1. Apomixis is reproduction in which
(1) Fusion of gametes but no fusion of central cell
(2) Egg form complete plant
(3) Pollen forms seeds
(4) Seeds are formed without union of gametes

Apomixis is a type of asexual reproduction in plants where seeds are formed without the union of gametes. Seeds develop without fertilization, producing offspring that are genetically identical to the parent plant.

Therefore, the correct answer is:

(4) Seeds are formed without union of gametes.

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Introduction

Apomixis is the formation of seeds without the typical sexual process of fertilization. Unlike sexual reproduction, where genetic material from male and female gametes combines, apomixis produces clonal seeds, ensuring offspring are genetically identical to the mother plant. This process occurs naturally in many plants and has significant implications for agriculture and plant breeding.

Definition of Apomixis

• Derived from Greek terms meaning “away from mixing,” apomixis refers to seed formation bypassing meiosis and fertilization.

• The embryo arises from an unreduced egg cell or other sporophytic cells without genetic contribution from pollen.

• As a result, the seed contains a clone of the maternal genotype, maintaining desirable traits exactly.

Types of Apomixis

• Gametophytic Apomixis: An unreduced embryo sac develops directly into an embryo without fertilization, common in many angiosperms.

• Sporophytic Apomixis: Embryos arise directly from somatic cells of the ovule such as nucellus or integuments.

Biological and Agricultural Significance

• Apomixis allows rapid multiplication of hybrids without genetic segregation, preserving hybrid vigor.

• It is energy-efficient, bypassing the complex reproductive process and reducing dependence on pollinators.

• Many major crops like maize and wheat show apomictic traits, important for breeding stable high-yield varieties.

Distinction from Sexual Reproduction

• Unlike sexual seed formation involving gamete fusion and genetic recombination, apomixis seeds are formed entirely asexually.

• Unlike vegetative reproduction (cuttings or grafting), apomixis involves seed formation and can be transmitted through seeds each generation.

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Summary Table: Key Features of Apomixis

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Conclusion

Apomixis represents a unique reproductive strategy in plants where seeds develop without fertilization, producing genetic clones of the parent plant. This asexual seed formation is significant in preserving desirable traits and offers valuable applications in plant breeding and agriculture.