Dear Tyler,

Which plant are you working with?

Dr. NL

Crops, mainly (e.g., maize, sorghum, soybean)

You can try with plant agar, placing the plates vertically to favor geotropism and normal root developmet.

Good luck!

@Marcos Augusto Lima Nobre, I appreciate the recommendation towards suspended root systems; however, I am more interested in root development in something close to in situ, therefore I am trying to move towards a material that adds some amount of resistance (as well as support) to root growth. Also, it is my opinion that thermal imaging tends to be expensive. Otherwise, it is a very useful tool.

@Elisa Graña, I have seen gellan gum to successfully suspend root systems; however, rice seems to be the only plant that takes well to this type of growing environment.

hi tyler w davis,

following links might serve your purpose:

https://www.researchgate.net/publication/234089315_High-throughput_noninvasive_imaging_of_root_systems

http://www.plantphysiol.org/content/early/2010/01/27/pp.109.150748.full.pdf

Article High-Throughput, Noninvasive Imaging of Root Systems

@Pardha Saradhi Attuluri, thanks for the links. It looks like gels are the medium of choice. I am still on the lookout for thin rigid materials.

Dear Tyle,

The only suggestion to this scientific puzzle is consider that roots grow in darkness environments which mean that you need two environments: one for above ground plant growth and other for root growth. In my opinion, and only opinion is possible in the current case, is to pay attention in the vegetative growth of the plant where the constraints will be attached. First, create an environment with perfect weather condition above-ground to favor the root/shoot ratio and avoid the lodging of the vegetative part of the species (Only a phytotron allows such environment). Fertilizers may be supplied by spraying nutritive solution to the vegetative part of the species. Be careful with plant etiolating because it will change the root/shoot ratio.

Now, the most difficult part: First, produce the seedlings in containers containing sand, but only during the period in which the seed reserves can supply the seedlings. Transplant these seedlings to the top the apparatus to grow the radicular system. Divide the root growth environment in two parts: the first part, close to the surface with no more than 5 cm must be separated from the whole system where the deep end of this first part is supported by a net made of inert material. In this upper part it is possible to have an inert growing medium to supply part of the root growth. The darkness avoids some typical chemical reactions in presence of light. The roots have to growth through the net, and they do it. Below the net, all the space is empty. Non-mobile nutrients required by the root system can be supplied by spray systems set up at the deep end of the apparatus, but spraying up to the radicular system. How many times, quantity and so on must be calculated. This radicular system can be photographed by cheap cameras available in the market using holes that can be open in the apparatus when necessary.

Finally, made a prototype to correct the mistakes (the choice of the net mesh, for example) and calculate the costs. Details you will see during the work, and will correct them. Testing five pieces, you can apply an Exploratory Data Analysis for your safety. You can believe me because during my professional life a saw similar systems working despite my objectives were completely different.

My best regards.

José Walter

@José Walter Pedroza Carneiro, thank you for your suggestions. I will keep these in mind as I prototype my system.

@Stephany Guataquira, I have looked into glass beads (or balls). My only concern is that the glass beads can hold some level of static charge on their surface. Also, while they are optically transparent, they introduce complicated distortions/refractions.

I have heard of certain types of fishing line that are supposed to be optically clear in water. I have considered building a type of "web" using such a material.

@Stephany Guataquira, I forgot all about magic sand! I need to check what chemical compounds they use to make it hydrophobic to make certain it can last days to weeks in solution without degrading. 

Sand is a bit too compact. Turface MVP is the solution to your root problem! It is typically used for drying out baseball fields after rain; Turface is essentially baked clay, no additives. I used this extensively with my soybeans to produce nicely nodulated, easy to harvest root systems. Hummert carries it, but check with farm supply stores in your area.

@Ray Collier, we also use turface! It can be a little rough on roots. Any recommendations on how to protect the root system (and preserve the rooting architecture) when washing it away? We've tried spacing plastic mesh discs through the rooting profile, but it doesn't appear to be as scalable as we would like.

In Eucalyptus we used washed sand (sand from rivers) in containers of 50L to check roots architecture. After leave the plants to grow for 6 months we stopped watering to dry the sand. After some days it was possible to see the architecture just taking the plants out from the containers.  

@Tyler, if I understand correctly you want to be able to see the how the root system looks in situ? Benfey's lab at Duke has developed a system for Arabidopsis, but I think for larger plants it is (as you already know) a really difficult challenge. Perhaps some sort of x-ray, sonor, or MRI technology could be used on undisturbed root systems? There is a Plant Phys paper about x-ray tomography...http://www.plantphysiol.org/content/158/2/561.full.pdf+html

Dear Dr. Tyler:

I´ve also analyzed root architecture in Lotus tenuis, an herb forage legume. As you, I broke my head to solve the problem of root growth, nutrient solution x sustrate interactions, nutrient solution gradients in sustrate and easy root handling (i needed isolate root RNA after the assay). My final solution was a hydroponic system with a drop irrigation automatic system employing a mix of sand diameters to avoid substrate compactation (thick sand=0.5-1.0 mm diameter and fine sand=0.5-0.2mm diameter) in a ratio 1:1. The mixture was washed 6 times with distilled water to remove salts present therein, and reaching a pH and electical consuctivity close to that of distilled water (pH = 7.0 and EC = 0.05 mS.cm-1). The unique disvantage is that this substrate isn´t transparent.

Here I attach you a schematic image of my growth system and the paper where I analyze root architecture.

Good luck!!! Best regards, Rosalia

you could use the solid media of tissue culture but after taking all aseptic conditions and for growing for short psriod then you can photograph roots and in boiling water  you can remove media totally without harm for roots

you could use gelrite solidifying agent without the salts and growth regulators 

How about combo of a cold air return filter (like that use for a furnace) in a wood box with turface? I grow potatoes at home in vertical boxes made of recycled pallet wood; I simply add slats to the box as the plant grows and dump in more soil to promote tuber formation. I could see starting with the same type of setup, but with one or more filter bodies suspended from the top of the box, and with the box already fully slatted up and filled with your gowth medium. When you are at the point you want to examine the root architecture you simply disassemble the box from the top down, and the filters would (in theory) provide sufficient support to gently move away the turface. An example of the box is here:https://imperfecturbanfarm.files.wordpress.com/2010/05/img_1535.jpg

@Ray Collier, the cold air return filter is a clever idea; however, I still don't see how to get a 3D image from the stacked box. It would work marvelously for 2D imaging (remove one wall, let the turface filter out, and image at the exposed roots). But how to rotate the roots without removing them from the box?

I have been looking into woven/welded wire mesh discs that may be welded or braced together on one side (cantilever tower of meshes) to provide a post for rotation. I recently came across fiberglass-reinforced mesh discs for grinding wheels that may also prove as a useful material. Someone also mentioned to me to string fishing line across an annulus to make an "invisible" mesh under water.

@Rosalia Paz & Teotônio Francisco Assis, thank you for your suggestions. Mixing different grades of sand and allowing them to dry before removal sounds promising, but the delay for waiting for sand to dry may slow down throughput. 

Finally, in response to in situ observations, I agree that this is the most ideal media for monitoring roots; however, it is something of a holy grail in terms of (1) practicality, (2) cost, (3) resolution, and (4) scale. I am looking into old methods of capacitance-resistance style sensors for "observing" roots in situ. With the latest developments in technology, low-cost micro-controllers and sensors may bring new feasibility to sensing finer root systems.