Q1. Explain different types of phyllotaxy with suitable examples.
Ans: Phyllotaxy refers to the arrangement of leaves on a stem, and it comes in three primary types:
Q2. Describe the modifications of the stem. Give examples for the same.
Ans: Stem modifications manifest in various forms:
Q3. What role do the roots of the aquatic plants play?
Ans: The roots are green and branched in plants like Trapa and Tinospora. This provides an increased photosynthetic area for the plants. They get inflated because the air projects out of the water, which helps the plant in floating and gaseous exchange.
Q4. Ginger grows underground like any other root. Then why is it considered a stem and not root?
Ans: Ginger is an underground modification of stem which bears internodes, nodes, buds and scaley leaves that give rise to aerial shoots. The lower surface of the nodes gives rise to adventitious roots. Also, it does not play any role in anchorage and absorption. It only serves as a reservoir to store food. This proves that ginger is a stem, not a root.
Q5. Why is sunflower not a flower?
Ans: Sunflower is a kind of inflorescence called capitulum with a flat receptacle. It has sessile and small florets. The oldest floret lies in the periphery while the youngest lies in the centre. The cluster of florets is surrounded by bracts. The florets are of two types; ray florets and disc florets.
Q6. Describe the various functions of the root system.
Ans: Root systems help in maintaining the proper balance of water. The major functions of the root system are described as follows:
(a) Water absorption and minerals from the soil via diffusion.
(b) To provide proper anchorage to the plant parts.
(c) To store reserve food material
(d) Synthesise and generate the plant growth regulators.
Q7. Write a short note on the stem.
Ans: The stem is also called the ascending part of the axis as it bears branches, leaves, flowers, and fruits. It originates from the plumule of the embryo, which belongs to a germinating seed. The stem bears internodes and nodes. Nodes are the region of the stem where leaves are born, while on the other hand the internode is the portion between two nodes. The stem is generally green when it’s young and later matures to woody and dark brown.
Q8. Describe the important parts of a leaf.
Ans: The leaf consists of three main parts: leaf base, petiole, and lamina.
(a) Leaf base: The leaf base is the part where the leaf is attached to the stem.
(b) Petiole: The petiole gives structural support to the blade.
(c) Lamina: Lamina is the green expanded part of the leaf with veins and veinlets.
Q9. Mention the role of cotyledons and endosperm in seed germination.
Ans: Cotyledons and endosperm store food in seeds. When the seed absorbs water, enzymes activate and break down stored food to nourish the germinating seed.
Q10. What do you mean by venation?
Ans: Venation refers to the organization of veins and veinlets in a leaf's lamina. When veinlets create a network, it's termed reticulate venation, and when veins run parallel within the lamina, it's called parallel venation. Typically, dicotyledonous plants exhibit reticulate venation, whereas monocotyledonous plants tend to display parallel venation in their leaf lamina.
Q11. Write a short note on different types of root systems.
(a) In most dicotyledonous plants, direct elongation of the radicle occurs, leading to the formation of primary roots. This primary root grows inside the soil. Further, The primary roots and their branches constitute the taproot system, for example-mustard plants.
(b) In most monocotyledonous plants, the primary root is short-lived and is mostly replaced by many roots. Further, the primary roots originate from the base of the stem and constitute the fibrous root system. For example, wheat plants.
(c) In other plants, the roots arise from parts of the plant other than the radicle. Such a type of root is called adventitious root—for example, grass, banyan trees etc.
Q12. What are the different functions of the petiole and lamina?
Ans: The major functions of the petiole are
(a) The petiole helps to hold the blade.
(b) It allows the leaf blades to flutter in the wind, thereby decreasing its temperature and cooling the leaf, which occurs when fresh air is attached to the leaf’s surface.
The functions of the lamina are-
(a) The veins of the lamina help to provide rigidity to the leaf blade.
(b) It acts as a channel that helps to transport water, minerals, and food materials through the plant.
Q13. Describe the term phyllotaxy.
Ans: Phyllotaxy is described as the pattern of arrangement of leaves on the stem or branch of a plant.
It is the majority of three main types:
(a) Alternate: Alternate phyllotaxy is when a single leaf arises at each node alternately, the most common example being China rose.
(b) Opposite: Opposite phyllotaxy is when a pair of leaves arise at each node and lie opposite each other. The most common example is Calotropis and guava plants.
(c) Whorled: Whorled phyllotaxy is when more than two leaves arise at a node and form a whorl. The most common example is Alstonia.
Q 14. Write a short note on the symmetry of the flower.
Ans: The flower is classified as actinomorphic, which comes in radial symmetry or zygomorphic, which comes in bilateral symmetry.
(a) Actinomorphic Symmetry: A flower is said to be actinomorphic when divided into two equal radical halves in any radical plane that passes through the centre. Its most common examples are mustard, datura and chilli.
(b) Zygomorphic Symmetry: A flower is said to be zygomorphic when the flower divides into two halves only in one vertical plane, like peas, beans, and cassia.
Q15. Write a note on the different regions of the root.
Ans: At the apex of the root, it is covered by a thumb-like structure called a root cap. The main function of the root cap is the protection of the tender apex of the root that penetrates the soil. The region of meristematic is situated a few millimetres above the root cap. The cells in the meristematic region are small, thin-walled and contain dense protoplasm.
The cells adjacent to this region undergo rapid elongation and enlargement, which are also responsible for the growth of the root. This region responsible for growth is called the region of elongation. The cells in this region gradually differentiate and mature. So, the zone adjacent to the elongation region is called the region of maturation, and root hairs are adjacent to the region of maturation. Root hair consists of epidermal cells that are very fine, delicate, and thread-like structures. The main functions of these root hairs are the absorption of water and minerals from the soil.