) A(5) G(2̅)
Ray Floret: Br ⚥ ↑ K(pappus) C(5) A0 G(2̅)
Systematic Position:
Class – Dicotyledonae
Subclass – Gamopetalae
Series – Inferae
Order – Asterales
Family – Asteraceae (Compositae)
Genus – Helianthus
Species – annuus