Question : Discuss the external factors that affect seed germination.

1.	Question : Discuss the external factors that affect seed germination.
Answer» SOLUTION :External Factors: a. Water: It activates the enzymes which digest the complex reserve foods of the seed. If the water content of the seed goes below a critical level, seeds fail to germinate. b. Temperature: Seeds fails to germinate at very low and high temperature. The optimum temperature is `25^@C` to `35^@C`for most tropic species. c. OXYGEN: It is necessary for GERMINATION. Since aerobic respiration is a physiological REQUIREMENT for germination most will germinate well in air containing 20% oxygen. d. Light: There are many seeds which respond to light for germination and these seeds said to be photoblastic. e. Soil Conditions: Germination of seed in its natural habit is influenced by soil conditions such as holding capacity, mineral COMPOSITION and aeration of the soil.

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