Question

In Citrus, embryos develop from diploid cells of nucellus along with the zygotic embryo, resulting in polyembryony. This type of polyembryony is called:

• A. adventive
• B. cleavage
• C. true
• D. defective

Hint:

{Remember:}
{Citrus and Mango} commonly show {adventive polyembryony} where embryos arise from {nucellar cells}. These embryos are genetically identical to the parent plant and are widely used in horticulture for producing uniform plants.

Answer 1

The Correct Option is A

Concept:
Polyembryony is the phenomenon in which more than one embryo develops within a single seed. It is commonly observed in certain plant species such as Citrus and Mango. Polyembryony can arise in different ways depending on the origin of embryos:

• True polyembryony: Multiple embryos develop from a single fertilized egg (zygote).
• Cleavage polyembryony: The zygote divides into several embryos.
• Adventive polyembryony: Embryos arise from somatic tissues of the ovule such as the nucellus or integuments, in addition to the normal zygotic embryo.

In plants like Citrus, embryos develop from the diploid nucellar cells surrounding the embryo sac along with the fertilized zygote. These additional embryos are genetically identical to the parent plant because they originate from somatic tissue.
Step 1: Understanding the origin of embryos in Citrus.
In Citrus seeds, apart from the zygotic embryo formed by fertilization, several embryos arise from diploid nucellar cells present in the ovule.
Step 2: Identifying the type of polyembryony.
Since these extra embryos arise from somatic cells (nucellus) rather than from the zygote, the phenomenon is called: \[ Adventive Polyembryony \]
Step 3: Eliminating incorrect options.

• (A) Adventive $\rightarrow$ Embryos arise from nucellus or integuments (Correct)
• (B) Cleavage $\rightarrow$ Zygote splits into multiple embryos
• (C) True $\rightarrow$ Multiple embryos formed from fertilized egg
• (D) Defective $\rightarrow$ Not a recognized biological term for polyembryony

Final Answer: \(\boxed{\text{Adventive}}\)