Q.4. What is Sorus ? Where does it occur ? Describe. (2008)
Ans. Sorus: -
Group of sporangium on the leaves is called as sorus. Generally sporangia are available on the top of the vein and they are connected with receptacle with the help of a long circle. Receptacle in a small bulg. Sorus is secured by circinate vernation. Scales and sporangium groups are also helpful in security. A security cover is also found around the sorus, which is known as indusium.
From the development view point following are the types of sori -
1. Simple Sorus - These are existed in vertical position. e.g. Botrychium. It is the most beginning type of sorus.
2. Gradate Sorus - These are found in basipetal position. Sporangium can be seen on receptacle. Thus it is derived from easiest type of sorus.
3. Mixed Sorus - In this type of sorus sporangium are found in uncertain position.
Q.5. Describe the sporophyte of Pteridium.
Ans. Sporophyte of Pteridium: -
The pteridium is a sporophytic plant divided into root, stem and leaves. This is paronnial plant. Stems subterranean and hence it is called the rhizome.
The Rhizome - This is subterranean and grows 6 to 20 centimeters below from the surface. They are long, creeping and profusely branched. Generally the three types of branches arise from the sympodium branches.
(a) Long shoot - Arise from parent plant with an internode.
(b) Intermediate shoot - After their from parent axis.
(c) Short shoot - Grow obliquely upwards.
The young plant has and unbranched rhizome with 4-10 to alternating leaves. They are grow in subterranean of soil and shows the dichotomously branched system. Each dicthotomous branch bear a leaf near its point of origin from the main axis. Leaves are arranged in a spiral manner. In shorter branch bear leaf.
Roots - They are arise to irregular intervals along the ventral surface of rhizome. They are endogenous in origin. They are adventitious, and sparingly branced.
Leaves - The leaves are arise on the upper side at the Rhizome and are borne in at alternate manner. They are circinately coiled when young. The legnth of leaf varying from 2-15 feet long. They are tripinnately compound and has a distinct petole. The portion of petiole and patiole is equal is size, patiole is called the Rachis. The pinnuals transvered by a large and prominent midrib. Mid-rib arise from the lateral veins. The petiole are covered with unbranched and multicellular hairs called ramenta.
The leaf of Pteridium is differentiated into two parts:
1. Rachis - In the transverse section of the rachis, the outermost layer is epidermis. The epidermis is followed by hypodermis which has 2 or 3 rows of sclerenchymatous cells. Below the hypodermis cortex is present which is made up of parenchymatous cells. In the cortex region several meristeles lie irregularly scattered in the tissue.
2. Lamina - The pinnule of Pteridium shows distinct upper and lower epidermis. The lower epidermis is provided with stomata. The mesophyll is differentiated into an upper zone of palisade parenchyma and lower of spongy parenchyma. The spongy parenchyma has large intercellular spaces. The vascular strands lie embedded in mesophyll. Each strand is generally amphicribal with its own endodermis and pericycle.
Q.6. Draw a well labelled diagrams of the following -
(a) T.S. of Rhizome (b) T.S. of root of Pteridium. (2007)
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Q.7. Draw well labelled diagram of vertical Pteridium sporophyll.
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Q.8. Differentiate between Eusporangiate and Leptosporangiate ferns.
Ans. Engler and Diels (1936) classified Filicinae into two series Eusporangiatae and leptosporangiatae. Important differences are as follows:
