Sexual Reproduction in Flowering Plants — Questions & Answers

Sample questions from Sexual Reproduction in Flowering Plants

1. Q1. The egg apparatus of the embryo sac consists of:

   • A.One egg cell and two synergids✓
   • B.One egg cell and three antipodals
   • C.Two egg cells and one synergid
   • D.Polar nuclei only
   Solution

   The egg apparatus consists of two synergids and one egg cell, located at the micropylar end of the embryo sac.

2. Q2. Outbreeding devices in flowering plants prevent:

   • A.Cross-pollination
   • B.Self-pollination and promote cross-pollination✓
   • C.Pollen germination
   • D.Fruit formation
   Solution

   Outbreeding devices like dichogamy, self-incompatibility and herkogamy prevent self-pollination and encourage cross-pollination, ensuring genetic diversity.

3. Q3. The flower of Amorphophallus is notable in pollination biology because:

   • A.It is pollinated exclusively by water
   • B.Its inflorescence is about six feet tall and provides a safe place for insects to lay eggs✓
   • C.It produces the smallest pollen grains known
   • D.It never opens and is strictly cleistogamous
   Solution

   Amorphophallus bears the tallest flower (inflorescence), about six feet in height, and along with Yucca is cited as a plant that offers insects a safe place to lay eggs as a floral reward.

4. Q4. If in a particular ovule the two polar nuclei fused into a secondary nucleus BEFORE the pollen tube arrived, the ploidy of the primary endosperm nucleus formed afterwards would be:

   • A.2n, because only two nuclei fuse at the final step
   • B.3n, because the secondary nucleus is already diploid and adds a haploid male gamete✓
   • C.n
   • D.4n
   Solution

   The two haploid polar nuclei together contribute two haploid sets, whether they fuse before or at the moment of triple fusion. Adding one haploid male gamete gives three sets in all, so the primary endosperm nucleus is 3n either way.

5. Q5. A transverse section of a young dithecous anther shows the microsporangia arranged as:

   • A.Two microsporangia, one in each theca
   • B.Four microsporangia, two in each theca, located at the corners✓
   • C.One central microsporangium surrounded by the connective
   • D.Eight microsporangia arranged in a ring
   Solution

   A typical angiosperm anther is bilobed and dithecous; each theca contains two microsporangia, so the anther is tetrasporangiate. In transverse section the four microsporangia appear at the four corners, two in each lobe, separated by the connective tissue.

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