Phytochrome, Cryptochrome, and Phototropins in Plant Biology

Front

What are phytochromes and their role in plants?

Back

Phytochromes are light-sensitive receptors that detect red light (600-700 nm) and regulate key plant processes like seed germination, seedling growth, shade avoidance, and flowering.

Front

How do phytochromes affect seed germination?

Back

Phytochromes help detect light, triggering germination and greening. In the absence of light, seedlings undergo etiolation, growing long and thin in search of light.

Front

What is the significance of red and far-red light in plant growth?

Back

Red light (630–680 nm) promotes seed germination, while far-red light (710–740 nm) inhibits it. They play key roles in regulating plant growth.

Front

What are the two forms of phytochrome and their functions?

Back

Phytochrome acts as a photoreceptor in two interchangeable forms: Pr (P660), which absorbs red light, and Pfr (P730), which absorbs far-red light.

Front

What is the chemical nature of phytochrome?

Back

Phytochrome is a soluble protein made of two subunits, each containing a light-sensitive molecule called phytochromobilin.

Front

What happens to Pfr when activated by light?

Back

When activated, Pfr undergoes phosphorylation and moves from the cytoplasm to the nucleus.

Front

What are cryptochromes and their role in plants?

Back

Cryptochromes are flavoproteins involved in the circadian clocks of plants and animals, and in sensing magnetic fields.

Front

What is the discovery history of cryptochromes?

Back

Cryptochromes were first found in Arabidopsis when a mutation affecting blue light signaling was traced to a gene coding for a protein similar to photolyases.

Front

What is the chemical nature of cryptochromes?

Back

Cryptochromes contain a light-absorbing molecule called Flavin adenine dinucleotide (FAD) and Methylenetetrahydrofolate (MTHF), which helps capture light for FAD.

Front

What are phototropins and their function?

Back

Phototropins are plant photoreceptors that sense light and control plant responses such as bending toward light (phototropism), chloroplast movement, and stomatal opening.