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Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892

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BuyFindarrow_forward

Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

Which of the following steps is not part of the sequence that triggers flowering?

a. Cycles of light and dark stimulate the expression of theCONSTANS gene in a plant’s leaves.

b. CO proteins accumulate in the leaves and trigger expression of a second regulatory gene.

c. mRNA transcribed during expression of a second regulatorygene moves via the phloem to the shoot apical meristem.

d. Interactions among regulatory proteins promote theexpression of floral organ identity genes in meristem tissue.

e. CO proteins in the floral meristem interact with florigen, a so-called flowering hormone, which provides the final stimulus for expression of floral organ identity genes.

Summary Introduction

Introduction:

Flowering in plants is a process affected by photoperiodism. These photoperiodic responses presented by the plants are predictable and help in categorizing plants into two major categories. These are long-day plants, which flower during the season when days are longer than nights, and short-day plants, which flower in a season when nights are longer.

Explanation

Justification/explanation for the correct answer:

Option (e) is given as: CO proteins in the floral meristem interact with florigen, a flowering hormone that provides the final stimulus for the expression of floral organ identity genes. Florigen is a hypothesized plant hormone-like molecule considered responsible for triggering flowering. The CO proteins that are produced provide stimuli for the expression of genes responsible for floral organ identity by accumulating and triggering transcription of secondary regulatory proteins. They do not interact with florigen. The stimulus is caused by the accumulation of CO and not the interaction with florigen. Hence, option (e) is correct.

Explanation for the incorrect answers:

Option (a) is given as: cycles of light and dark stimulate the expression of the CONSTANS gene in a plant’s leaves. The start of the pathway for flower signal is marked by the expression of a gene CONSTANS in the leaves of the plant. The expression of the gene is seen in tune with the natural light and dark cycle...

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