Question:
In Cycas, the fertilization is
In Cycas, the fertilization is
Updated On: Jul 5, 2022
- zoidogamous only
- siphonogamous accompanied with zoidogamy
- siphonogamous only
- zoidogamous accompanied with siphonogamy
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The Correct Option is D
Solution and Explanation
In Cycas, pollen grains absorb water in pollen chamber and germinate to form a pollen tube. Pollen tube carries two male gametes towards archegonial chambers. The process is named as siphonogamy (siphonos - tube+gamos - fusion). A male gamete is top-shaped, broad, spirally coiled structure whose anterior half contains thousands of small cilia emerging from the spiral grooves. Pollen tube bursts and discharges its content in archegonial chamber. Male gametes swim in the fluid of archegonial chamber to reach egg. Due to presence of dlia, gametes show movements to reach egg for fertilization. This process is named as zoidogamy. So, in Cycas fertilization is siphonogamous followed by zoidogamy (fertilization by the means of motile sperms).
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Concepts Used:
Gymnosperms
Gymnosperms are flowerless plants that produce cones and seeds. It literally means "naked seed". They sit exposed on the surface of leaf-like structures called bracts. Gymnosperms are vascular plants of the subkingdom Embyophyta and include conifers, cycads, ginkgoes, and gnetophytes. They are abundant in temperate forest and boreal forest biomes with species that can tolerate moist or dry conditions.
Characteristics of Gymnosperms
- They do not produce flowers.
- Seeds are not formed inside a fruit.
- They are found in colder regions where snowfall occurs.
- They form cones with reproductive structures.
- Xylem does not have vessels and the phloem and it has no companion cells and sieve tubes.