Cycas: Morphology, Anatomy, Reproduction and Life Cycle (Part 1)

Part – 1: Morphology of Cycas
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Systematic Position (Sporne, 155)

Division: Gymnosperms
Class: Cycadopsida
Order: Cycadales
Family: Cycadaceae

Distribution of Cycas

Ø  Cycas belongs to an ancient plant group called Cycadophyta of the Division Gymnosperms

Ø  Cycadophyta were the major vegetation of Jurassic and Cretaceous periods.

Ø  The genus Cycas is the only living genera of the family Cycadaceae.

Ø  Cycas genus consists of about 113 species.

Ø   Plants shows typical Xerophytic Adaptations.

Ø  There are both Wild and Cultivated species of Cycas.

Ø  Cycas is mainly distributed in Tropical and Sub-tropical regions

Ø  In India: ~ 9 species of Cycas are reported

Ø  Important Indian species of Cycas : Cycas circinalis,  C. revolute, C. annaikalensis, C. beddomei, C. indica, C. zeylanica etc.

Ø  Cycas circinalis is endemic to India, It is the first described species of Cycas (Type genus)

Ø  Cycas annaikalensis is critically endangered and endemic species of Cycas present in the Annaikal Hills of Palakkad, Kerala

You may also like: Cycas PPT (Download)

Morphology of Cycas

Ø  Sprophyte is the prominent generation in the life cycle of Cycas, which is differentiated into root, stem and leaves.

Ø  Cycas is an evergreen plant.

Ø  All living Cycas species are dioecious (male and female plants are separate).

Ø  Palm like appearance, having a cylindrical stem with a crow of leaves at the apex.

Morphology of Stem

Ø  Stem (caudex) is cylindrical and erect.

Ø  Stem surface is covered by leaf scars.

Ø  Usually the stem un-branched, sometimes branched

Ø  The branching occurs due to the wound-healing activity of the stem.

Ø  The growth rate of the plant is very slow.

Ø  Cycas live for many years.

Ø  New leaves are produced as crown in each growing seasons.

Ø  Stem covered with persistent leaf bases.

Ø  Stem undergo secondary thickening.

Morphology of Leaves

Ø  Leaves are produced as crown on the apical portion of the stem.

Ø  Leaves are produced as a bunch.

Ø  Leaves are pinnately compound and frond-like (like the leaves of Pteridophytes)

Ø  Young leaves of Cycas shows circinate vernation.

Ø  Circinate vernation: Young leaves are curved inward, a character of ferns

Ø  Cycas plants produce TWO types of leaves

(1). Scale Leaves

(2). Foliage Leaves

(1). Scale leaves

Ø  Scale leaves are small, scaly and brown in colour

Ø  The brown colour is due to the presence of ramental hairs.

Ø  These leaves are non-photosynthetic leaves.

Ø  Function: Protection of younger parts

(2). Foliage leaves

Ø  Foliage leaves are large and pinnately compound

Ø  Consists of a long rachis with many laterally placed leaflets

Ø  They are green coloured and hence photosynthetic.

Ø  Foliage leaves shows circinate vernation

Ø  Function: Perform photosynthesis

Ø  The crown of scale leaves and foliage leaves are produced alternatively.

Morphology of Roots

Ø  Cycas possess TWO types of roots

(1). Tap-root

(2). Coralloid Root

(1). Tap-root

Ø  The primary root (root developed from the radicle of embryo) forms the tap-root in Cycas.

Ø  The tap root is less branched

Ø  They are positively geostrophic and grow downward.

Ø  They undergo secondary thickening

Ø  Function: Anchorage and absorption of water and minerals from the soil

(2). Coralloid roots

Ø  Coralloid roots are a special type of root present in Cycas.

Ø  They are developed from the normal roots.

Ø  They are highly branched roots.

Ø  They are negatively geostrophic (grown up-ward).

Ø  They have Coral like appearance due to the severe branching.

Ø  They possess nitrogen fixing algae in its cortex.

Ø  Coralloid roots helps in nitrogen fixation.

Ø  Usually secondary thickening is absent in coralloid roots.

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