Problem 149 - Objective Biology for NEET

Question

Gymnosperms (a) Are naked seeds plants (b) Have tap roots (c) Are heterosporous (d) All of these

Step-by-Step Solution

Answer

The correct answer is (d) All of these. Gymnosperms are naked seed plants with tap roots and are heterosporous in nature.

Step 1: Understand Naked Seeds

Naked seeds are seeds that aren't enclosed in an ovary. Gymnosperms, which means 'naked seeds', are indeed naked seed plants. Their seeds mature on the surface of cone scales or other reproductive structures.

Step 2: Understand Tap Roots

Tap roots are a type of root where the primary root is dominant, growing downward and producing smaller lateral roots. Many gymnosperms, such as conifers, have a taproot system.

Step 3: Understand Heterosporous Nature

Heterosporous plants produce two morphologically different types of spores. Male spores (microspores) and female spores (megaspores) are differentiated in these plants. Gymnosperms are heterosporous in nature. They produce male and female cones, each bearing the respective spores.

Step 4: Conclude

Given that gymnosperms possess all the characteristics mentioned in the options: they have naked seeds, tap roots, and they are heterosporous, the correct answer is that gymnosperms have all these features.

Key Concepts

Naked Seeds

In the world of plants, some seeds come without coverings. These are known as 'naked seeds'. The term originates from the fact that these seeds are not enclosed in a fruit or ovary like those you might find in flowering plants. Instead, they lie bare on surfaces like cones or other formations. Gymnosperms, including conifers, cycads, ginkgoes, and gnetophytes, belong to this category. Their seeds develop exposed on the scales of cones, hence the name 'gymnosperm', which literally translates to 'naked seed'.
This feature distinguishes them from angiosperms, where seeds are enclosed within fruits. The naked seeds allow for a different method of reproduction and adaptation that is typical to gymnosperms. This makes them unique and fascinating within the plant kingdom.

Tap Roots

Tap roots serve as a vital structural and nutrient-gathering part of many plant species, including gymnosperms. A taproot system features one main large root that penetrates deeply into the soil, anchoring the plant effectively. This primary root is called the taproot, and it can grow quite large, with smaller lateral roots branching off from it.
Taproots help in reaching underground water sources, which is especially important for plants living in dry conditions. For gymnosperms, such as pines and firs, this type of root system is common. They provide stability and allow the plant to thrive even in less fertile soils. Unlike fibrous root systems seen in some other plants, taproots are particularly robust and effective at anchoring large trees.

Heterosporous Plants

Heterospory is a fascinating concept where plants produce two different kinds of spores: microspores and megaspores. Gymnosperms exhibit this trait, leading them to develop separate male and female reproductive structures. The microspores develop into male gametophytes, and the megaspores develop into female gametophytes.
In gymnosperms, you often see this separation vividly manifested in the form of male and female cones. Male cones produce pollen, which are essentially the sperm-carrying microspores. Female cones contain ovules, which are the future megaspores. This differentiation allows for more specialized reproductive strategies and contributes to genetic diversity.

• Microspores lead to pollen grains.
• Megaspores grow into structures that house the eggs.

This heterospory is a crucial part of gymnosperm reproduction, setting it apart from homosporous plants, which produce only one type of spore.