Thursday, November 8, 2018
Seed Germination
Author: Izyan Binti Kamaludin, 2018227252 (Seed Germination)
In botany, seeds refer to the embryonic plants growing in hard or semi-hard outer coverings.
The seedling stage is an essential part of propagation in seed plants. They emerge from the ripened ovule after pollen fertilization. While germination is the process of seeds developing into new plants. Seed germination is the beginning or the process of development of a seed (a fertilized ovule containing an embryo, which form a new plant upon germination).
The seedling stage is an essential part of propagation in seed plants. They emerge from the ripened ovule after pollen fertilization. While germination is the process of seeds developing into new plants. Seed germination is the beginning or the process of development of a seed (a fertilized ovule containing an embryo, which form a new plant upon germination).
When water is plentiful, the seed fills with water in a process called imbibition. The water activates special proteins, called enzymes, that begin the process of seed growth. First, the seed grows a root to access water underground. Next, the shoots growth above ground, begin to appear. The seed sends a shoot towards the surface, where it will grow leaves to harvest energy from the sun. The leaves continue to grow towards the light source in a process called photomorphogenesis.
Next, seedling growth can be of two types which are Epigeal germination and Hypogeal germination. Both refer to the position of the cotyledons during germination.
Epigeal germination occur when the hypocotyl elongate and pulling the cotyledon above the surface of the soil. Epicotyl structures, known as the plumule, are protected by two cotyledons from any kind of damage. The seed coat swells and bursts open. The radicle grows downwards and forms the root system. The hypocotyl elongates, exposing the cotyledons above the soil. When hypocotyl arch emerges out of the soil, it continues growing straight, the direction of growth being influenced by the direction of light. Cotyledons supply nutritional matter to the developing plant and they also turn green (owing to the production of chlorophyll), which enable the plant to acquire nutrition via photosynthesis.
Hypogeal germination occur when the cotyledons remains underground with only the shoot(plumule) emerging from the soil surface. The seed absorbs water and swells. The seed coat bursts and the radicle emerges out. It grows downwards into the soil and forms the root system. In the initial stages of development, the plumule is arched and thus protects the young shoot from damage during its emergence from the soil. The epicotyl elongates and the plumule emerges out of the soil. The plumule grows upwards and forms the shoot of the seedling. The cotyledons supply food to the young seedling till it is able to manufacture its own food. They wither away later.
In conclusion, germination ends with the formation of a seedling. The seedling is a stage in plant growth where the plant is still dependent on the reserve food of the seed or the food manufactured by the cotyledons. The seedling consists of five part which are radicle or the embryonic root, hypocotyl, epicotyl, plumule and cotyledons. The roots of the seedling absorb water and minerals from the soil. The leaves manufacture food for the young plant, which keeps growing and becomes a mature plant. It produces flowers and seeds.
References:
- Schopfer P, Plachy C. 1984. Control of seed germination by abscisic acid. II. Effect on embryo water uptake in Brassica napus L. Plant Physiology 76: 155–160.
- Manz B, Müller K, Kucera B, Volke F, Leubner‐Metzger G. 2005. Water uptake and distribution in germinating tobacco seeds investigated in vivo by nuclear magnetic resonance imaging. Plant Physiology 138: 1538–1551.
- Seed germination : Structure and germination, Retrieved November 5, 2018, from https://www.topperlearning.com/
germination_of_seed
germination_of_seed
