Environmental Plant Physiology - Science topic

To optimise most plant growth it is recommended that they receive 500–1000 µmols of PAR light for every m² (PPFD). Less than this and growth rates will be low :)

Dear Nicolò Maria Villa,

As far as I understood from your question, you are asking about a holistic approach that can overcome the issue of salt tolerance in plants and also the ecological cost. Moreover, you have also highlighted the negative impacts of salt tolerance on plants. This paper may help you for revealing new approaches to address salinity issues in the agricultural sector. Front. Plant Sci., 22 March 2022 Sec. Plant Abiotic Stress https://doi.org/10.3389/fpls.2022.843994.

Manish Sutradhar.

Please also see the following RG links.

Please check the following useful links.

The nature of the explants is hidden in the source, the epigenetically different structure of the genome of the so-called meristematic or stem cells. In a developed leaf or stem, there are such cells only if it is a young leaf in the epidermal layer, capable of forming cells of stomata and their surroundings (rarely) and in cells surrounding the vessels, about the same in other organs, but somewhat more complicated. Questions arise because of the widespread "legend" about the totipotency of plant cells. In fact, just like in animal cells, the bulk of cells is characterized by the fact that it develops along the path of terminal differentiation. That is, it functions without dying until it is damaged irreversibly. Apparently, microautophagy was the solution to eliminate minor lesions, and to localize large autophagy and apoptosis of a separate fragment. At least we came to this conclusion after our research and their cytological analysis of various objects. Perhaps this should be discussed in the review so that the data does not disappear. If someone is interested, we will be glad to participate. In short - there is a meristematic cell - an explant is possible, if it is not - there is no explant.

Dear Sir,

See next link:

Good luck,

Leaf and petiole analysis is an established tool. Protocol for perennial crops have been standardized for nutrient analysis.

Howdy Stancho,

First Chlrorphyll fluorescence is not a photophysical or photochemical phenomenon, but a photobiological one.

Chlorophyll fluorescence is light re-emitted by chlorophyll molecules (yes

chlorophyll!) during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in higher plants, algae and bacteria. Excited chlorophyll dissipates the absorbed light energy by driving photosynthesis (photochemical energy conversion), as heat in non-photochemical quenching or by emission as fluorescence radiation. As these processes are complementary processes, the analysis of chlorophyll fluorescence is an important tool in plant research with a wide spectra of applications.

The Kautsky effect

Upon illumination of a dark-adapted leaf, there is a rapid rise in fluorescence from Photosystem II (PSII), followed by a slow decline. First observed by Kautsky et al., 1960, this is called the Kautsky Effect. This variable rise in chlorophyll fluorescence rise is due to photosystem II. Fluorescence from photosystem I is not variable, but constant.

The increase in fluorescence is due to PSII reaction centers being in a "closed" or chemically reduced state. Reaction centers are "closed" when unable to accept further electrons. This occurs when electron acceptors downstream of PSII have not yet passed their electrons to a subsequent electron carrier, so are unable to accept another electron. Closed reaction centres reduce the overall photochemical efficiency, and so increases the level of fluorescence. Transferring a leaf from dark into light increases the proportion of closed PSII reaction centres, so fluorescence levels increase for 1–2 seconds. Subsequently, fluorescence decreases over a few minutes. This is due to; 1. more "photochemical quenching" in which electrons are transported away from PSII due to enzymes involved in carbon fixation; and 2. more "non-photochemical quenching" in which more energy is converted to heat.

Chlorophyll fluorescence appears to be a measure of photosynthesis, but this is an over-simplification. Fluorescence can measure the efficiency of PSII photochemistry, which can be used to estimate the rate of linear electron transport by multiplying with light intensity. However, researchers generally mean carbon fixation when they refer to photosynthesis. Electron transport and CO2 fixation correlate well, but may not correlate in the field due to processes such as photorespiration, nitrogen metabolism and the Mehler reaction.

A powerful research technique is to simultaneously measure chlorophyll fluorescence and gas exchange to obtain a full picture of the response of plants to their environment. One technique is to simultaneously measure CO2 fixation and PSII photochemistry at different light intensities, in non-photorespiratory conditions. A plot of CO2 fixation and PSII photochemistry indicates the electron requirement per molecule CO2 fixed. From this estimation, the extent of photorespiration may be estimated. This has been used to explore the significance of photorespiration as a photoprotective mechanism during drought.

Fluorescence analysis can also be applied to understanding the effects of low and high temperatures.

Chlorophyll fluorescence can measure most types of plant stress. Chlorophyll fluorescence can be used as a proxy of plant stress because environmental stresses, e.g. extremes of temperature, light and water availability, can reduce the ability of a plant to metabolise normally. This can mean an imbalance between the absorption of light energy by chlorophyll and the use of energy in photosynthesis.

A portable multiparametric fluorometer using the ratio between chlorophyll and flavonols can be applied to detect nitrogen deficiency in plants Because of the link between chlorophyll content and nitrogen content in leaves, chlorophyll fluorometers can be used to detect nitrogen deficiency in plants, by several methods.

Based on several years of research and experimentation, polyphenols can be assigned as indicators of the nitrogen status of a plant. For instance, when a plant is under optimal conditions, it favours its primary metabolism and synthesises the proteins (nitrogen molecules) containing chlorophyll, and few flavonols (carbon-based secondary compounds). On the other hand, in case of lack of nitrogen, we will observe an increased production of flavonols by the plant.

The NBI (Nitrogen Balance Index), allows the assessment of nitrogen conditions of a plant by calculating the ratio between Chlorophyll and Flavonols (related to Nitrogen/Carbon allocation) .

Hence Stancho,

I hope this short summary elucidates soma aspects of the photobiology of plant chlorophyll fluorescence. A lot more information is available. For example models to simulate plant fluorescence. An interesting one can be found at:

Success with your studies,

Frank

Dear Ibrahim Abd El Khalek Abd El Mola,

Please also have a look at these useful ResearchGate links.

...

Good luck!

Alternatively, you can break your directions into a north-south and an east-west aspect component.You require assignation of angles or compass directions in degrees. Depending on your study system, one of these slope aspect components might be of greatest interest (for example if working at a temperate latitude, most likely you would expect the degree of N-S orientation to matter more biologically, due to the difference in solar incidences). If you take the cos (angle) this will give you the N-S component as a numeric form ranging from 1 to -1, with 1 being N (0 or 360 degrees) and -1 being S (180), zero indicates a compete east or west exposition. The Sin(angle) is the E-W component, again ranging from 1 (East) to -1 (West). Then you can run correlations and linear regressions with your data.

The next Xylem International meeting will most likely be organized by the University of Padova in Italy i September/October 2019. We are finalizing the organisation right now and I will let you know when I know more.

And yes, Cavitation will be "la part du lion" in this meeting!

Hervé

For certain ABA responsive genes that I worked on, I imbibed the seeds on different salt concentrations for 48hours (during stratification) and did RNA extraction at different times after transferring to normal growth conditions (0, 24h,48h so on) for my Real time PCR assays.

please check the following link.

Yes , you can use it as effective as leaves , since leaves are considered to act as both sink and source for various stages of grains...

Infact , P is such a nutrient which i is intervened maximum  by root interception mainly  through  diffusion , because of processes like adsorption , fixation and release , more stringently than any other nutrient . The extreme immobility of P also encourages to be intercepted by roots through diffusion , but there is some  P-uptake through mass flow as well depending upon the soil moisture level. 

Dr Pegman, thank you very much, your answer is very helpful.I am studying the book chapter you recommmed now.

Dear Jayson Enciso

Plant phenotyping is the comprehensive assessment of complex plant traits such as growth, development, tolerance, resistance, architecture, physiology, ecology, yield, and the basic measurement of individual quantitative parameters that form the basis for the more complex traits.

There are some methods for non-destructive phenotyping, for example you can use from handy Plant Efficiency Analyzer (PEA) to determine chlorophyll a fluorescence emotion. This technique allows evaluating plant vitality especially photosynthesis efficiency under unfavorable environmental conditions through analysis of the fluorescence transients.

All the Best,

Ramin Lotfi

I believe the key to the answer is in the evolutionary or physiological significance of the metabolites. Were they produced as a response to stress or as a result of the promotion of certain processes that are influenced by changes in the environment such as light intensity, quality and duration; temperature, pressure, [CO2] etc? If these metabolites are a response to stress conditions prevalent at high altitudes, reversion to low altitudes may reduce the concentrations produced. In the same vein plants from high altitudes may produce less at low altitudes. However this still needs to be validated by appropriate experimentation

Perhaps you have calculated cell membrane stability as:

CMS = (1 – (EC40°C / EC100°C)) × 100

Sometimes, this equation is not producing correct results, since electrolyte leakage from cells at 100°C is more than that at 40°C, and this difference increases with increasing water deficit. Therefore, I suggest to apply the following altered equation for estimating CMS:

CMS = (EC40°C / EC100°C) × 100

If you want to develop full potential Ecophysiology lab you need following infrastucture

1. Water potential measurement system (Wescor is good)

2. Portable photosynthesis system (Li Cor 6400xt is good)

3. Fluorescence monitoring system (Walz machines are Good)

4. Conductivity bridge for assessing membrane damage etc.

5. If you want assess oxidative damage in plants you need a spectrophotometer

6. Portable leaf area meter etc.

7. LAI measurement systems

Good luck for having adequate funds  because all these equipments are bit costly.

Dr. Annamalainathan

Dear Mehdi and Juan Antonio,

Yes, indeed a 1 m bar-type quantum sensor would be the best instrument for measuring PAR in a canopy. Using a small sensor is not impossible, but would require many replicate measurements (in the order of hundreds per location).

What is usually the difference between expensive and cheap quantum sensors?

1) Spectral response: Li-Cor is best with this, you can use Li-Cor sensors under different white light sources with the same calibration and relatively small systematic errors: say less than 10% or so. Cheaper sensors are not really true PAR sensors, they are calibrated as PAR sensors but tend to need recalibration for each different light source. Even some of Apogee's sensors suffer from this problem http://www.apogeeinstruments.co.uk/quantum/ and while Apogee is outspoken about it, other cheap sensors for which makers do not publish the spectral response may be even worse in this respect. For the Spectrum Technology's sensors you can find in their website a manual where the spectral response is plotted, if you compare this curve to that for the "original Apogee" sensor and the true PAR response one can see that the spectral response of this cheaper sensor is really not at all like PAR. However, if the spectral quality of the light is known and the calibration has been done for this same spectral quality, measurements can be almost as good, but you need to take into account that the calibration is strongly light-source dependent. In any case I would not buy any light sensor unless the manufacturer publishes the sensor's spectral response curve as part of the specifications.

2) Cosine correction. Usually only the most expensive sensors get close to the theoretical response as the angle of incidence of light changes. This is especially important, for a horizontal sensor, when solar angles are low, or in any other situation when light is received at a low angle, possibly under a bush in a discontinuous canopy. Again I would not buy any sensor unless the manufacturer specifies the cosine-correction errors.

Other considerations:

a) Buy a sensor that is attached to the meter with a long cable, otherwise you will be unable to avoid your own shade affecting the measurements. Even with a long (2-3 metres) cable make sure to be as low as possible (not standing) and blocking as little of the light as possible. Be also aware that if wearing white or light-coloured clothes you can also increase the readings by acting as a reflector if suitably positioned. The best way to work out what is safe is to rehearse and experiment.

b) For measurements to be reliable and comparable, the sensor needs to be levelled. Li-Cor, Apogee, and most other makers of sensors for field use sell levelling bases with a spirit level. These bases do also play another role: they are heavy enough to keep the sensor where you want while you move some distance away from it to take the readings without causing shading.

c) Temperature stability should be o.k. for most quantum sensors. Weather/water proofing will vary.

Additional thoughts:

1) With care, if you can borrow one of the expensive sensors or a good spectrometer you can calibrate a cheap or even a home-made sensor. This may make sense if you need many sensors.

2) Any sensor should be recalibrated regularly. Calibration of cheap sensors may drift more, requiring more frequent recalibration under continuous field use. Li-Cor sensors are very stable in my experience: recommendation is to recalibrate at least every two years. For Li-Cor sensors this really holds even for continuous measurements in harsh climates. I have no experience with other makes.

3) In addition be aware that the absolute values, and the ratio between above and below canopy irradiance will depend on solar elevation, as well as on how diffuse daylight is. This last point means that measurements on cloudy and sunny conditions, even if expressed as a ratio will not be comparable.

After writing all this, I need to add that in my experience the two most important sources of errors in this type of measurements are: using "subjective" sampling (not well designed protocol for deciding at which points under the canopy to take readings in an objective way), insufficient replication to account for the high spatial heterogeneity and shading (most frequently partial shading by the operator).

Pedro.

Dear Colleagues,

I like the topic very much and I recommend you also these two papers:

Kind regards,

Michał Filipiak 

Prof. Achour, Your insight has given me some idea on why in majority of the hydroponic fodder system they use sprinkler system instead of drip or other system of irrigation. Certainly a drought resistant genes can create many possibilities and the food we produce is not only consumed by humans but also by domestic animals.

I would like to have your some wisdom in this regard. I live in a place where humidity used to vary from 50-80 % depending upon season. As you have mentioned that stomata opens in high humid condition and for that we found that majority of the hydroponic fodder production is done with sprinkler system. Can you suggest some other techniques by which I can increase the chambers' humidity.

Regards,

Kapil

I thank you very much for your answers. What about the molecular analysis?

Dear Researchers can you tell me something about the methods used for plant cytology.

Hello Juliana,

Water potential is a state of energy and not a plant trait per se. Water potential is a measurement, like temperature, so you could also ask: Can changes in plant temperature be characterized as phenotypic plasticity? It would be difficult to argue that plant temperature is a phenotypic trait; rather a series of co-ordinated plant traits can act to regulate plant temperature. Similarly, a series of plant traits can co-ordinate to regulate plant water potential.

I recently visited a Andean site (paramo) in Ecuador at 3800m and observed many species with rosette growth forms. UV, temperature, and wind were mentioned as possible evolutionary drivers. Can anyone explain the mechanism driving these trends? For example, hormones that promote stem elongation are less active at colder temperatures? Or secondary compounds that act to protect the cells from Uv rays?

Methyl mannas estarase is an enzymes... Dear Enrique. Thanks indeed

Look up the literature on the pollination of Rafflesia (American Journal of Botany?).  What about succulent inflorescences?  There's a lot of literature on pollination in Araceae. and most insect-pollinated species are associated with a highly succulent spadix, right?  If you are going to look up ajclepiads in South Africa it's my impression that Hoya spp. from Asia are even more succulent.  

Also, would you regard some eumagnoliids and ANITA group families (Magnolia, Anona, Degenaria, Zygogynum, Winterys. Nymphaea, Nuphard, Schizandra, etc.) as succulent based on  their fleshy tepals and turgid ovaries?  There's a lot of literature on their pollination systems.  Once again, many epidendroid and cypripedioid orchids are treated as succulent flowers due to their thick, long-lived perianth segments that retain water due to increased, internal vascularization and heavy, external cutinization. That's supposed to be the main reason why they tend to out-live flowers of other taxa in the same habit (see attached).

Guess its simply differences in dry matter content!

Thank you so much Dr. Guido.

Graham Farquhar and his team (CSIRO) did lots of work on isotope discrimination (field crops) and TE or WUE. Blum, Fischer, Rebetzki, and few others  also discussed about  the relationship between CID &  TE  or WUE for breeding and the +ves and -ves. The definition of WUE is important to understand the relationship between other parameters.

Amanina,

Positive correlation between Photosynthesis and WUE(i)? Yes and No.

Basically A_N/g_s (Net assimilation / srtomatal conductance) simply indicates the amount of carbon fixed / stomatal conductance if it is  derived from stable  carbon isotopes. Or Carbon fixed / unit water lost if derived from gas exchange measurements. Nevertheless you can find the following: a) increase in WUE with an increasing A while g_s remains constant or increases moderately. b) an increase in WUE if A remains constant but g_s decreases c) decreasing A_N and gs decreases significantly. The latter usually occurs under drought situations. An incerease in WUE does not necessarily mean an increase in A_N or increase in Biomassproduction. E.g. Tree rings often show a decrease while WUE increases (mostly found under increasing or chronic drought). You can find further details under

Saurer, M., R. T. W. Siegwolf, and F. Schweingruber, 2004: Carbon isotope discrimination indicates improving water-use efficiency of trees in northern Eurasia over the last 100 years. Global Change Biology, 10, 2109-2120.

I canonly add another link to a road side effect in NZ https://researcharchive.lincoln.ac.nz/bitstream/handle/10182/820/aeru_rr_156.pdf?sequence=1, For all kind of claim it seems advisable to run in situ tests by using upwind and downwind positions

Please follow Dr. Shapiro instructions.

1. Measure the change of absorbance in time.

2. Get line equation, y = mx, (if you substract t0 lecture to all your data). m is the slope and indicate change of absorbance by time unit (ie. Abs U at 270 nm/min). You have to adjust the real slope, substractin the slope of the reaction mixture without enzyme.

3. Look for Millimolar extinction coefficient of transcinnamate.

4. Calculate the moles of Transcinnamate liberated by min.

5. Define your Enzyme Unit. I propose, that Instead of 0.01 Abs U/hour, you can use the following: 1 enzyme Units is the requiered enzyme to liberate 1 micromole of transcinnamte from LPhenylalanine, by min.

6. Consider the volume of enzyme you use (and dilution), in the reaction mixture and calculate the Enzyme U/ml.

7. Dividing by protein concentration  (mg/ml), you can calculate specific activity of your extract.

Yours

Hector

CIBNOR, México

ps. I include a similar protocol, file.

Microgravity is the condition in which people or objects appear to be weightless. Means the individual quantum particles situates a resultant gravity which is theoretically equals to zero.

In the case of plants the chlorophylls are formed with huge number of quantum particles within. As the micro-gravity is said the photosynthesis must not be affected by this issue. But as the hormonal systems affects by the micro-gravity, the photosynthesis or photosynthetic activities could be affected. 

It is well known that different plants are having different different cycles like C1, C2, C3, C4 etc. and all of them are mutually dependent on photosynthesis for that reason the photosynthesis would be affected if the cycles got imbalanced. This is my best to give the answer regarding your query.

thanks Mr. David Lawlor

I am happy to communicate with your presence

Hi Anju,

To measure water soluble carbohydrate you can use either the phenol-sulfuric acid  (Dubois et al.1956) method or by using Anthrone reagent (Yemm, EW. and Willis, AJ. (1954) The estimation of carbohydrates in plant extracts by anthrone The Biochemical Journal 57, 508–514). Look at the references and find out which one will be suitable for your sample. In past while I worked with drought stressed tissue I used the latter one. Regarding the sample numbers you can use a microplate reader where in you can measure a large number of samples at a time. Remember that you are dealing with conc. acids, so you need to standardize  the assay along with your sample before putting  a large batch of samples into a plate reader. However, if you want to know specific carbohydrate, then go for HPLC. Hope this will help. You can find more information to assay carbohydrates by using Phenol-sulfuric acid, please refer my paper Mishra et al. 2009. Hope this will help. If any question, please feel free to contact me.

Good luck 

13C composition of plant tissue is primarily a function of CO2 fixation (C3 v. C4 pathway).  However, if a plant is water stressed d13C values in plant tissue and endproducts such as sugars or lipids become more positive since closure of stomata results in CO2 fixation now drawing from a limited CO2 reservoir (isotopic fractionation) in contrast to using CO2 from an unlimited reservoir (= atmosphere) when the stomata are open.Plant tissue d13C should not be confused with Farquhar's Delta(d13C) term as proxy for water stress as this term becomes smaller with increasing water stress (or decreasing WUE).

Other, secondary factors influencing 13C composition are temperature and availability of nutrients (minerals) since these impact on biochemical activity.  Deconvoluting these factors from precipitation (as in precipitation level or water stress) will not be easy unless you have (monthly) data for all these to build an input (CO2) - output (tissue C) model that translates these factors into fluxes and turn-over rates.

18O composition of plant tissue is a more complex issue since here we are looking at three precursor pools and not just one as for 13C.  These precursor pools are water, CO2 and atmospheric O2.  The latter is of particular importance when looking at d18O values of lignin or basically any compound in the shikimate pathway.

In analogy to Farquhar's Delta(d13C) term (using d13C of atmospheric CO2 as reference point) a Delta(d18O) term has been defined (using d18O of source water as reference point).  This term becomes more positive as WUE increases.

Due to the 2 amu difference between 16O and 18O isotopic fractionation during biochemical reactions has a much more pronounced impact on plant tissue (plant product) d18O values (cf. H-J Schmidt's papers).  Biochemical reactions (= enzyme activity) are temperature dependent which will make it challenging to correlate plant tissue d18O simply to (monthly) precipitation.

In short, there are plent of processes or factors impacting on d13C and d18O that will make it difficult to determine a (significant) correlation to monthly precipiation levels.  For the reasons mentioned by Guido Bongi already It is quite unlikely lenticles will have a significant effect on d13C and d18O values.

The main drivers for mass discrimination and hence isotopic fractionation are physico-chemical processes such as evaporation/condensation (thermodynamic isotope effect) or chemical processes involving breaking / formation of chemical bonds (kinetic isotope effect).

Dear Reza and Karl,

Yes, all right, and it confirms the available data on the trophic relations of these bees (all from the genus Dasypoda, Melittidae).

Thank you for a quick and correct answer, as I myself would have spent a lot of time searching for such data (and time, as always, is not enough).

With best wishes,

Vladimir

Dear Salvadora as per your request here is your answer

Yes you can confirm drought tolerance in plants through drought susceptibility index. Lower DSI values reflected higher drought tolerance

INDICES OF DROUGHT RESISTANCE          

Drought susceptibility index (DSI)

Drought susceptibility index (DSI) was calculated by the formula given by Fischer and Maurer (1978).

DSI= (1-Yd / Yp) /D

Where,

Yd =     Seed yield of the genotypes under moisture stress condition.

Yp =     Seed yield of the genotypes under irrigated condition.

D=       Mean yield of all strains under moisture stress condition/ Mean yield of all strains under irrigated condition.

Drought tolerance efficiency (DTE)

Drought tolerance efficiency (DTE) was estimated by using formula given by Fischer and Wood (1981).

DTE (%) = Yield under Stress / Yield under non stress X 100

Stress susceptibility index (SSI)

The SSI was calculated based on the formula given by Fisher and Maurer (1978):

SSI= [1-(Ysi/Ypi)]/SI,

SI=1-(Ys/Yp)

Where,

Ypi=    yield of individual genotypes without stress,

Ysi=    yield of individual genotypes with stress,

Ys =    average yield of all genotypes with stress and

Yp =    average yield of all genotypes of without stress.

Lower stress susceptibility index (SSI) rates reflect higher drought resistance.

Stress tolerance index (STI) and Tolerance against stress (TOL)

Stress tolerance index (STI) and tolerance against stress (TOL) indices were calculated according to Fernandez (1992):

STI = (Ypi) (Ysi)/(Yp)2

TOL= (Ypi- Ysi)

Higher rates for the stress tolerance index (STI) indicates higher potential yield.

Geometric mean productivity (GMP) and mean productivity (MP) were calculated according to Fernandez (1992)

GMP = √(Ysi) (Ypi),

MP = (Ysi+Ypi) / 2

My example would be Silene (verecunda complex in particular), but I see that it is already on your radar. We described a new species (Silene krantzii) that is part of this complex and discuss some aspects of the radiation in our paper. These species are included in the section that extends into South America. Unclear just how many 'daughter lineages' we are talking about, but I know it is more than is currently recognized!

Solanum mauritianum is found in India

The method i used as follows: Leaf samples (4cm in length) were kept in 95% ethanol overnight to remove the chlorophyll.Then the completely chorophyll removed leaf samples were washed using distilled water and transfered to 0.05% Toluidine blue solution for 2hrs to stain the trichomes and observed under light microscope.I obtained good pictures and measurement of trichomes using this method.

Dear Andrzej, all papers are in my RG contribution at Guido Bongi box. I was visiting Ismael Moya but after my stay they pursued the activity with other people.

That is fine as long as one respects the plant associations and the soil. When interpreting the results, be careful to see that you do not overestimate things. Please refer to some publications coming from the New Zealand (Christchurch) David Whitehead' s group.

The relative growth rate in terms of aboveground biomass (RGR) for each standard plant was calculated as (ln W2−ln W1)/(t2−t1), where W2 is the final biomass, W1 is the initial biomass, and t2−t1 is the time interval (days), respectively. You can refer to the paper of "Effects of phosphorus application on photosynthetic carbon and nitrogen metabolism, water use efficiency and growth of dwarf bamboo (Fargesia rufa) subjected to water deficit"

we take a photograph of each leaf inside the cuvette after measurements. then, we determine the leaf area with any software and extrapolate gas exchange parameters to the cuvette area. You have to avoid overlap of leaflets inside the chamber. 

Some plants show large changes in leaf lobe and/or tooth formation during development - or in relation to environmental variables - and area/perimeter relationships have commonly been used to assess such changes.  A reference from my own work is attached.

I think yes the leaf angle will affect the drought tolerance. this of course through affecting the efficiency of photosynthesis and light interception which is differing when leaves are arranged at right angle to stem facing directly the sun radiations or arranged at an acute angle with the stem. additionally also leaves will loose more water during evapo-transpiration when facing or obstructing wind current, and of course leaf arrangement is genetically controlled.  

Note that RWC was originally referred to as Relative Turgidity (RT) in the early work of Barrs & Weatherley published in the 1950's. I attach the relevant section about water content measurement from the Review by Barrs (1968) where he defines

WSD= 100-RT, i,e. WSD=100-RWC.    

Dear Portia

Please see these below mentioned paper as your response

I do not have an experience with rice but etiolation is related to light. You should check your ligth intensy. Then photosynthesis will be normal levels.

Dear Nazir, I hope these documents may contain helpful information for you.

Best regards

Valerio

Jacob sir Kindly send  me the material as mentioned.

my mail ID: rufi.bhat@gmail.com

@Vimarsh Gowda: I am appreciated your answer. Thank you a lot for this. I am looking for some statistics about this.

This is bad photo. What is wheat? Tetraploid or Hexaploid?  Is this the main ear?

1) Tetraploid wheat Triticum turdidum has such phenotype.

2) Very rarely branch spike may occur in very late heading plantы. In the next generation it will not. The mutant should have changed the main spike .

Hi,

Plant perception of environment always includes a variety of signals. Keep in mind that the plant ALWAYS perceives any environmental change through its signaling system, which is nowdays more broadly understood than it was before, and encompasses a variety of plant hormones (cytokinins, auxins, ethylene, ABA, salicylic acid, jasmonic acid, gibberellins, brassinosteroids) but also other signals, like light or even sucrose. Plant signaling is an extremely complicated system and it's still very poorly understood because it is HUGE (to get a picture, see attached manuscripts).

Another tip: If you're looking for toxicity, nutrient deficiency or any stress whatsoever, always pay attention to oxidative stress. Oxidative stress always follows any other kind of stress, be it water deficiency, osmotic stress, heat, frost or toxic compounds in the soil. Now, as it co-occurs with any other type of stress, it is rather non-specific, so if you just note that there is oxidative stress, you won't be able to make conclusions about what triggered it - but it is a good indicator that there IS some kind of stress.

As far as my knowledge I endorse the Wu Hanxiang statement, there are no commercial insecticide which show obvious shoot-to-root transport.

One of the harmful effects of high concentration of cyanide in growing substrate would be negative impact on photosynthesis through disturbing electron transport in the thilakoids membrane.

Thanks to Maria refs.There is circumstantial evidence of ascorbate involvement in stomatal closure, mainly resulting from Conkling's Arabidopsis mutants but the main drivers for stomata are the guard cell osmoregulators H+ ATP-ase and CO2 feedback, as in http://www.ncbi.nlm.nih.gov/pubmed/17557075 and ABA literature.

Potassium (K+) is an important cation regulates  plant metabolism. It involves in ionic transport across membranes in plant system. It osmotically regulates water movement in and outside of  cells. It plays a major role in guard cell regulation thereby stomata opening/closing. Under water deficit conditions it involves in stomatal closure partially/fully depends on mesophyll water availability. In that way it regulates transpiratory water  and minimize water loss during drought periods. Other than that K+ is essential for water absorption through root  system under deficit soil moisture conditions as explained by Dr. Swapna. Potassium application either through soil or foliar spay is an viable measure of drought mitigation in many crops.

Dear Mahbobeh zamani babgohari,

I too do impose stress by PEG 6000 in such a way in liquid Yoshida Nutrient medium solution for rice research, but for my work i am not autoclaving the media,just preparing the media n use it . But adjusting the pH regularly is must! Add PEG directly to the media n thoroughly mix before use. I am getting excellent results for the pilot study.

All the best.

Hi there,

I found this useful http://delta-intkey.com/angio/

It is not specific for any geographic region but, in the description of the taxa, it does highlight the possible variation in photosynthetic pathways.

Hope this helps a little.

Regards,

Dragana Filipovic

Hi,

we did quite a number of experiments in the recent years to address specifically these questions. We have not worked with tropical trees, but I think the processes are quite generic (see or global review paper in Nature Choat et al 2012). 

There is actually two questions:

1- Are trees able to refill embolised vessels? There is a lot of confusion in the literature on this point because many previous observations are biased by faulty methodologies. X-ray micro-CT is probably the most reliable technique available today to study these processes and we have used it intensively recently (through Synchrotron facilities, or with our lab based systems). So far, our conclusion is that trees can refill embolised vessels only if they can generate positive root pressures. In other words, we have not been able to confirm the so called 'novel' refilling with these robust techniques. This means that embolism can be reversed only when transpiration is null (at night) and when soil is fully hydrated. I've seen this phenomenon on temperate trees only during spring on few species. A point that should be made clear is that cavitation is not routine in trees. Cavitation forms only under extreme drought conditions, typically after stomata have closed and leaves loos their turgor. We have never been able to confirm daily cycles of embolism/refiling with our new technologies (micro-CT). 

2- Are trees able to recover once embolism has formed? How resilient are they ? We have addressed this question experimentally by exposing trees so increasing levels of drought, measuring embolism and quantifying mortality. We have data for about 10 species and if we can generalize from this small data set we can say that the lethal level of embolism is around 90% for angiosperms and 50% for gymnosperms. Above these levels tree never recovered (=death). Below, they were able to regrow, but their growth was impaired and they would have eventually die in the field (less competitive).

There is of course a lot of experiments that need to be done to confirm these preliminary conclusions. The real world is probably more nuanced and several species probably behave different (especially in the tropics!). However, the key point is that you should be extremely critical about the methods you use and it is essential to confirm your findings with robust techniques such as micro-CT. Very sadly there is a lot of confusion in the literature, so please do not bring more confusion ! 

Here is a list of recent papers from our group addressing these questions. You can find them here on Resarchgate or on my website: http://herve.cochard.free.fr/publi.htm

Torres-Ruiz JM, Jansen S, Choat B, McElrone A, Cochard H, Brodribb TJ, Badel E, Burlett R, Bouche PS, Brodersen C, Li S, Morris H, Delzon S. 2015 Direct X-ray microtomography observation confirms the induction of embolism upon xylem cutting under tension. Plant Physiology 167: 40-43.

Cochard H, Delzon S, Badel E. 2015 X-ray microtomography (micro-CT): a reference technology for high-resolution quantification of xylem embolism in trees. Plant Cell and Environment. 38: 201-206

Martin-StPaul N K, Longepierre D, Huc R, Delzon S, Burlett R, Joffre R, Rambal S, Cochard H. 2014 How reliable are methods to assess xylem vulnerability to cavitation? The issue of “open vessel” artifact in oaks. Tree Physiology 34: 894-805.

Torres-Ruiz JM, Cochard H, Mayr S, Beikircher B, Diaz-Espejo A, Rodriguez-Dominguez CM, Badel E, Fernández, JE. 2014 Vulnerability to cavitation in Olea europaea current-year shoots: more support to the open-vessel artefact with centrifuge and air-injection techniques. Physiologia Plantarum. 152: 465-474 doi: 10.1111/ppl.12185

Delzon S, Cochard H. 2014 Recent advances in tree hydraulics highlight the ecological significance of the hydraulic safety margin. New Phytologist. 203: 355–358 doi: 10.1111/nph.12798

Cochard H, Delzon S 2013. Hydraulic failure and repair are not routine in trees. Annals of Forest Science 70: 659-661

Urli M, Porté A, Cochard H, Guengant Y, Burlett R, Delzon S 2013. Xylem embolism threshold for catastrophic hydraulic failure in angiosperm trees. Tree physiology 33: 672–683

Cochard H, Badel E, Herbette S, Delzon S, Choat B, Jansen S 2013. Methods for measuring plant vulnerability to cavitation: a critical review. Journal of Experimental Botany 64: 4779-4791

Barigah ST, Charrier O, Douris M, Bonhomme M, Herbette S, Ameglio T, Fichot R, Brignolas F, Cochard H 2013. Water stress-induced xylem hydraulic failure is a causal factor of tree mortality in beech and poplar. Annals of Botany 112:1431-1437

Choat B, Jansen S, Brodribb TJ, Cochard H, Delzon S et al 2012. Global convergence in the vulnerability of forests to drought. Nature 491: 752–755

Brodribb TJ, Cochard H 2009. Hydraulic failure defines the recovery and point of death in water stressed conifers. Plant Physiology 149: 575-584

<p>First of all, I need to know which method you used to quantify TBARS. Some methods overestimated the concentrations of these lipoperoxydes.

Do you have interest to any Atriplex species or to someone specific species? I ask you because it is winter now, and determination of Atriplex plants to the species level may be difficult.

Electrical excitability and signalling, frequently associated with rapid responses to environmental stimuli, are well known in some algae and higher plants. The presence of electrical signals, such as action potentials (AP), in both animal and plant cells suggested that plant cells, too, make use of ion channels to transmit information over long distances. In the light of rapid progress in plant biology during the past decade, the assumption that electrical signals do not only trigger rapid leaf movements in ‘sensitive’ plants such as Mimosa pudica or Dionaea muscipula, but also physiological processes in ordinary plants proved to be correct. Summarizing recent progress in the field of electrical signalling in plants, the present review will focus on the generation and propagation of various electrical signals, their ways of transmission within the plant body and various physiological effects.

In general, two different methods are being used to measure electric potentials in plants, viz. extracellular and intracellular recording. Extracellular potential measurements on the surface of higher plants have been widely performed in the past, and offer the advantage of being able to detect electrical potential differences over long periods of time (several days). By contrast, intracellular measurements with penetrating glass microelectrodes are only effective for short periods of time such as 1–2 h, because some of the electrolyte within the electrode usually diffuses into the cell to be measured and changes its original bioelectric condition. However, intracellular recording has theadvantage of being more precise because membrane potentials and electrical signals may be deduced from specific cells.

Generally freezing of samples should not influence the levels of phenols or activities of enzymes, provided you freeze them instantaneously. But, whenever you want to estimate levels of phenols or activities of enzymes, you must homogenize the samples in respective solvents/buffer instantaneously. Slow freezing can enhance levels of phenolics and activity of peroxidases. Slow thawing can inactivate enzymes.

dear ahmed,

the reason this time is that the sun rays are entering perpendicular to the planet earth, a situation that allows for greater reliability in the determination of temperature without wome can determine the best time of reading, performing a temperature curve along the day and based on this information to determine the optimal range for determination, added to a correlation with parameters of gas exchange.

It depends what do you know. I had made measurements of gas interchange (with a Li-6400) in mangrove and banana using environmental conditions with good results. However I also made measurements in epiphytic bromeliads in a cloud florest. Here, the problem with 6400 was the high humidy (above 80% all day) which made the stabilization of the equipment slow. But I think that is possible to do good measurements with a gas analyser if you have some patience...

Hi Anya!

As far as I am concerned, this subject, tree health and it's defence against pest or other environmental stress, directly related to environmental or ecological factors including both abiotic and biotic factors affecting tree, forest and also whole plant community in terms of health and resistivity to any natural diseases.

May be there is indirectly a relation between tree growth and its defence but growing fast or not in trees  directly related to physiological and anatomical features under the same ecological condition.

So clearly, main answer is: Under the same ecological condition, we can not only say that fast growing trees healthier than the others. Its depend on ecological conditions.

SCENARIO 1: At general, Poplar is fast growing tree and it comsumes and needs more water than Oak species. So, If they grow in dry and semi dry condition, Poplar probably will have less resistivity than Oak. And this condition will be affect Poplar' physiological properties and finally it will be less resistivity to pest and the other env. stress. than oak. We can make an inference that.

SCENARIO 2: But, in humid contidion, we can not say that Poplar will be healtier than Oak. Can we?

Its one of the my little opinion:)

Good luck with your study.

Dear Dr Yousef Alaei,

I would like to thank you for your question. Their are different kinds of drought tolerance mechanism. 

you could determine the germination stage (germination percent with different % of PEG), or at seedling stage. You can germinate the seeds till have good seedling and then start do the treatment (stress) after one-two weeks and after that determine the seedling traits at control and different stress conditions

with best regards

Khaled

Drought tolerance in wild plant species is often defined as survival, but in crop species it is defined in terms of productivity (Passioura, 1983). Rosielle and Hamblin (1981) defined drought tolerance as the difference in yield between stress and non-stress environments, while productivity is the average yield in stress and non-stress. A different definition regards drought tolerance as minimization of reduction in yield caused by stress compared to yield under non-stress environments (Fischer and Maurer, 1978; Langer et al., 1979; Blum, 1983a; Blum, 1988). Also, it is defined as the relative yield of a genotype compared to other genotypes subjected to the same drought stress (Hall, 1993). Drought tolerance comprises drought escape, dehydration avoidance and dehydration tolerance mechanisms (Blum, 1988).