Question

Which is not essential for seed germination in most cases?
A. Oxygen
B. Light
C. Suitable temperature
D. Moisture

Answer 1

The process of sprouting of a seedling from the seed is called seed germination. It involves softening and swelling of seed coat which leads to rupture of the seed coat and release of radicle and plumule forming primary root and shoot respectively and division growth of the seedling.

Complete step by step answer: Development of plants from a single seed is called seed germination. Factors such as oxygen, water and temperature are required for seed germination, but the light is not an essential factor amongst other factors. The process of seed germination includes following steps:
i. In the beginning, water is taken up by seeds, seed coat swells and softens after the optimum temperature is attained. This process is named as imbibition. Stored food is metabolized inside the cell and this stage is called lag phase.
ii. Seed coat ruptures and radicle emerges and the primary root is formed. After that, plumule emerges and grows into a primary shoot.
iii. Seed cells become metabolically active and start dividing and develop into a seedling.
Important requirements for seed germination are as follows:
a. Water: Water provides dissolved oxygen for growth of the embryo, softens the seed coat. The hydration or moisture is provided by water which helps in performing vital activities in protoplasm. Softening of seed coat helps in rupture of the seed coat. Dry seeds need water relative to their dry weight. Water is a very important requirement for seed germination. Seeds have 4-12 % of moisture in the packaged state. For germination, moisture is increased to 25-50%
b. Oxygen: Seed gets oxygen from the soil particles because of which seeds present at large depth are not able to get oxygen sufficiently. Oxygen is an essential component for metabolic reaction until the plant grows green leaves. Hence, oxygen is a vital requirement for the growth of a seed.
c. Suitable temperature: For the seed to germinate, the optimum temperature of 25-30 C is required which is moderate temperature. Some seeds may require a temperature between 5-40 C
Hence, the correct answer is option B.

Note: The part of the plant that first emerges from the seed is the embryonic root, termed the radicle. It allows the seedling to become anchored in the ground and start absorbing water. After the root absorbs water, an embryonic shoot emerges from the seed. This shoot comprises three main parts: the cotyledons, hypocotyl and epicotyl.