Division - Cycadophyta
Class - Cycadopsida
Family - Cycadaceae
Cycas is the most widely distributed genus of the order Cycadales. There are about 20 species which occur in wild state in China, Japan, Australia, Africa, Nepal, Bangladesh, Burma and India.
1. C.pectinata : It is distributed in Nepal, Sikkim, Someshwar hills in Bihar and plains of Assam, Manipur, East Bengal.
2. C.revoluta : It is native of China and Southern Japan and widely cultivated as ornamental plant in India. It can be propagated by means of bulbils.
3. C.beddomei : It occurs in wild state in Andhra Pradesh. It has a dwarf trunk only up to 40 cm high.
4. C.circinalis :It is common in the western parts of Peninsular India, Western Ghats and Odisha hills. It is 1.5-3 m in height.
5. C.rumphaii : This species occurs in Andaman and Nicobar islands. The plant is 1.5-4 m in height.
6. C.siamensis : It is widely distributed in Burma, China and Thailand. In India it is grown as ornamental plant. It is about 3 m tall.
- Cycas is an evergreen slow-growing palm like small tree with an average height of 1.5-3 m; commonly found in xerophytic habitats.
- The sporophytic plant body is differentiated into roots, stem and leaves.
- There are two types of roots in Cycas : normal tap roots and coralloid roots.
- Long lived primary root forms tap root. The main tap root is usually thick and short but its lateral branches are thin and long.
- The coralloid roots are specialised apogeotropic roots which grow on the surface of soil.
- A specific algal zone with colonies of Anabaena or other blue-green algae is present in the cortex of these roots.
- The young stem is tuberous and covered with brown scale leaves.
- The stem is usually unbranched.
- Cycas has dimorphic leaves : foliage leaves and scale leaves.
|Transverse section of normal young root.|
|Cycas : Coralloid root|
|Transverse section of mature stem|
Cycas reproduces by vegetative and sexual means.
Vegetative Cycle :
This cycle is more prevalent in Northern India where male plants of Cycas revoluta are not found.
Sexual reproduction :
The sexual life cycle of Cycas is diplohaplontic. It shows heterologous or heteromorphic type of alternation of generations because the sporophyte (2n) and gametophyte (n) generations exhibit morphological differences. In Cycas, the sporophyte (2n = 22) is a complicated, independent and dominant generation whereas the gametophytes (n = ll) are inconspicuous and endosporic. The gametophytes of Cycas are of 2 types: male or microsporangia and female or megasporangia. Female gametophyte is retained whereas male gametophyte is transfer during pollination.
- Male Cone
Male cone is conical and grow up to 1.5 m. It has a central axis or cone axis surround by compactly and spirally arranged micro-sporophylls. Each microsporophyll has adaxial (upper) and abaxial (lower) surfaces. The adaxial surface is ridge like with sterile apophysis at the apex. The adaxial surface contains numerous microsporangia in group of 3-6 called sori. Each microsporangium filled with numerous haploid microspores or pollen grains (Fig. 9.5, 9.6 & 9.7).
2. Female cone
In Cycas true and compact female cone (ovulate strobilus) is absent, instead it is a lax where megasporophylls are loosely arranged at the stem apex that appears like a rosette. Each megasporophyll is a modified foliage leaf ranging from 15-30 cm. in length. It has a proximal petiole, middle ovule bearing part and upper pinnately dissected sterile region. The middle fertile part bears 2-12 sessile rounded ovules in two rows (Fig. 9.8 & 9.9).
Article By : Sandeep Pant
- Stems and seeds are used for extracting strach.
- Young leaves are often used as vegetable in some parts of India, Malaya and Indonesia.
- The Juice of young leaves of C.circinalis is used as remedy for disorders of stomach, blood vomiting and skin diseases.
- Leaves of C.revoluta are rich in nitrogen and they are used as green manure for rice, sweet potato and sugarcane.
- A text book of Botany : Singh, Pande and Other
Article By : Sandeep Pant