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.342Easy
Which of the following is true about microsporogenesis in plants?
Answer: B
Microsporogenesis is the meiotic division of the microspore mother cell (diploid) in the anther, producing four haploid microspores.
Q.343Medium
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.344Easy
The embryo sac in angiosperms is typically a seven-celled, eight-nucleate structure. Which cells are located at the micropylar end?
Answer: A
The micropylar end of the typical embryo sac contains the egg apparatus consisting of one egg cell flanked by two synergids that help guide pollen tube growth.
Q.345Medium
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.
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Q.346Easy
Double fertilization in angiosperms results in the formation of:
Answer: B
Double fertilization involves one sperm nucleus fusing with the egg cell to form a diploid zygote, while the second sperm nucleus fuses with the two polar nuclei to form a triploid primary endosperm nucleus.
Q.347Medium
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.348Medium
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.349Medium
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.350Medium
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.351Easy
In the typical angiosperm flower, after anther dehiscence, pollen grains are released in which stage of pollen development?
Answer: B
In most angiosperms, pollen is released at the two-celled stage (bicellular pollen) consisting of a large vegetative cell and smaller generative cell. Second mitosis occurs after pollination.
Q.352Hard
The phenomenon of pollen dimorphism is observed in which type of flowers?
Answer: B
Pollen dimorphism is associated with heterostyly, where plants like Primula produce different-sized pollen grains corresponding to different floral forms to promote cross-pollination.
Q.353Hard
Which of the following represents the correct ploidy level progression during the life cycle of a typical angiosperm?
Answer: B
Angiosperm life cycle: diploid sporophyte (2n) → haploid spores (n) → haploid gametophyte (n) → diploid zygote (2n) after fertilization, and triploid endosperm (3n) after double fertilization.
Q.354Easy
The integuments of an ovule serve primarily to:
Answer: B
Integuments are the outer layers of the ovule that develop into the seed coat (testa) after fertilization, providing protection to the seed.
Q.355Hard
In apomixis, the formation of seeds without meiosis and fertilization occurs through which mechanisms?
Answer: B
Apomixis includes apospory (diploid egg from vegetative cells), apomeiosis (unreduced spore formation), and parthenogenesis (unfertilized egg development), all bypassing meiosis and fertilization.
Q.356Medium
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.357Medium
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.358Medium
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.359Medium
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.
Q.360Easy
The ovule of a typical angiosperm is attached to the placenta through which structure?
Answer: B
The funiculus (also called funicle) is the stalk that attaches the ovule to the placenta. The raphe is a ridge formed by the fusion of funiculus with the integument in some ovules.
