To study the Morphological and Anatomical features of Cycas
Morphological features of Cycas plant
Cycas is an evergreen gymnosperm grown as an ornamental plant in gardens. The plant body is a sporophyte differentiated into an underground root system, aerial and unbranched, erect stem with a crown of leaves on the top.
Roots are of two types – Normal, primary tap root and symbiotic coralloid roots. Normal tap root is positively geotropic and grows deep into soil. Coralloid roots are negatively geotropic and appear as coralline masses above the soil surface.
Leaves are large, pinnately compound bearing 80-100 pairs of leaflets (pinnae) arranged on a rachis. Each pinna is tough, leathery and sessile.
Anatomical features of Cycas
C.S of Cycas Leaflet
- The C.S leaflet section shows a definite swollen midrib and narrow winged margins.
- Single layered upper epidermis with thick Cuticle
- Schlerenchymatous hypodermis that is multi-layered in midrib region
- Mesophyll differentiated into upper palisade layers and lower spongy cell layers
- Palisade cells are compactly arranged, while spongy parenchyma are loosely arranged with inter-cellular spaces
- Presence of elongated, thin walled transfusion tissue on either side of the centrally located vascular bundle is characteristic feature of Cycas leaflet
- Lower side has lower epidermis with sunken stomata
- A single vascular bundle is present in the midrib with parenchymatous bundle sheath
- V. B is conjoint, collateral, open and diploxylic with triangular patch of centripetal xylem and small groups of centrifugal xylem. Phloem is present towards the lower side
T.S of Coralloid Root
- Outermost single layered epidermis without cuticle
- Multi-layered parenchymatous cortex
- Cortex is differentiated into outer and inner cortex, between which is the middle algal zone
- Algal zone has radially elongated cells that have blue-green algae in them
- The stele is marked by a single layered endodermis, followed by few layered Pericycle within
- V. B are closed, radial and xylem is exarch and diarch to tetrarch
T.S of Cycas leaf Rachis
- It is rhomboidal, biconvex or roughly cylindrical in outline
- Two arms representing the bases of the leaflets are present on each side of rachis
- The outermost layer consists of epidermis which is heavily cuticularized
- Presence of chlorenchyma below the epidermis, followed by thick- walled schlrenchymatous region
- Ground tissue consisting of thin-walled parenchymatous cells below the has many mucilaginous canals and vascular bundles.
- Each mucilaginous canal is a double-layered structure having an inner layer of epithelial cells surrounded by an outer layer.
- Vascular bundles are arranged in omega (Ω) – shaped manner – which is the typical feature of Cycas rachis
- Each V.B is conjoint, collateral and open, and surroundeded by a bundle sheath. The xylem is diploxylic, i.e., consisting of centripetal and centrifugal xylem and present towards inner side with no vessels
- The vascular bundles show different structures at different levels of rachis starting from the base to the tip with regard to their diploxylic nature
- Vascular Bundles at the apex of rachis have well developed centripetal xylem, while centrifugal xylem is much reduced and present in the form of two patches lying one on each side of the centripetal xylem
Note: Foldscope is being used as a teaching tool in Practical classes @ GGDSD College, Chandigarh and tutorials have been developed for the respective classes