I have worked on salinity stress and I succeed to develop one method to create artificial salinity in the Pots. So my advice to you that you have two ways to introduce the drought in to the pots by giving irrigation intervals or to irrigate your pots regarding to the weight of the Pots and this you can achieve by knowing the soil weight, soil with water (different percentage) and the soil saturated with water this will be your control. Maybe you will have inquires so I will be happy to help anytime.

I forget to tell you that you will give the drought stress after completion of the germination.

Thank you Wassem Naguib for your feedback.

So, if I understand you first suggestion (after the completion of germination, I irrigate ( controls) daily, and i stoped the irrigation (stressed) for some days or weeks...

So, i have two questions about this way :

1- what is best stage after the completion of germination to start the drought stress ( in terms of days or in terms of number of leaves)

2- and what is the lapse of times ( in terms of weeks, or month or...) for stress to be involved and for the genes to be expressed.

You can stop irrigation at a time of your choice depending on your goals. You can also have different stress levels by varying the capacity in the field of the substrate.

Welcome anytime my friend, see first for the complete germination it varies from plant to plant and this you can know from the crop properties for example my work on Sugar Beet and complete germination is 4 leaves so you can search about you crop otherwise you can say that your crop life cycle is 6 months and introduced the stress after one month from germination. This will be your wish when you want to give the stress and at which stage you want to test your stress.

For the second point this will need some work from your side if no one mentioned before about the crop and it's strength to tolerate the drought. Means you will need to search if someone done work before and if you didn't find you will need to standardize it by giving different stress levels like you can say control, irrigation every 3 days, 4 days, 5 days so on but this will be depend on your plant, pots size, temperature and soil type.

For genes part you need someone know about this crop and the part if Gene expression or you have to find papers that can help you.

Staggering irrigation and its frequency/intensity is one way.

Many thanks Wassem Naguib Your answer was very helpful.

Thank you Carine Temegne Nono and Kulvir Singh for your answers.

Welcome dear

Hi, you could use a substrate moisture sensor which you could calibrate for your substrate. This would allow you to irrigate with known water volumes once a certain moisture level is reached. The attached might be of interest which describes an automatic irrigation system and how water stress was detected with respect to VPD in polytunnel grown tomato plants.

A simple way of applying periodic water stress is to wait for the plants to show signs of wilting before watering. This was effective in Portugal in greenhouse-grown potted plants of Eucalyptus globulus, pruned to produce stem cuttings. In that case the cuttings from the periodically stressed plants were less physically fragile and so had less mortality prior to rooting under intermittent mist.

There are some good comments above regarding the application of drought related stress. However, quantifying the level of stress applied can be difficult, plants can be sensitive to even relatively small amounts of water stress. Also, as plants grow the water demand increases and the issue of substrate water content becomes one of substrate water conductivity, which may become the limiting factor. One example of a plant's sensitivity to water stress is being evaluated in commercial Poinsettia production in the UK where short periods of water stress are being applied to regulate plant growth - thus removing the need for chemical plant regulators. In this work 4,000 plants were grown this way, more details can be found here:

https://www.delta-t.co.uk/perfect-poinsettias-for-christmas-controlling-soil-moisture-can-remove-the-need-for-chemical-growth-retardants/

Best regards, Martin