The arrangement of the nuclei in a normal embryo sac in the dicot plants is

  • 2+4+2

  • 3+2+3

  • 2+3+3

  • 2+3+3


B.

3+2+3

In angiosperms (dicots), the Polygonum type of embryosac is most common. In this embryosac, the arrangement of the nuclei is 3+2+3 i.e., 3 in antipodal cells, 2 as polar nuclei (which later fuse and form a diploid secondary nucleus); and 3 in egg appratus (2 in synergids and 1 in egg cell).

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Which one of the following is surrounded by a callose wall?

  • Microspore mother cell

  • Male gamete

  • Egg

  • Egg


A.

Microspore mother cell

The wall of the pollen mother cell (microspore mother cell) is deposited by callose 

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Parthenocarpic tomato fruits can be produced by

  • Removing androecium of flowers before pollen grains are released

  • Treating the plants with low concentrations of gibberellic acid and auxins

  • Raising the plants from vernalized seeds

  • Raising the plants from vernalized seeds


B.

Treating the plants with low concentrations of gibberellic acid and auxins

Parthenocarpy is the development of fruits without prior fertilization which results in the formation of seedless fruits. In some plant species, parthenocarpic (seedless) fruits may be produced naturally or they may be induced by treatment of the unpollinated flowers with auxin e.g. Parthenocarpic tomato fruits can be produced by treating the plants with low concentration of gibberellic acid (promotes fruit set) and auxin (completes the development process).
Removal of androecium, before pollen release, is called emasculation which is helpful in preventing unwanted poor pollination.
Vernalized seeds are the chill treated seeds for breaking dormancy.
Phenyl mercuric acetate is an antitranspirant.

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Long filamentous threads protruding at the end of a young cob of maize are

  • anthers

  • styles

  • ovaries

  • ovaries


B.

styles

In cob of maize, each ovary has a long silky (hairy) style, called as corn silk. Collectively these styles protrude at the end of a young cob. The grains are formed on the cob which remain covered by the leafy bracts.

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Conifers differ from grasses in the

  • production of seeds from ovules

  • lack of xylem tracheids

  • absence of pollen tube

  • absence of pollen tube


D.

absence of pollen tube

The conifers (gymnosperm) differ from the endosperm before fertilization. In fact, in gymnosperms,  the endosperm is formed before the fertilization, thus, it is a haploid tissue while in angiosperms, endosperm is formed after fertilization as a result of triple fusion or double fertilization, thus, it is a triploid tissue.
In both conifers and grasses seeds are produced from ovules.
Xlem tracheids are present in both conifers and grasses.
Pollen tubes are also formed in both conifers and grasses.


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