Problem 60 - Objective Biology for NEET

Question

In pteridophyta and gymnosperms, which cells are present in place of companion cell? (a) Sclereids (b) Albuminous cells (c) Idioblasts (d) None of these

Step-by-Step Solution

Answer

The type of cells present in pteridophyta and gymnosperms in place of companion cells are (b) Albuminous cells.

Step 1: Identify the given information

The exercise mentions two types of plants: pteridophyta and gymnosperms. It is asking to identify which cells are present in these plants in place of companion cells.

Step 2: Understand the function of companion cell

Understanding the function of companion cells is key here. Companion cells assist in the control and support flow of nutrients and other substances through sieve-tube members, another type of plant cell.

Step 3: Identify the replacement cell

In pteridophyta and gymnosperms, albuminous cells substitute companion cells. Both albuminous and companion cells play a significant role in assisting in the transfer of substances around the plants, but they differ slightly in their structure and function.

Key Concepts

Pteridophyta

Pteridophyta are a group of plants that include ferns, horsetails, and club mosses. They are primitive vascular plants, which means they have specialized tissues for conducting water and nutrients throughout the plant.
Pteridophyta do not have seeds or flowers but reproduce through spores. You can usually find them in moist and shady environments, as they rely on water for reproduction.
These plants possess a true stem, roots, and leaves, which differentiates them from more primitive plant forms like bryophytes. Despite lacking a seed, their complex vascular system allows them to grow taller and live in varied habitats compared to non-vascular plants.

Gymnosperms

Gymnosperms are a diverse group of seed-producing plants that include conifers, cycads, ginkgoes, and gnetophytes. Unlike angiosperms, they do not produce flowers or fruit.
Gymnosperms are characterized by having naked seeds, meaning their seeds are not enclosed within a fruit. These seeds typically develop on the scales of cones, a common reproductive structure in these plants.
Their vascular system is advanced, allowing them to adapt well to various environments, including temperate and arid regions. Gymnosperms have been around for a long time, providing vital resources like wood and resin. They play significant ecological roles, enriching biodiversity and the global carbon cycle.

Companion Cells

Companion cells are crucial components in the phloem of flowering plants (angiosperms). They work closely with sieve-tube elements to facilitate the transport of organic substances, such as sugars and amino acids, throughout the plant.
These cells are unique because they are living and actively share their resources and energy with the sieve-tube elements.

• Companion cells regulate the flow of sap within the phloem.
• They maintain the functionality of the sieve-tube elements.
• Due to their active metabolism, they provide energy for phloem loading and unloading.

Companion cells are specially adapted to sustain sieve-tube elements, ensuring that the transport system in angiosperms is efficient and responsive to the plant's needs.

Albuminous Cells

Albuminous cells, also known as Strasburger cells, are found in gymnosperms and some other vascular plants in place of companion cells. These cells assist in the transport of nutrients alongside sieve cells, analogous to the system in angiosperms.
One key difference between albuminous and companion cells is their anatomical presence: albuminous cells are not derived from the same mother cell as sieve cells. Despite this, they perform similar functions.

• Albuminous cells help in nutrient distribution, particularly proteins.
• They provide structural support to adjacent sieve cells.
• These cells have a significant role in maintaining the transport efficiency in non-flowering plants.

Understanding albuminous cells helps illustrate how diverse plant systems achieve the vital task of nutrient circulation, even without the specialized structures found in more evolved plants like angiosperms.