69. Which one of the following treatments is required for flowering in a winter annual typeof
Arabidopsis plants?
(a) A short pulse of cold temperature
(b) A short pulse of high temperature
(c) High expression of Flowering Locus C (FLC) gene
(d) Prolonged cold period

Understanding Flowering in Winter Annual Arabidopsis

Winter annuals, such as Arabidopsis thaliana, require specific environmental cues to transition from vegetative to reproductive growth. One of the key factors in this process is the exposure to cold temperatures. Let’s explore why this treatment is vital for flowering in winter annual Arabidopsis.

Correct Answer:

(d) Prolonged cold period

Why Cold Exposure Triggers Flowering

Arabidopsis, as a winter annual, needs a period of cold, often referred to as vernalization, to trigger the genetic pathways for flowering. This process involves the following steps:

1. Vernalization: When exposed to cold temperatures (around 4°C), the plant undergoes a series of molecular changes.

2. Flowering Locus C (FLC) suppression: The cold treatment suppresses the expression of the FLC gene, which normally inhibits flowering.

3. Transition to Flowering: Once the cold period is over, the plant is able to initiate flowering, as FLC repression allows other flowering genes to become active.

This cold treatment is essential for Arabidopsis to correctly time its flowering, ensuring it occurs in the optimal season for seed production.

Why Not the Other Options?

Let’s examine the incorrect choices:

• (a) A short pulse of cold temperature: A short pulse is typically not sufficient to induce flowering. The plant needs a prolonged cold period for the full effect.

• (b) A short pulse of high temperature: High temperatures would not trigger flowering in winter annual Arabidopsis. In fact, extreme heat could be detrimental to plant growth.

• (c) High expression of Flowering Locus C (FLC) gene: High FLC expression inhibits flowering, so increasing its expression would delay or prevent flowering, not promote it.

Conclusion

For winter annual Arabidopsis to flower, a prolonged cold period is necessary. This cold exposure suppresses the FLC gene and allows the plant to flower at the right time, making it a key process in the plant’s lifecycle.