Steps of Seed Germination

You will see a wide variety of trees in your surroundings. Trees play important role in maintaining ecosystem and keeping the environment refreshing and pollution-free. Whenever you watch small or big trees, plants or shrubs, you must be curious about their growth and life cycle. Life cycle of any plant is divided in different phases and seed germination is basic stage to start the growth of plant. You may think that seed is lifeless, but it is not true. It consists of plant in a resting, embryonic condition. Whenever it gets favorable environmental conditions, it starts to germinate. This process occurs through different steps of seed germination. Inactive seed lying in the ground needs warmth, oxygen and water to get developed into plant. Off-course, all the seeds lying in ground are not lucky enough to get proper environment to germinate. Many seeds tend to get dried and cannot develop into a plant. Some seeds get sufficient amount of water, oxygen and warmth and seed germination starts.

Seed structure

Seed coat is outer covering of seed, which protects embryo from any kind of injury, entry of parasites and prevents it from drying. Seed coat may be thick and hard, or thin and soft. Endosperm is a temporary food supply, which is packed around embryo in the form of cotyledons or seed leaves. Plants are classified as monocots and dicots depending upon number of cotyledons.

Requirements for seed germination

All seeds need adequate quantity of oxygen, water and temperature for germination. Some seeds also need proper light. Some can germinate well in presence of full light, while others may require darkness to start germination. Water is required for vigorous metabolism. Soil temperature is equally important for appropriate germination. Optimum soil temperature for each seed varies species to species.

Factors affecting seed germination

There are several factors that can affect germination process. Over watering can prevent the plant to get enough amount of oxygen. If seed is deeply planted in soil, then it can make to use all the stored energy before reaching soil surface. Dry conditions can prevent germination, as seed doesn’t get enough moisture. Some seeds have so hard seed coats that oxygen and water get through it. If soil temperature is extremely low or high, then it can affect or prevent germination process.

Steps of seed germinations

Process of germination occurs in different stages. Some steps of seed germination are as follows:

• Seed absorbs water and seed coat gets burst. It is the first sign of germination. There is an activation of enzymes, increase in respiration and plant cells get duplicated. A chain of chemical changes starts which leads to development of plant embryo.
• Chemical energy stored in the form of starch is converted to sugar, which is used during germination process. Soon, embryo gets enlarged and seed coat burst opens.
• Growing plant emerges out. Tip of root first emerges and helps to anchor the seed in place. It also allows embryo to absorb minerals and water from soil.
• Some seeds require special treatment of temperature, light or moisture to start germination.
• Steps of seed germination can be different in dicots and monocots.

Germination in dicots

During germination process of dicots, primary root emerges through seed coat when seed is buried in soil. Hypocotyl emerges from seed coat through soil. As it grows up, it takes the shape of hairpin, known as hypocotyl arch. Epicotyl structures, plumule, are protected by two cotyledons from any kind of mechanical damage. When hypocotyl arch emerges out from soil, it becomes straight, which is triggered by light. Cotyledons spread apart exposing epicotyl, which contains two primary leaves and apical meristem. In many dicots, cotyledons supplies food stores to developing plant and also turns green to produce more food by the process of photosynthesis.

Germination in monocots

During germination of grass seeds such as oats or corn, primary root emerges from the seed and fruit and grows down. Then, primary plant’s primary leaf grows up. It is protected by a cylindrical, hollow structure known as coleoptile. Once the seedling grows above soil surface, growth of coleoptile is stopped and it is pierced by primary leaf.