cycas-230224101427-a6ce27nbjjjiiiiiiiii6c.pptx

cycas-230224101427-a6ce27nbjjjiiiiiiiii

1. Life cycle of cycas BSc. Botany Honours 2 nd Semester Core - 4

2. Cycas is commonly found in tropical and subtropical regions of the world Cycas revoluta (sago palm) is most common and widely studied species in the sub-continent It is cultivated for yield of starch-rich sago used as food Cycas circinalis is cultivated as ornamental for its large attractive palm-like leaves

3. Systematic Position Gymnospermae Division: Cycadophyta Class: Cycadopsida Order: Cycadales Family: Cycadaceae Genus: Cycas (Greek word kykos means a palm/ cocopalm )

4. Plant Body Cycas plant body is a heterosporous sporophyte Cycas plant shows a short, tuberous, unbranched stem which bears a crown of large fern-like leaves Stem is covered with tough leaf bases In some species large adventitious buds called bulbils develop on the basal part of the stem These bulbils contain reserve food material and help in vegetative propagation

5. Leave of caycas are pinnately compound and exhibit circinate vernation Shoot apex is protected by a rosette of brown scale leaves Plants grow very slowly adding a new crow of leaves every 2 or 3 years, alternating with a crown of scale leaves Each crown remain on the stem for many years

6. Root of cycas plant is of two types; Normal and Coralloid Normal roots: Normal tap roots grow from radical deep inside the soil giving out lateral branches Some of the lateral roots grow apogeotropically towards the surface of soil and branch dichotomously These roots are short, thick and swollen at the tips

7. Much branched mass appears like a coral on the soil surface hence called as coralloid roots Do not bear root caps Cluster has lenticel like apertures Become infested with blue green algae to fin atmospheric N2 In this way a symbiotic relationship is established

8. Female Cone

9. Structure of Ovule Ovule is erect and has an opening called as micropyle The part opposite to micropyle is called as chalaza Massive nucellus is surrounded by a single integument Integument is differentiated into outer, inner and middle layer (thick that become stony during seed formation) The nucellus is equivalent to megasporangium and consists of thin walled parenchyma having dense cytoplasm Nucellus grows into a beak called nucellor beak The upper part of beak form pollen chamber and pollens are lodged into it after pollination

10. Thank You