Question

(a) (i) Explain the structure of a typical monocotyledonous embryo of a flowering plant.
(ii) How are multiple embryos formed in a citrus fruit? What is the mechanism known as?

OR

(b) (i) Name and explain the structural organization of the male sex accessory ducts in the human male reproductive system.
(ii) Describe the role of gonadotropin FSH (Follicle-Stimulating Hormone) in the regulation of spermatogenesis.

Hint:

Monocot embryos have a single cotyledon, and polyembryony is a common asexual phenomenon in citrus. In males, accessory ducts ensure sperm transport, and FSH is crucial for initiating and sustaining spermatogenesis.

Answer 1

(a) (i) Structure of a Typical Monocotyledonous Embryo:

A typical monocotyledonous embryo (such as in maize or grass) has the following key components:

• Single Cotyledon (Scutellum): Located on one side of the embryonic axis, it absorbs nutrients from the endosperm.
• Embryonic Axis: Differentiated into:
  • Plumule: Future shoot tip enclosed in a protective sheath called the coleoptile.
  • Radicle: Future root tip enclosed in the coleorhiza.
• Mesocotyl: The region between the scutellum and the plumule.

(ii) Polyembryony in Citrus Fruit:

In citrus fruits, multiple embryos often arise within a single seed. This happens because, in addition to the zygotic embryo formed through fertilization, other embryos can develop from the nucellar cells of the ovule.

This phenomenon is called: Adventive Polyembryony

It is a form of apomixis where embryos arise asexually from diploid somatic tissues of the ovule, bypassing meiosis and fertilization.

OR

(b) (i) Male Sex Accessory Ducts and Their Structure:

The male accessory ducts serve to store, transport, and mature sperm. The main ducts include:

• Rete Testis: Network of tubules that collect sperm from seminiferous tubules.
• Vasa Efferentia: Thin ducts that transport sperm from rete testis to the epididymis.
• Epididymis: A long, coiled duct where sperm mature and are stored temporarily.
• Vas Deferens: A muscular duct that transports sperm from the epididymis to the ejaculatory duct.
• Ejaculatory Duct: Formed by the union of vas deferens and duct of seminal vesicle; opens into the urethra and discharges sperm and seminal fluid during ejaculation.

(ii) Role of FSH in Spermatogenesis:

Follicle-Stimulating Hormone (FSH) is secreted by the anterior pituitary gland and plays a crucial role in regulating spermatogenesis.

Functions of FSH:

• Stimulates Sertoli cells in the seminiferous tubules.
• Promotes the production of nutrients and growth factors essential for the development of spermatogonia into spermatozoa.
• Works synergistically with LH (Luteinizing Hormone), which stimulates Leydig cells to produce testosterone, further promoting spermatogenesis.