Progress 02/15/16 to 02/14/18
Outputs
Target Audience:
Nothing Reported
Changes/Problems: Technical challenge in investigating the water stress: One of the original objective during this one-year exploratory research was to investigate the seedling root responses to mechanical stresses in aeroponic condition with humidity controlled at different levels. The intention was to observe the combined or separated effects of mechanical stress and water deficit stress on seedling root growth to simulate the combined abiotic stress of water deficit and soil compaction. However, the seeds grew well only with an environment with water-saturated wet air (i.e. 100% relative humidity) in the device. Therefore, all data were obtained in saturated air. Hydroponic growth environment: Instead of the original plan of aeroponic conditions with different levels of humidity, the initial design of the device (for aeroponics) was modified to enable a hydroponic approach. The seedling root (except top ~ 2 mm portion) was in direct contact with a Hoagland nutrient solution. The experiments demonstrated that the penetrometric device can clearly distinguish different root behaviors in two conditions. This opens new possibilities to investigate various abiotic stresses by changing the solution composition to evaluate the effects of different concentrations of salt, nutrients, and other pertinent agrochemicals. What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Two-dimensional root penetrometer rhizobox, Missouri Transect Annual Meeting (NSF EPSCoR), Rolla, Missouri, September 16, 2016 (poster presentation) What do you plan to do during the next reporting period to accomplish the goals?An invention disclosure was submitted to the Technology Transfer Office of Missouri University of Science and Technology. With some additional developmental work on instrumentation, we plan to further pursue a provisional patent. We will actively search an industrial partner in the plant bleeding community.
Impacts
What was accomplished under these goals?
Abstract (non-technial): Only approximately 11% of the global soils are considered suitable for agricultural production without limitations. Many of today's farmers use soils with considerable physical or chemical limitations for crop growth. To improve crop yields, healthy root growth in soils is critically important. Environmental stresses, such as mechanical impedance (soil compaction) and water deficit (drought and irrigation), during root growth significantly limit the crop production. The objective of this research is to demonstrate a very simple, inexpensive 3-D printed micromechanical systems for measuring the force of maize seedling roots to investigate the behaviors of roots experiencing mechanical impedance. The device may be used to investigate the responses of roots of other cash crops to mechanical stress combined with other environmental stresses including salinity, nutrients, humidity and temperature. The outcomes of this project will contribute to developing stress-tolerant crops that counter possible climate change to secure food supply. Summary of findings (datails available in the attachment): The proposed penetrometric device platform utilizes a simple helical spring serving as the sensor/actuator to measure the axial force of seedling roots in real time. We demonstrated that it is a very simple, inexpensive and quantitative approach for measuring the force of maize seedling radicals. The penetrometric device allows assessment of root responses to axial mechanical impedance over a longer period of growth than the digital balance approach described in the literature. As such, the growth responses of the radical observed using the novel device simulate distinct conditions from those simulated by root force/pressure measurement procedures reported in the literature. The device may be used to investigate the responses of roots to mechanical impedance in either aeroponic or hydroponic environments combined with other abiotic conditions including salinity, nutrients, humidity and temperature. A large, 3-D printed array of this device can be used for high-throughput phenotyping of radical axial force of various crops responding to abiotic stress combinations. Technical details (a 6-page pdf file delivered to the program director): Penetrometric device design: We designed an unprecedented 3D-printed device incorporating a simple micromechanical energy storage device (helical spring) to investigate the behaviors of maize seedling root radicals experiencing mechanical impedance. As the root radical grows downward and compresses an underlying spring down in a miniaturized rhizobox, the root tips experience a gradually increasing mechanical impedance generated by the spring. The compressed spring visualizes the axial root force by imaging with a web camera. A helical spring (coil of metallic wire) requires an incremental force to linearly increase the displacement (F = k·x, where k and x are the spring constant and root elongation, respectively). It is expected that the root elongates until an equilibrium condition is established between the root strength and the spring force (i.e. the maximum root axial force). Therefore, it is a very simple, effective and inexpensive approach for measuring the axial force of seedling roots during active growth in real time. Results: A comparison between B73 inbred maize line and four commercial maize hybrids (P1395AM, P1690AM, P0636AMX, P0589AM) was investigated with the fabricated penetrometric device. P1395AM and P0636AMX seeds exhibited faster growth at an initial stage reaching a lower maximum force than P1690AM and B73. P0636AMX had the lowest growth duration and maximum force, whereas B73 growth continued for a longer time and reached a maximum force. Also, P0636AMX and P0589AM showed an almost identical behavior. It is interesting to note that the inbred B73 rather than the commercial hybrids exhibited the maximum radical axial force in this experiment. The considerable differences in maximum force and time required to reach the maximum force among the four genotypes indicate differences in the root growth physiology. In addition, radicals exhibited a faster growth rate in hydroponic conditions (radicals exposed to Hoagland nutrient solution) than in aeroponics conditions (radicals exposed to 100% relative humidity wet air). We hypothesize that the aeroponic vs hydroponic conditions differ in their influence on root water potential and thus results in the differences in root elongation and maximum force measured. Discussion: The results show that the penetrometric device can differentiate the temporal dynamics of axial root force and the maximum forces achieved by different genotypes. Thus, it provides a novel approach to identify genotypes differing in root growth responses to mechanical impedance and to characterize the molecular, physiological, and genetic mechanisms underlying responses of radical growth to mechanical impedance stress. The force measured by the penetrometer reflects a different mechanical stress imposition over the course of root growth than the force measured by the balance approach, and may relate to different scenarios that roots may experience in the real world (i.e. soils of different density, porosity, presence of rocks, etc.). Therefore, the proposed device appears to simulate a more dynamic environment during active elongation in rooting media (e.g. soil) more closely than the balance method reported in the literature. Potential impact: Overall, the device can simulate the dynamic root responses, in other words the force that the root tip experiences during growth, to the different levels of compaction of the rooting medium (e.g. soil), provided that the equivalent spring constant that can represent this hardness of the medium is known. Characterization of mechanical impedance stress in combination with other abiotic stress factors (salts, nutrients, temperature and water, etc.) can also be readily achieved, and, given the simplicity and small size of the device, scaling up to high-throughput phenotyping is feasible by generating large arrays of the penetrometric device.
Publications
- Type:
Other
Status:
Published
Year Published:
2016
Citation:
Two-dimensional root penetrometer rhizobox, Missouri Transect Annual Meeting (NSF EPSCoR), Rolla, Missouri, September 16, 2016 (poster presentation)
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