Flowering plants, also called angiosperms, use a sexual mode of reproduction. Reproduction in plants, mainly revolves around the flower, which has both the male and the female gametes. All parts of a flower aid in the process of reproduction, although some of them are sterile. Therefore, to understand the process of reproduction in flowering plants, we need to look at the different parts of the flower and their functions.
Explore sexual reproduction in flowering plants notes to learn about the reproductive structure of the flower and the process of pollination.
Structure of a FlowerA flower comprises the following parts-
Calyx: It is the outermost whorl of a flower. It comprises units called sepals. In the bud stage, calyx encloses the rest of the flower. They usually exhibit green colouration, at some other instances, they may be a colour like petals. This state of Calyx is termed as petaloid. Calyx can either be prominent or absent.
Corolla: It consists of many numbers of petals and it is the second whorl of the flower. These petals are sometimes fragrant. They are coloured, thin and soft that would help in the process of pollination as they would attract animals and insects.
It is the male reproductive part of a flower, comprising stamens and it is the third whorl. Each stamen comprises two parts, namely, anther and filament. The tip of the anther is supported by the filament. Here pollens are produced by meiosis and disappear eventually.
The transverse section of an anther is microsporangia that further forms a pollen sac. The pollen sac contains pollen grains.
Microsporangia and Microsporogenesis
Microsporogenesis involves the formation of microspores from microspore mother cells by meiotic division.
The structure of anther: The anther is the breeding part of stamens. Each anther is connected by two lobes. Each anther lobe comprises two pollen chambers located longitudinally. The microsporangium is sufficiently supplied with a number of pollen microspores.
Traverse Section of Anther
Microsporangia consist of:
It is the female reproductive organ and the last whorl of the flower. It is composed of pistil and occupies the central position of the thalamus. The stigma, style, and ovary are the components of the pistil. The ovary produces ovules internally. Through meiosis, ovules produce megaspores which in turn develops into female gametophytes. As a result, egg cells are produced.
Gynoecium can be:
Pistil- Each pistil has three parts:
The ovule is connected to the placenta with a stalk called funicle. It yields megasporocytes that form megaspores. Megasporogenesis is the process of arrangement of megaspores of the megaspore mother cell. The megaspore mother cell divides meiotically. One of the three megaspores is utilized while the others degenerate. The functional megaspore forms the female gametophyte.
Pollination is an ecological process carried out by all flowering plants. In this process, the matured pollen grains are transferred from the anther to the stigma for the purpose of sexual reproduction in flowering plants.
There are two types of pollination:
After pollination, the pollens are transferred to the ovary through the pollen tube. After reaching the ovary, one of the male gametes mates with the ovule, or the female gamete (fertilization) and the other joins with the polar nuclei. The gamete uniting with the eggs results in the production of a zygote, that gradually develops to be an embryo. The second gamete that unites with the polar nuclei results in the formation of endosperm nucleus. It supplies nourishment to the embryo. The fertilization ultimately turns ovules into seeds while the ovary develops into the fruit.
Fertilization in Plants
Q1. Do all flowering plants show sexual reproduction?
Ans: Only angiosperms show sexual reproduction. The gymnosperms or non-flowering plants cannot undergo sexual reproduction because they have no reproductive organs.
Q2. How do flowers reproduce?
Ans: Flowers reproduce by the process of pollination. The pollen grains are transferred from the anther of the male flower to the stigma of the female flower, enabling fertilization resulting in the production of seeds.
Q3. What are the different stages of a plant life cycle?
Ans: The different stages of the plant life cycle include:
Q4. Which plants die after flowering?
Ans: Monocarpic flowers die after flowering. They flower, set seeds and fall. Alphonse De Candolle gave the term monocarpic flowers.
Q5. What is gregarious flowering?
Ans: Gregarious flowering is the most attractive pattern of flowering in bamboo. This occurs when all the flowers of a particular bamboo species bloom at once. This usually happens at an interval of 60-130 years.