Please find enclosed some interesting enclosures..Root traits are perhaps more important ..

Seed distribution and soil seed bank formation especially persistant soil seed bank can be important for drought toleramce. Root traits on selection for drought-stress tolerancem :)

Many grasses have C4 photosynthesis, which means they lose less water per molecule of CO2 fixes compared with C3 plants.

Under this link you will find some traits made in Austria in your issue:

https://www.researchgate.net/search.Search.html?type=publication&query=schrabauer

Also important are leaf traits for regulating transpiration, e.g. stomatal density or stomatal length to better regulate water loss under drought stress.

Hi Mohammed,

From the biochemical point of view, plants have three types of metabolism for carbon fixation: The C3 Cycle (Calvin Cycle); the C4 cycle (PEP Cycle) and the Crassulacean Acid Metabolism (CAM cycle).

High crop yields are pretty important—to keep people fed, and also to keep rural economies going. If you note that a single factor exists that - with drought - reduces the yield of wheat by 20% and the yield of soybeans by 36% for instance, you might be curious to know what this factor is and where the difference between the two species comes from.

As it turns out, the factor behind those (real-life) numbers is photorespiration. This metabolic pathway begins when rubisco, the carbon-fixing enzyme of the Calvin cycle, which grabs O2, rather than CO2 (by competitive inhibition actually). It uses up fixed carbon, wastes energy, and tends to occur when plants close their stomata (leaf pores) to reduce water loss when high temperatures occur, or drought increases.

Some plants, unlike wheat and soybean, can escape the worst effects of photorespiration. The C4 and CAM pathways are two metabolic pathways in plants - adaptations and hence beneficial features which have been developed in plants by natural selection. They allow certain species to minimize photorespiration. These pathways work by ensuring that Rubisco always encounters high concentrations of CO2, which reduces the binding to O2 (competitive inhibition is reduced).

Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration (ETR), but they open at night to collect carbon dioxide (CO2) by the formation of malate (an acid). Hence the water efficiency of photosynthesis in CAM plants is much higher than for C3 and even C4 plants.

Comparison of C3, C4, and CAM plants

C3, C4 and CAM plants all use the Calvin cycle to make sugars from CO2. These pathways for fixing CO2 have different advantages and disadvantages and make plants more or less adapted for different habitats. The C3, mechanism works well in cool environments, while C4 and CAM plants are adapted to hot, dry areas. Both the C4 and CAM pathways have evolved independently, which suggests they may give plant species in hot climates a significant evolutionary advantage. The following table icompares the three types of meatobism and the environments to which they are well adapted.

___________________________________________________________________

Metaboiism /Initial CO2 fixation and Calvin cycle /Stomata open /Best adapted to

___________________________________________________________________

C3 No separation Daytime Cool, wet environments

C4 Between mesophyll & bundle-sheath Daytime Hot, sunny environments

cells (in space)

CAM Between night and day (in time) Night Very hot, dry env.

___________________________________________________________________

This info might help you to determine which ecosystems are most resilient against drought. It looks rather obvious. In Cool, wet environments C3 plants will dominate, in Hot and sunny environments a lot of C4 species will occur, and in dry arid environments CAM plants will dominate, mainly in semi-desert conditions.

Cheers

Frank

Relative Growth Rate and growth life form (position of meristems and so on) are traditionally used as a way for identifying such traits as are related to stress tolerance vs. disturbance tolerance. See works by Grime et al for a whole view of such idea

Root configuration is perhaps sensitive of all traits of a plant...

Yes I think for drought root morphology, architecture and biochemical pathways of plants are important eg. enzyeme Proline is considered an indicator for drought resistance trait but when we select trait it can not be single trait basis rather a matrix of traits along with edapho-climatic condition .

What about size and shape of leaves? Leaf size governs evapo-transpiration. Small sized leaves reduce water loss by transpiration and makes the plant adapt to droughts.

Very i teresting question Birhanu, but we need to differentiate between cultivated crops versus naturally growing plants , since latter is well adopted u see such extreme conditions...

Hi everyone, this link also could help:

http://journals.tubitak.gov.tr/botany/issues/bot-14-38-3/bot-38-3-11-1308-9.pdf

Root system may play significant role. Mostly those plants that they have strong root system inhabited dry and desert like ecosystems.

Thank you for this great question Dr. Abu Sayed Arfin Khan, Dr. Bardhan suggests heat and that is my emphasis as we consider plant traits responding to drought conditions. Thank you Dr. Veroustraete for that eloquent foundational general description. Certainly, plant morphology and physiology characteristics influence drought effect on yield.

With reference to a wet system here, heat and drought stress plant effects are difficult to disentangle. I encounter well-watered experimental plants terminating due to extreme heat, which I presume is a genetic defined physiological kinetic breakdown.

Also interesting is the relationship between environmental latent and sensible heat, relative to plant growth. High heat and high humidity is another stress situation with unique plant phenotypic implication.

Is it not yet another type of plant drought condition where transpiration is limited solely due to very high Rh rather than low water supply?

RG Community - Please define the observable difference between heat and drought plant stress.

Photosynthetic pathways of plants can good first indicators of drought tolerance but depending on the scale of focus that you have there can be additional traits that predict resilience to drought. Hydraulic traits and hydraulic safety margins have increasingly been found to be good predictors as well as stomatal regulation. There are quite a few studies on this but these two are pretty useful.

Sources:

https://www.nature.com/articles/s41586-018-0539-7

Article Plant resistance to drought depends on timely stomatal closure

Phenotypic plasticity could be an answer. However, not all species show this character.

Heat stress belongs to the category of abiotic stress effects on a plant. Agricultural plants respond to Heat stress by changing the composition and ratio of pigments in the leaves and stems. In the top figure, I show the measured spectra of winter wheat and soil. In the lower figure, the spectra processed by hyperspectral indices LPI-O: the green spectra of plants successfully resisting stress,

the red spectra of plants - changed the composition of pigments due to stress,

blue indicate anomal crops that die from stress,

and brown show the spectra of the earth and crops that died from stress.

In more detail, materials on this topic can be viewed:

https://www.researchgate.net/project/Remote-Sensing-of-plant-communities-agricultural-crops

Nonetheless, the effect of drought is rather effect of water deficit/low water activity stress, than heat stress. The native ecosystems are commonly adapted to high temperature. But real droughts are not restricted only to hot areas of Earth. Droughts are common even in Arctic / mountain tundras/deserts (not really hot places), as well as in saline / alkaline environments.

Hello Mohammed

Please check this paper we recently published. It may be useful

Article Deciphering the stability of grassland productivity in respo...

There are many morphological (stem length, leaf and root area, dry weight of shoot and root, and the root/shoot ratio), physiological traits (leaf relative water content, membrane stability index, photosystem II photochemical efficiency, stomatal resistance, chlorophyll index, and water use efficiency) and biochemical (proline content, soluble protein content, and the activity of antioxidant enzymes including superoxide dismutase, polyphenol oxidase, and peroxidase)

Good question, Mohammed. I have been asking myself similar questions regarding woody plants from dry forests. From this point, these forests cover a series of characteristics associated with environmental conditions and the use of resources that make them more or less resistant/resilient to drought. These characteristics can include deciduous habit, wood density, bark hardness and leaf thickness. In the case of pastures, characteristics that are common to dry forests, such as the ability to resprout/clonality after disturbances, should also have important implications for ecosystem resilience based on rapid recovery rates.

In my oppinion, it is not just the characteristics of the plants, but also the soil. Considering mainly cultivated plants, their mechanisms are dependent on the soil, such as the possibility of root growth, soil protection and others, which can improve the plants to adapt (water stress).

Several hydraulic traits such as turgor loss point, hydraulic safety margin, PL50 and WUE are by definition related with and even directly define drought tolerence. some "soft" traits like SLA and Huber value (HV) also have indicative value.

LDMC and Leaf phenology, please see a paper "Traits link drought resistance with herbivore defence and plant economics in semi-arid grasslands: The central roles of phenology and leaf dry matter content" in detail. Hope it works for you.