Botany

Pollination and Fertilization in the Gymnosperm



Tweet
Sammy Stein's image for:
"Pollination and Fertilization in the Gymnosperm"
Caption: 
Location: 
Image by: 
©  

The word gymnosperm means 'naked seed'. The seeds of gymnosperms - a branch of the flowering plants- are not protected by ovarian tissue or ovaries. Usually the seed are borne on cones and plants of the gymnosperm order include pines,firs, spruce, cycads and ginkgos.

Both gymnsosperms and angiosperms belong to the spermatophyta or flowering plants family, the difference being mainly how the seed are borne. However, the pollination and fertilization mechanisms, though similar in actual context also have differences.

Gymnosperm flowers, like their seeds, are borne on conical or flattened cone-like structures. Often the flowers are wind pollinated, unlike most angiosperms, who use mainly insect, mammal or bird vectors.   Gymnosperm flowers are often non conspicuous and  difficult to spot because they are not out to attract flying pollinators.

However, there is still the need for gametes to meet and to this end, flowers produce male gametes (pollen) and female gametes (ova). Pollination involves the transfer of male gametes from the anthers to the female gametes in the ovary. Upon reaching the stigma of the female flower, the pollen tube germinates, just like in other flowering plants. Only pollen grains compatibel i.e. from the same or closely related species are allowed to germinate thus reventing interspecies pollination. This is pollination.

On reaching the female gamete in the ovary, the pollen tube openus up, the male gamete travels along it and fuses with the ovum and forms a zygote. This is fertilisation.

So, the processes of pollination and fertilisation in both angiosperms and gymnosperms involve the germination of the pollen tube in pollination and the fusion of the gametes in fertilization. In both cases, the resulting fused gametes creates a zygote or embryonic plant for the next generation. In angiospermes, fertilisation is followed by changes in ovarian tissue to become the seed case or fruit and in gymnosperms the seeds are borne outside the ovary tissue on a cone.

Both types of plant make up the most common plants on our planet and are vital to life.

Seed is the commonest method by which flowering plants reproduce naturally whether angio or gymnosperm. Being sexual, it means genes from (usually, apart from when self pollination occurs) two individuals join to form a new plant. This ensures a variety of possible genetic combinations, meaning plants have more chances to adapt to subtle or major changes in their environment.

Seeds are the result the combination of genetic material from both the female plant parts and male plant parts whether they of gymno or angiosperms) and it is this combination which results in the zygote – which is contained in the seed. This is the embryonic plant.

A plant can be said to be successful when the plant can produce seeds. It is the ultimate aim of a plant whether gymno or angiosperm, in its natural environment, to reproduce sexually and, hopefully, produce viable seed. This is sexual reproduction for a plant and both gymnosperms and angiosperms, though different anatomically and botanically, have characteristics which are common.

Gymnosperms, being generally non-reliant on vectors for pollination (and thererfore germination) are though to have an evolutionary advantage over angiosperms and are now thought to be a more recent evolutionary development rather than an older one. This may or may not be correct but whichever way you look at it, the fact that gymnosperms come to be pollinated and fertilised is a remarkable achievement on the part of the plant. Plants remain, as always,a constant fascination.


Tweet
More about this author: Sammy Stein

From Around the Web




ARTICLE SOURCES AND CITATIONS