Hydroponically grown plants of chickpea, pearl millet or sorghum (25 DAS or 6-7th leaf stage) are standardly used to measure root hydraulic conductivity, using a pressure chamber (PMS instruments, Corvallis, Oregon, USA). The shoot is cut using a razor blade and the detached root, which is submerged in water, is carefully placed in the pressure chamber and sealed around the stem, below the cut stem area, using silicon glue and polyvinylsiloxane (Coltene President Company, Switzerland) to prevent pressure leakage. Gas pressure (nitrogen gas) is applied to the root system inside the chamber, within a range from 0.1 to 0.3MPa. The root exudate (xylem sap) from the cut surface is collected at each pressure level thrice at 5 minutes intervals using pre-weighed Eppendorf tubes stuffed with tissue paper (Kimtech Science, Ontario, USA). These measurements give three replicated values of sap exudation rate (g min-1) for each of the values of pressure applied.
Difference between the initial and final weight of the Eppendorf gives the amount of root exudate in multiple of technical replications at each MPa. The sap exudation rate is then normalized by the root surface area (or any other measure for surface of exchange) (g min-1 cm-2).
The root hydraulic conductance is then the slope of the regression between the normalized sap exudation rate (in the Y-axis) and the pressure applied in MPa (g min-1 cm-2 MPa-1). The root surface area is estimated by scanning with Shimadzu scanner and analyzed with Winrhizo software (Winrhizo, Regent Ltd, Canada).
Root exudation [g H2O]=Eppendorf with collected exudate – original Eppendorf weight
For us gems means GEMS, or G*E*M*S (genotype by environment by management by society) interactions, i.e. the fact that crop yields results from complex biophysical interactions while acceptance depends on farmer/consumer preferences. This complexity becomes an opportunity when it is cracked into components that can be analysed, understood, predicted, and then used to prioritise research investments to maximise return. This is what we do, and this is when GEMS become gems!
For us gems means GEMS, or G*E*M*S (genotype by environment by management by society) interactions, i.e. the fact that crop yields results from complex biophysical interactions while acceptance depends on farmer/consumer preferences. This complexity becomes an opportunity when it is cracked into components that can be analyzed, understood, predicted, and then used to prioritize research investments to maximise return. This is what we do, and this is when GEMS become gems!
A crop performs in different ways in different sites, years and agronomic managements. These are called genotype-by-environment-by management(G*E*M) interactions, and they are a main challenge for breeders and agronomists. There is one more layer of interaction, even more complex: the society (S). Farmers and consumers have different desires, needs, expectations, and a cultivar that fits one may not fit the other (G*E*M*S interactions). The puzzle is complex and challenging but if its components are understood, specific interventions can be undertaken.For instance, breeding for a particular genotype (G, with particular physiological characteristics), for a particular environment (E, with a particular kind of drought pattern that requires a specific adaptive trait), in a particular management practice (M, for instance a sowing density, or a N fertilizer treatment), and targeted to particular farmer/consumer (S, for instance a genotype that produces a lot of rich stover for cattle ranchers) is the need of the hour.