58. Seeds of Arabidopsis thaliana placed on Murashige and Skoog (MS) media without anyhormones
germinates faster than in the medium that contains:
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Jasmonic acid

Introduction

The germination of seeds is a critical process in plant development, influenced by various environmental factors and internal regulatory molecules. In plants like Arabidopsis thaliana, hormones play a significant role in regulating this process. The use of Murashige and Skoog (MS) media, a commonly used growth medium for plant tissue culture, can further enhance our understanding of these effects. In this article, we explore how specific hormones affect seed germination, specifically when placed on MS media.

Hormones Affecting Seed Germination

1. Abscisic Acid (ABA):

   • Effect on Germination: Abscisic acid is a key player in seed dormancy and inhibits germination. Seeds treated with ABA will typically exhibit delayed or inhibited germination because ABA induces a state of dormancy in the seeds. This makes ABA one of the primary inhibitors of seed germination.

2. Auxin:

   • Effect on Germination: Auxin is a plant hormone known for its role in growth and development, particularly in promoting root initiation and cell elongation. While auxin can influence germination indirectly, it does not directly inhibit seed germination. However, excessive auxin concentrations can delay germination due to its role in maintaining cell division and elongation.

3. Cytokinin:

   • Effect on Germination: Cytokinins are involved in promoting cell division and shoot formation. They are generally associated with promoting growth rather than inhibiting seed germination. However, too much cytokinin can have an adverse effect, especially when the balance of hormones is disturbed.

4. Jasmonic Acid:

   • Effect on Germination: Jasmonic acid is involved in stress responses and can inhibit seed germination. This hormone is often associated with plant defense mechanisms and, in some cases, can delay germination as part of the plant’s response to unfavorable conditions.

Why Do Arabidopsis Seeds Germinate Faster Without Hormones?

When Arabidopsis thaliana seeds are placed on MS media without added hormones, they generally germinate faster. This is because hormones like abscisic acid (ABA) and jasmonic acid, which are involved in regulating dormancy and stress responses, can inhibit germination. In contrast, a hormone-free environment allows the seeds to bypass these inhibitory effects, leading to faster germination.

The answer to the question is:

• (a) Abscisic acid: As ABA inhibits germination by inducing dormancy, seeds placed on MS media without ABA germinate faster.

Conclusion

The germination of Arabidopsis thaliana seeds is influenced by the presence of various hormones. Abscisic acid (ABA), in particular, inhibits germination and delays the process. Therefore, the absence of ABA in the growth medium results in faster seed germination. Understanding these hormonal effects is critical for optimizing plant growth conditions in research and agricultural practices.

Correct Answer: (a) Abscisic acid