Name: phytochrome signals in plant growth
Uploaded: 2020-02-27T08:54:10.000Z
Duration: 2 min
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.7

LS.7.b

photoreceptors-and-plant-responses-to-light

Photoreceptors and Plant Responses to Light

When a seed germinates, the roots extend into the soil and the shoot towards the light. Plants also modify their growth to maximize light exposure. How do plants sense the direction and quality of light?&nbsp;

Light-sensitive receptors, also called photoreceptors, mediate a plant&rsquo;s response to light. Photoreceptors contain a protein component bound to a light-absorbing pigment called the chromophore.&nbsp;

Plants may possess multiple families and variants of photoreceptors. Together, they respond to wavelengths of light ranging from ultraviolet to the far-red regions of the light spectrum.&nbsp;

Each chromophore in a specific photoreceptor absorbs light of a particular wavelength, causing a structural change in the receptor. Activation of the photoreceptor triggers a signaling cascade within the plant cells. This, in turn, can lead to gene expression affecting plant growth and morphology.

For example, plants alter their growth in response to shade using the family of phytochrome photoreceptors. Each phytochrome has two distinct, interconvertible forms: the physiologically inactive Pr and the active Pfr.&nbsp;

Pr absorbs red light and is quickly converted to the active Pfr form. Pfr absorbs far-red light and is converted back to the inactive Pr form. &nbsp;The successive conversion of Pr and Pfr reaches a dynamic equilibrium in daylight.

Taller plants can filter the red light out of the light spectrum, leaving plants underneath with more far-red light than direct sunlight. The phytochrome system allows the plant to sense the ratio of red to far-red light and adjust its growth.

photoreceptors and plant responses to light

Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.

What Is a Photoreceptor?

Plants respond to light using a unique set of light-sensitive proteins called photoreceptors. Photoreceptors contain photopigments, which consist of a protein component bound to a non-protein, light-absorbing pigment called the chromophore. There are several different types of photoreceptors, which vary in their amino acid sequences and the type of chromophore present. These types maximally respond to different specific wavelengths of light, ranging from ultraviolet B (280-315 nanometers) to far-red (700-750 nanometers). The chromophore&#39;s absorption of light elicits structural changes in the photoreceptor, triggering a series of signal transduction events that result in gene expression changes.

The Phytochrome System

Many types of photoreceptors are present in plants. Phytochromes are a class of photoreceptors that sense red and far-red light. The phytochrome system acts as a natural light switch, allowing plants to respond to the intensity, duration, and color of environmental light.

The phytochrome system plays a significant role in photomorphogenesis&mdash;the growth and development of plants in response to light. Bright sunlight contains more red light than far-red light. Chlorophyll strongly absorbs red light, so shaded plant regions receive more far-red light than red light.

Plants use phytochromes to adapt their growth in response to red and far-red light. Exposure to far-red light in shaded regions triggers the elongation of stems and petioles in search of light. On the other hand, exposure to red wavelengths from unfiltered sunlight enhances lateral growth and branching.

Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides ...

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KEY TERMS AND CONCEPTS

phytochrome signals in plant growth

Plants use light as both an energy source and a signal that guides growth and development. Light helps control developmental and physiological responses, not just photosynthesis. In plant biology, these light-driven changes are part of how plants adjust to their environment.

Plants sense light with special proteins called photoreceptors. Each photoreceptor contains a photopigment made of a protein and a light-absorbing pigment called a chromophore. Different photoreceptors have different amino acid sequences and different chromophores, so they respond best to different wavelengths of light. These wavelengths range from ultraviolet B, about 280 to 315 nanometers, to far-red light, about 700 to 750 nanometers.

When the chromophore absorbs light, the photoreceptor changes shape. That change starts signal transduction, a chain of internal signals inside the plant cell. The result is a change in gene expression, which helps the plant respond to the light it receives.

Phytochromes are a class of photoreceptors that detect red and far-red light. They act like a natural light switch because they help plants respond to light intensity, duration, and color. Phytochromes are especially important in photomorphogenesis, which is plant growth and development in response to light.

Sunlight contains more red light than far-red light. In shaded areas, chlorophyll absorbs much of the red light, so the light that remains has relatively more far-red light. Plants use phytochromes to sense these conditions and change growth. Far-red light in shade can trigger stem and petiole elongation as plants reach for light, while red light from unfiltered sunlight can promote lateral growth and branching.

Phytochrome Signals in Plant Growth

plant hormones

How Plant Hormones Guide Growth

Plant hormones are chemical signals that guide growth and development in plants. They are also called phytohormones. Unlike animals, plants do not have hormone-producing glands. Instead, these molecules are often made in active growth regions such as the tips of roots and shoots. Even very small amounts of plant hormones can have major effects on plant development. Auxins are produced mainly in shoot tips and move from cell to cell down the stem. They help control cell elongation, fruit...

Plants use light as both an energy source and a signal that guides growth and development. Light helps control developmental and physiological responses, not just photosynthesis. In plant biology, these light-driven changes are part of how plants adjust to their environment. Plants sense light with special proteins called photoreceptors. Each photoreceptor contains a photopigment made of a protein and a light-absorbing pigment called a chromophore. Different photoreceptors have different amino...

biological clocks and seasonal responses

Plant Flowering Signals and Day Length

Plant flowering signals are controlled by biological clocks and changes in day length. The circadian clock is an internal, molecular timekeeping system that helps plants coordinate activities across 24-hour cycles, also called circadian rhythms. Photoperiodism is the set of plant responses to different lengths of light and dark. The photoperiod is the period of light exposure. Seasonal flowering is one example of photoperiodism. Plants are thought to use their circadian clocks to match...

responses to gravity and touch

How Roots and Shoots Grow in Response

Plants grow in response to gravity and touch through two linked movements called gravitropism and thigmotropism. These responses help roots and shoots change direction as they grow. In gravitropism, higher plants sense gravity with statocytes, which are cells near the vascular tissue in shoots and in the root cap columella in roots. Statocytes contain starch-filled organelles called statoliths. The statoliths settle at the bottom of the statocyte in the direction of gravity, and this starts a...

responses to drought and flooding

How Plants Survive Drought and Flooding

Plants need water, but too little or too much water can stress them. Under normal conditions, plants lose water from leaves and other parts through transpiration, which is the evaporation of water from the plant. During drought stress, water loss through transpiration can be much greater than water taken up from the soil, and the plant may wilt. Plants respond to drought by making the hormone abscisic acid. This hormone helps keep stomata closed and lowers transpiration. In severe water...

responses to heat and cold stress

Plant Strategies for Temperature Stress

Plant strategies for temperature stress help cells stay stable when the environment becomes too hot or too cold. Each organism has an optimum temperature range for healthy growth and normal function. At the low and high ends of that range, minimum and maximum temperatures can disrupt biological processes and cause stress. In plants, stress triggers changes in gene expression that shift metabolism and development toward homeostasis. Plant cell membranes are often affected first when ambient...

responses to salt stress

How Plants Handle Salty Soil

Salt stress affects plant growth when too much salt builds up in the plant’s environment. It can reduce photosynthesis and make it harder for roots to absorb water and nutrients. High soil salt changes the balance of water movement, so plants have less ability to draw water in by osmosis. Inside plant cells, the cytoplasm already contains many dissolved solutes. That normally helps water move from the soil into the plant. But excess salt in the soil raises the solute level outside the roots.

defenses against pathogens and herbivores

defenses-against-pathogens-and-herbivores

Plant Barriers and Chemical Defenses

Plants use barriers, chemicals, and proteins to defend against herbivores and pathogens. Because they are rich in nutrients, plants attract animals that eat them and infectious agents that try to invade them. Even without a true immune system, plants have built both constant defenses and defenses that turn on after attack. Mechanical defenses are the first line of protection. Bark forms a thick outer layer that helps protect plants from herbivores. Hard shells, thorns from modified branches,...

key terms and concepts

Learn how plant photoreceptors and phytochromes sense red and far-red light to shape growth, gene expression, and branching in different light conditions.

Phytochrome Signals in Plant Growth | JoVE K12

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South Carolina College and Career Ready Science Standards

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Ecosystems: Interactions, Energy, and Dynamics

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SBO1.

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The effect of hormones on structural growth of a plant in response to an external stimulus. (Focus on phototropism, geotropism, and thigmotropism).

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The circadian&#8212;or biological&#8212;clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities ...

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Gravitropism: Plant Responses to Gravity

Higher plants sense gravity using statocytes, cells found near the vascular tissue in shoots, and in the root ...

Responses to Drought and Flooding

Water plays a significant role in the life cycle of plants. However, insufficient or excess of water can be detrimental and pose a serious threat to ...

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Phytochrome Signals in Plant Growth

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