Identify the correct sequence: Microspore → ? → Pollen grain → Male gametophyte
Answer: D
A microspore undergoes mitosis to form the male gametophyte (2-celled or 3-celled pollen grain consisting of generative and vegetative cells). The pollen grain itself is the male gametophyte.
Q.162Medium
In the mature female gametophyte (embryo sac) of angiosperms, how many nuclei are present at maturity?
Answer: D
The mature female gametophyte (7-celled, 8-nucleate) contains: 1 egg cell, 2 synergids, 2 polar nuclei (in central cell), and 3 antipodal cells = 8 nuclei total.
Q.163Medium
The phenomenon of vegetative reproduction in bryophyllum (Kalanchoe) by leaf margins is an example of:
Answer: C
In Bryophyllum, small adventitious buds form at the margins of leaves, which can develop into new plants when they fall to the soil.
Q.164Medium
Microsporogenesis differs from megasporogenesis in flowering plants primarily in that:
Answer: A
In microsporogenesis, all four microspores produced from meiosis are typically functional. In megasporogenesis, usually three of the four megaspores degenerate, leaving only one functional megaspore.
Q.165Medium
The tapetum in the anther is primarily involved in:
Answer: B
The tapetum is a nutritive tissue layer that provides nutrients to developing microspores and pollen grains through absorption and transfer.
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Q.166Medium
In apomixis, the embryo develops from:
Answer: B
Apomixis is asexual reproduction through seeds where the embryo develops from an unfertilized egg cell (apomeiotic parthenogenesis) or other cells without meiosis or fertilization.
Q.167Medium
The nucellus in an ovule functions primarily to:
Answer: C
The nucellus is the nutritive tissue surrounding the megasporangium that provides nutrients to the developing megaspore and female gametophyte.
Q.168Medium
The polar nuclei in the central cell of the embryo sac fuse with the second sperm nucleus to form the:
Answer: A
The fusion of two polar nuclei (2n) with one sperm nucleus (n) produces the primary endosperm nucleus (3n), which develops into the endosperm tissue.
Q.169Medium
In the pollen grain, the generative nucleus is located in the:
Answer: C
The generative nucleus lies within the vegetative (or tube) cell in mature pollen. The vegetative cell also contains a large vacuole.
Q.170Medium
The ploidy level of the endosperm in a typical angiosperm is:
Answer: C
The endosperm is triploid (3n) because it develops from the primary endosperm nucleus, which is formed by fusion of two polar nuclei (2n) and one sperm nucleus (n).
Q.171Medium
In angiosperms, the tapetum is responsible for providing nutrients to developing pollen grains. Which layer of the anther wall gives rise to the tapetum?
Answer: C
The tapetum is derived from the innermost layer of the anther wall, which develops from the middle layers. It undergoes mitotic divisions to form the nutritive tissue for pollen development.
Q.172Medium
A plant exhibits heterospory with distinct megaspores and microspores. This characteristic is found in:
Answer: A
Heterospory (production of two types of spores) is a characteristic of advanced groups including most gymnosperms and all angiosperms, where microspores develop into male gametophytes and megaspores into female gametophytes.
Q.173Medium
In a mature anther, what is the primary function of the fibrous thickening in the endothecium?
Answer: B
The fibrous thickening of endothecial cells creates differential drying patterns that generate mechanical stress, causing anther rupture and pollen dehiscence.
Q.174Medium
Which of the following statements about megagametogenesis (female gametophyte formation) is correct?
Answer: C
In Polygonum type (typical angiosperm), the functional megaspore undergoes three successive mitotic divisions producing eight nuclei in seven cells. The three degenerate megaspores are absorbed.
Q.175Medium
The synergids in the embryo sac are believed to have evolved for:
Answer: B
Synergids secrete attractants and guide pollen tubes. One synergid nucleus disintegrates on pollen tube entry, controlling the number of sperm cells entering the embryo sac.
Q.176Medium
Which type of placentation is found in the ovary of legumes and has ovules attached to the ventral suture?
Answer: B
In marginal placentation, ovules are attached along the ventral suture (margin) of the carpel. This is characteristic of legumes and many other families with unilocular ovaries.
Q.177Medium
Pollen grains of which plant show the longest viability period under room temperature?
Answer: C
Date palm pollen can remain viable for several months under room temperature due to low moisture content and thick protective wall. This is unusual compared to most angiosperms.
Q.178Medium
Which statement about the generative cell in pollen is incorrect?
Answer: B
The generative cell typically divides after pollination (not before pollen release) to form two sperm cells. In some plants it divides before release, but this is not the general pattern.
Q.179Medium
The phenomenon of protandry in flowers refers to:
Answer: A
Protandry is when anthers mature and release pollen before the stigma of the same flower becomes receptive, preventing self-pollination and encouraging cross-pollination.
Q.180Medium
In monocarpellary ovaries, marginal placentation occurs in plants like:
Answer: A
Gram (chickpea) is a legume with a monocarpellary ovary showing marginal placentation where ovules are attached along the ventral suture.
