Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Seed germination is the process where the embryo inside a seed wakes from a state of dormancy and starts to grow into a seedling under favorable environmental conditions like , , and optimum temperature.
The first step of germination is Imbibition, a physical process where the dry seed coat adsorps , leading to the swelling of the seed and the eventual rupture of the seed coat.
Gibberellins () play a crucial role by stimulating the aleurone layer to produce hydrolytic enzymes such as -amylase, which break down stored starch into glucose to provide energy for the growing embryo.
In Epigeal germination, the hypocotyl elongates rapidly, pushing the cotyledons above the soil surface (e.g., Bean, Castor, Onion).
In Hypogeal germination, the epicotyl elongates, and the cotyledons remain below the soil surface (e.g., Pea, Maize, Gram).
The transition from dormancy to germination involves a shift in respiration from anaerobic to aerobic, significantly increasing the uptake of and the release of .
Abscisic Acid () acts as an antagonist to and is responsible for maintaining seed dormancy, preventing germination during unfavorable conditions.
📐Formulae
💡Examples
Problem 1:
During the germination of a castor seed (rich in lipids), the volume of evolved is and the volume of consumed is . Calculate the Respiratory Quotient ().
Solution:
Explanation:
The value of is characteristic of fats or lipids being used as the primary respiratory substrate during the germination process.
Problem 2:
Identify the type of germination where the hypocotyl grows first and forms a loop to pull the cotyledons out of the soil.
Solution:
Epigeal Germination
Explanation:
In Epigeal germination, the hypocotyl elongates faster than the epicotyl. This brings the cotyledons above the ground, where they often turn green and perform photosynthesis temporarily until the first true leaves develop.
Problem 3:
Explain the role of the Aleurone layer in the germination of a Monocot seed like Barley.
Solution:
The Aleurone layer synthesizes -amylase in response to Gibberellic Acid ().
Explanation:
When the embryo absorbs , it releases , which diffuses to the aleurone layer. This triggers the synthesis of enzymes that hydrolyze the endosperm's starch into maltose and glucose for embryonic growth.