Multiple Choice Questions
Pollen is produced in the :
Reason — The anther consists of four sac-like structures that produce pollen for pollination.
Reproductive whorls of a flower are:
- Stamens and carpels
- Sepals and petals
- Sepals and stamens
- Petals and carpels
Stamens and Carpels
Reason — Stamens are the male reproductive parts of the flower.
Carpels are the female reproductive parts of the flower.
Grafting is a method of :
- Artificial vegetative propagation
- Sexual reproduction
- Artificial pollination
Artificial vegetative propagation
Reason — Grafting is a process of joining two plants together to grow as one and is one of the methods of Artificial vegetative propagation.
Short Answer Questions
Write two ways in which pollination may occur in plants.
Two ways in which pollination may occur in plants are —
Name the three agents of pollination.
Three agents of pollination are —
Give two features of flowers which favour pollination by insects.
Two features of flowers which favour pollination by insects are —
- These flowers are large with coloured petals, to attract insects.
- These are scented so that insects locate the flowers by the smell.
Name two characteristics of flowers in which pollination occurs by wind.
Two characteristics of flowers in which pollination occurs by wind are —
- They are usually small and are of dull colours.
- They generally have long anthers protruding out of the flowers so that pollen grains may get blown off easily.
Fill in the blanks by selecting suitable words: (unisexual, fertilisation, fruit, stamen, anther, bisexual, pollination, seed, ovary)
(a) A flower that bears both the male and the female parts is known as ............... flower.
(b) A flower bearing only male or female parts is known as ............... flower.
(c) Transfer of pollen grains from the anther to the stigma is known as ...............
(d) Fusion of male cell with female cell is called ...............
(e) The ovule develops into a ...............
(f) The ovary of the flower develops into a ...............
(i) A flower that bears both the male and the female parts is known as bisexual flower.
(ii) A flower bearing only male or female parts is known as unisexual flower.
(iii) Transfer of pollen grains from the anther to the stigma is known as pollination.
(iv) Fusion of male cell with female cell is called fertilization.
(v) The ovule develops into a seed.
(vi) The ovary of the flower develops into a fruit.
Long Answer Questions
What is vegetative reproduction?
Vegetative reproduction is a method where in new plants are produced by vegetative parts of a plant called propagules and the process is known as vegetative propagation. The vegetative parts mean the leaf, stem and root. Vegetative propagation can either be natural or artificial.
Briefly explain why a gardener prefers to grow certain plants vegetatively?
Gardener prefers to grow certain crops by vegetative method because of the following reasons —
- Reproduction by vegetative parts takes place in a shorter time.
- New plants, thus produced, spread very fast in a small area.
- It is a surer method of propagation.
- All the good characters of the mother plant are retained by the daughter plants.
Why is it disadvantageous to grow plants vegetatively?
It is disadvantageous to grow plants vegetatively because —
- As all plants developed by vegetative reproduction are genetically identical, they are likely to be affected simultaneously if a disease spreads in the farm.
- Dispersal of plants does not take place on its own. Daughter plants, so developed, tend to remain nearby and are restricted to a particular area leading to competition for resources.
What is meant by pollination? Explain the structure of germinating pollen grain with the help of a labelled diagram.
Pollination is the process in which the pollen grains from the anthers are transferred to the stigma of a flower of the same species.
Labelled diagram showing the structure of germinating pollen grain is shown below:
Upon observing moisture, the pollen grain starts germinating and grows a pollen tube that starts lengthening in the direction of ovule through the style towards the egg cell.
Imagine all the seeds produced by a plant happen to fall under the same plant and sprout into new plants. Mention any two problems that will be faced by the new plants.
Some of the problems faced by the new plants will be —
- The new plants will not get sufficient amount of air and sunlight which is required for their proper growth because the parent plant will shade over them.
- New plants will lack space for their growth because comparatively large number of plants are growing at a particular place.
- The new plants will face competition among themselves to get nutrient from the soil which will hamper their growth and development.
What is a flower? Draw a neat labelled diagram showing the LS of a typical flower.
A flower is the reproductive part of a plant which produces new seeds. It consists of reproductive organs (stamens and carpels) that are typically surrounded by a brightly coloured corolla (petals) and a green calyx (sepals) and are usually scented. Flowers attract pollinators who help in pollen transfer.
Labelled diagram showing the LS of a typical flower is given below:
Write short notes on the following —
(c) Vegetative reproduction
(a) Micropropagation — Micropropagation is the propagation of plants by tissue culture techniques. If vegetative propagation is not possible in a plant, then tissue of vegetative buds, shoot apex or any other suitable part of the plant can be used as explant for micropropagation. The explants are treated with sterilisation chemicals to prevent microbial growth, and then cultured in a particular nutrient medium. Cells grow and divide to form a cell mass called callus. Some growth regulators (plant hormones) are added. The callus differentiates into plant parts looking like a tiny plant called plantlet. After 4-6 weeks the plantlets are transferred to the soil.
(b) Bryophyllum — Bryophyllum is the plant whose leaves produce adventitious buds in their margin. When such leaves with adventitious buds fall in moist soil, their buds in the margins begin to grow as young tiny plants.
(c) Vegetative reproduction — New plants can be produced by certain parts of a plant such as the leaf, stem and root. These vegetative parts of a plant that are capable of giving rise to new plants are called propagules and the process is known as vegetative propagation. It can be either natural or artificial.
(d) Grafting — In Grafting, a small shoot or bud of a desired variety of plant is intimately fixed on the stem of another plant of the same or related species. The plant receiving the bud or the shoot is called the stock and the shoot fixed on it is called the scion.
For a successful graft, it is important that the cambium layers of the stock and the scion must come into very close contact so that growth may continue. The grafted points are bound with tape and the joint is covered with wax to prevent dehydration and protect against bacterial infection.
How is artificial pollination is useful to plant breeders? Discuss briefly.
Artificial pollination is practiced by plant breeders for developing new varieties. The breeders select two different varieties of a crop plant with desired characteristics. For example, one variety maybe high yielding while the other maybe disease-resistant. Cross breeding between them is done by artificial pollination. Many high-yielding varieties of rice, wheat, maize, etc. have been produced by this process.
With the help of suitable diagrams, describe:
(a) Binary fission in plants
(b) Budding in yeast cell
(a) Binary fission in plants — Binary fission is a type of asexual reproduction. It is the most common form of reproduction in lower organisms such as bacteria. In this method, the nucleus splits or divides into two and then the cell splits across the middle, forming two small identical cells called the daughter cells. Below diagram shows Binary Fission:
(b) Budding in Yeast cell —
Budding is a type of asexual reproduction common in Yeast. Here, the parent cell produces an outgrowth called a bud. The bud grows, and then gets detached (along with its daughter nuclei) from the parent body to lead an independent life. Below diagram shows budding in yeast cell: