Tag: pictorial feature of plant kingdom

In siphonogamy, pollen tubes are developed for the transfer of male cells to the eggs. The seed plants are siphonogamous. But in the lower plants male cell actually swim to the egg. As a consequence, spermatocytes are sometimes called siphonogamous. It is a characteristic of all spermatocytes. So the correct answer is option A.

 Phloem is the vascular tissue responsible for transport of sugars and other liquid materials. Phloem is composed of several cell types including sclerenchyma, parenchyma, sieve elements and companion cells. The function of companion cells is uncertain though it appears to regulate the activity of the adjacent sieve elements. Albuminous cells have a similar role to companion cells, but are associated with sieve cells only and are hence found in gymnosperms.

Gymnosperms are archegoniate spermatophytes. Spermatophyte is another term from phanerograms which are the seeded plants- gymnosperms and angiosperms. Archegonia is the female sex organ which is present in bryophytes, pteridophytes and gymnosperms. So, the gymnosperms are the only one which are both spermtophyte and archegoniate.

Gymnosperm undergo double fertilization, therefore in haploid stage of the gynosperm life cycle the plants have only one set of chromosome, thus haploid microspores are released into air as pollen and in gymnosperm endosperm is formed before fertilization from the female gametophyte(n). Hence it is haploid.

A male cone contains microsporophylls where male gametophytes ( pollen ) are produced and are later carried by wind to female gametophytes. The megaspore mother cell in the female cone divides by meiosis to produce four haploid megaspores; one of the megaspores divides to form the female gametophyte. So the correct option is 'Male and female gametophytes are independent of the sporophyte'.

The Gymnosperms originated during the late paleozoic era but floursihed very well during mesozoic era. Hence, the mesozoic period is called as 'Age of Gymnosperms'.

Gymnosperms are naked seed plants. The ovules are freely exposed before and after fertilisation.

The derivation of the word "gymnosperm" means naked seeds and is from the Greek words 'gymno' meaning naked or bare and 'sperm' meaning seed.