Cycas is a gymnosperm and is the only living genus identified in the family Cycadaceae, containing more than 100 species. It is mainly distributed in the eastern and southeastern Asian regions, with many species native to China, Australia, and India.

Cycas are perennial evergreen trees that resemble a palm tree. These plants are characterized by the presence of naked seeds, meaning that the ovules are not enclosed within the ovary. The main body part is the diploid sporophyte and Cycas are dioecious, meaning male and female plants are separate.

Table of Contents

Classification

Morphology of Cycas

Reproduction and Life Cycle

[Economic Importance of Cycas](#Economic Importance of Cycas)

Frequently Asked Questions

Classification

| Kingdom | Plantae |

| Subkingdom | Tracheobionta |

| Superdivision | Spermatophyta |

| Division | Cycadophyta |

| Class | Cycadopsida |

| Family | Cycadaceae |

| Genus | Cycas |

The subkingdom Tracheobionta comprises all vascular plants, and the superdivision Spermatophyta includes all seed plants.

Check Out: NEET 2022 Answer Key

Some of the common species of Cycas include:

C. revoluta (sago palm)

C. circinalis (fern palm) - Endemic to India

C. media (Australian nut palm)

C. rumphii

Structure

The Important Features of Cycas Include:

• A diploid sporophyte as the main plant body
• Vascular plant
• Differentiated into roots, stems, and leaves

Morphology of Cycas

It is an evergreen and perennial plant, some of which can grow up to 40 feet in height.

It is a dioecious plant, meaning male and female reproductive parts are borne on different trees.

It possesses two types of roots: tap root and coralloid root.

The primary roots are tap roots, which serve the main functions of anchorage and absorption of water and minerals.

The normal roots of plants give rise to coralloid roots, which are associated with cyanobacteria that can perform biological nitrogen fixation.

The stem or caudex is mostly unbranched, thick and woody, with a rough surface due to persistent leaf bases.

**Leaves form a crown at the top of the stem in Cycas. There are two types of leaves found in this species: foliage leaves and scaly leaves.

The scaly leaves are small and brown in colour. They have a protective function, protecting reproductive structures and the shoot apex. These scaly leaves alternate with the foliage leaves.

The green foliage leaves are pinnately compound, with multiple leaflets arranged on a long rachis.

The leaves have a coiled arrangement when they first emerge and have a midrib without lateral veins.

The foliage leaves are not permanent and eventually fall off, leaving behind the leaf bases.

Xylem contains tracheids and xylem parenchyma, but does not contain vessels.

Phloem consists of sieve tubes and phloem parenchyma, with no presence of companion cells.

They exhibit secondary growth.

The megaspores and microspores are produced in the megasporangia and microsporangia, respectively, which are borne on spirally arranged megasporophylls and microsporophylls. This is a characteristic of heterosporous plants.

In Cycas, the megasporophylls and microsporophylls are present on different trees, thus making them dioecious.

The megasporophyll does not form a cone or a strobili.

Reproduction and Life Cycle

Cycas shows both vegetative and sexual reproduction. Vegetative reproduction occurs through the formation of bulbils or adventitious buds, while sexual reproduction occurs through the formation of seeds.

Vegetative Reproduction

The adventitious buds or bulbils develop in the axils of scaly leaves. They detach from the stem and develop into new plants. The bud from the male plant develops into a male plant and the bud from the female plant develops into a female plant.

Sexual Reproduction

Cycas is heterosporous, producing two kinds of spores, and is dioecious, with male and female reproductive parts borne on different plants. Sexual reproduction is oogamous, with the egg being quite large in size and non-motile compared to the male gametes.

Development of the Male Gametophyte

The microsporangia, which produce the microspores, are borne on microsporophylls. These microsporophylls are arranged in a spiraling fashion in an acropetal succession along the axis, forming a cone or compact strobili. The male cone of Cycas is the largest of its kind in the plant kingdom.

The microspores are haploid and produced by meiosis in microspore mother cells. These microspores develop into male gametophytes, which are reduced and are called pollen grains. The development of pollen grains is initiated within the sporangia. The microsporangia dehisce at the 3-celled state of pollen grains that consist of a prothallial cell, a generative cell and a tube cell. Further development of the male gametophyte occurs after pollination. Pollen grains are wind pollinated.

Development of the Female Gametophyte

The megaspores are produced in the megasporangia, which are borne on megasporophylls. Megasporophylls are arranged spirally in the acropetal succession on the crown of leaves but do not form a cone or strobili. The ovules or megasporangia of Cycas are the largest in the plant kingdom.

The megaspores are haploid and are produced after meiosis in the megaspore mother cell. One of the megaspores develops into a multicellular female gametophyte within the megasporangium. The female gametophyte bears two or more archegonia that are female sex organs. The female gametophyte is retained within the megasporangium.

Fertilization

The pollen grains are transported through air to the ovule. The pollen tube grows towards the archegonia in the ovules and discharges its contents, the male gametes, near the mouth of the archegonia. The male gamete then fuses with the egg nucleus to form a diploid zygote. This zygote then gives rise to the embryo and the ovule develops into a seed. The seeds of gymnosperms are naked (not covered).

#Economic Importance of Cycas

Cycas are widely used for various purposes, such as decoration, horticulture, ceremonies, food, and medicine.

Many species of Cycas are used as ornamental plants.

Starch is obtained from Cycas revoluta (sago palm) and some other species.

Some parts of the Cycas species plants are also used to prepare alcoholic beverages.

Some of the Cycas species produce edible seeds.

Leaves are often used for decorative purposes, as well as to create baskets, hats, and other items.

Seeds and raisins obtained from certain species are used as a remedy for ulcers, sores, and swellings.

The juice of young leaves is utilized to treat vomiting and flatulence.

Young succulent leaves of various species are often cooked and enjoyed as vegetables.

Cycas seeds have been used to treat hypertension and musculoskeletal disorders.

Frequently Asked Questions

What are the distinguishing features between Cycas and extinct Cycads?

The female cone in a Cycas species is a megasporophyll that is held in a lax rosette manner in comparison to Cycads that have a tightly held female cone.

Is Cycas Edible?

Yes, some species of Cycas are edible.

The Cycas seeds contain cycasin toxin and should not be eaten.

No, Cycas is not a flowering plant.

Cycas is a gymnosperm that produces naked seeds, but does not produce flowers and fruits.