(a) What are the benefits of choosing a dioecious plant species for plant breeding experiments ?

(b) How would you proceed to cross-pollinate a monoecious flower?

(c) Draw a labeled schematic diagram of T.S. of an anther of an angiosperm.

OR

(a) Explain the hormonal regulation of spermatogenesis in humans.

(b) Draw the diagram of a human sperm. Label and write the functions of the components of its head.

(a) A dioecious plant is where the male and female reproductive systems occur on separate plants. While both plants produce flowers, one plant has the male reproductive parts, and the other plant has the female parts. But in the monoecious plant, both male and female flowers present in one plant. A dioecious plant requires two separate plants to successfully pollinate, and only the female plant bears the fruit; example Holly plant. Plant breeding is changing the traits of a plant to produce desired characteristics. The benefit of the dioecious plant is, it avoids self-pollination like in monoecious plant and emasculation is not required. Removal of stamens or anthers or killing the pollen of a flower without the female reproductive organ is known as emasculation.

(b) In monoecious, both incomplete flowers are borne on the same plant, corn is an example of a monoecious plant. Cross-pollination is when one plant pollinates a plant of another variety. The two plants’ genets combine and the resulting seeds from that pollination will have characteristics of both varieties and is a new variety. Cross-pollinating is used intentionally in agriculture to create new varieties. The cross-pollination of the monoecious plant by bagging, spraying desired pollen and emasculation.

(c)

OR

a) In males origin of puberty is controlled by two major hormones: FSH initiates spermatogenesis and LH signs the release of testosterone. In the period of puberty physical growth and psychological changes occur which leads to sexual maturity. The distinctive physiological changes and physical changes influenced by hormonal activity. At the onset of puberty, the hypothalamus begins secreting high level of, or gonadotropin-releasing hormone. As to signal the pituitary gland releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) into the males. FSH begins its role in the testes, stimulating the Sertoli cells, which help to support the sperm cells to begin aiding spermatogenesis. LH also enters the testes and stimulates the interstitial cells, called Leydig cells to make and release of testosterone into the testes and to the blood. Testosterone is responsible for the secondary sexual characteristics that develop in the male after puberty, it stimulates spermatogenesis also secondary sex characteristics. With rising levels of testosterone the negative feedback system acts on the hypothalamus and anterior pituitary to inhibit the release of GnRH, FSH, and LH. The inhibin is produced and released by Sertoli cells into the blood when the sperm count is too high, this inhibits the release of GnRH and FSH. The inhibition cause spermatogenesis to slow down and if the sperm count reaches the upper limit the Sertoli cells stop the release of inhibin and allowing increase sperm count.

b)

The head of the sperm contains the nucleus. The nucleus holds the DNA of the cell. The head also contains enzymes which lyse the cell membrane of an egg.