There is a strong interaction between plants and its environmental. It means, any abiotic stress will be recognised and translated by the plant in a positive or negative internal change. Remember they can not move! They must develop different chemical reactions to say I´m alive!!!.

Yes, plants exposed to increasing levels of abiotic stress will render them increasingly vulnerable to biotic stress....a very strong relation , both the types of stresses have..

Crosstalk between abiotic and biotic stress responses: a current view from the points of convergence in the stress signaling networks

Plants have evolved a wide range of mechanisms to cope with biotic and abiotic stresses. To date, the molecular mechanisms that are involved in each stress has been revealed comparatively independently, and so our understanding of convergence points between biotic and abiotic stress signaling pathways remain rudimentary. However, recent studies have revealed several molecules, including transcription factors and kinases, as promising candidates for common players that are involved in crosstalk between stress signaling pathways. Emerging evidence suggests that hormone signaling pathways regulated by abscisic acid, salicylic acid, jasmonic acid and ethylene, as well as ROS signaling pathways, play key roles in the crosstalk between biotic and abiotic stress signaling. Source : Current Opinion in Plant Biology 2006, 9:436–442 ...PDF enclosed

Do we have similar clues in other crops whereby abiotic induced biotic stress played havoc.

I strongly feel so, for the simple reason, increasing exposure of plant to abiotic stress facilitates greater accumulation of free radicals , thereby , weakening the immune system of the plant and making such plants physiologically more vulnerable to biotic stress later on compared to otherwise ...

Definitely, Dr Anoop, you are absolutely right.Damage causing radicle are mainly responsible for any kind of stress.Can we expect that application of osmoprotectants can help to alleviate stress induced by weather.

Dear Hayati, you are right in giving your views.your rust reference example is also very justified.Thanks

I agree with Ximena, Annop and Hayati. Responses of plants to abiotic and biotic stress may influence each other. There are a lot of examples described in phytopathological literature. May be the plant is weakened by a abiotic stress and thus it may be infected easier by plant pathogenic fungi but the opposite is known also. During the adaptation processes to biotic stresses the plants not only compensate for the effects caused by pest organisms, but sometimes their productivity is also stimulated beyond the level of performance achieved by healthy plants. In the view of whole plant physiology, the host-parasite-relationship in compatible systems will be for some duration a new and complicated balance. Responses of organisms, plants too, to abiotic and biotic stresses are described by the so called ‘adaptationssyndrom’: This is a cascade of responses of the organism, including a period of resistance and tolerance, characterized by enhanced strength and altered metabolism. The norm of reaction to stresses is specific for each organism, but interrelations between different organisms, like host-parasite, may change it dynamically.

I am in agreement with the views expressed by Petra wrt reciprocal realationships among plants for biotic and abiotic stress.

There could be some cases , Petra, i agree with you , but generally accepted scientific notion is that only . A classical example is the citrus , the crop , we have been working over the years . The ominous problem of CITRUS DECLINE was triggered due to Phytophthora and greening , more so in those trees deficient of multiple nutrients than well supplied nutritionally healthy trees...

The interface between abiotic and biotic stress responses

Organisms are under strong selection to respond adaptively to environmental stress, even when different stresses occur simultaneously or in rapid succession, as they often do in natural environments. Biotic and abiotic stressors often elicit systemic responses which depend on signalling from local sites of exposure to other areas of the plant . At the cellular or tissue level, the possible interplay between the various signalling pathways can be complex, especially when two or more stressors are combined as is often the case in the field.

Please have a look at fascinating PDF , worth reading...

Dr Anoop, really good information from your current update for enrichment of researchers.Thanks

You are right, Anoop, thank for this interesting link. It is really difficult give a short characterization of the interesting and complex phenomenon of tolerance responses, particularly ability of plants for compensation or stimulation under stress with only few words or sentences. Compensation and stimulation are a special kind of response – that’s true, of course . Mostly we find damages and yield loss after infection of plants with diseases and pests. However it happens. We found it in our experiments e. g. with barley and net blotch disease (Drechslera teres) or wheat and snow mold disease (Microdochium nivale) under certain conditions. If it would be possible to predict and utilize this phenomenon of ability of plants for compensation or overcompensation, it would also be of some economic and environmental interest. That means for instance such effects can be used for more sophisticated antifungal control strategies or for minimizing pesticide usage. But before realizing this idea under practical conditions it is necessary to answer some questions and get some more knowledge in detail. Besides Current crop growth models are not able to simulate compensation and stimulation responses and changes in reaction norm of diseased plant.

Well taken Petra. Do you feel, plants pre-exposed to multiple nutrient deficiencies will behave differently to incidence of pests and diseases as two contrasting mechanisms operating at various organisational level of plant..??.

Plants exposed to abiotic stress will accumulate more free radicals weakening the antioxidant profiling of the plant which weakens the tolerance level of plant when exposed to biotic stress like pathogens..??

In our studies on Citrus Nutrition , we observed greater intensity of greening in those plants suffering out of Zn-deficiency than in the absence of greening...Surprisingly Petra, intensity

of greening disease was drastically reduced with foliar spray of Zn...

I agree with Dr Srivastava as I have witnessed similar experience in cotton.So can we imagine that any application of osmoprotectants to curtail abiotic stress (high temperature and water deficit due to poor rainfall) with a view to suppress free radicals as specified by you for the shorter period of time may lead to any beneficial effects in a indeterminate crop like cotton.

I mean to cope with harsh weather and still leading to some yield or say not going towards complete crop failure as witnessed in North India in 2015.

To answer Anoop: I enjoy our discussion Anoop, it is very inspiring!

Here some of my spontaneous thoughts: 1.

yours: "Do you feel, plants pre-exposed to multiple nutrient deficiencies will behave differently to incidence of pests and diseases as two contrasting mechanisms operating at various organisational level of plant..??. "

Answer: Yes, it could be so, see also next answer please.

2. Yours: "Plants exposed to abiotic stress will accumulate more free radicals weakening the antioxidant profiling of the plant which weakens the tolerance level of plant when exposed to biotic stress like pathogens..??"

Answer: It may be so in some cases, but it is also possible that free radicals induce the production of more antioxidant, oxygen scavengers or any other mechanisms that enhance the tolerance level. This is the question of concrete circumstances in a certain case like which plant? which organism?(meaning which mode of infection, which mode of action, which disease pressure, and so on ?), which source of free radicals (mode of action e.g. ) and the concentration of it, on which stage of ontogeny of the plant the abiotic and biotic stresses are acting?... with other words all the multiple factors that could influence the whole system, interaction between components of the investigated systems inclusive.

3. Yours: "In our studies on Citrus Nutrition , we observed greater intensity of greening in those plants suffering out of Zn-deficiency than in the absence of greening...Surprisingly Petra, intensity of greening disease was drastically reduced with foliar spray of Zn..."

Here I have a question: What mode of action has Zn in this system? Could Zn influence the level of cytokinins of the plant directly or indirectly by influencing other components of phytohormone balance? I don’t know enough about Zn to answer the question by myself. Best regards, Petra

Fascinating response Petra. I too enjoy having such quality discussion with you..

Let me put another quarry , please don't take it otherwise..

What is the current level of understanding about the underlying mechanisms involved in response to biotic versus abiitic stress??

And what is that condition of the plant where abiotic stress acts in tandem with biotic stress..??

It's very heartening talking to you Petra..love the whole interaction...

Really wonderful discussion and fruitful outcome to learn something.I think ,role of Zinc as a key constituent of many enzymes and proteins. It plays an important role in a wide range of processes, such as growth hormone production and internode elongation.This particularly assumes importance during any kind of stress.Though I donot know in depth in fruit plants but in Punjab ,zinc deficiency is most widespread and it's foliar application are really ameliorating.

Similarly like Petra thinks,do we have any documented information which hints upon overproduction of anti oxidants due to free radicals emerging due to stress on plant system.

Sure, but in general abiotic stresses are so bad and have ability to kill plant or decreasing plant productivity

You’re right Mohammad, in the most cases abiotic stresses cause damages. However, compensation and stimulation responses of plants occur. That’s a process, not only the final result of the damage on the end of this process. During all the processes, which occur as a part of General adaptation syndrome, we can find also some efforts of the plant to avoid and overcome the damage. Now it is not possible to exploit this fascinating ability in the most cases, we don’t know enough about it, e. g. the underlying molecular mechanisms, the internal and external conditions under which it occurs, the interactions between several stresses and the influences of agricultural and horticultural management practices and instruments. I’m sure if we understand all these processes we’ll able an innovative new kind of plant protection and agricultural or horticultural production methods. Please have not only a look at the existing limits (currently stresses causes damage as a result), have also a look at the inherent possibilities. More interdisciplinary research is needed to close all the knowledge gaps. This is also the answer to Anoop’s latter queries. These are the right questions because they describe the complex problem.

Thank you for information concerning Zn, Kulvir!

Interesting feedbacks of alte , especially from Petra and oth rlearned colleagues...

Somewhere i feel , when such responses( either in response to abiotic stress or biotic stress) are studied at molecular levels , and later interpreted at tissue level , organ level or even whole plant level , many descrepancies emerge...

Plants are constantly confronted to both abiotic and biotic stresses that seriously reduce their productivity. Plant responses to these stresses are complex and involve numerous physiological, molecular, and cellular adaptations. Evidence shows that a combination of abiotic and biotic stress can have a positive effect on plant performance by reducing the susceptibility to biotic stress. Such an interaction between both types of stress points to a crosstalk between their respective signaling pathways. This cross talk may be synergistic and/or antagonistic and include among others the involvement of phytohormones, transcription factors, kinase cascades, and reactive oxygen species (ROS). In certain cases, such crosstalk can lead to a cross-tolerance and enhancement of a plant’s resistance against pathogens.

It is also our experience that for a short period , effects of abiotic stress plus biotic stress could be encouraging in terms of plant performance , but while gauging the plants longevity on a long term basis , the joint effects are not so encouraging , unless supplemented with some more experimental evidences. Petra has already given some candid statements covering this issue...

In continuation to above response, classical example of low temperature exposure as chilling requirement for inducing dormancy as a predisposing factor for the induction of flowering in apples could be cited. Likewise , citrus also function on same principles , needs some kind of stress , either low temperature stress or water deficit stress to induce dormancy facilitataing plants flower upon resumption of normal conditions conducive for growth and development...

I think that kind of stress is altogether different in the sense that it is required to initiate flowering phase.Do we think that it shall be having any negative effect on these plants per se (apple or other chilling requiring fruits).Dr Kumar to enlighten?

I agree with all of you guys!!

You are welcome,Ximena.

Yes Dr Kulvir , you are right. Here we are debating about the terminal stress which runs through all growth stages of crop , especially when the crop is in reproductive stage. Chilling requirement or stress required for induction of flowering is distinctively different...But somewhere such stresses especially water deficit stress even to induce flowering could cut down the productive life span of trees. Whether or not, different types of biotic or abiotic stress operates through different sequence of biochemical or physiological events , it remains to be seen. Petra can opine further..It has been blistering debate in the past , to use growth regulators ( retardants) as synonyms to such stress meant for induction of flowering but met with limited success...

Definitely, in most of horticulture crops, life of orchard giving productive returns over the years is desirable.

Going back, in the previous opinions, to this complex interaction plant- environmental, add the obvious climate change that brings untimely low temperatures, unwanted in agriculture. It's a drama. It is the most uncertain factor that influences the productivity of plants.

Definitively more researchers are needed willing to address this research....

Ximena, actually temp. Is affecting in both directions.You are narrating about low temperature extreme but here in North India,we have reverse trend.

Wheat crop is presently in fields here and base temperature or 5 degree C for this crop remained only for few days and most of the time it is 3-4 degree higher.

I am afraid if this prevails for a fortnight from now,it will have a dent on wheat productivity.

Similarly during summer we are having 47-48 degree,which is burning young cotton seedlings in the field leading to sub optimal plant stand and poor yield.Shocking is that pests like whitefly are emerging early in season leading to farmers headache.

A similar conditions might be on your side where low temperature extremes are disturbing crop.

I think crops tolerant to any kind of climate change need to be tailored and worked upon.

Absolutely agree, Kulvir. I also believe that it is the course to focus research with a futuristic sense..

Absolutely agree, Kulvir. I also believe that it is the course to focus research with a futuristic sense.

With respect to the global thermal imbalance, which affects everyone, in both hemispheres, I tend to think that Gaya follows a natural course in wich human beings are almost simple spectators and nothing can change...perhaps only accelerating the caos...we call it "Climate Change", but it is perhaps its natural cyclical process and we do not know...WEll, I moved away from the original theme, but I think it is important to also comment....to have a holistic view that includes, as someone said in this panel, all the disciplines, to solve with more efficiency the current agronomic problems, wich are nany.

Winter grain crops require cold hardening in the autumn. This provides them the normal development and gives the resistance to biotic stresses. The result of such impacts can be evaluated by using their stress reactions by optical methods in situ.

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Going back to Xinema’s previous opinion concerning the complex interaction plant- environmental under climate change and our knowledge gaps… These knowledge gaps are not limited to untimely low temperatures or extreme heat in summer, discussed by Kulvir. These knowledge gaps includes the impacts of all the known extreme weather events: heat, drought, dryness heat, heavy down pours, flooding, black frost, early frost, late frost, wet snow, storm, hail, freeze thaw cycles, radiation. Climate Change is likely to increase the frequency, intensity, spatial extent, duration and timing of weather and climate extremes and can result in unprecedented extremes. Literature related to climate change is being published at prolific rates. There are a lot information concerning impacts of extreme weather events on crops. Thus we have some information about impacts of extreme weather events as abiotic stress. Pests (weeds, insect pests and plant pathogens) are the biotic stresses and represent a major constraint to crop production. The rapidly growing body of climate change literature in the past 25 years gave a lot of hinds that plant pests will be influenced by climate change. Surprisingly only a handful of work has dealt with impacts of extreme weather on plant pests. Our literature survey started on 2013 and demonstrated it. Thus we know almost nothing about the impacts of extreme weather events (as abiotic stresses) on plant pest (as biotic stresses), the damage caused by plant pests and plant protection. Thus the question of interaction of these abiotic and biotic stresses is still open yet. Besides this, the special aspect of Vladimir “winter grain crops require cold hardening in the autumn” is an interesting one too. What ever will be with winter wheat production, if the temperatures will be too warm for vernalization? Yes, we can plant spring wheat. But what should we do during interim period of cold and warm autumns/winters?

Absolutely! Agree with your complete opinion, Petra!

Well explained Petra.

Still I have few reservations about it.You said that little is known about effect of any abiotic stress on pests.

Interesting thing is that this is the point from which our questions started?

I told that due to abiotic stress (high temperature and little rainfall), whitefly flared to such an extent that there was a complete cotton crop failure in North India.

Taking wholistic approach of the subject,one thing is clear that extreme on both the sides are increasing and also there frequency.

Now ultimately it has to be perceived that how plants esp. domesticated ones adapt to this crusts and trough.

Sorry Kulvir, our literature survey didn't include cotton and white fly :-( . . In the database “Web of Science” the mode “Advanced Research” was used and a combination of “extreme weather terms + plant terms + plant pest terms” was entered. We made querries concerning important crops for German agriculture and horticulture (wheat, barley, maize, beet, potato, rape, forage crops and grasslandand, wine, hope, apple and asparagus) for pests which are typical here and which may be influenced by climate change. 6, 244 914 single combinations queried until nov 2017. The latest results we will published soon. Older papers you can find here in research gate. However, sorry, are writen in German only, especially for our German farmers, advisors and politicians. But summary is writen in English and the tables contains latin names of pests and crops.

And, Kulvir you are making a good and important job with your studies on cotton, white fly and abiotic stresses. Such experiments are urgently needed worldwide. We wanted ith our literature suveys wake uo the politicians here in Germany and prepare our farmers and gardeners to better adaptation on climate change. This should be done world wide too.

I am in complete agreement with your statement.

It has to start ASAP with a view to counteract any future problems on Agriculture per se.

Please have a look

Yes....abiotic stress leads to biotic stress...it is true... if plant is growing in alkaline soil which will be having more pH as well as high amount of exchangeable sodium ions, then root will not be able to take nutrients from the soil as permeability, infiltration are reduced due to disturbances in soil structure...there might be problem of actinomycetes which proliferate at high pH conditions rather than acidic to neutral pH...potato scab disease might be one of the important example which is cause by actinomycetes...

It is very complex question, because both are diverse problems yet they can be intriguing. When abiotic stress increases, obviously, it has direct effect on yield and later the competition for food among the biological entities increases creating biotic stress. I hope you got it Kulvir Singh