Pollination is the process of transferring pollen from the male reproductive organ (anther) to the female reproductive organ (stigma) of a flower, facilitating fertilization in plants.
Self-pollination is a type of pollination in which pollen from the anther of a flower is transferred to the stigma of the same flower or another flower on the same plant, leading to fertilization. It occurs without the involvement of external agents like wind or insects.
Cross-pollination is a significant reproductive strategy in the plant kingdom, and it plays a crucial role in ensuring genetic diversity and the overall health of plant populations. In this process, pollen from the anther of one flower is transferred to the stigma of another flower, and it often involves the assistance of external agents like wind, insects, birds, or other organisms.
Fruit formation is the process where the flower’s ovary develops into a mature fruit after fertilization. The ovule within the ovary grows into seeds, and surrounding tissues become the protective or fleshy part of the fruit, aiding in seed dispersal and protection. It’s crucial for plant reproduction and propagation.
Formation of fruit without fertilization, known as parthenocarpy, involves the development of fruit without the need for pollination and fertilization of the ovules. This process can occur naturally or be induced artificially and often results in seedless fruits.
Adaptations in the structure of wind-pollinated and insect-pollinated flowers ensure efficient pollen transfer by their respective agents.
Adaptive characters of wind and water pollinated plants.
Adaptive character in insect pollinated plants.
A seed is a remarkable and essential part of a plant’s life cycle, serving as a means of reproduction and dispersal. Its structure is well-adapted to ensure the survival and growth of a new plant. The key components of a seed and its structure include:
The outer protective layer of a seed, known as the seed coat or Testa, shields the embryo and its stored nutrients from environmental factors, such as pathogens and desiccation.
At the heart of the seed is the embryo, the miniature plant-to-be. It consists of several vital parts:
These are thick, fleshy structures that store the seed’s food reserves. In dicotyledonous plants, like beans or sunflowers, there are typically two cotyledons. In monocotyledonous plants, such as corn or lilies, there is usually only one cotyledon.
The plumule is the future shoot of the plant. It will grow upwards, developing into leaves and stems.
The radicle is the embryonic root. It grows downward into the soil, anchoring the plant and absorbing water and nutrients.
This small pore in the seed coat serves as a point of entry and exit for gases and water during germination. It is where the radicle emerges during seed germination.
In some seeds, there is an additional tissue called the endosperm. This tissue stores nutrients and provides nourishment to the developing embryo, and, in some cases, to the seedling after germination.
Germination is the process by which a dormant seed awakens and begins to sprout, leading to the growth of a new plant.
Only living seeds can sprout, and they need the ideal amounts of moisture, oxygen, and heat.
Role of Water – Water is essential for seed germination as it activates enzymes that break down stored nutrients in the seed, providing energy for growth.
Role of Oxygen – Oxygen is crucial for the respiration of germinating seeds, allowing them to convert stored sugars into energy.
Temperature – Proper temperature is vital for seed germination, as it influences enzyme activity; different plant species have specific temperature requirements for optimal germination.
In Epigeal Germination, the cotyledons emerge above the soil surface and become the first green structures during seedling growth.
Cotyledons in Epigeal Germination play a crucial role in photosynthesis, providing the energy required for the initial growth of the seedling.
Cotyledons serve as photosynthetic organs, contributing to the nourishment and development of the young plant.
Some examples of plants that exhibit Epigeal Germination include beans, sunflowers, peas, and tomatoes.
In Hypogeal Germination, the cotyledons remain below the soil surface and do not emerge above ground.
Cotyledons in Hypogeal Germination primarily serve as a source of stored energy for the developing seedling, as they do not become photosynthetic organs.
The young plant initially relies on the energy reserves stored in the cotyledons to fuel its growth.
Plants such as oak trees, peanuts, beans, and peas often exhibit Hypogeal Germination.