© 2013 american society of plant biologists plant-plant interactions photo courtesy of ronald...
TRANSCRIPT
© 2013 American Society of Plant Biologists
Plant-plant interactionsPhoto courtesy of Ronald Pierik
© 2013 American Society of Plant Biologists
Plants sense and respond to other plants植物感知和响应其他植物
Often, but not always, plants compete with each other for limiting resources, such as light and nutrients通常,但不一定是,植物对有限资源是相互竞争的,如光和营养。How do they perceive competitors?他们是如何感知竞争对手的?Are all of their interactions competitive? 所有植物之间的交互作用都是竞争性质的吗?How do interactions between plants affect higher organizational levels (e.g., communities)? 植物之间的相互作用是如何影响更高水平的组织结构的?如群落
Photo credit: Tom Donald
© 2013 American Society of Plant Biologists
Outline概要Key definitions and concepts关键的定义和概念Competition竞争•Competition for light 光•Competition belowground地下竞争•Do plants perceive “self” or “kin”?•植物自我和亲属是怎么感知的?
Cooperation / Facilitation协同和促进•Environmental modulation环境的调节•Enhanced nutrient availability提高营养物质的有效性•Stress cues胁迫信号Putting knowledge to work
Photo credit: Mary Williams
© 2013 American Society of Plant Biologists
Key definitions and concepts
Reprinted by permission from Wiley from Drew, M.C. (1975). Comparison of the effects of a localised supply of phosphate, nitrate and ammonium and potassium on the growth of the seminal root system, and the shoot, in barley. New Phytol. 75: 479-490. Reprinted from Vandenbussche, F., et al. (2005). Reaching out of the shade. Curr. Opin. Plant Biol. 8: 462-468 with permission from Elsevier, Reprinted from Sultan, S.E. (2000). Phenotypic plasticity for plant development, function and life history. Trends Plant Sci. 5: 537-542 with permission from Elsevier. See also Bradshaw, A. D. (1965). Evolutionary significance of phenotypic plasticity in plants. Adv. Genet. 13: 115–155.
The capacity of an individual (or a genotype) to exhibit a range of phenotypes in response to variation in the environment 个人的能力 ,表现出一系列的表型 ,以应对环境的变化
Phenotypic plasticity 表型可塑性
Polygonum lapathifolium酸膜
Low light光 High light
Nicotiana tabacum烟
Low Red: 远红外的比率
High Red: Far-red ratio
Low phosphate
Low phosphate
High phosphate
P水平
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Phenotypic plasticity in plants植物的表型可塑性
Reprinted by permission from Wiley from Drew, M.C. (1975). Comparison of the effects of a localised supply of phosphate, nitrate and ammonium and potassium on the growth of the seminal root system, and the shoot, in barley. New Phytol. 75: 479-490. Photo credit Michael Clayton.
Root plasticity in response to localized nutrient availability
Shoot plasticity in response to light光
根可塑性响应局部营养的可用性
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Signals and cues
Signals are generally considered to be an intended information broadcast and can include: hormones, bacterial metabolites, electrical signals, light quality, stress signals
Cues are considered to be without intent and can include:Nutrient resources, water, light
Signals and cues convey information
Semaphores are signals
Odors and light can be cues
See for example, Aphalo, P.J. and Ballare, C.L. (1995). On the importance of information-acquiring systems in plant-plant interactions. Funct. Ecol. 9: 5-14. Aphalo, P.J., Ballaré, C.L. and Scopel, A.L. (1999). Plant-plant signalling, the shade-avoidance response and competition. J. Exp. Bot. 50: 1629-1634. Image from Nesnad.
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Signals and cues affecting plants
INFORMATION
Internal Signaling
Primary metabolitesHormonesElectrical pulses
ExternalCueing Signaling
Biotic only Abiotic: Physical and chemical environment atmospheric, edaphic.
Biotic: Secretions, exudates, volatiles etc
External cueing: Can be observedExternal signaling: Initially, only a hypothesis. Whether it is adaptive for the emitter as well as the receiver must be determined
Some hormones, such as ethylene and strigolactones, serve as communication vectors both internally and externally
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Cues inform decisions about when and how to allocate finite resources
Like a poker player, plants have limited resources. Gambling on a bad hand, or expending resources at the wrong place or time can be a big mistake
Signals and cues indicate the “best bet”
Cues that indicate future conditions and circumstances are particularly important. Plants grow slowly, and can’t run away, so they have to live with the consequences of their behaviors
See for example Shemesh, H, BF Zaitchik, T Acuna, and A Novoplansky (2012) Architectural plasticity in a Mediterranean winter annual. Plant Signal. Behav. 7:492 – 501 and Shemesh, H. and Novoplansky, A. (2012) Branching the risks: architectural plasticity and bet-hedging in Mediterranean annuals. Plant Biol., In press. Photo credit Tom Donald.
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Plant behavior
What a plant does in the course of its lifetime, in response to an event or change in the environment
Example: Phototropic curvature towards a light source
Images: Wisconsin fast plants, Tangopaso
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Plant behavior affects morphological and biochemical phenotypes
Shaded
Full sun One of the most studied plastic responses is shade-induced stem elongation
The induction of defense responses to herbivory or pathogens is another type of phenotypic plasticity. For example, herbivore attack can induce the synthesis of an anti-nutritive such as a protease-inhibitor
Franklin, K.A. and Whitelam, G.C. (2005). Phytochromes and shade-avoidance responses in plants. Ann. Bot. 96: 169-175. Ryan, C.A. (1990). Protease inhibitors in plants: Genes for improving defenses against insects and pathogens. Annu. Rev. Phytopathol. 28: 425-449.
Plants can’t run away – they have different forms of behavior
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Plant behavior is affected by many environmental parameters
Genome and epigenome
Abiotic factors: Light, moisture, nutrients, etc.
Biotic factors: competitorssymbionts, pathogens, herbivores, etc.
Phenotypic outcomes:•Number and length of root and shoot•Number, size and architecture of leaves, branches and lateral roots•Production of metabolites •Etc.
Plant behavior is mediated through phenotypic plasticity
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Case study: Plasticity of leaf morphology in aquatic plants
Lin, B.-L. and Yang, W.-J. (1999). Blue light and abscisic acid independently induce heterophyllous switch in Marsilea quadrifolia. Plant Physiol. 119: 429-434.
Submerged leaf phenotype
Many species prone to periodic submergence show phenotypic plasticity of their leaf forms. Submerged leaves are often thinner and without stomata or cuticle.
Aerial leaf phenotype
The hormone ABA is one signal that initiates the switch to the aerial form, and in this plant, Marsilea quadrifolia, blue light is another. The plant was irradiated with blue light at the position indicted by the arrowhead
© 2013 American Society of Plant Biologists
Summary: Behavior is the variable response to the environment
The mechanisms by which plants perceive their environment and integrate information into a behavioral response are not well understood, but under intense investigation
Plant interactions involve perception through cues and signals, and plastic behavioral responses
Photo credit: Tom Donald
© 2013 American Society of Plant Biologists
Victoria Nuzzo, Natural Area Consultants ; Easy Stock Photos; Hassanali, A., Herren, H., Khan, Z.R., Pickett, J.A. and Woodcock, C.M. (2008). Integrated pest management: the push–pull approach for controlling insect pests and weeds of cereals, and its potential for other agricultural systems including animal husbandry. Phil. Trans. R. Soc. B 363: 611-621 copyright 2008 The Royal Society; Karban, R., Baldwin, I.T., Baxter, K.J., Laue, G. and Felton, G.W. (2000). Communication between plants: Induced resistance in wild tobacco plants following clipping of neighboring sagebrush. Oecologia. 125: 66-71. Max Planck Institute for Chemical Ecology, Jena, Germany / Rayko Halitschke.
Plants are affected by each other positively and negatively
Negative effect:
Competition for light
Negative allelopathic effect:
Here, the invasive species Alliaria petiolata (garlic
mustard) suppresses all others
Positive effect: Nutrient sharing and suppression of parasitism
Positive effect: Stress cues
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“We can dimly see why the competition should be most severe between allied forms, which fill nearly the same place in the economy of nature...”
Charles Darwin, 1859, On the Origin of Species, Ch 3 Struggle for Existence
With similar needs, competition between plants can be intense
Light information governs shoot phenotype, but also affects root development and interactions
Self-shading Shading by non-self
Nutrient and water distribution and various signals and cues govern root phenotype
Competition and cues from
non-self
Plants compete with themselves and others
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Trees growing in forests can grow more than 100 meters high, shading plants below them, including their own offspring
Light can be a limiting resource in many environments
Photos courtesy Ariel Novoplansky
© 2013 American Society of Plant Biologists
Confront
Avoid
TolerateShade tolerant morphology and physiology
Elongation response, Increased apical dominance
Growing away from competitorsLight- or fire-dependent germination
Responses to shading: confrontation, avoidance, tolerance
Reprinted from Vandenbussche, F., Pierik, R., Millenaar, F.F., Voesenek, L.A.C.J. and Van Der Straeten, D. (2005). Reaching out of the shade. Curr. Opin. Plant Biol. 8: 462-468 with permission from Elsevier, See also Novoplansky, A. (2009) Picking battles wisely: plant behaviour under competition. Plant Cell Environ. 32: 726-741. Photo credits: Lennart Suselbeek; Ariel Novoplansky
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Light
Plants perceive light levels and color (or- light quantity and quality)
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Detection of light levels and quality
UltravioletShort wavelengthHigh energy
InfraredLong wavelengthLow energy
UV receptor
Blue light receptors
Red / far-red receptors
Plants perceive light through photoreceptors that are sensitive to light of various wavelengths
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Absorption spectra for
chlorophyll and accessory pigments
Photosynthetically active radiance
(PAR)
Far- Red light – too little energy for photosynthesis
Phytochrome detects the boundary of photosynthetically active radiance
Phytochrome detects both photosynthetically active red light (660 nm) and photosynthetically inactive far-red (730 nm) light
Cryptochrome detects blue (450 nm) light
Act
ion
sp
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© 2013 American Society of Plant Biologists
Reprinted by permission from Macmillan Publishers Ltd from Smith, H. (2000). Phytochromes and light signal perception by plants - an emerging synthesis. Nature. 407: 585-591; Adapted from Jaillais, Y. and Chory, J. (2010). Unraveling the paradoxes of plant hormone signaling integration. Nat. Struct. Mol. Biol. 17: 642-645.
A low ratio of red to far-red light is indicative of vegetative shading
Shaded
Full sun
R FR
R FRRed light is depleted as light passes through the canopy
Phytochrome identifies the ratio of Red to Far-red light
(R:FR), an indicator of vegetative shading
PAR
Green and red light are not absorbed by the photosynthetic pigments – they reflect and pass through leaves
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Phytochrome’s conformation and absorption spectra “switch”
Phytochrome changes conformation when it absorbs light: Red light converts it to the Pfr form, which mainly absorbs far-red light;Far-red light converts it to the Pr form, which mainly absorbs red light
Reprinted by permission from Macmillan Publishers Ltd from Smith, H. (2000). Phytochromes and light signal perception by plants - an emerging synthesis. Nature. 407: 585-591.
© 2013 American Society of Plant Biologists
Transduction of light information downstream of photoreceptors
Reprinted from Gommers, C.M.M., Visser, E.J.W., Onge, K.R.S., Voesenek, L.A.C.J. and Pierik, R. (2013). Shade tolerance: when growing tall is not an option. Trends Plant Sci. 18: 65-71 with permission from Elsevier.
Many of the molecular events that contribute to shade avoidance have been elucidated, and include effects on transcription factor activity and hormone levels and responses
Many of the molecular events that contribute to shade avoidance have been elucidated, and include effects on transcription factor activity and hormone levels and responses
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Shade avoidance is a collection of responses to vegetative shading
Reprinted from Casal, J.J. (2012) Shade Avoidance. The Arabidopsis Book 10:e0157. doi:10.1199/tab.0157
Light
Vegetative shading
Delayed or suppressed germination
Stem and hypocotyl elongation
Petiole elongation, leaf hyponasty, narrow leaves
Early flowering
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From Ballaré, C.L., Scopel, A.L. and Sánchez, R.A. (1990). Far-red radiation reflected from adjacent leaves: An early signal of competition in plant canopies. Science. 247: 329-332. reprinted with permission from AAAS, de Wit, M., Kegge, W., Evers, J.B., Vergeer-van Eijk, M.H., Gankema, P., Voesenek, L.A.C.J. and Pierik, R. (2012). Plant neighbor detection through touching leaf tips precedes phytochrome signals. Proc. Natl. Acad. Sci. USA (2012) 109: 14705-14710.
Plants elongate less when wearing a collar that filters out far-red light reflected from adjacent leaves
Touch is another cue that signals future competition and stimulates elongation
Shade
R FR
Future Shade?
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Case study: Portulaca oleracea, light responses in recumbent plant
Reprinted with permission from Novoplansky, A., Cohen, D., and Sachs, T. (1990) How Portulaca seedlings avoid their neighbours. Oecologia 82: 490-493.
Portulaca oleracea grows and branches in a way that minimizes self shading
When lower red/far-red ratios are provided from one direction, the plant grows away, suggesting that phytochrome controls the growth directionality
Low R:FR light
Growth direction; probability
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Future shade can be more important than present shade
Grey
Green
Adapted from Novoplansky, A. (1991). Developmental responses of portulaca seedlings to conflicting spectral signals. Oecologia 88: 138-140.
Filters were set up on opposite sides of Portulaca seedlings
One side (grey) transmitted very little photosynthetic light, equally low in R and FR
The other side transmitted and reflected more photosynthetic light but much more far-red than red light
Do the plants grow towards the side with more light now (green) or more light later (grey)? The low R / FR ratio on the “green” side implies the presence of potential competitor…
Little red
Little far-red
Portulaca grows away from far-red light, even when it means that they are growing towards less light
Low R:FR cues indicate the presence of a competitor, so growing away from the direction of such cues might improve the plant’s fitness
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Some plants have evolved to tolerate shade – life in the dim lane
Shade-tolerant species are adapted to low light environments
Shade-tolerant species are adapted to low light environments
Photos courtesy Tom Donald and Ariel Novoplansky
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Shade tolerance takes many forms
Reprinted with permission from Valladares, F. and Pearcy, R.W. (1998). The functional ecology of shoot architecture in sun and shade plants of Heteromeles arbutifolia M. Roem., a Californian chaparral shrub. Oecologia. 114: 1-10; Coley, P.D. (1988). Effects of plant growth rate and leaf lifetime on the amount and type of anti-herbivore defense. Oecologia. 74: 531-536.See also Valladares, F. and Niinemets, Ü. (2008). Shade tolerance, a key plant feature of complex nature and consequences. Annu. Rev. Ecol. Evol. Syst. 39: 237-257 and Gommers, C.M.M., et al. (2013). Shade tolerance: when growing tall is not an option. Trends Plant Sci. 18: 65-71. Photo courtesy of Ronald Pierik
Full sun Shade
Adaptations to maximize light interception: Increased leaf areaLeaves oriented to intercept lightLeaves positioned to minimize overlapHigh chlorophyll b to a content
Growth rate
Def
ense
sLong-lived shade-tolerant plants invest relatively more resources into defenses against herbivores and pathogens
Shade
Sun Reduced stem-elongation response
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Energetics of shade tolerance: max. assimilation, min. expenditure
Typically, shade tolerant plants have a lower rate of respiration in the dark, lower light compensation point, and lower light saturation point
Light intensity(μmol/m2/sec)
0
0C
O2 a
ssim
ilatio
n
(μm
ol/m
2/s
ec)
Dark respiration
Lig
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Shade plant
Sun plant
10
200 400 800
Light saturation point
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Light information: Angle, gradients, quality, and time of day
See for example Sellaro, R., Pacín, M. and Casal, J.J. (2012). Diurnal dependence of growth responses to shade in Arabidopsis: Role of hormone, clock, and light signaling. Mol. Plant. 5: 619-628.
Light information is MORE than just quantity and spectrum. It is likely that plants respond to a richer gamut of light cues
Vertical, mid-day shade (possibly low R:FR) might indicate a very tall neighbor – don’t bother trying to catch up!
Horizontal and late-day low R:FR cues might indicate similarly-sized neighbors – go for it!
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Germination plasticity: light and other cues for seed germination
Photo credits: Forest & Kim Starr, Starr Environmental; Howard F. Schwartz, Colorado State University, Bugwood.org
One of the most
important decisions a plant makes is when to germinate
Many seeds germinate in response to white or red light, but far-red light is inhibitory
R FR
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Fire (heat and smoke) can promote seed germination
Image sources: pfern, Hesperian, © Kurt Stueber, 2003
Fire stimulates seed release or germination in some plants
Some cones and seed pods are fire-serotinous, opening in response to fire
Banskia spp, before and after fire
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Karrikins are germination-promoting compounds found in smoke
Reprinted from Chiwocha, S.D.S., Dixon, K.W., Flematti, G.R., Ghisalberti, E.L., Merritt, D.J., Nelson, D.C., Riseborough, J.-A.M., Smith, S.M. and Stevens, J.C. (2009). Karrikins: A new family of plant growth regulators in smoke. Plant Science. 177: 252-256 with permission from Elsevier, and see also Flematti, G. R., et al., (2004). A compound from smoke that promotes seed germination. Science 305: 977.
Fire-induced germination lets seedlings become established with less competition from taller plants.
Karrikins are cues from smoke that promote germination.
However, following a fire, there can be increased competition between similarly-sized seedlings….
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Plants produce many redundant organs that compete with each other
Somatic competition can increase plant performance by putting resources into more successful organs
See Sachs, T. and A. Novoplansky (1995) Tree form: architecture models do not suffice. Israel J. Plant Sci. 43:203-212; Photos courtesy Ariel Novoplansky.
Somatic competition: When plants compete with themselves
Are these branches shedding as a direct result of them growing in low light ? Or is it a result of competition with other, more successful branches on the same tree?
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Branch autonomy may vary according to circumstances
Adapted from Kawamura, K. (2010). A conceptual framework for the study of modular responses to local environmental heterogeneity within the plant crown and a review of related concepts. Ecological Research. 25: 733-744.
Full sun Full shade Partial shade
L R L R L R
Gro
wth
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L R L R L RIndependent Competitive Cooperative
There is experimental evidence to support all three types of responses between shoots: independent, competitive and cooperative
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Case study: Two-shoot peas and correlative inhibition
See Novoplansky, A., Cohen, D., and Sachs, T. (1989) Ecological implications of correlative inhibition between plant shoots. Physiol. Plant. 77: 136-140; Snow, R. (1931). Experiments on growth and inhibition. Part II. New phenomona on inhibition. Proc. Roy. Soc. B. 108: 305-316. Sachs, T. and A. Novoplansky (1997) What does a clonal organization suggest concerning clonal plants? in de Kroon, H. and J. van Groenendael (eds.) The Ecology and Evolution of Clonal Growth in Plants, pp. 55-78, SPB Academic Publishing, Leiden, The Netherlands.
Two shoot peasRemoving the shoot from a pea seedling causes two shoots to regenerate – a good system to study somatic competition!
5-day old pea
Shoot removal
5 days
“Two-shoot pea”
Two equal shoots can co-exist, but very often one becomes dominant and the other dies
Why does the smaller shoot die?
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Case study: Two-shoot peas and correlative inhibition
Redrawn with permission from Novoplansky, A., Cohen, D., and Sachs, T. (1989) Ecological implications of correlative inhibition between plan shoots. Physiol. Plant. 77: 136-140; Snow, R. (1931). Experiments on growth and inhibition. Part II. New phenomona on inhibition. Proc. Roy. Soc. B. 108: 305-316.
A shoot in the dark can survive 10 days (using nutrient reserves), but in competition with a more successful shoot in the light, the darkened shoot dies. The plant selectively allocates reserves to the stronger shoot….
Model: Resources are allocated to the best option. In A, the best (only) option is the shoot in the dark. In B, resources are allocated to the shoot in the light, at the expense of the other shoot.
A. Dark only:100% survival of dark shoot
B. One dark and one light shoot: 20% survival of dark shoot
A. Dark only B. One dark and one light shoot
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Within and between trees, branches in the best conditions prevail
Less successful branches, e.g. shaded by neighbors or self are discriminated against and shed
Photo credit: Tom Donald
© 2013 American Society of Plant Biologists
Summary: Perception of and response to vegetative shading
Light is a resource and also a source of information that affects plant behavior
Adaptive responses to competition for light can be architectural (shoot position, size and number), morphological (stem elongation, increased leaf area), physiological (amount of chlorophyll or Rubisco), etc.
Photo credits: Ariel Novoplansky; Reprinted from Vandenbussche, F., et al. (2005). Reaching out of the shade. Curr. Opin. Plant Biol. 8: 462-468 with permission from Elsevier
© 2013 American Society of Plant Biologists
Competition belowground: Root growth is extremely plastic
Reprinted by permission from Wiley from Drew, M.C. (1975). Comparison of the effects of a localised supply of phosphate, nitrate and ammonium and potassium on the growth of the seminal root system, and the shoot, in barley. New Phytol. 75: 479-490.. Reprinted from Bouguyon, E., Gojon, A. and Nacry, P. (2012). Nitrate sensing and signaling in plants. Sem. Cell Devel. Biol. 23: 648-654, with permission from Elsevier. See also Gersani, M. and Sachs, T. (1992). Development correlations between roots in heterogeneous environments. Plant Cell Environ. 15: 463-469.
When soil resources are abundant, plants allocate less biomass to their roots
When nutrient distribution is patchy, roots proliferate in the nutrient rich patches
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Competition belowground: Root growth is extremely plastic
Reprinted with permission from Fang, S., Clark, R.T., Zheng, Y., Iyer-Pascuzzi, A.S., Weitz, J.S., Kochian, L.V., Edelsbrunner, H., Liao, H. and Benfey, P.N. (2013). Genotypic recognition and spatial responses by rice roots. Proc. Natl. Acad. Sci. USA 110: 2670-2675. Muller, C.H. (1946) Root development and ecological relations of Guayule. USDA Technical Bulletin 923, see also Schenk et al., 1999, Adv. Ecol. Res 28: 145–180, and Gersani, M. and Sachs, T. (1992). Development correlations between roots in heterogeneous environments. Plant Cell Environ. 15: 463-469.
Roots respond to other roots
Many studies have found that roots have a tendency to grow away from each other
Many studies have found that roots have a tendency to grow away from each other
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Confront (overproliferate)
Avoid (underproliferate)
Tolerate
Resource limitation
Root-exuded chemicals
Other
Belowground competition: Cues, signals and responses
© 2013 American Society of Plant Biologists
Plants compete for nutrients, which are frequently limiting for growth
Fisher, J.B., Badgley, G. and Blyth, E. (2012). Global nutrient limitation in terrestrial vegetation. Global Biogeochemical Cycles. 26: GB3007. Credit: NASA JPL/Caltech.
This map shows the difference between actual vegetation productivity and maximum theoretical productivity based on availability of water and sunlight; the difference is attributed to nutrient limitation
© 2013 American Society of Plant Biologists
Photo credits: Gerald Holmes, Valent USA Corporation, Ulrike Mathesius, Bugwood.org, Sara Wright, USDA; Kristine Nichols, USDA
Most plants enhance nutrient uptake through associations with mycorrhizal fungi or nitrogen-
fixing bacteria 大多数植物提高养分吸收通过对菌根真菌或固氮细菌Some plantsNitrogen-fixing bacteria
Most plantsMycorrhizal fungi
Extensive fungal surface area facilitates nutrient and water uptakeBacteria in nodules
produce reduce atmospheric nitrogen
Fungus inside plant root
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Control roots without contact or with a physical barrier
Plants exposed to the chemical exudates of another root system decreased their rate of root growth
In some cases, roots avoid contact or proximity to other roots
Reprinted with permission from Mahall, B.E. and Callaway, R.M. (1991). Root communication among desert shrubs. Proc. Natl. Acad. Sci. USA 88: 874-876.
How do roots respond to the roots of another plant? Plexiglass boxes were set up to record root responses…
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Reprinted from Cahill, J.F., McNickle, G.G., Haag, J.J., Lamb, E.G., Nyanumba, S.M. and St. Clair, C.C. (2010). Plants integrate information about nutrients and neighbors. Science . 328: 1657 with permission from AAAS.
Plants integrate information about nutrients and neighbors
Plants were planted alone or with a neighbor, in uniform soil or soil with nutrient rich patches (shaded bar), and root distribution analyzed
In uniform soil, roots avoided each other
But they proliferate in a nutrient-rich patch, in spite of their neighbor
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Many plants make allelochemicals that deter competitors
Allelopathic chemicals (allelochemicals) interfere with growth of nearby plants
Sorgoleone is produced in Sorghum bicolor root hairs and exuded as oily drops. It accumulates in the soil and acts as a pre-emergence herbicide affecting photosynthesis in very young seedlings
Reprinted from Dayan, F.E., Howell, J.L. and Weidenhamer, J.D. (2009). Dynamic root exudation of sorgoleone and its in planta mechanism of action. J. Exp. Bot. 60: 2107-2117 with permission of Oxford University Press; Howard F. Schwartz, Colorado State University.
Juglone is an allelochemical produced by black walnut (Juglans nigra)
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Allelochemicals can suppress plant growth directly or indirectly
Reprinted with permission from Bertin, C., Weston, L.A., Huang, T., Jander, G., Owens, T., Meinwald, J. and Schroeder, F.C. (2007). Grass roots chemistry: meta-Tyrosine, an herbicidal nonprotein amino acid. Proc. Natl. Acad. Sci. USA 104: 16964-16969, copyright National Academy of Sciences.; Victoria Nuzzo, Natural Area Consultants, Jil Swearingen, USDI National Park Service, Bugwood.org; See also Callaway, R.M., et al., (2008). Novel weapons: Invasive plant suppresses fungal mutualists in America but not in its native Europe. Ecology. 89: 1043-1055.
m-tyrosine is a nonprotein amino acid from fescue (Festuca spp) roots, that
inhibits plant growth directly
Alliaria petiolata (garlic mustard) is an invasive plant in the US that indirectly suppresses plant growth through the inhibition of their mycorrhizal fungal symbionts
© 2013 American Society of Plant Biologists
Summary: Plants compete belowground
©2011 David Graber
The Monterey manzanita (Arctostaphylos montereyensis) suppresses competitors through allelopathy
Besides resource competition, the best understood form of belowground competition is the production of toxic or inhibitory allelochemicals
Additional cues likely contribute to belowground interactions
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Is that me?
Plants can respond differently to self, kin and alien
You seem familiar…
Photo credits: Tom Donald
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Do plants respond differently to relatives and unrelated plants?
Reprinted with permission from Fang, S., Clark, R.T., Zheng, Y., Iyer-Pascuzzi, A.S., Weitz, J.S., Kochian, L.V., Edelsbrunner, H., Liao, H. and Benfey, P.N. (2013). Genotypic recognition and spatial responses by rice roots. Proc. Natl. Acad. Sci. USA 110: 2670-2675.
Same genotype: More overlap Different genotype: Less overlap - avoidance
YES- This study showed that roots tend to avoid roots of plants that are not related
© 2013 American Society of Plant Biologists
Do roots discriminate self from non-self?
Yes, plants discriminate self from non-self. Plant B, competing with non-self, makes ~50% more root mass than plant A, competing only with self
A B
Reprinted with permmission from Falik, O., Reides, P., Gersani, M. and Novoplansky, A. (2003). Self/non-self discrimination in roots. J.Ecology. 91: 525-531. Reprinted with permission from Gruntman, M. and Novoplansky, A. (2004). Physiologically mediated self/non-self discrimination in roots. Proc. Natl. Acad. Sci. USA 101: 3863-3867 copyright National Academy of Sciences USA.
These studies showed more root growth in the presence of “other” than “self”. What cues and signals are involved?
Yes, When cuttings that originate from the very same node are separated, they become progressively alienated from each other and relate to each other as genetically alien plants
© 2013 American Society of Plant Biologists
S/NS may rely on self recognition, rather than on NS discrimination
Reprinted with permission from Falik, O., Reides, P., Gersani, M. and Novoplansky, A. (2003). Self/non-self discrimination in roots. J. Ecol. 91: 525-531.
INTACT TWINS“Double plants” were produced with two shoots and two roots. Some double plants were split, to make “twins”. Some of the split plants were paired up with an unrelated alien. Does a plant recognize self without a physiological connection?
ALIEN
Split pea “Twins” and alien make more roots than intact peas, indicating that physiological connections are important for recognizing “self”
Split pea “Twins” and alien make more roots than intact peas, indicating that physiological connections are important for recognizing “self”
Spatially, intact peas produced more roots toward nonself than toward self roots. Pairs of severed plants developed similarly towards their neighbors, regardless of whether these neighbors were their own twins or alien
© 2013 American Society of Plant Biologists
Case study: Parasitic plants are extreme competitors
HeavyModerateLight
Striga asiaticaStriga hermonthica
Adapted from Ejeta, G. and Gressel, J. (eds) (2007) Integrating new technologies for striga control: towards ending the witch-hunt. World Scientific Publishing, Singapore; Image sources: USDA APHIS PPQ Archive, Florida Division of Plant Industry Archive, Dept Agriculture and Consumer Services.
•Parasitic plants cost approximately 10 billion USD in crop losses annually
•They infest major cereal crops including corn, sorghum, millet and rice, in over 70 million hectares
•Food production for 300 million people is affected
•No effective control measure has been developed
Parasitic Striga
infestation
© 2013 American Society of Plant Biologists
Parasitic plants perceive their hosts through chemical cues
Reprinted from Runyon, J.B., Mescher, M.C. and De Moraes, C.M. (2006). Volatile chemical cues guide host location and host selection by parasitic plants. Science. 313: 1964-1967 with permission from AAAS. Umehara, M., Hanada, A., Yoshida, S., Akiyama, K., Arite, T., Takeda-Kamiya, N., Magome, H., Kamiya, Y., Shirasu, K., Yoneyama, K., Kyozuka, J., and Yamaguchi, S. (2008). Inhibition of shoot branching by new terpenoid plant hormones. Nature 455: 195-200 Dörr, I. (1997). How Striga parasitizes its host: a TEM and SEM study. Ann. Bot. 79: 463-472, by permission of Oxford University Press.
Host-exuded strigolactones and flavonoids promote germination and attachment of Striga and other parasitic plants
Host root
Striga
Cuscuta pentagona (dodder) uses tropisms, touch and volatile cues, to locate its hosts
© 2013 American Society of Plant Biologists
Facilitative behaviors: Plants benefitting from their neighbors
Tempering of harsh abiotic environments
Enhancing nutrient uptake
Stress cues can induce anticipatory responses
Walder, F., Niemann, H., Natarajan, M., Lehmann, M.F., Boller, T. and Wiemken, A. (2012). Mycorrhizal networks: common goods of plants shared under unequal terms of trade. Plant Physiol. 159: 789-797.
© 2013 American Society of Plant Biologists
Reprinted by permission from Macmillan Publishers Ltd from Callaway, R.M., Brooker, R.W., Choler, P., Kikvidze, Z., Lortie, C.J., Michalet, R., Paolini, L., Pugnaire, F.I., Newingham, B., Aschehoug, E.T., Armas, C., Kikodze, D. and Cook, B.J. (2002). Positive interactions among alpine plants increase with stress. Nature. 417: 844-848.
Benefit from others is commonly higher in harsher environments
In harsher, high-elevation environment, plants whose neighbors were removed fared relatively poorly, indicating that they benefited from their neighbors
© 2013 American Society of Plant Biologists
Plants can protect others from harsh abiotic and biotic environments
Images used by permission of Lohengrin A. Cavieres, Fernando T. Maestre, Pierre Liancourt, and Georges Kunstler. See Brooker, R.W et al. . (2008). Facilitation in plant communities: the past, the present, and the future. J. Ecol . 96: 18-34,.
High AndesBuffered substrate and air temperature, enhanced soil moisture and nutrient content
Semi-arid plains of SpainProtection from drought
Southern FranceProtection from browsing
Semi arid environment, Jordan Protection from browsing and drought
© 2013 American Society of Plant Biologists
Plants can benefit from amelioration of abiotic stresses by their
neighbors• Wind breaking• Increased retention of soil
moisture• Improved physical
characteristics of soil • Increased soil
oxygenation in water-logged environments
• Increased nutrients• Decreased evaporation
and soil salinity
Photo credits: Tom Donald, Joy Viola, Northeastern University, Bugwood.org
Palo verde (Parkinsonia spp) can act as a “nurse plant” for saguaro cactus (Carnegiea gigantean). Tiny cactus seedlings need shade to get established. Often, though, the cactus later outcompetes its nurse plant
© 2013 American Society of Plant Biologists
Intercropping and crop rotation confer many benefits
Different crown heights can
accommodate different light requirements
Different root distributions can minimize competition for nutrients
The total yields of fields grown with two or more species at the time or in alternating years can be higher than the most productive monocultures
Legumes increase
nitrogen content of soil
Ground-hugging plants can suppress weeds
Rotating crops reduces pest populations
See Horton, J.L. and Hart, S.C. (1998). Hydraulic lift: a potentially important ecosystem process. Trends Ecol. Evol. 13: 232-235. Lee, J.-E., Oliveira, R.S., Dawson, T.E. and Fung, I. (2005). Root functioning modifies seasonal climate. Proc. Natl. Acad. Sci. USA. 102: 17576-17581.
© 2013 American Society of Plant Biologists
Walder, F., Niemann, H., Natarajan, M., Lehmann, M.F., Boller, T. and Wiemken, A. (2012). Mycorrhizal networks: common goods of plants shared under unequal terms of trade. Plant Physiol. 159: 789-797.
A common mycorrhizal network can facilitate resource sharing
Flax SorghumMixed
Intercropping with sorghum drastically enhanced flax’s growth (+46% increase). Nutrient uptake was facilitated via the common mycorrhizal network (CMN)
© 2013 American Society of Plant Biologists
Case study: Community-level effects of phenotypic plasticity
Republished with permission of Ecological Society of America from Callaway, R.M., Pennings, S.C. and Richards, C.L. (2003). Phenotypic plasticity and interactions among plants. Ecology. 84: 1115-1128; See also Callaway, R.M., Nadkarni, N.M. and Mahall, B.E. (1991). Facilitation and interference of Quercus douglasii on understory productivity in central California. Ecology. 72: 1484-1499.
How does phenotypic plasticity and facilitation affect other community members?
Variation in root architecture affects the plant communities associated withQuercus douglasii; only shallow-rooted trees compete with grasses
© 2013 American Society of Plant Biologists
Cues from other plants can prime plants for defense or tolerance
Reprinted from Glinwood, R., Ninkovic, V. and Pettersson, J. (2011). Chemical interaction between undamaged plants – Effects on herbivores and natural enemies. Phytochemistry. 72: 1683-1689 with permission from Elsevier. Photo credits: Snowmanradio, Justin Johnsen, D. Gordon E. Robertson
Alarm signals are well described in social animals. Stressed plants may emit cues to which other plants respond Be
prepared
cues
cues
© 2013 American Society of Plant Biologists
Induction and priming of defense responses
Volatile emission
Stomatal closure
Perception of and responses to stress and stress cues
Mechanical damage
Herbivore-derived chemicals
Pathogens
Drought or UV light
Volatile compounds
Root exudates
Genomic instability
Other?
© 2013 American Society of Plant Biologists
Sagebrush (Artemisia tridentata)
Wild tobacco (Nicotiana attenuata)
Volatile compounds from damaged plants can initiate defenses in others
Karban, R., Baldwin, I.T., Baxter, K.J., Laue, G. and Felton, G.W. (2000). Communication between plants: Induced resistance in wild tobacco plants following clipping of neighboring sagebrush. Oecologia. 125: 66-71. see also Kessler, A., Halitschke, R., Diezel, C. and Baldwin, I. (2006). Priming of plant defense responses in nature by airborne signaling between Artemisia tridentata and Nicotiana attenuata. Oecologia. 148: 280-292. Photo courtesy Ian Baldwin Copyright Max Planck Institute for Chemical Ecology, Jena, Germany / Rayko Halitschke
When nearby sagebrush was mechanically damaged, wild tobacco increased production of defense compounds (PPO) and suffered less herbivore damage
Volatile compounds emitted by damaged
plants can induce defenses in their
neighbors
Volatile compounds emitted by damaged
plants can induce defenses in their
neighbors
The signal(s) travel through air
© 2013 American Society of Plant Biologists
What are the active compounds and how far do they spread?
Reprinted from Baldwin, I.T., Halitschke, R., Paschold, A., von Dahl, C.C. and Preston, C.A. (2006). Volatile signaling in plant-plant interactions: "Talking Trees" in the genomics era. Science. 311: 812-815 with permission from AAAS.
methacrolein cis-3-hexenal
MeJA
trans-2-hexenal
cineole
© 2013 American Society of Plant Biologists
Why do plants emit volatile signals?
Reprinted from Arimura, G.-i., Shiojiri, K., and Karban, R. (2010). Acquired immunity to herbivory and allelopathy caused by airborne plant emissions. Phytochemistry 71: 1642-1649 with permission from Elsevier, see also Heil M, Karban R (2010) Explaining evolution of plant communication by airborne signals. Trend Ecol Evol 25: 137–144.
• Volatile signals may have evolved for intra-plant communication
• Having defensive neighbors can enhance the emitter’s fitness
• Some volatiles are also inhibitory allelochemicals that reduce competition
• Some volatiles promote indirect defenses by acting as signals to attract predatory arthropods
© 2013 American Society of Plant Biologists
Case study: Plants may also communicate drought stress
Drought, high salt
?
Stressed Oblivious
Can other stresses be communicated between plants?Can unstressed plants respond to stress cues emitted from their stressed neighbors?
Novoplansky, A. (2012) Learning plant learning.
© 2013 American Society of Plant Biologists
Testing for root-to-root and relay communication
Novoplansky, A. (2012) Learning plant learning.
© 2013 American Society of Plant Biologists
Stress cue moves from the stressed plant via the roots
Stomatal aperture was measured in plants without a soil connection and plants whose roots share soil with the induced (IND) plant
Falik O, Mordoch Y, Quansah L, Fait A, Novoplansky A (2011) Rumor has it…: Relay communication of stress cues in plants. PLoS ONE 6(11): e23625. See also Falik, O., Mordoch, Y., Ben-Natan, D., Vanunu, M., Goldstein, O. and Ariel Novoplansky (2012) Plant responsiveness to root-root communication of stress cues, Ann. Bot., 110: 271-280.
Before treatment all the plants had the same stomatal width
After treatment, stomatal aperture was reduced in plants whose roots were in contact (directly or indirectly) with the stressed plant
No response in plants that did not share their rooting volume
© 2013 American Society of Plant Biologists
Summary: Cooperative and facilitative behaviors
Plants can benefit from other plants, which can• Modulate the abiotic environment, • Facilitate nutrient uptake, and• Emit cues that prime for stress
Like competition, facilitative encounters occur between and within species
Photo credit: Tom Donald
© 2013 American Society of Plant Biologists
Putting knowledge to work
Water hyacinth (Eichhornia crassipes)
Photo credits: Ted Center, USDA; William M. Ciesla, Forest Health Management International; John D. Byrd, Mississippi State University; Howard F. Schwartz, Colorado State University,
Leafy spurge (Euphorbia esula) Kudzu
(Pueraria montana var. lobata)
Understanding plant behavioral responses can contribute to combatting highly competitive invasive species…
And to developing novel crop combinations, such as the intercropping of dry beans, coffee and papaya near Palmira, Colombia
© 2013 American Society of Plant Biologists
Do invasive plants have shared phenotypes?
Davidson, A.M., Jennions, M. and Nicotra, A.B. (2011). Do invasive species show higher phenotypic plasticity than native species and, if so, is it adaptive? A meta-analysis. Ecolo.Lett. 14: 419-431. Godoy, O., Valladares, F. and Castro-Díez, P. (2011). Multispecies comparison reveals that invasive and native plants differ in their traits but not in their plasticity. Funct. Ecol. 25: 1248-1259. Jil Swearingen, USDI National Park Service,
C EDBA
Are invasive plants more plastic, and so more able to succeed in diverse environments?
Some invasive plants show greater than average phenotypic plasticity, but many do not.
Some invasive plants succeed by making lots of small seeds, growing very quickly, producing allelochemicals, or competing effectively for water or nutrients
Kudzu (Pueraria lobata), also known as “The vine that ate the South”
© 2013 American Society of Plant Biologists
Case study: Knotweed, “from prize-winners to pariahs”
See Bailey, J. P., and Conolly, A. P. (2000). Prize-winners to pariahs - a history of Japanese knotweed s.l. (Polygonaceae) in the British Isles. Watsonia 23: 93-110; Murrell, C., Gerber, E., Krebs, C., Parepa, M., Schaffner, U. and Bossdorf, O. (2011). Invasive knotweed affects native plants through allelopathy. Am. J. Bot. 98: 38-43, Richards, C.L., et al., (2008). Plasticity in salt tolerance traits allows for invasion of novel habitat by Japanese knotweed s. l. (Fallopia japonica and F.×bohemica, Polygonaceae). Am. J. Bot. 95: 931-942. Photo credit Fallopia japonica MdE 2.jpg, © MdE at Wikimedia Commons, CC-BY-SA 3.0 German.
Prize-winnersIn 1847, the Society of Agriculture & Horticultureawarded a gold medal to Fallopia japonica, “for the most interesting new ornamental plant of the year”
PariahsNow they are one of the most aggressive plant invaders, and cause considerable economic and ecological damage.
Allelochemical production and rapid growth rate contribute to their ecosystem dominance
Knotweed shows a highly plastic response to salt, which allows it to succeed in salty environments
© 2013 American Society of Plant Biologists
Case study: Backfiring biocontrol of invasive knapweed?
See Callaway, R.M., DeLuca, T.H. and Belliveau, W.M. (1999). Biological-control of herbivores may increase competitive ability of the noxious weed Centaurea maculosa. Ecology. 80: 1196-1201; Knochel, D.G. and Seastedt, T.R. (2010). Reconciling contradictory findings of herbivore impacts on spotted knapweed ( Centaurea stoebe) growth and reproduction. Ecol. Appl. 20: 1903-1912.Photo credits: L.L. Berry, Bugwood.org; USDA Agricultural Research Service Archive, Bugwood.org; Steve Dewey, Utah State University, Bugwood.org
Spotted knapweed (Centaurea stobe ssp. micranthos / Centaurea maculosa) was introduced into North America in the 1890s. It is a “noxious weed” that competes very effectively with native plants
Agapeta zoegana
Starting in the 1980s, the specific herbivore knapweed root moth has been introduced as a biocontrol agent, with mixed results
Herbivory may induce allelochemical production, further harming native plants – a case of biocontrol backfiring!
© 2013 American Society of Plant Biologists
Case study: Maize, bean, squash – the three sisters
Photo credit: Howard F. Schwartz, Colorado State University, Bugwood.org; Reprinted from Postma, J.A. and Lynch, J.P. (2012). Complementarity in root architecture for nutrient uptake in ancient maize/bean and maize/bean/squash polycultures. Ann Bot. 110: 521-534 by permission of Oxford University Press.
Archeological records show that Native Americans have grown corn, beans and squash together for millennia
The corn provides a structure for the climbing bean vines, and the ground-covering squash maintains soil moisture and suppress weeds
A recent study found that the root systems of the three plants are complementary, minimizing belowground competition
Maize Bean Squash
© 2013 American Society of Plant Biologists
Case study: Push-pull planting systems to enhance productivity
Pests are a particular problem in tropical agriculture. An agronomic system called push-pull was developed to protect corn crops from stem borer caterpillars
See Hassanali, A., Herren, H., Khan, Z.R., Pickett, J.A. and Woodcock, C.M. (2008). Integrated pest management: the push–pull approach for controlling insect pests and weeds of cereals, and its potential for other agricultural systems including animal husbandry. Phil. Trans. R. Soc. B 363: 611-621; Pickett, J.A., Hamilton, M.L., Hooper, A.M., Khan, Z.R. and Midega, C.A.O. (2010). Companion Cropping to Manage Parasitic Plants. Annu. Rev. Phytopath. 48: 161-177. Push-pull.net
This involves intercropping maize with a legume Desmodium, in a field surrounded by Napier grass (Pennisetum purpureum)
© 2013 American Society of Plant Biologists
Case study: Push-pull planting systems to enhance productivity
Reprinted from Khan, Z.R., Midega, C.A.O., Bruce, T.J.A., Hooper, A.M. and Pickett, J.A. (2010). Exploiting phytochemicals for developing a ‘push–pull’ crop protection strategy for cereal farmers in Africa. J. Exp. Bot. 61: 4185-4196, by permission of Oxford University Press.
Desmodium also produces allelochemicals that interfere with Striga parasitism, protecting the crop from yet another pest
Desmodium PUSHES away the insects by producing repellent volatile chemicals
Napier grass PULLS away the insects by producing attractive volatile chemicals
© 2013 American Society of Plant Biologists
Case study: Allelopathic rice plants
Image source: IRRI. Belz, R.G. (2007). See also Allelopathy in crop/weed interactions — an update. Pest Management Science. 63: 308-326.
Momilactones are allelopathic compounds produced by rice that interfere with the growth of a common paddy weed, barnyard grass (Echinochloa crus-galli)
Momilactone B
Efforts are underway to increase momilactone production in cultivated rice varieties, to reduce the need for herbicide use and mechanical weed removal
© 2013 American Society of Plant Biologists
Case study: Exploiting light-response plasticity for increased productivity
Greenhouse covers, including a fluorescent pigment that absorbs some of the blue and green sunlight and emits additional red light, increases the ratio between RED and FAR-RED light.
In response to such spectral cues, some plants reduce their allocation to competitive organs and increase allocation to agriculturally-important organs such as flowers and fruits. LEDs can produce similar effects.
Novoplansky, A., T. Sachs, D. Cohen, R. Bar, J. Budenheimer and R. Reisfeld (1990) Increasing plant productivity by changing the solar spectrum. Solar Energy Materials 21: 17-23. See also Stamps, R.H. (2009). Use of colored shade netting in horticulture. HortScience. 44: 239-241. .
© 2013 American Society of Plant Biologists
Partially adapted from Cahill, J.F. and McNickle, G.G. (2011). The behavioral ecology of nutrient foraging by plants. Annu. Rev. Ecol. Evol. System. 42: 289-311.
Summary of plant-plant interactions
A plant’s phenotype depends on its genotype and environment, and relies on its plasticity. The environment includes cues from and interactions with other plants, many of which we are just beginning to understand, and which continue to be very active research areas
A plant’s phenotype depends on its genotype and environment, and relies on its plasticity. The environment includes cues from and interactions with other plants, many of which we are just beginning to understand, and which continue to be very active research areas
Plasticity
Stochasticity
Fixed development
Phenotype Ecological interactions
Local conditions
Genotype
Cues from other plants
Interactions with other
plants
Biodiversity
Ecosystem functioning
Plant production and
agriculture
Evolution
© 2013 American Society of Plant Biologists
Reprinted from Kegge, W. and Pierik, R. (2010). Biogenic volatile organic compounds and plant competition. Trends Plant Sci. 15: 126-132 with permission from Elsevier.
Summary of plant-plant interactions
Plants perceive other plants through changes in the light spectrum, volatile and root-exuded chemicals, effects on nutrients, water and soil microbes, and other unknown signals
Their responses depend on their age, genotype and other endogenous and exogenous factors, and may include confrontation, avoidance or tolerance
© 2013 American Society of Plant Biologists
Future directions (1)
Aggressive aliens, moved by human actions, damage ecosystems
Can fragile ecosystems and biological diversity be protected by better understanding plant – plant interactions?
Can fragile ecosystems and biological diversity be protected by better understanding plant – plant interactions?
Japanese knotweed(Fallopia japonica )
Giant hogweed(Heracleum mantegazzianum)
Photo credits: Fallopia japonica MdE 2.jpg, © MdE at Wikimedia Commons, CC-BY-SA 3.0 German. Randy Westbrooks, U.S. Geological Survey
© 2013 American Society of Plant Biologists
Future directions (2)
David Nance USDA ARS Bugwood.org
Can food yields be increased by suppressing competition and competitive responses, enhancing facilitation and increasing production of desired organs?
Can food yields be increased by suppressing competition and competitive responses, enhancing facilitation and increasing production of desired organs?
• Human population growth demands more food production, and higher crop yields
• Plant-plant interactions can decrease yields, but these effects can be ameliorated
© 2013 American Society of Plant Biologists
Future directions (3)
Can crop yields be increased, especially in marginal agricultural land, by inducing and priming plants to better fit their particular expected growth conditions, forthcoming opportunities and stresses?
Can crop yields be increased, especially in marginal agricultural land, by inducing and priming plants to better fit their particular expected growth conditions, forthcoming opportunities and stresses?
J.S. Quick, Bugwood.org