Question:
Mutation which occurs in one layer and along the side of the apex is known as
Mutation which occurs in one layer and along the side of the apex is known as
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To easily distinguish somatic chimeras: Periclinal = entire layer mutated (stable); Mericlinal = partial layer mutated (unstable); Sectorial = pie-shaped slice through all layers mutated (highly unstable).
Updated On: Jul 31, 2026
- Mericlinal Chimera
- Sectorial chimera
- Periclinal chimera
- Segmented chimera
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
A chimera is a plant or plant part composed of two or more genetically distinct layers of cellular tissues.
These tissue variations arise from spontaneous or induced somatic mutations occurring in the actively dividing cells of the shoot apical meristem (SAM).
The angiosperm shoot apex is highly organized and structured into distinct layers: the tunica (comprising the outer L1 and L2 layers) and the corpus (comprising the inner L3 layer).
Based on how the mutated cells are arranged across these histogenic layers, chimeras are classified into periclinal, mericlinal, and sectorial types.
Step 2: Detailed Explanation:
A mericlinal chimera is formed when a mutation arises in a single cell of one of the histogenic layers (L1, L2, or L3) and, through subsequent divisions, occupies only a localized portion or a strip along the side of that specific layer.
Because the mutated tissue does not encompass the entire circumference of the histogenic layer, the plant exhibits a mosaic or variegated pattern only on certain parts or organs derived from that sector of the apex.
Mericlinal chimeras are structurally unstable.
During continuous vegetative growth and lateral bud formation, they tend to either revert to a completely wild-type state or stabilize into a periclinal chimera.
A periclinal chimera is characterized by a mutation that completely occupies one or more entire layers of the meristem, making it highly stable during vegetative propagation.
A sectorial chimera is one in which the mutated tissue spans across all three layers (L1, L2, and L3) but only occupies a wedge-shaped sector of the stem.
This type is extremely rare and highly unstable due to the dynamic cell divisions at the shoot tip.
Segmented chimera is not a standard horticultural classification used to define meristematic tissue arrangements.
Step 3: Final Answer:
Consequently, a mutation restricted to only a part of a single layer along the side of the apical dome is classified specifically as a Mericlinal Chimera.
A chimera is a plant or plant part composed of two or more genetically distinct layers of cellular tissues.
These tissue variations arise from spontaneous or induced somatic mutations occurring in the actively dividing cells of the shoot apical meristem (SAM).
The angiosperm shoot apex is highly organized and structured into distinct layers: the tunica (comprising the outer L1 and L2 layers) and the corpus (comprising the inner L3 layer).
Based on how the mutated cells are arranged across these histogenic layers, chimeras are classified into periclinal, mericlinal, and sectorial types.
Step 2: Detailed Explanation:
A mericlinal chimera is formed when a mutation arises in a single cell of one of the histogenic layers (L1, L2, or L3) and, through subsequent divisions, occupies only a localized portion or a strip along the side of that specific layer.
Because the mutated tissue does not encompass the entire circumference of the histogenic layer, the plant exhibits a mosaic or variegated pattern only on certain parts or organs derived from that sector of the apex.
Mericlinal chimeras are structurally unstable.
During continuous vegetative growth and lateral bud formation, they tend to either revert to a completely wild-type state or stabilize into a periclinal chimera.
A periclinal chimera is characterized by a mutation that completely occupies one or more entire layers of the meristem, making it highly stable during vegetative propagation.
A sectorial chimera is one in which the mutated tissue spans across all three layers (L1, L2, and L3) but only occupies a wedge-shaped sector of the stem.
This type is extremely rare and highly unstable due to the dynamic cell divisions at the shoot tip.
Segmented chimera is not a standard horticultural classification used to define meristematic tissue arrangements.
Step 3: Final Answer:
Consequently, a mutation restricted to only a part of a single layer along the side of the apical dome is classified specifically as a Mericlinal Chimera.
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