How Do Radicle and Plumule Function During Seed Germination?
Radicle and plumule are two essential parts of an embryo plant but they are both different from each other. The experts at Vedantu have summarised these differences for an easy understanding. To understand this difference between radicle and plumule, we must first understand the process of their origin which begins from a seed. A seed is an important part of flowering plants as it plays a crucial role in the life cycle of these plants.
Every seed contains an embryo that turns into a plant after germination. For the embryo to grow into a plant it must receive all the ingredients needed for its growth like warmth, sunshine, moisture, and nutrient-rich soil. The young plant that germinates or grows from the seed has three primary parts; roots, shoot, and embryonic leaves.
The main difference between plumule and radicle is that while plumule is the embryonic shoot of this seedling, the radicle is the embryonic root. The embryonic leaves are called cotyledons. Both plumule and the radicle are present inside the seed and are joined to the cotyledons.
The Radicle
After germination, the first part of the embryo that grows from the seed is called the radicle. It is an embryonic root of the seedling and later grows on to become the root of the plant. The radicle grows from the micropyle of the seed and develops further down into the soil. As it grows into the soil, it starts to absorb water from it for the growth and development of the embryo. After the emergence of the radicle, the plumule comes out from the seed. It supports the cotyledons and performs photosynthesis, a process that produces food required by the plant for its growth.
There are two types of radicle: antitropous and synchronous. They are different from each other because of the direction of their growth. When the radicle grows away from the hilum, it is known as Antitropous and when it grows towards the hilum, this type of radicle is known as synchronous.
The Plumule
The primary shoot that comes out of the embryo in the seed is the plumule. This plumule later develops into the first leaves of the seedling and is found above the cotyledons during the germination process. The growing tip of the tiny shoot called epicotyl is the part that is known as the plumule. Epicotyl develops into leaves, stems, and flowers as the plant grows.
The process of germination of the seed can be classified into two parts: epigeal germination and hypogeal germination. Epigeal germination is when the plumule appears after the cotyledons have grown above the ground. Hypogeal germination occurs when the plumule grows above the soil while the cotyledons are below the surface of the soil.
Most of the plumules are conical in shape and as cotyledons start to store food, the plumule starts to become small. Sometimes the seed stores less food and in such a scenario, the plumule becomes large and grows well-formed leaves. These leaves then capture more sunlight to perform photosynthesis.
Let’s look at some key points that differentiate between plumule and radicle.
Difference Between Radicle and Plumule
One of the essential factors that help to differentiate between radicle and plumule is that they both grow into different parts of the plant.
FAQs on Radicle vs Plumule: Complete Comparison for Students
1. What is the main difference between a radicle and a plumule?
The main difference lies in what they develop into. The radicle is the embryonic root that grows downwards into the soil to form the plant's root system. The plumule is the embryonic shoot that grows upwards towards the light to form the stem, leaves, and flowers.
2. What is the primary function of the radicle in a germinating seed?
The radicle is the first part of the embryo to emerge from the seed. Its primary function is to anchor the seedling in the soil and absorb water and nutrients. It develops into the primary root of the new plant, forming the foundation for the entire root system.
3. What does the plumule develop into, and what is its main role?
The plumule develops into the shoot system of the plant. This includes the stem, leaves, branches, and eventually flowers and fruits. Its main role is to grow towards sunlight to begin photosynthesis, which provides the energy for the young plant to grow.
4. Why does the radicle always grow downwards and the plumule upwards?
This happens because of their response to environmental signals. The radicle is positively geotropic, meaning it grows towards the pull of gravity, and positively hydrotropic, growing towards water. The plumule is positively phototropic, meaning it grows towards a light source. These responses ensure the plant is properly oriented for survival.
5. Is the plumule the same as the shoot?
Not exactly, but they are directly related. The plumule is the tiny, embryonic shoot found within the seed. Once the seed germinates and the plumule starts to grow and develop leaves, it is then referred to as the shoot. So, the plumule is the precursor to the shoot.
6. Can you see the radicle and plumule when a bean seed sprouts?
Yes, absolutely. If you soak a bean seed and let it sprout, the first small, white part that comes out is the radicle (the future root). Shortly after, you will see the plumule, which looks like a tiny pair of folded leaves, emerging and growing upwards.
7. How do cotyledons help the radicle and plumule grow?
The cotyledons act as the food source for the embryo. They store energy (in the form of starch, proteins, or fats) that the radicle and plumule use to grow before the plant can produce its own food through photosynthesis. Once the plumule develops leaves and starts photosynthesis, the cotyledons usually wither and fall off.
8. What protects the young plumule and radicle as they push through the soil?
The delicate tips of the radicle and plumule are protected by special sheath-like structures. In monocots like maize or grass, the radicle is protected by the coleorhiza, and the plumule is protected by the coleoptile. These sheaths act like a cap, shielding the growing tips from damage as they navigate the soil.
