Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Seed Structure: A seed is a mature integumented ovule. It consists of a seed coat (outer and inner ) and an embryo.
The Embryo: Consists of the (future root), (future shoot), and one or two (seed leaves).
Micropyle: A small opening in the seed coat that allows the entry of and during germination and serves as the exit for the radicle.
Albuminous Seeds: Seeds that retain the endosperm at maturity to provide nourishment (e.g., , ).
Exalbuminous Seeds: Seeds where the endosperm is completely consumed during development and food is stored in cotyledons (e.g., , , ).
Conditions for Germination: Essential factors include water ( for enzyme activation), oxygen ( for aerobic respiration), and optimum temperature ( to ).
Epigeal Germination: The hypocotyl elongates rapidly and arches, pulling the cotyledons above the soil surface (e.g., - Bean).
Hypogeal Germination: The epicotyl elongates while the hypocotyl remains short, keeping the cotyledons below the soil surface (e.g., - Pea, - Maize).
Viviparous Germination: Seed germinates while still attached to the parent plant, common in mangrove plants like .
📐Formulae
syntax for aerobic respiration during germination
conversion of stored food into soluble sugar
💡Examples
Problem 1:
Identify the type of germination in a seed where the cotyledons are pushed above the soil, and explain the reason behind this movement.
Solution:
The type of germination is Epigeal Germination.
Explanation:
In Epigeal germination, the (the region of the embryo axis below the cotyledons) elongates faster than the epicotyl. This rapid growth pushes the cotyledons out of the soil into the air and light, where they often turn green and perform photosynthesis temporarily.
Problem 2:
During an experiment, seeds were placed in a flask with moist cotton wool and the temperature was maintained at . Will the seeds germinate? Support your answer with chemical reasoning.
Solution:
No, the seeds will not germinate at .
Explanation:
Germination requires the activation of enzymes like and to break down stored food. These enzymes are inactive at low temperatures (). The optimum temperature for enzymatic activity in most seeds is between and . Without active enzymes, the embryo cannot access energy () for growth.
Problem 3:
Contrast the function of the in with the in a seed.
Solution:
In (Albuminous), the is the primary food storage tissue. In (Exalbuminous), the store the food.
Explanation:
In monocots like , the endosperm remains as a separate tissue to provide nutrition. In dicots like , the endosperm is absorbed by the developing embryo, and the food reserves are transferred into the two fleshy .