Question

Plants continuously monitor environmental conditions and modify their growth and/or development in response to these conditions. List five distinct responses to environmental conditions and for each indicate: a) the environmental property being monitored b) if it is known, the receptor that perceives the environmental condition c) what is known about the signaling pathway and mechanism of response d) the developmental and/or growth outcome of the response e) the benefit of the response Your list should include at least one response each for seeds, seedlings and plants.

Answer 1

Plants continuously monitor environmental conditions and modify their growth and/or development in response to these conditions. List five distinct responses to environmental conditions and for each indicate: a) the environmental property being monitored b) if it is known, the receptor that perceives the environmental condition c) what is known about the signaling pathway and mechanism of response d) the developmental and/or growth outcome of the response e) the benefit of the response Your list should include at least one response each for seeds, seedlings and plants.

Plants respond to their environment in a variety of ways. The response of an organism (here considering plant) to an environmental stimulus is called a tropism. Response may be negative or positive in nature and in over all plant needs to respond to environmental stimulus and adjust their growth and development in accoradance. Below list summarize the type of environmental stimuli and distinct plants response to environmental conditions

Tropism plant growth toward or away from a stimulus.

Phototropism the response of a plant to light; stems bend toward the light, roots move away from the light

Geotropism the response of the plant to gravity

Hydrotropism the bending of a plant’s roots toward water

Thigmotropism the response of a plant to touch; Some plants have leaves that close when they are touched. Afterwards they will return to their original position.

Heliotropism the movement of plant leaves and flowers in the direction of the sun

Plants responses to environmental conditions	environmental property being monitored	receptor that perceives the environmental condition	signaling pathway and mechanism of response	developmental and/or growth outcome of the response	benefit of the response	Example
Phototropism	light	photoreceptor: a specialized protein that is able to detect and react to light	The chromophore of the photoreceptor absorbs light of specific wavelengths, causing structural changes in the photoreceptor protein. The structural changes then elicit a cascade of signaling throughout the plant.	Plants respond to light stimuli by growing, differentiating, tracking the time of day and seasons, and moving toward or away from the light	The sensing of light in the environment is important to plants; it can be crucial for competition and survival. Plants can differentiate and develop in response to light (known as photomorphogenesis), which allows plants to optimize their use of light and space. Helps in synthesis of nutrients in photosynthetic plants.	Plants kept in shade try to grow towards sunlight. seed will only germinate if exposed to light at the surface of the soil
Geotropism	gravity	Amyloplasts (also known as statoliths ) are specialized plastids that contain starch granules and settle downward in response to gravity.	Amyloplasts settle at the bottom of the cells of the shoots and roots in response to gravity, causing calcium signaling and the release of indole acetic acid. Indole acetic acid inhibits cell elongation in the lower side of roots, but stimulates cell expansion in shoots, which causes shoots to grow upward.	Plant shoots grow away from gravity, toward sunlight, while plant roots grow into the soil in the direction of gravity.	Roots growing downwords in response to gravity provide anchorage and help in absorption of nutrients water and mineral.	roots grown downward in the direction of gravity, which is positive gravitropism, and the shoot grows upward away from gravity, which is negative gravitropism.
Hydrotropism	water	ABA receptor	Stress harmone i.e., abscissic acid are involved in plants response to water stress	Seed germination, rootgrowth absorption of water and nutrients	Plants meet their nutritional needs for growth by absorbing soil nutrients, water, and carbon dioxide, in addition to the required sunlight.	Roots growing towards water Seed germination require moisture.
Thigmotropism	touch	mechano-receptors Ethylene and jasmonate are likely involved in thigmomorphogenesis.	Thigmomorphogenesis is a slow developmental change in the shape of a plant subjected to continuous mechanical stress. When trees bend in the wind, for example, growth is usually stunted and the trunk thickens. Strengthening tissue, especially xylem, is produced to add stiffness to resist the wind’s force	Plants respond to wind and touch by changing their direction of growth, movement, and shape.	Thigmonastic responses include opening and closing leaves, petals, or other parts of the plant as a reaction to touch. Through thigmomorphogenesis, plants change their growth in response to repeated mechanical stress from wind, rain, or other living things	Shy plants(Mimosa pudica) Tendrils coiling
Heliotropism	Direction of sun Also known as solar tracking	Photoreceptors	Same as that of light signaling pathway	diurnal motion or seasonal motion of plantparts (flowers or leaves) in response to the direction of the sun	provide an advantage in groeth by allowing flowers move throughout the day, absorbing as much light as possible, maximizes photosynthesis in low-light environments.	Sunflower plant

Apart from these stimuli, plants also respond to biological factors such as herbivores, plant pathogens, symbionts and modulate their growth and development. Harmones such as auxin, gibberllin, cytokonin, ethylene, abscissic acid play an vital role in plants response to defferent stimuli and helps in modulating their germination growth stress tolerance etc.

Plants responses to environmental conditions	environmental property being monitored	receptor that perceives the environmental condition	signaling pathway and mechanism of response	developmental and/or growth outcome of the response	benefit of the response	Example
Phototropism	light	photoreceptor: a specialized protein that is able to detect and react to light	The chromophore of the photoreceptor absorbs light of specific wavelengths, causing structural changes in the photoreceptor protein. The structural changes then elicit a cascade of signaling throughout the plant.	Plants respond to light stimuli by growing, differentiating, tracking the time of day and seasons, and moving toward or away from the light	The sensing of light in the environment is important to plants; it can be crucial for competition and survival. Plants can differentiate and develop in response to light (known as photomorphogenesis), which allows plants to optimize their use of light and space. Helps in synthesis of nutrients in photosynthetic plants.	Plants kept in shade try to grow towards sunlight. seed will only germinate if exposed to light at the surface of the soil
Geotropism	gravity	Amyloplasts (also known as statoliths ) are specialized plastids that contain starch granules and settle downward in response to gravity.	Amyloplasts settle at the bottom of the cells of the shoots and roots in response to gravity, causing calcium signaling and the release of indole acetic acid. Indole acetic acid inhibits cell elongation in the lower side of roots, but stimulates cell expansion in shoots, which causes shoots to grow upward.	Plant shoots grow away from gravity, toward sunlight, while plant roots grow into the soil in the direction of gravity.	Roots growing downwords in response to gravity provide anchorage and help in absorption of nutrients water and mineral.	roots grown downward in the direction of gravity, which is positive gravitropism, and the shoot grows upward away from gravity, which is negative gravitropism.
Hydrotropism	water	ABA receptor	Stress harmone i.e., abscissic acid are involved in plants response to water stress	Seed germination, rootgrowth absorption of water and nutrients	Plants meet their nutritional needs for growth by absorbing soil nutrients, water, and carbon dioxide, in addition to the required sunlight.	Roots growing towards water Seed germination require moisture.
Thigmotropism	touch	mechano-receptors Ethylene and jasmonate are likely involved in thigmomorphogenesis.	Thigmomorphogenesis is a slow developmental change in the shape of a plant subjected to continuous mechanical stress. When trees bend in the wind, for example, growth is usually stunted and the trunk thickens. Strengthening tissue, especially xylem, is produced to add stiffness to resist the wind’s force	Plants respond to wind and touch by changing their direction of growth, movement, and shape.	Thigmonastic responses include opening and closing leaves, petals, or other parts of the plant as a reaction to touch. Through thigmomorphogenesis, plants change their growth in response to repeated mechanical stress from wind, rain, or other living things	Shy plants(Mimosa pudica) Tendrils coiling
Heliotropism	Direction of sun Also known as solar tracking	Photoreceptors	Same as that of light signaling pathway	diurnal motion or seasonal motion of plantparts (flowers or leaves) in response to the direction of the sun	provide an advantage in groeth by allowing flowers move throughout the day, absorbing as much light as possible, maximizes photosynthesis in low-light environments.	Sunflower plant