1
$\begingroup$

In gymnosperms the plant body is predominantly sporophytic. It produces microspores or megaspores my textbook says that these undergo reduction division in order to form male gametophytes pollen grains and female gametophytes that is egg.

The thought of a spore being diploid is revolting, as I have learned in the case of bryophytes and pteridophytes that it's haploid. Can anyone help me asap.

Improve this question
$\endgroup$
2
  • $\begingroup$ Sadly I don't have a lot of time to study gymnosperms in details again, but my book (Campbell's "Biology", 11th edition) says that "Microsporocytes divide by meiosis, producing haploid microspores. A microspore develops into a pollen grain (a male gametophyte enclosed within the pollen wall)." It says as well: "While the pollen tube develops, the megasporocyte undergoes meiosis, producing four haploid cells. One survives as a megaspore." So microspores and megaspores seem to be haploid. $\endgroup$
    – justdoit
    Jan 26, 2018 at 17:13
  • $\begingroup$ Hi Susan. If either of the answers you received are acceptable and useful, please consider upvoting them (by clicking the up arrow to the left of the answer) and/or "accepting" them (by selecting the check mark below the vote triangles). Thanks. $\endgroup$
    – theforestecologist ♦
    Mar 12, 2019 at 1:55

2 Answers 2

Reset to default
2
$\begingroup$

The spores (microspores or megaspores) in gymnosperms are haploid. The microspores came from the microsporocytes which are diploids cells of the sporophyte, divided via meiosis. So the haploid microspores do mitosis and form the male gametophytes (pollen grains), containing two male gametes (sperm cell) and a generative cell which will form the pollen tube. The process conducting to female gametes in the ovule is very similar. A megasporocyte (diploid cell of the sporophyte) via two meiosis form four megaspores (haploid). Only one megaspore is functional (the others will degenerate) and do 3 consecutive mitosis to form eight nucleus with different functions, one of them is the egg cell (female gamete). So the meiosis happens before the formation of the spores (actually it forms the spores) so they are haploid. Source: R. F. Evert & S. E. Eichhorn "Raven Biology of Plants"

Improve this answer
$\endgroup$
1
  • 1
    $\begingroup$ Hi Maso and welcome to Bio.SE. Rather than commenting on your sources, it would be better to include them in the answer by using the edit function. $\endgroup$
    – James
    Oct 3, 2018 at 14:58
2
$\begingroup$

Short answer:

A microspore is haploid.

Gymnosperm life cycle

Long Answer:

Gymnosperms are heterosporous, and therefore create two types of spores: male and female -- microspores and megaspores, respectively. These spores will develop into gametophytes which then undergo fertilization (i.e., the male/female gametophytes combine their chromosomes). To avoid constantly increasing the chromosome number of these plants, these gametophytes (and therefore the male/female spores), must only contain half of the "proper" number of chromosomes. In other words, these male/female structures must be haploid (1n). Haploid cells develop via meiosis, a process in which cells essentially split twice even though their chromosomes have only been duplicated (replicated) once. In a diploid cell, this means that the resulting cells (4 of them per parent) have only 1/2 the chromosomes as the mature organism.

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .