For practical results, it is better to combine the study of 3 factors: osmotic, water, and salt stress, like done by Gzik A. "Accumulation of proline and pattern of α-amino acids in sugar beet plants in response to osmotic, water, and salt stress." Environmental and experimental botany. 1996 May 1;36(1):29-38.

Hello Niccolò Conti

It's Screening depend upon stage of plant on which you have to induce drought stress.

1. if its seed growth and quality investigation- go for PEG 6000 at different concentration.

2. If it is for Seedling growth or vegetative phase- go for Silica Gel or Hydrogel because practical application PEG-6000 costs you high.

3. if it is for Reproductive stage- go for water holding.

Methods for Water withholding (Traditional method)

1. Withholding of water irrigation at crop critical stage for 15 days for which you can monitored by Tensiometers

2. Maintaining Filed Capacity- different set of field capacity can be used to know its effect.

* by this all two methods can exhibit your experiment at different drought level in filed condition.

Hope for the best.

Hello Niccolo,

Your question is part of a much larger and often discussed problem of how to study plant responses to water deficit, within the plant and in the environment. It is a complex problem, and you really need to first think carefully about what the question is. It is not possible (see Lawlor 2013) to control a given water deficit in soils which are drying, despite so many studies claiming to maintain a given percentage soil water content by adding water to the surface soil. When water is added to dry soil a volume of wet soil results and the rest stays dry. So the plant uses the water from the wet soil and does not experience a water deficit. When the water is used the plant become water deficient. The best way of doing studies in soil is very frequent measurement during drying. This is technically demanding and not satisfactory if growth over a period is what you want to relate to soil water deficit.

PEG ( see two very old papers of mine) is a good method for rapidly altering plant water status and maintain it relatively constant for a period. To use PEG there are several things to take care of - aeration and prevention of damage to the root system. There is no point in adding PEG to plants growing in soil, a is sometimes done.

Having used both methods over many years I suggest you try both in pot studies!

All the best

David Lawlor

Below three references which might help

Plant Growth in Polyethylene Glycol Solutions in Relation to the Osmotic Potential of the Root Medium and the Leaf Water Balance

D. W. LAWLOR

Journal of Experimental Botany, Volume 20, Issue 4, November 1969, Pages 895–911, https://doi.org/10.1093/jxb/20.4.895

Abstract

The changes in leaf extension, plant dryweight, leaf area, net assimilation rate (E), relative growth-rate (RW), and relative leaf growth-rate (RL), have been studied for four species grown for 2 weeks in solutions of polyethylene glycol 4000 of controlled osmotic potentials. All aspects of growth were decreased by decreasing the osmotic potential (πsol) of the root medium and the leaf water potential (π), and ceased when π/ was greater than — 10 bars in bean, cotton, maize. These plants were more susceptible than ryegrass to water stress. Growth of bean stopped at π equal to about —6 bars, but even at —10 bars ryegrass was capable of some growth. Slight decrease in π from the values in the control plants decreased growth during the first week but partial recovery was apparent during the second week's growth in solution culture, when leaf extension, E, RL and RW increased in plants subjected to stress. Examination of the water balance, water potential, osmotic potential and turgor of the leaf in relation to relative water content suggests that recovery was related to increased turgor and that the ability of the plants to grow at reduced values of the osmotic potential of the root medium and of the leaf water potential depend on the maintenance of turgor.

New Phytologist

ABSORPTION OF POLYETHYLENE GLYCOLS BY PLANTS AND THEIR EFFECTS ON PLANT GROWTH

D. W. LAWLOR April 1970

https://doi.org/10.1111/j.1469-8137.1970.tb02446.x

Genetic engineering to improve plant performance under drought: physiological evaluation of achievements, limitations, and possibilities

David W. Lawlor

Journal of Experimental Botany, Volume 64, Issue 1, January 2013, Pages 83–108, https://doi.org/10.1093/jxb/ers326

I think with hold water at different DAS is good for pot culture experiments

Hi everyone, sorry for replying to you so late.

Thank you to all of you for helping me in elucidating which method to use in tomato pot culture. Each of your answers is really important.

David, your suggestion is quite interesting, I could try both the two methods on pot culture.

Based on my experimental design, the drought stress will be applied to 5-6 weeks-old tomato plants.