The SaltyBuckwheat

Could a living organism be used as an alternative salinity sensor ?

Hi everyone ! We are the SaltyBuckwheat team and we are proud to present you our Biosensors project. It is a one week teamwork project based on interdisciplinary knowledges involving biology, chemistry, physics and computing skills .

The theme of this Biosensors week was chemical gradients. But what are chemical gradients you will say. Well, don’t freak out ! Chemical gradients are strongly linked with the notion of concentration, which refers to how many molecules or any other object are sitting in a volume of solution. It can be measured in grams per liter, molecules per liter, cars per liter… A concentration gradient consists in a gradual change of concentration between two regions. For instance, a few drops of lemon juice in a glass of water diffuse along the concentration gradient. The diffusion continues until the concentration of lemon juice in the glass has become uniform. Thus, a chemical gradient can be defined as a measurement of how the concentration of  chemicals changes in solutions.  

Our goal was to compare a biological sensor to an electronic one. After some thinking, we came to the statement that soil salinization is a major issue in agriculture nowadays. As electronic salinity soil sensors can be very expensive we thought about finding a low-priced living organism that could be used as a salinity sensor. That is how we chose to study buckweats as a biological sensor. We compared it to an electronic sensor which was a water sensor.

To do this project, we realized two different experiments : a biological and an electronic one.

First, we launched our biological experiment :  we prepared 3 solutions with different salt (NaCl) concentrations : 0%,   0.5%,   1%. We wanted the concentrations to be relatively low and close together, as salinization issues are caused by a quite sensible variation in salt concentration in the soil. We made our seeds germinate in three different growth conditions :  cotton humidified with respectively 0%, 0,5% and 1%  salty solutions. We let them germinate for 36 hours in their preferred growth conditions. When our little seeds finaly entered the world of young adults, we cut their newborn stems and measured them using an adapted software.

Next, we started the electronic experiment using the arduino grove water sensor, and simply measured the conductivity in the three solutions of different salt concentrations (0, 0.5 and 1%).

As we expected, the stronger the salt concentration is, the smaller the germs grow.

The most plausible reason is the following: when the amount of salt is too high, the germs require a lot of energy to balance the difference of concentration between their environment and their intra-cellular environment. They don’t use all their available energy to grow, and consequently grow smaller.

We then compared the obtained results using the electronic sensor to the results acquired by measuring the average size of the seeds in relation to the environment (in terms of saltiness) they grew in.

Our results are highly convincing ! The accuracy of both the biological and the electronical sensor is almost the same (see below the perfectly linear curve we obtained combining biological and electronic measurements).

We could demonstrate the efficiency of  buckwheat germs as an indicator of the soil salinity: they do grow smaller when the soil is salty ! Sow a handful of buckwheat seeds in a garden or a field, come back the next morning and observe the germ’s size. The average height of the young plants approaches 0.3 cm ? The earth is free of  salt .. It nears 0,2 cm ? The salt concentration of the soil is of about 0.5% !

Of course the indicator can be disturbed by many  factors, such as temperature, quality and nature of the soil, natural predators, competition factors,  seeds quality or influence of other chemicals  in the soil, and can definitely not reveal with enough exactitude and relevancy the salt content of the soil. However we hope our results will lead other young researchers who are strongly attached to environmental issues to continue in this direction and make a most essential tool out of our friendly seeds !

Inf you want to know more…

Here  is an interesting scientific article about buckwheat’s resistance to salinity:

N. Arya, V. P. Singh, Protection of buckwheat (Fagopyrum esculentum Moench) from different salinity stress by triazoles

Here is a video about salinity’s effect on earth: https://www.youtube.com/watch?v=4DMYqQSGMMs

Maryam Arif, Noémie Paillon, Louis Gallard and Xander Hampel