Question

Early embryogeny in Cycas is characterized by
A) Absence of suspensor cell
B) Presence of expanded free nuclear division
C) Reduced free nuclear division
D) Many cotyledons

Answer 1

Hint: Cycas is a genus of plants belonging to ancient lineage the Cycadophyta. These are evergreen perennials which achieved worldwide distribution during the Jurassic and Cretaceous period. These plants are Dioecious plants and are gymnosperms distinguished by large pinnately compound leaves.

Complete answer:
 Early embryogeny in Cycas is characterized by the presence of expanded free nuclear division. The zygote is the first sporophytic cell, which then undergoes free nuclear divisions. The interval between pollination and fertilization is several months in case of Cycas.

The zygote (2n) secretes cell walls and then forms into the oospore. The zygote also known as the oospore is the first cell of the sporophyte. The oospore undergoes free nuclear division followed by the formation of a wall to form a small cellular mass called pro-embryo. The pro-embryo is differentiated into three parts:- basal embryonal zone, middle suspensor and upper haustorium

Additional Information:The mature Cycas seed consists of an orange-red- coloured outer thick layer testa of seed coat. Seed cost is formed from the 3-layered integument of the ovule. The inner flesh layer and the nucellus are used during the embryo development, and, therefore, the two later are represented only by thin layers. A well- developed endosperm is present, which stores a large amount of food material to be used during scarcity. The embryo remains embedded within the endosperm. It consists of plumule, radicle and two large cotyledons The embryo remains suspended in the endosperm with the help of a long and spirally coiled suspensor.

Hence the correct answer is option ‘B’.

Note: Cycas is an important plant which is full of nutrients. Processed sagu obtained from the cycas plant can be used as a substitute for rice for the carbohydrate. The processed sagu is also a main ingredient in bread making. Cycas plant also has high scale medicinal purposes. Raw materials obtained from cycas plants are also used in making oils.