Plant-Plant Interactions Literature

What is the main idea of the article?

Plants actively sense and respond to neighboring plants through environmental information such as light, chemicals, nutrients, roots, touch, and volatile compounds. These interactions can affect growth, physiology, productivity, and plant communities.

What is phenotypic plasticity?

The ability of an individual or genotype to produce a range of phenotypes in response to environmental variation.

Give two examples of phenotypic plasticity in plants.

Producing more roots in a nutrient-rich area and selectively shedding a shaded branch.

Why are plants especially capable of phenotypic plasticity?

Plants continuously produce new organs such as leaves and roots, giving them many opportunities to alter growth in response to the environment.

What is allometry?

The study of changes in the relative size, scale, or growth rate of different body parts during development.

What is the main difference between allometry and phenotypic plasticity?

Allometry describes developmental changes in body proportions, while phenotypic plasticity describes changes caused by environmental variation.

What is a signal?

Information that functions as an intended information broadcast.

What is a cue?

Information that can be detected and used by an organism but is not necessarily intended as communication.

How should external biological information generally be classified?

As a cue unless there is evidence that it functions as an intentional signal.

Which hormones in the article can function as both internal and external information vectors?

Ethylene and strigolactones.

What is plant behavior?

What a plant does during its lifetime in response to an event or change in the environment.

What is an example of plant behavior?

Phototropism, or curvature of a plant toward a light source.

How do physiological and morphological plant behaviors differ?

Physiological responses can be rapid and short term, while morphological or growth responses are generally slower and more permanent.

Why do plants respond to cues about their future environment?

Growth responses take time, so plants benefit from responding to reliable information that predicts future conditions before competition or stress becomes severe.

What basic resources do plants often compete for?

Light, water, nutrients, space, and substrate for growth.

What three broad responses can plants have to competition?

They can avoid, tolerate, or confront the competitor.

What is shade avoidance syndrome?

A set of developmental responses that helps a plant avoid or compete with vegetation that may shade it.

What is a common growth response during shade avoidance?

Stem elongation, which may allow a plant to grow above its competitors.

What are photoreceptors?

Molecules that allow plants to detect light intensity and light quality, or wavelength.

What does PAR stand for?

Photosynthetically Active Radiation.

What wavelength range is PAR?

Approximately 400–700 nm.

What are phytochromes?

Photoreceptors that detect red and far-red light and help plants perceive neighboring vegetation.

What are the two forms of phytochrome?

Pr and Pfr.

What wavelength does Pr preferentially absorb?

Red light, about 660 nm.

What happens to Pr after it absorbs red light?

It changes into Pfr.

What wavelength does Pfr preferentially absorb?

Far-red light, about 730 nm.

What happens to Pfr after it absorbs far-red light?

It changes back into Pr.

Which phytochrome form initiates many downstream responses?

Pfr.

What does R:FR mean?

The red-to-far-red light ratio.

Why does light reflected or transmitted through leaves have a lower R:FR ratio?

Leaves absorb much of the red/PAR light while relatively more far-red light passes through or is reflected.

What does a low R:FR ratio tell a plant?

It can indicate that neighboring vegetation is nearby and future shading may occur.

Why can phytochrome help plants anticipate competition?

It detects changes in the red-to-far-red ratio before severe shading actually occurs.

What are major responses included in shade avoidance syndrome?

Increased stem and leaf elongation, more vertical leaves, fewer branches, stronger apical dominance, accelerated flowering, and sometimes delayed germination.

What is hyponasty?

A more vertical or upward orientation of leaves.

What is apical dominance?

Suppression of lateral bud growth so that the main shoot has stronger growth dominance.

Does shade avoidance always mean growing taller?

No. Some plants can grow away from the source of expected shade instead.

How does Portulaca oleracea respond to anticipated shade?

It can alter its growth direction and grow away from sources of far-red-rich light, reducing future competition and self-shading.

What is shade tolerance?

The ability of a plant to survive and grow successfully under low-light conditions rather than trying to outgrow competitors.

How do shade avoidance and shade tolerance differ?

Shade avoidance attempts to escape or overcome shade, while shade tolerance involves traits that make living in low light more efficient.

What leaf traits are common in shade-tolerant plants?

Relatively thin leaves with a larger area for light capture.

How does chlorophyll composition often differ in shade-tolerant plants?

They tend to have a higher chlorophyll b : chlorophyll a ratio.

How does stomatal density often differ in shade-tolerant plants?

It is generally lower than in sun-loving plants.

How does Rubisco abundance often differ in shade-tolerant plants?

Shade-tolerant plants generally have less Rubisco than sun-loving plants.

What is the light saturation point?

The light intensity above which increasing light no longer substantially increases photosynthesis.

How does the light saturation point differ in shade-tolerant plants?

It is generally lower.

What is the light compensation point?

The light intensity at which CO₂ uptake by photosynthesis equals CO₂ release by respiration.

How does the light compensation point differ in shade-tolerant plants?

It is generally lower, helping them maintain a positive carbon balance in low light.

What environmental cues can influence seed germination?

Light, moisture, heat, smoke, and other environmental conditions.

What effect can far-red light have on many sun-loving seeds?

It can strongly suppress germination.

What effect can red or white light have on light-sensitive lettuce seeds?

It can stimulate germination.

What does photoreversible germination mean?

The effects of red and far-red light can reverse one another, demonstrating phytochrome control.

Why might a seed remain dormant under vegetation?

Far-red-rich light can indicate strong future competition, so remaining dormant may help the seed avoid unfavorable conditions.

What are karrikins?

Smoke-derived compounds that can strongly promote seed germination.

Why can fire be a useful germination cue?

Fire can open the canopy, reduce competition, and return nutrients to the soil.

What is serotiny?

A condition in which seeds remain enclosed in cones or fruiting structures for long periods until conditions such as fire heat cause release.

What is somatic competition?

Competition among different organs of the same plant for resources.

Give an example of somatic competition.

A well-lit branch may receive more resources while a heavily shaded branch receives fewer resources and may eventually be shed.

What is correlative inhibition?

The integration of signals and cues that causes some organs of a plant to become stronger while others are suppressed.

Which factors contribute to apical dominance?

Auxin, cytokinin, strigolactones, and nutrient availability.

What role does auxin play in apical dominance?

Auxin flowing from the shoot apex contributes to suppression of lateral bud outgrowth.

What did the two-shoot pea experiment demonstrate?

Resources are preferentially allocated to the more successful shoot, showing that growth of different shoots on the same plant is interdependent rather than independent.

What is root foraging?

The ability of roots to alter their growth, branching, root-hair formation, and nutrient uptake in response to resource availability.

What is optimal foraging theory in plants?

Plants should allocate growth and resources in ways that maximize their net gain of energy and resources.

What does a root often do when it encounters a nutrient-rich patch?

It increases root proliferation and/or nutrient transporter activity in that area.

What may a plant do when soil nutrients are scarce relative to light?

Allocate a greater proportion of biomass to its root system.

Approximately what proportion of plant species can recruit mycorrhizal fungi according to the lecture?

About 90%.

What do plants give mycorrhizal fungi?

Photosynthate/carbohydrates.

What do mycorrhizal fungi provide plants?

Increased nutrient-acquiring surface area, especially improving phosphate uptake.

What compound can nutrient-limited roots release to recruit mycorrhizal fungi?

Strigolactones.

What is an allelochemical?

A chemical produced by one plant that affects another organism or plant.

What is allelopathy?

A plant–plant interaction in which chemicals produced by one plant affect the growth, germination, or performance of another plant.

What is juglone?

A well-studied allelochemical produced by black walnut.

What is sorgoleone?

A well-studied allelochemical produced by sorghum.

Why are allelochemicals of agricultural interest?

Some can suppress weeds and potentially function as natural herbicides.

What is one agricultural disadvantage of allelochemicals?

Chemical residues may remain in soil and negatively affect later crops.

What is the novel weapon hypothesis?

An invasive species may dominate because it introduces chemicals or traits that native organisms have not had enough evolutionary time to adapt to.

How does garlic mustard support the novel weapon hypothesis?

It produces allelochemicals that inhibit mycorrhizal fungi relied on by many native plants.

What evidence suggests plants may distinguish self from non-self?

Some studies show roots compete more strongly with roots from other individuals than with their own roots.

What evidence suggests plants may distinguish kin from non-kin?

Rice roots of different genotypes showed less overlap than roots of the same genotype.

Is the mechanism of plant self- and kin-recognition fully understood?

No. The article states that the precise signaling mechanisms are still unclear.

What is parasitism in plant–plant interactions?

An extreme form of competition in which one plant penetrates another and extracts water and nutrients.

About what percentage of angiosperms are parasitic according to the article?

About 1%.

What is a haustorium?

A specialized invasive structure that penetrates host tissue and serves as a conduit for water and nutrient transfer to the parasite.

What are two examples of important parasitic plants mentioned in the article?

Striga (witchweed) and Orobanche/Phelipanche (broomrape).

What types of cues can parasitic plants use to recognize hosts?

Chemical and tactile cues.

How do strigolactones affect Striga?

Strigolactones released by host roots can act as cues that promote Striga germination and parasitism.

Why are strigolactones both beneficial and risky for a plant?

They can recruit beneficial mycorrhizal fungi, but they can also be detected by parasitic plants such as Striga.

What is facilitation?

A positive interaction in which both partners benefit.

What is commensalism?

An interaction in which one organism benefits while the other is neither helped nor harmed.

What is a nurse plant?

An established plant that shelters a younger plant or seedling and helps it survive harsh environmental conditions.

What types of protection can nurse plants provide?

Protection from heat, excessive radiation, desiccation, and sometimes herbivory.

What is intercropping?

Growing two or more crop species together so their complementary traits can increase productivity and reduce competition.

How can legumes benefit neighboring crops?

They can increase the availability of fixed nitrogen and may indirectly improve other nutrient availability.

What is hydraulic lift?

A process in which a deep-rooted plant moves water toward the soil surface, making it available to shallower-rooted plants.

How can shared mycorrhizal networks facilitate plant interactions?

They can connect plants and contribute to the movement or sharing of resources such as carbohydrates and nutrients.

What are plant stress cues?

Information released during stress that can be perceived by other tissues or neighboring plants and influence their future responses.

What type of chemicals can plants release after herbivore attack?

Volatile chemicals.

What does it mean when the article says plants can “eavesdrop” on each other?

Plants can detect chemicals released by neighboring plants and use that information to alter their own responses.

What happened to tobacco plants growing near clipped sagebrush?

They showed higher polyphenol oxidase levels and lower herbivory, suggesting they detected information released by the wounded sagebrush.

What volatile compounds are identified as possible information carriers in plant–plant interactions?

Methyl jasmonate, methacrolein, and trans-2-hexenal.