Reading Questions 1) Why have roots been studied so much less than the above-ground components of plants?2) What was the “Green Revolution” and why does Dr. Lynch think ”roots are the key to a second green revolution”?3) How did crop breeders accomplish most of the yield gains achieved during the 20th century and how does Dr. Lynch think they should shift their focus? 4) The article discusses 4 promising strategies for root research under theheadings “Designer roots”, “Stealth scavengers”, “Microbial manipulations” and “A healthy fixation”. For each of the 4 research strategies, describe (in your own words), something that you thought was particularly interesting.5) If you had an opportunity to be involved with innovative root research (e.g., as an intern at a lab or a farmer trying a new technology), briefly describe what you would like to try. Submit your answers to the these questions using WO before the start of class on Friday 8/31.
Have you ever taken the timeto look closely at crop roots?
What should you look for? extensive white color growth into Healthy shoot growth the sub-soilproliferate and high minimal in all yields evidence ofdirections deformities Efficient use of soil resources
Getting dirty with 2 champions of Vertical Farming Francis ChildsRay Rawson VF = Management system for optimum root extension and function
Ken Ferrie inspectingcorn roots on a farm in central IL.
"One of our primary goals is to get the first three sets of crown roots deep intothe soil… In vertical-tillage, no-till or strip-tillconditions, the first set of crown roots will go down. But, when we do horizontal tillage before planting, except in a few conditions like sand, no matter what we did in the fall, the first two sets of crown roots almost always turn on the dense layer. Hopefully, with fall vertical tillage, the third set will penetrate.“Ken Ferrie – Farm Journal, September 2006
You really won’t know what is happening underground unless you take a look…
All you need is a shop-vac and a hose :-> !Its just like going to the dentist!
Understanding corn root developmentThe seed roots stopgrowing shortly after the coleoptile emerges from the soil surface. The nodal root system becomes visible at ~ V1. The nodal root system becomes the dominant system by V6.
Have you ever heard of “floppy corn” or “rootless corn” syndrome? Where are the nodal roots?
“Floppy corn” or “rootless corn” occurs when surface soil is toodry for healthy elongation of roots from the first node (V2 to V4). Young roots emerging from the first node will die if themeristematic tissue desiccates prior to extension into moist soil. The crown of a young corn plant is typically located only 3/4 inch or so below the soil surface and so is particularly vulnerable to dry upper soil conditions.
4 weeks Corn root development documented in the 1920s If this was possible 90 8 weeks years ago, just think what is possible today? 16 weeks Crops grown on modern rowspacings generally do not grow such wide root systems 7 feet deep !!
Wading pool gardens in my back yard How is it possible for healthy crops to grow with such a limited rooting volume?
Watermelon roots that grew in a wading poolWading pools do NOT provide an optimal rooting zone but a small root system can support healthy shoot growth with adequate moisture and nutrition.
All you need to do to grow healthy corn rootsis use rootworm resistant genetics… right??When rootworm pressure is high, rootworm resistant genetics normally result in much healthier roots
Rootworm resistant genetics are not a silver bullet ! Severe damage by corn rootworm larvae to roots of a biotech corn rootworm hybrid http://www.ipm.iastate.edu/ipm/icm/2006/11-13/btcorn.html
A significant correlation was found between the number of years Cry3Bb1 corn had been grown in a field and survival of western corn rootworms. Interviews withfarmers indicated Cry3Bb1 corn had been grown for at least three consecutive years in all of the fields containing resistant corn borers. The researchers concluded insufficient planting of refuges and non-recessive inheritance of resistance is likely to have contributed to the development of resistance.They noted a 2009 study done by the Center for Science in the Public Interest indicated only 50% of Bt maize planted in Midwest complied with EPA requirements for refuge size and proximity to Bt fields. http://cornandsoybeandigest.com/blog/bt-resistant-corn-borers-spur-concerns
“Most important, though, for effective corn rootwormmanagement is to consider a long-term, integrated approachthat includes multiple tactics, such as adult suppressionprograms, use of soil insecticides at planting, rotation of Bthybrids that express different Cry proteins, and rotation tononhost crops.Many producers have relied on a single tactic for too manyyears, and unfortunate consequences are beginning to emerge.As harvest gets under way this fall, I suspect that moreproducers in northwestern Illinois will encounter lodged cornthat has been severely damaged by western corn rootworms.As I learn more about this evolving situation, I will keep youinformed”.Mike Gray – U of I Extension Entomologist - 2011
In North and South America, corn rootworms are attacked by many pathogens, predators and parasitoids, some of which are specialized natural enemies of corn rootworms. European entomologists are studying natural predators of corn rootworms (collected from soils in N. and S. America) for use incontrolling corn rootworms in Europe (where rootworms are not native)
Studies have shown thatmany of the natural enemiesof CRW are more common inreduced-tillage systems, andin fields with higher levels of organic matter.
Journal of Economic EntomologyArticle: pp. 330-339 | Abstract | PDF (1.44M)Disruption of Host Location of Western Corn Rootworm Larvae withCarbon DioxideE. J. Bernklau, E. A. Fromm, and L. B. BjostadDepartment of Bioagricultural Sciences and Pest Management, ColoradoState University, Fort Collins, CO 80523Elevated concentrations of carbon dioxide (CO2) prevented western cornrootworms from locating the roots of growing corn in behavioral bioassaysconducted in soil tubs. When CO2 was pumped into one end of a soil tub,significantly more larvae were recovered from soil at the treated end thanfrom soil around a growing corn plant at the opposite end of the tub. Incontrols with ambient air pumped into one end of a soil tub, significantlymore larvae were recovered from the soil around the corn plant than fromsoil on the treated side. Larvae were unable to locate the roots of cornseedlings when CO2-generating materials were mixed into the soil.
When damaged by corn rootworms, the roots ofsome corn plants release a chemical called (E)-β-caryophyllene that recruits an entomopathogenic nematode (Heterorhabditis megidis) to feed on corn rootworms. Modern corn breeding has resulted in loss of the (E)-β- caryophyllene signal in many hybrids, reducing their ability to recruit H. megidis. Under field conditions, the infection rate of corn rootworms with H. megidis were found to be 5x higher on a corn variety producing the below-ground signal than on a variety that doesnot. Moreover, spiking the root system of a non-producing variety with synthetic (E)-β-caryophyllene decreased the emergence of corn rootworm adults by > 50%.
The root promoting effects of soil biology are underappreciated
Dramatic effect of steamsterilization and compost on growth of pepper plants
competition parasitism Don’t forget that soil biology can both promote and inhibit crop root growth and functionantibiosis induced resistance
This unfortunately is the norm in agriculture Acute root VS.disease Chronic root malfunction Chemical, physical and biological factors can cause CRM!
Chemical toxicities caninhibit root growth & function Aluminum toxicity Aluminum toxicity Al toxicity is very common in the SE US and in tropical countries like Brazil Brady and Weil
Understanding aluminum toxicity Fe and Mn toxicities also occur at lower pHs Toxic forms of Al are bioavailable at pHs < 5.5 Aluminum toxicity is minimal above a water pH of 5.5 http://www2.ctahr.hawaii.edu/tpss/research_extension/rxsoil/alroot.gif
What damaged these corn roots? Boron was included in starter fertilizer
On-line tool for estimating maximum rates of in-row fertilizer Damage is most likely in dry coarse textured soilshttp://www.sdstate.edu/ps/soil-lab/loader.cfm?csModule=security/getfile&PageID=788496
N and P promote root branching and proliferationhttp://www.naicc.org/meeting/2011/In%20Reduced%20Tillage%20-Vocasek.pdf
Soil block system for growing transplants Air pruning promotes root branching
Why do crops on tiled-drained land tend to be more drought resistant ?Ontario Ministry of Ag and Food
Do crop roots grow toward water? Roots elongate directed by gravity in aerobic soil!Ontario Ministry of Ag and Food
Soil aeration affects soil temperaturewhich strongly affects rate of root growth http://www.naicc.org/meeting/2011/In%20Reduced%20Tillage%20-Vocasek.pdf Soil can get too hot for optimal root growth!
Compaction strongly impacts root growth and function Sub-soil water and nutrients Brady and Weil (2002) Brady and Weil (2002)
What causes sidewall compaction? Waiting for drier soilis the most important solution
Tillage systems affect root growth and function Adapted from Hunt et al. (1986)
Long term no-till (w/ healthy soil biology) Intensive tillage Network Plow pan of cracks and bioporesOntario Ministry of Ag and Food
Why are healthy roots so important? Roots perform many valuable functions !
In addition to the most obvious functionsphysical support and uptake of water and nutrients ROOTS are: Carbon pumps that feed soil organisms and contribute to soil organic matter Energy and nutrient storage organs Chemical factories that change soil pH, poison competitors, filter out toxins, concentrate rare elements, etc. A sensor network that helps regulate plant growth
What’s Macro-missing anatomy of roots if this was a cornplant?
Micro-anatomy of rootshttp://www.sparknotes.com/biology/plants/plantstructures/section2.rhtml
Physical protection source of lubrication, & sensor of gravityWhat is the function of the root cap?
What is the function of root hairs?• Increased surface area for uptake of water and nutrients• Anchoring of roots allowing root extension
The cell wall of the endodermis (pink inner strip of cells) is waterproofed by theCasparian strip, which forces water to enter the symplast before it can enter theroot xylem phloem root hair xylemepidermis endodermis cortex
Apoplast vs. symplastThe movement of fluids from the root hairs to the xylemcan occur through one of two conductive pathways– theapoplast and the symplast.The apoplast route consists of inter-cellular spaceswithin the root cortex along which water and solutes candiffuse.The symplast route consists of channels through cellsalong which water and solutes are actively transported.
K+ H+ - The pH of a plant’s NO3 rhizosphere changes as the plant regulates itsH+ internal charge balance.
Which plant received nitrate (NO3-)?Which plant received ammonium (NH4+)? http://departments.agri.huji.ac.il/plantscience/topics_irrigation/uzifert/4thmeet.htm
The ins and outs of plant nutrition H20 Root exudates N, S, P activate soil microbes Transpirational Root growth stream H 20 Diffusion Microorganisms produce most but not all of theenzymes need to digest OM
Plants take up mostly inorganic forms of nutrientswhen inorganic forms of nutrients are readily available In some natural ecosystems (e.g., tundra), organic forms of nutrients are very important
Why does water move up into plants?Water moves upward through plantswhenever there is anegative gradient ofwater potential along the soil-plant- atmosphere continuum
H20A continuous Solar energychain of water drives the molecules is process pulled up through the Plants provide plant the conduit H20 H20 H20
Rhizosphere Roots normallyoccupy < 1% of topsoil volume The rhizosphere is normally << 10 % of Zone of root topsoil volume influence
Navigating the rhizosphere End of the Rhizoplane rhizosphere Endo- Rhizosphere Ecto-RhizosphereMicrobial activity > 90% < 10% of soil volume of soil volume A few millimeters (Lavelle and Spain, 2001)
Subterranean clover* Inoculation groups for commonly grown legumes White clover Cowpea Group Alyceclover (Bradyrhizobium japonicum spp.) Cowpea Kudzu Peanut Lespedeza Joint vetch Lupine Group Blue lupine (Rhizobium lupini) White lupine Pea and Vetch Group Bigflower vetch (Rhizobium leguminosarum) Common vetch Hairy vetch Roughpea Winter pea Other** Bird’s-foot trefoil (Rhizobium loti) Cicer milk vetch Crown vetch Sainfoin (Rhizobium)Soybean has its own inoculation group!! Soybean (Rhizobium japonicum) Kura clover Leucaena
How much N do soybeans fix and how much of this N is left behind after harvest? N -N A good soybean crop will fix >150 lbs of N/ac but>200 lbs of N may be removed in the harvested beans.
2 main types of mycorrhizal associations Ectomycorrhizae AM endomycorrhizaeArbutoidmycorrhizae Ericoid endomycorrhizae Orchid endomycorrhizae Lavelle and Spain (2001)
Mycorrhizal Networks: Connecting plants intra- and interspecifically •Many plants are connected underground by mycorrhizal hyphal interconnections. •Mycorrhizal (AM) fungi are not host specific.Illustration by Mark Brundrett
Increase nutrient (P) uptake suppress pathogens Mediate plant competition Improve soil structure Glomalin Superglue of the soil ??
There are many mycorrhizal inoculants on themarket and growing evidence that they can increase cropperformance but it isimportant to keep inmind that they are a much less proven technology than legume inoculants
Some of the most dramatic responses to mycorrhizal inoculation occur during reforestation projects
Have you ever wondered how far out tree roots extend? ?
Tree roots often extend >2 times farther than the canopy