Itr is better to go for water potential because just RWC does not give you the energy needed to use that water
Dear Hayati,
I agree that soil water potential is probably the most valuable parameter to quantify drought. But one can use the plant itself to quantify soil water potential, (at least if one doesn´t need very much sleep). When you measure the so-called "pre-dawn water potential", i.e. the potential in plant leaves at the end of the night period, plant water potential should have had enough time to equilibrate with soil water potential, since leaves with closed stomata do not transpire and, thus, there is no water movement in the plant body and no potential loss by friction in the moving water column. If you do these measurements with a Scholander-type pressure chamber, you can then extend the information in the field by measuring a day-course, and in the lab by determining pressure-volume curves. The litteraure will show you examples.
All the best and good luck,
Hanno
Dear Hayati,
It is good to measure several parameters when estimating stress level as also mentioned above; additionally one has to consider the evaporative demands. Denmead and Shaw (1962, Agron Jour. 45 385-90) illustrate this nicely and referred to in many textbooks. The dynamics of drought nearly need diurnal simulations when going more advanced for inclusion of plant, soil and climate effects.
Good luck
Christian
Actually drought means different for different plants. Some plants are more drought-tolerant than others and show no signs of stress and actually are not stressed at levels where other plant species may wilt. Therefore, energy needed by plants to extract water from soil should also be considered in addition to soil water contents.
Dr. Zafar
I agree with Miguel's response. RWC alone does not provide energy status of soil water. I think plant based indices provide better indication of drought than the SWC.
Best regards,
Attila
RWC is an important stress indicator. However, you can add more data, as water potential, and its components, to corroborate your data. There are other parameters thatyou can easely find them as water status indicators.
Go an intensive review and choose the best indicators to achieve the objectives.
measure hyperspectral signature and compute water related indices using short wave infra red and near infra red reflectance
RWC is not the best way to quantify water status of plants;however RWC measurements can be combined with SWC or water potentials and leaf water potential measurements.
Species behave differently to different levels of RWC. The idea behind Pressure-Volume Curves, please see the work by Sack (https://www.researchgate.net/profile/Lawren_Sack), is to determine at what point different species present Turgor Loss Point (TLP) and other ecophysiological variables related to their RWC. A certain RWC for a Mediterranean species will have totally different ecophysiological consequences on a tropical species.
The best way to assess drought, in my opinion, would be to use pre-dawn water potential measurements.
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