Problem 160 - Objective Biology for NEET

Question

Assertion: Flower is zygomorphic in family Fabaceae Reason: Corolla shows vexillary aestivation.

Step-by-Step Solution

Answer

The assertion is correct. Flowers in family Fabaceae are zygomorphic due to their vexillary aestivation, allowing them to be divided equally along only one plane.

Step 1: Identification of Family

Identify which family the flower belongs to. In this case, it is stated that the flower is part of the Fabaceae family.

Step 2: Understanding of Zygomorphic

Understand what is meant by a flower being zygomorphic. Zygomorphic flowers are ones that can only be divided into two equal halves along one particular plane.

Step 3:Understanding the Vexillary Aestivation

Understand the nature of vexillary aestivation. This is a method of petal arrangement often found in the Fabaceae family, where one large petal is outermost, two smaller petals are in the middle and two smallest petals are innermost.

Step 4: Linking Zygomorphic with Vexillary Aestivation

Make the connection between vexillary aestivation and zygomorphic flowers. With vexillary aestivation, the asymmetrical arrangement of petals only allows the flower to be divided equally along one plane, showing that it is zygomorphic in nature.

Key Concepts

Zygomorphic Flowers

In the plant world, flowers can come in many diverse shapes and forms. One intriguing type of flower is the zygomorphic flower. These flowers possess a unique symmetry, only allowing them to be divided into two equal halves by a single, specific plane. This characteristic is often likened to how human faces have bilateral symmetry. Just like you can't divide a face into two equal halves using any line other than the one going down the middle, zygomorphic flowers have one such distinct dividing line.
This form of symmetry is significant to the flower’s role in nature, primarily concerning their interaction with pollinators. It helps direct pollinators toward the reproductive organs of the flower, ensuring efficient pollination.
In the Fabaceae family, zygomorphic flowers are common and play a substantial role in their pollination mechanics. Zygomorphism allows them to specialize in attracting specific pollinators, which can help increase the efficiency of pollination.

Vexillary Aestivation

Vexillary aestivation is a fascinating feature of many flowers, particularly noticeable in families like Fabaceae. This term describes a specific arrangement of the flower’s petals. In vexillary aestivation, the flower contains a large petal known as the "standard," which typically holds the other petals.

• The standard petal: The largest petal, often colorful and prominent, drawing in pollinators.
• The wings: Two lateral petals, often overlapping, on either side of the flower.
• The keel: Two smallest, inner petals that are often fused together, forming a protective enclosure for the reproductive parts.

This structure isn't just for looks; it has a functional importance for the plant. The standard acts as a flag to attract pollinators, while the keel helps safeguard the stamens and pistil from environmental elements and unwanted visitors. Vexillary aestivation thus aids in both the attraction and protection necessary for successful reproduction.

Petal Arrangement

The arrangement of petals in flowers is not just for aesthetic appeal but serves crucial biological roles. The way petals are organized can affect everything from attracting pollinators to protecting the reproductive parts of the plant. One common arrangement, especially in the Fabaceae family, is the vexillary aestivation, which involves strategic positioning of the petals. This arrangement results in a distinctive form wherein the petals lay in overlapping clusters, akin to a butterfly shape. Such arrangements are vital for effective pollination. For example, the keeling portion of the petals acts like a cocoon, sheltering the flower’s essential reproductive components. Moreover, petal arrangements can be an ecological adaptation, promoting interactions between specific plants and their preferred pollinators. Thus, the arrangement stands as a testament to the adaptations that plants undergo to survive and thrive in their environments.