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प्रश्न
Mention two strategies evolved to prevent self-pollination in flowers.
उत्तर
Continued self-pollination decreases the vigour and vitality of a particular race. Thus, flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.
- Dichogamy: Maturation of anther and stigma at different times in a bisexual flower prevent self-pollination.
- Self-sterility: (or self-incompatibility) - Due to the presence of the self-sterile gene in some flowers, pollen grains do not germinate on the stigma of that flowers. e.g.,- tobacco, potato.
- Herkogamy: The anther and the stigma are placed at different positions or have a mechanical barrier so that anthers cannot come in contact with the stigma of the same flower. Ex : Hibiscus, Gloriosa.
- Heterostyly: Styles of the flowers of the same species are in different heights.
- Male sterility: The pollen grains of some plants are not functional. Such plants set seeds only after cross-pollination.
Notes
Students can refer to the provided solutions based on their preferred marks.
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संबंधित प्रश्न
A flower of tomato plant following the process of sexual reproduction produces 200 viable seeds.
Answer the following questions giving reasons :
(a) What would have been the minimum number of ovules present in pre-pollinated pistil ?
(b) How many microscope mother cells would minimally be required to produce requisite number of pollen grains ?
(c) How many pollen grains must have minimally pollinated the carple ?
(d) How many male gametes would have used to produce these 200 viable seeds ?
(e) How many megaspore mother cells were required in this process ?
Can cross-pollination occur in cleistogamous flowers? Give reason for your answer.
What is self-incompatibility?
Why does self-pollination not lead to seed formation in self-incompatible species?
Describe the structure of its microsporangium.
Fill in the blank:
Male sex cells in plants are called _________.
Can a unisexual flower be self pollinated?
Name of the part of the ovary which gives rise to:
Fruit ______
Describe pollination. How many types of pollinations are found?
Cleistogamous flowers are ______.
Male and female flowers are present on different plants (dioecious) to ensure xenogamy, in ______.
Plants with ovaries having only one or a few ovules are generally pollinated by ______.
In some plants anther and stigma mature at the same time this condition is called ______.
Which type of flower has ovary superior?
In the dioecious aquatic plant shown, identify the characteristics of the male flowers that reach the female flowers for pollination:
| Size of the flower | Colour of flower | The characteristic feature of pollen grain | |
| A | small | brightly coloured | Lightweight and non-sticky |
| B | large | colourless | large and sticky |
| C | small | white | small, covered with mucilage |
| D | large | colourless | non-sticky |
Choose the correct statement from the following:
From among the situations given below, choose the one that prevents both autogamy and geitonogamy.
What is self-incompatibility?
Describe any three adaptations in hydrophilous flowers.
What are the major abiotic factors that influence habitat?
