Tag: pictorial feature of plant kingdom

Fruits are not formed in gymnosperms due to absence of ovary. The ovules of a gymnosperm do not develop in an ovary but are "naked". Seeds develop from the ovules that are found in the developed ovaries but in the case of gymnosperms, the ovules are located directly on the surface of the flower or cone. 

Gymnosperms and angiosperms are the phenerogames or spermatophytes. 

Gymnosperms are the most primitive of the seed plants. A seed comprises two parts: an endosperm, which nourishes the embryo, and the embryo itself, which is fed by the endosperm.

The sporophyte (2n) phase is the longest phase. The gametophytes (1n), microspores and megaspores, are reduced in size. This phase may take more than one year between pollination and fertilization, while the pollen tube grows towards the megasporocyte (2n), which undergoes meiosis into megaspores. The megaspores will mature into eggs (1n) .
Gymnosperm seed is made up of three generations of tissues. 
1) maternal sporophyte tissue (seed coat and nucellus), 
2) gametophyte 
3) daughter sporophyte (embryo)

Gymnosperms were the first plants to have seeds. They are often referred to as having naked seeds because they do not have flowers and they develop on the surface of the reproductive structures of the plants rather than being contained in a specialized ovary. These seeds are often found on the surface of cones and short stalks.

Gymnosperms are a group of plants with the following unique characteristics:

• They do not have an outer covering or shell around their seeds.
• They do not produce flowers.
• They do not produce fruits.
• They are pollinated by the wind.

Gymnosperms are more ancient than angiosperms. They formed dominant vegetation on the earth about 200 million years ago, and have been replaced by the angiosperms with the changing time and climatic conditions. They are now maintaining their dominance only in the colder regions, where instead of rain, snow is the source of water. Only a few gymnosperms, like cycads thrive in warm whether.

In Pinus, the dwarf shoots are specialized branches of limited growth. They are typically shed after 2 to 3 years.

In gymnosperms, the pollen grain typically produces two male gametes. These are formed during the development of the male gametophyte.

Gymnosperm endosperm is haploid because it is formed from the female gametophyte tissue before fertilization. In contrast, angiosperm endosperm is triploid and forms after fertilization via double fertilization.

Gymnosperms are vascular plants that lack true vessels in their xylem and companion cells in their phloem, which are characteristic features of angiosperms.