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.22Medium
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.23Medium
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.24Medium
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.25Medium
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.
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Q.26Medium
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.27Medium
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.28Medium
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.29Medium
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.30Medium
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.
Q.31Medium
Which of the following is a correct statement about mature embryo sac organization in angiosperms?
Answer: A
Antipodal cells (typically three) are located at the chalazal end and are vegetative in nature, containing vacuoles for nutrient storage. They eventually degenerate.
