1. What is thalamus? Write its function.
2. Write three modifications each of stem and leaves.
3. Explain the structure of the flower with diagram.
4. How are fruits and seeds formed?
5. Differentiate between self and cross-pollination.
6. Explain the different types of venation with the example.
7. What is the advantage of transpiration?
8. List out the important functions of the leaf.
Answers
Answer:
1.The thalamus is a mostly gray matter structure of the diencephalon that has many essential roles in human physiology. The thalamus is composed of different nuclei that each serve a unique role, ranging from relaying sensory and motor signals, as well as regulation of consciousness and alertness.
2.A)Leaves are the part of a plant that contains chlorophyll and carries out the process of photosynthesis but sometimes it got modified to perform various functions. They are:-
Tendrils-present in climbers and help them to climb as seen in pea.
The phyllode-green expanded structure formed by the modification of petiole or rachis and carry out photosynthesis as seen in Acacia.
Leaf pitcher- modified into a lid like structure and helps in capture seeds to fulfill nitrogen deficiency as seen in Nepenthes.
B)The stem is the part of a plant that grows above the ground and provides support to the plant but gets modified to help plant in various functions. They are:-
Thorn- The axillary buds of some plants become arrested and get modified into the stiff, sharp and pointed structure for reducing transpiration and protection as seen in Citrus.
The phylloclades-the stem of xerophytes to carry out photosynthesis as their leaves are reduced to prevent transpiration as seen in Opuntia.
Cladodes-The stem and branches modified to carry out photosynthesis as in Ruscus.
3.Plants have a root system, a stem or trunk, branches, leaves, and reproductive structures (sometimes flowers, sometimes cones or spores, and so on). Most plants are vascular, which means they have a system of tubules inside them that carry nutrients around the plant.
Vascular plants are differentiated from plants such as algae, which do not have a vascular system. Most vascular plants are seed plants, and seed plants are most often the model used in biology and botany textbooks and the type of plant with which you’re probably the most familiar.
4.Seeds and fruits are formed by fertilization. In angiosperms, two structures are formed as a result of double fertilization – a diploid zygote and a triploid primary endosperm cell. The zygote develops into an embryo, whereas, the endosperm cell gives rise to endosperm. It provides nourishment to the growing embryo.
5.Self-pollination occurs when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant. Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species.
6.Venation is the phenomenon of arrangement of veins in the lamina of the leaf surface. It is of three types, reticulate, parallel and furcate venation. In reticulate venation, veins form the network like structure. For example, leaves of dicot plants. In parallel venation, veins arise from the mid rib and run parallel. For example, leaves of monocot plants. In furcate venation, veins form dichotomous branching. For example, leaves of fern.
7.Advantages of transpiration: It helps in the exchange of gases. It helps in sending out excessively absorbed water by plants. It helps in the development of the plant body.
8.Leaves are vital to the survival of plants. There are following two main functions of the leaf:
(i) Transpiration: The extra water comes out of the leaves in the form of vapor. This process is called transpiration.
(ii) Photosynthesis: The process by which leaves prepare their food from water and carbon dioxide, in the presence of sunlight and a green-colored substance, is called photosynthesis.
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