Recent Hot San Diego Weather and Palm Damage

[palmaddict]

We recently went through a four to five day stretch of weather that combined temperatures of 100 degrees with humidity that was as low as 5-10%. Basically it was what we call a Santa Ana event but this is really atypical for the month of May which is usually overcast. Normally you would see this Santa Ana event in late September or early October.

I have a number of palms that now show heat damage and many were in nearly full shade. Its as if the palms could not keep up the transpiration rate and thus leaf burn resulted. What I find interesting, is that these same palms have been through Santa Ana's in the Fall for many years and had no damage. I am thinking our normal dry hot summers prepare the palms for the Santa Ana's in the Fall. Since this very hot/dry Santa Ana event occurred in mid-May (really rare) just after spring I am thinking the palms were not yet conditioned for the traumatic event. May is often an overcase month here in San Diego.

I was fortunate in that although palm fronds did burn (on ten to fifteen palms), they all are in a state that they will recover. When I saw Matt's Beccariophoenix that suddenly died, it suggested to me that is was a palm under a bit of stress due a dry winter suddenly hit by an uncharacteristic baking heatwave just after the end of spring. Both Matt and I are about six to eight miles off of San Diego bay which means we do get hot days come summer.

This event stressed palms in a way I have not see in my garden which has been established for over 12 years. The palms were well irrigated but the baking still was widespread.

Patrick

[trioderob]

I had the same heat as you and zero damage to the palms.

I would bet that what you think is enough water in those conditions is not.

they need ALOT of water.

I am now convinced that they need alot more water and fertilizer than many believe and for sure alot more than i

realized the first few years

Edited May 21, 2014 by trioderob

[LJG]

Patrick, I watered once a day to try and combat what was coming and I have many palms that would never burn in Oct that burnt with this heat wave. I tried thinking what would make the difference between a May blast that did this damage and an Oct blast that doesn't phase the same palms. The only thing I could come up with is the soil is still cool so many tropicals are still stressed and struggling to take in nutrients and also the day is a little longer. A healthy plant taking in nutrients helps the plant in drought and heat. Normal protective plant functions are stalled so the plant that is stressed just can't do what in can in Oct. I would assume had this hit in late June we would not see the same damage as by then soils have warmed up and a lot of my winter yellow Tropicals (Euterpe, Hyophorbe, etc) would be better prepared. Also it wasn't just palms for me, many tropical plants got torched.

[Pando]

I'm 6 miles from the ocean, on a west side of the hill, and my palms loved the hot weather. My 15G Cyphophoenix nucele (in a pot) pushed a spear nearly an inch during those few days last week. Baronii is a rocket - grew a few inches! No damage to any of them.

A few weeks earlier during hot days, the leaves started to turn crispy on both Australian tree ferns I have in pots. I found that the soil dried up in just a few hours. I added wood chips and bark to the pots and the ferns came through last week totally unharmed.

[trioderob]

I just did a calculation:

if i did not make a mistake -a garden on Hilo which is 100 x 100 foot would get approx 7.5 million pounds of water from mother nature spread out over the year.

that's the weight of (10 ) jet air liner 747's

now here is Cali we put up a few drippers and bubblers and call it good.

no wonder they grow monster palms there that are lush green and dont die

Edited May 21, 2014 by trioderob

[palmaddict]

My garden contains 300-400 palms and a similar number of specimen aloes, trees etc (one acre). My water use is enormous as in 700 gallons a day during the summer and over half the garden is on drip irrigation. Watering every day like some of you do when this weather hits is not an option. Again I have had this weather hit late in Fall and this has never happened. Perhaps over the course of the summer palms are able to adjust to the heat and thus better regulate water loss when scorching weather comes in the Fall. However this kind if heat in May and the transpiration rates have not adjusted so leaf burn occurs. Maybe this can be overcome with additional water (as in every day) but this is not an option when the water bill for two months in the summer is already $750. I would think that palms like Brahea and many others increase the production of waxy substances in response to hot weather to reduce water loss. Thats why they are more blue in full sun. Others probably due the same (greener palms) but it might be different substances or mechanisms. They did not have time to adapt to this event. Again if you water every day during these periods you can make up the transpiration rates that are higher than they would be at the end of the summer. If I had a typical San Diego yard which is much smaller and not 800 specimen plants, then I would simply turn the water timer to run every day until the event passed.

patrick

[sonoranfans]

leaf transpiration is affected by ambient temps(check 100F+), low humidity(check, 5%), wind(santa anas keep any evaporation moving, humidity stays low around plants), and sunlight(heats leaves as cholophyll absorbs light and converts some to heat). If you combine these effects you will see that the sun is more intense now than october and the days are longer. This high transpiration rate from leaves will require lots of uptake from roots to replace the water lost. Root uptake will depend on wetted root area(big wet root systems do best). In the case of a green palm(doesnt reflect heat like silver) with huge leaf mass(lots of area to absorb heat and lose water) but small root system, it may not be able to keep up. Perhaps santa anas are best survived by palms with big root systems. If you look at transplants you have the same problem, reduced root systems, so they tend to trim up the fronds to prevent excessive transpiration losses. In the mid may scenario, we are 1 month from the longest day of the year, so sunlight(and perhaps the 100F+ heat as well) could be what makes this event more severe. If you want to develop large root systems, you have to water deep and thoroughly with drip, and that means watering for several hours at low drip rates in clay based rocky soils. But also you have to worry about channeling of water which will reduce the wetted volume.

[trioderob]

Patrick-

I am going to guess that a guy like you has a Dragon tree.

did yours go into flower during the middle of the heat wave ??

mine threw out insane flower shafts which they only do every 15 years.

the growth rate on those things was jaw dropping growing approx a foot a day for 2 days

[sonoranfans]

If you have developed small root systems due to watering frequently for 1 hr or less and/or not using much moisture retaining soil mix I dont expect watering every day is going to have a big impact on a small root systems rate of uptake of water. If you dont have big roots, frequent watering only gets you so far. In the arizona desert I found watering every 3 days was enough in any circumstance if the palms had deep root systems. The size of a palms root system, depends on many factors, but certainly are not all genetic. The soil mix you use and the watering regimen(longer watering gives deeper roots) matters.

[Matt in OC]

Another vote for palms that loved the heat wave. My Pritchardia Hillebrandii in particular went noticeably crazy. My big box store Woody get a little burn in full sun, but everything else did great.

[trioderob]

didnt Gary state that he lost his water system once and the palms made it for a month at the worst part of summer ?

he claimed to have "deep roots"

Edited May 21, 2014 by trioderob

[LJG]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess. I know I will be paying for it.

Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

[palmaddict]

I guess this is my point. See article below. Plants can clearly adapt to a changing environment but hit them early with an event they are not used to and they struggle to cope. Give them time to get used to the heat (expression of heat shock proteins for example) and they can adjust to the harsh conditions. A plant at the end of summer is a very different beast that the one that emerges in the spring. Whole sets of genes are producing protective substances that are absent four month earlier. Read on as partially related.

Most models of how climate change affects species apply projected climate conditions to the species’ assumed preferred climate conditions based on its current range. Move the climate envelope, and it follows that the species will have to track that to survive. But our understanding of species adaptive capacity, or their ability to change and respond to new climate conditions, is virtually nil for the vast majority of life on earth.

Two recent studies shed some light on this important issue. Both report on phenotypic changes of plants in response to climate change. However, they both point to future challenges in planning and adapting to climate change.

The first study, by Nicotra et al. (2010) brings attention to the importance of phenotypic plasticity in the ability of plants to respond to climate change. Phenotypic plasticity is the mechanism that allows plants to respond to environmental changes, and depends on the genetic arsenal of the plant species. The paper evaluates current molecular and genetic mechanisms underlying a species’ ability to change relevant to climate change, and the authors argue that, in the context of rapid climate change, phenotypic plasticity can be a crucial determinant of plant responses, both in the short- and long-term. High levels of genetic variation within natural populations improve the potential to withstand and adapt to environmental changes related to climatic change.

According to the authors, because it is hard to predict patterns of plasticity in key traits in response to climate change, it is important to identify the traits more likely to show relevant responses to changing environmental conditions, and predict what species would likely exhibit those plastic responses. The traits could then be tested under various climate conditions to determine the actual outcome and extent of plasticity. Among the various functional traits listed for assessment of plant response to climate change is altering of plant stoma, the little pores in plant leaves that allow gas exchange.

That leads to the second study of this post, by Lammertsma et al. (2011). The authors describes how nine common plant species found in Florida respond to increased CO2 in the atmosphere by altering the number, structure, and functioning of their stomata. Plant metabolism and water content is mediated through stomata, and when CO2 concentration in the atmosphere increases, a main response is to change stomata in various ways in order to decrease transpiration and loss of water. This response has been observed in short term studies in greenhouses and controlled environments, where plants were submitted to increased levels of CO2 and responded in that manner. However, in this study, the authors show that this type of response can be enhanced by growing leaves with reduced stomatal density and altered stomatal structure. Furthermore (and more importantly), the response is species specific, and individual plants species alter the number, structure, and functioning of their stomata in different ways to obtain similar metabolic results. This strongly suggests that plants can and do adapt to changing conditions to optimize their individual survival. In fact, an accompanying paper by De Boer et al. (2011) states that although the process is likely to be eventually limited by species-specific limits to phenotypic plasticity, their model predicts that adaptation will continue beyond double current CO2 concentrations.

[palmaddict]

I have half dozen dragon trees and three are now in flower. A remarkable looking plant and I wish I had planted them years ealier.

patrick

[LJG]

Patrick-

I am going to guess that a guy like you has a Dragon tree.

did yours go into flower during the middle of the heat wave ??

mine threw out insane flower shafts which they only do every 15 years.

the growth rate on those things was jaw dropping growing approx a foot a day for 2 days

I wouldn't say that is necessarily true. Dracos flower all the time. Each growing point can produce a new flower any time. My trees have at least one flower on them every year. Some years I have so many I just cut them off to prevent all the seed that follows.

[Mauna Kea Cloudforest]

I am three miles from the ocean in the Santa Cruz Mountains and I had some damage even in shade from 103F and 15% RH. Ironically I had zero damage in full sun because those palms were acclimated. The shade stuff surprised me. A b. hapala tool the brunt of the beating, not looking so hot but it's not horrible either. My c. nucele on the other hand is totally beat up. I wonder if it will ever grow out of that damaged look. Looking at it now makes me want to throw in the towel on it, too freakin' difficult. Those two appear to be the only damaged palms. I did not run the water but the soil on both was moist and well mulched.

[trioderob]

but each growing point only flowers every 10 years or so.

after flowing they split at the growing point

you do agree with this ?

AXEL - thats brutal

Edited May 21, 2014 by trioderob

[sonoranfans]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess.

Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates, ambient conditions do. the water concentration gradient determines evaporation rate, and that is a law of physics, Ficks law of diffustion. Evaporation is also heavily impacted by leaf temps. transpiration of plant leaves, like human moisture loss is a mechanism for cooling that that must change to match the balance the environmental conditions or else they and we die. There is a lot of material to read from the horticultural departments of universities.

[LJG]

I guess this is my point. See article below. Plants can clearly adapt to a changing environment but hit them early with an event they are not used to and they struggle to cope. Give them time to get used to the heat (expression of heat shock proteins for example) and they can adjust to the harsh conditions. A plant at the end of summer is a very different beast that the one that emerges in the spring. Whole sets of genes are producing protective substances that are absent four month earlier. Read on as partially related.Most models of how climate change affects species apply projected climate conditions to the species’ assumed preferred climate conditions based on its current range. Move the climate envelope, and it follows that the species will have to track that to survive. But our understanding of species adaptive capacity, or their ability to change and respond to new climate conditions, is virtually nil for the vast majority of life on earth.Two recent studies shed some light on this important issue. Both report on phenotypic changes of plants in response to climate change. However, they both point to future challenges in planning and adapting to climate change.The first study, by Nicotra et al. (2010) brings attention to the importance of phenotypic plasticity in the ability of plants to respond to climate change. Phenotypic plasticity is the mechanism that allows plants to respond to environmental changes, and depends on the genetic arsenal of the plant species. The paper evaluates current molecular and genetic mechanisms underlying a species’ ability to change relevant to climate change, and the authors argue that, in the context of rapid climate change, phenotypic plasticity can be a crucial determinant of plant responses, both in the short- and long-term. High levels of genetic variation within natural populations improve the potential to withstand and adapt to environmental changes related to climatic change.According to the authors, because it is hard to predict patterns of plasticity in key traits in response to climate change, it is important to identify the traits more likely to show relevant responses to changing environmental conditions, and predict what species would likely exhibit those plastic responses. The traits could then be tested under various climate conditions to determine the actual outcome and extent of plasticity. Among the various functional traits listed for assessment of plant response to climate change is altering of plant stoma, the little pores in plant leaves that allow gas exchange.That leads to the second study of this post, by Lammertsma et al. (2011). The authors describes how nine common plant species found in Florida respond to increased CO2 in the atmosphere by altering the number, structure, and functioning of their stomata. Plant metabolism and water content is mediated through stomata, and when CO2 concentration in the atmosphere increases, a main response is to change stomata in various ways in order to decrease transpiration and loss of water. This response has been observed in short term studies in greenhouses and controlled environments, where plants were submitted to increased levels of CO2 and responded in that manner. However, in this study, the authors show that this type of response can be enhanced by growing leaves with reduced stomatal density and altered stomatal structure. Furthermore (and more importantly), the response is species specific, and individual plants species alter the number, structure, and functioning of their stomata in different ways to obtain similar metabolic results. This strongly suggests that plants can and do adapt to changing conditions to optimize their individual survival. In fact, an accompanying paper by De Boer et al. (2011) states that although the process is likely to be eventually limited by species-specific limits to phenotypic plasticity, their model predicts that adaptation will continue beyond double current CO2 concentrations.

Patrick, this is over time they are talking about. This is not a single season event. The discussion on stomata is what I brought up in my reply to you. Those cells are set when the leaf is created. Hence why when you bring a FL plant or GH grown plant and put it in the ground in SoCal it can take years before the plant produces the correct leaf for California. The stomata cells are so large that in some cases they never close fully as they need to transpire a lot to live. Those leaves desiccate quickly outside in SoCal. The next few leaves burn too. Eventually the palm gets it right. A California palm leaf will have smaller stomata that can close fully to retain moisture during Santa Ana's or drought.

[sonoranfans]

Here is an article detailing how plants respond top ambient conditions and ALTER their transpiration rates.

http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1092853841&topicorder=6

exerpt

ENVIRONMENTAL CONDITIONS – Some environmental conditions create the driving force for movement of water out of the plant. Others alter the plant’s ability to control water loss.

Relative humidity – Relative humidity (RH) is the amount of water vapor in the air compared to the amount of water vapor that air could hold at a given temperature. A hydrated leaf would have a RH near 100%, just as the atmosphere on a rainy day would have. Any reduction in water in the atmosphere creates a gradient for water to move from the leaf to the atmosphere. The lower the RH, the less moist the atmosphere and thus, the greater the driving force for transpiration. When RH is high, the atmosphere contains more moisture, reducing the driving force for transpiration.

Temperature – Temperature greatly influences the magnitude of the driving force for water movement out of a plant rather than having a direct effect on stomata. As temperature increases, the water holding capacity of that air increases sharply. The amount of water does not change, just the ability of that air to hold water. Because warmer air can hold more water, its relative humidity is less than the same air sample at a lower temperature, or it is ‘drier air’. Because cooler air holds less water, its relative humidity increases or it is ‘moister air’. Therefore, warmer air will increase the driving force for transpiration and cooler air will decrease the driving force for transpiration.

Soil water – The source of water for transpiration out of the plant comes from the soil. Plants with adequate soil moisture will normally transpire at high rates because the soil provides the water to move through the plant. Plants cannot continue to transpire without wilting if the soil is very dry because the water in the xylem that moves out through the leaves is not being replaced by the soil water. This condition causes the leaf to lose turgor or firmness, and the stomata to close. If this loss of turgor continues throughout the plant, the plant will wilt.

Light – Stomata are triggered to open in the light so that carbon dioxide is available for the light-dependent process of photosynthesis. Stomata are closed in the dark in most plants. Very low levels of light at dawn can cause stomata to open so they can access carbon dioxide for photosynthesis as soon as the sun hits their leaves. Stomata are most sensitive to blue light, the light predominating at sunrise.

Wind – Wind can alter rates of transpiration by removing the boundary layer, that still layer of water vapor hugging the surface of leaves. Wind increases the movement of water from the leaf surface when it reduces the boundary layer, because the path for water to reach the atmosphere is shorter.

[LJG]

but each growing point only flowers every 10 years or so.

after flowing they split at the growing point

you do agree with this ?

AXEL - thats brutal

Well, we got you down from 15 years to 10 years. just giving you a hard time Rob. But no, I don't believe this. I have seen a flower come 5 years or so after it branched. But I get where you are going. Just guessing I bet after flowering and branching, maybe on average it takes 10 years in most yards. These trees when well watered and fertilized grow much faster than people think. I hope yours flowered when it had a good sized trunk. If it flowered while low, it becomes a big bush.

[sonoranfans]

here is an article how drought stress changes plants, including the size of the root system

http://hal.archives-ouvertes.fr/docs/00/88/64/51/PDF/hal-00886451.pdf

[LJG]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess.

Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates, ambient conditions do. the water concentration gradient determines evaporation rate, and that is a law of physics, Ficks law of diffustion. Evaporation is also heavily impacted by leaf temps. transpiration of plant leaves, like human moisture loss is a mechanism for cooling that that must change to match the balance the environmental conditions or else they and we die. There is a lot of material to read from the horticultural departments of universities.

Keep googling Tom. You might find the stuff you need to read where it tells you it does just that. Hence the function of Stomata.

http://www.eoearth.org/view/article/156262/

I don't have the energy to get into some long debate with Google assisted URLs to be honest. I just tried helping possibly explain why we see this based of my understanding and what I was taught. Take it in to account or throw it in the trash. Either way won't hurt my feelings.

[sonoranfans]

and an article showing mechanisms

http://water.me.vccs.edu/courses/SCT112/lecture3_print.htm

here is an exerpt explaining the cooling mechanism

Why Transpiration Occurs

There are several reasons why plants utilize transpiration. The direct effect of transpiration is to regulate the temperature of the plant and to provide water for photosynthesis. It also serves to move nutrients and sugars through the vascular tissues of the plant. Transpiration also helps to regulate turgor pressure in the plant's vascular tissues. Plants sweat through transpiration. The water that dissipates into the atmosphere pulls excess heat with it away from the plant. This reduces overheating and cools the leaves. Water is one of the substances needed for photosynthesis and must be pumped from the roots of the plant. The "engine" pulling water and nutrients up the plant is transpiration. Nutrients are absorbed from the soil and moved throughout the plant's cells by way of transpiration. The minerals distributed during this process are necessary for biosynthesis in the leaves.

Just like people if you dont sweat, you die from heat stroke.

[sonoranfans]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess.

Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates, ambient conditions do. the water concentration gradient determines evaporation rate, and that is a law of physics, Ficks law of diffustion. Evaporation is also heavily impacted by leaf temps. transpiration of plant leaves, like human moisture loss is a mechanism for cooling that that must change to match the balance the environmental conditions or else they and we die. There is a lot of material to read from the horticultural departments of universities.

Keep googling Tom. You might find the stuff you need to read where it tells you it does just. Hence the function of Stomata.

http://www.eoearth.org/view/article/156262/

I don't have the energy to get into some long debate with Google assisted URLs to be honest. I just tried helping possibly explain why we see this based of my understanding and what I was taught. Take it in to account or throw it in the trash. Either way won't hurt my feelings.

Len, I only google this for people that want to learn, those who know it all already wont need to read it. In extreme heat the plant must cool itself or die. If it is a hot sun, the plant heats, not only by conduction but radiation. I have had plenty of heat transfer and physiology of humans, its easy to read the plant literature, its less complex. when I need info I can research it from the horticultural depts in universities. This is where I have learned it, not by word of mouth. there is no single over riding mechanism other than plants must replace water they lose and they must lose it to keep cool. The comment you made on transpirations not changing with seasons is in direct conflict with the fundamental principles in these articles.

[OB Burt]

I'm .4 of a mile from the ocean, and I've had burning unlike ever before. Even some Pritchardias. The previous Santa Ana which I think was only a week to 10 ten days prior didn't do much damage. Could it be the back to back had something to do with unprecedented burning?

[sonoranfans]

Environmental Effects

There are many environmental factors that can affect the rate of transpiration. I will address five of the most important here; light, temperature, humidity, wind, and soil water.

[trioderob]

LEN-

I think it will end up looking like this:

stay thirsty my friends:

Edited May 21, 2014 by trioderob

[LJG]

The comment you made on transpirations not changing with seasons is in direct conflict with the fundamental principles in these articles.

And your comment on aperture size not having a play in evaporation rates goes against everything I posted and is in conflict with the article I posted. Here is one simple fact. Stomata controls gas and water exchange. The 5 environment effects you listed I am pretty sure anyone that grows plants already understood. But one common denominator remains, the stomata is where the action happens. Read the article. Argue with it, not me. It seems to me that you have taken one comment (out of tons of other stuff I wrote) out of context or I just came across wrong. I am not saying the amount of gas and water exchange doesn't change with the seasons. Of course it would. I guess a better way I should have said it is that the place where it happens is already set in size and the amount. There is preset min and max that can happen there and that cannot change with the seasons. As my prior example, a GH grown plant will lose much more moisture if just planted out in a Santa Ana verses an established plant with smaller stomata and fewer in number.

I think the point Patrick and others that actually live here and deal with Santa Ana conditions every year are trying to make is that it interesting that some plants were greatly effected by this May event and don't have any issue with Sept/Oct events we see every year. We have seen hotter days, lower RH and greater winds before. The two factors that are different is soil temp and length of day. Perhaps a plant that is stressed from winter and having a hard time taking up nutrients like potassium might explain it. We already know the fact that colder soils often reduce the availability of K. Potassium is key in stomata function. Again, just a theory on my part. Like you, I am no botanist.

[trioderob]

[sonoranfans]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess.

Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates, ambient conditions do. the water concentration gradient determines evaporation rate, and that is a law of physics, Ficks law of diffustion. Evaporation is also heavily impacted by leaf temps. transpiration of plant leaves, like human moisture loss is a mechanism for cooling that that must change to match the balance the environmental conditions or else they and we die. There is a lot of material to read from the horticultural departments of universities.

Again here Len your comment: Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. . If this is not what you meant, fine. But the transpiration rates are not fixed when the leaf opens, they can change with the seasons and the environment. Just answering what you were "not sure of". And yes I am not a botanist, but I doubt any credible botanist would agree that "transpiration rates are fixed" once the leaf opens.

[palmaddict]

Readers should Google the term "heat shock proteins" and see what comes up. In animals and plants there is a whole genetic cascade of protein activation which comes from exposure to heat. It has been extensively studied in genetics as an event that turns on entire families of genes (hence the interest in trying to understand how this occurs). I assume this is a coping mechanism and this activation may take some time to produce a more resiliant plant. Summer may represent the time this activation occurs and produces a palm that is protected going into fall. A major heat event in May activates the heat shock genes but they are incapable of protecting the plant from that event as protection takes time and damage occurs from the ongoing "who opened the oven door" event.

[Mauna Kea Cloudforest]

Readers should Google the term "heat shock proteins" and see what comes up. In animals and plants there is a whole genetic cascade of protein activation which comes from exposure to heat. It has been extensively studied in genetics as an event that turns on entire families of genes (hence the interest in trying to understand how this occurs). I assume this is a coping mechanism and this activation may take some time to produce a more resiliant plant. Summer may represent the time this activation occurs and produces a palm that is protected going into fall. A major heat event in May activates the heat shock genes but they are incapable of protecting the plant from that event as protection takes time and damage occurs from the ongoing "who opened the oven door" event.

That would explain why full sun grown specimens are often much hardier to Winter cold than shaded ones. it's interesting to see zero damage on my full sun rhopies during a Winter frost, but the same species under canopy will get nipped wherever there is even the slightest exposure to the night sky. Cold hardiness is proportional to drought and heat hardiness, and this heat tolerance gene activation would explain for example why many brahea are USDA 8b in hot dry climates but can't even survive a 9b-grade freeze in Seattle.

[Dypsisdean]

Is it possible that the air was just drier for longer than in previous events? I have a feeling nobody could tell me how long humidity levels were sub-5%, sub-10%, or sub-15%. Or how this compared with other hot dry events.

Like minimum temperatures, most of us cite an ultimate low, but have no idea how long it stayed there. I would guess that a solid sub-10% humidity that lasted 24 - 48 hrs. would cause much more leaf damage than the same level for 4-6 hours each afternoon for two days. But without the data.....??? --- just like a palm may survive 28º for a half hour, but not for 6 hours --- but when you look at the hi/low thermometer in the morning, the only thing you see is that the temp got down to 28º.

So it seems to me the humidity (or more importantly the time of desicatting humidity) would be as important, if not more so, than soil moisture, wind, or temps - and could be the variable that makes one event tolerable, and another one not.

[LJG]

I actually have a fully planted out acre with just as many plants and a huge water bill. I still ran the water once a day. As did many people I know with more land and plants then you have. Just a choice I guess.Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. Stomata cells are the size they will be on that leaf regardless of month. I would assume the thing that changes is the process or mechanism that controls that plant function. Hence why I am guessing it has to do with soil temps and the ability for these plants to take in the nutrients required. Too bad there are no botanist on here that could better explain.

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates, ambient conditions do. the water concentration gradient determines evaporation rate, and that is a law of physics, Ficks law of diffustion. Evaporation is also heavily impacted by leaf temps. transpiration of plant leaves, like human moisture loss is a mechanism for cooling that that must change to match the balance the environmental conditions or else they and we die. There is a lot of material to read from the horticultural departments of universities.

Again here Len your comment: Not sure how "Transpiration rates" adjust through a season when the leaf structure of a palm is set once opened. . If this is not what you meant, fine. But the transpiration rates are not fixed when the leaf opens, they can change with the seasons and the environment. Just answering what you were "not sure of". And yes I am not a botanist, but I doubt any credible botanist would agree that "transpiration rates are fixed" once the leaf opens.

Well then I guess a green house plant put right out into the Santa Ana will lose the same amount of moisture as a same sized one growing outside here in a pot because nothing is fixed? I guess if I bring a plant in from FL that it will lose the same amount of water as a same sized plant grown in California because nothing is fixed? I guess the fact (I know you like bold) the plant has an already min and max of how much it can move thanks to an already determined set size and amount of stomata has no bearing on anything to you? Sorry Tom, but the overall rates are fixed. Simple math. If you have a half inch hose, you can only get so much out. So sure there is no set amount if you stay within the confines and of course transportations levels fluctuate within those confines, but how much a plant can lose for example is set by the total number and size of stomata on a leaf. That leaf just doesn't magically remove stomata or shrink them to help in times of Santa Ana's.

Tom does it make any sense to you that I would think there is no change in transportations levels when the very point I made to start depends on changes in these levels? Does it make sense to you that I would discuss Stomata in other threads and this one and not grasp this fact? It's a variable aperture for a reason. To manage these fluctuations. Again, the point trying to be made is once the leaf is made, it is fixed. No more stomata appear, they don't grow bigger or smaller. It is set.

Here is your comment that you loaded into this thread with:

I cant agree with the stomata size being ultimately limiting in transpiration rates. The aperature size does not determine evaporation rates

Pretty sure any credible botanist would disagree. Tom do you know what stomata are?

[LJG]

Readers should Google the term "heat shock proteins" and see what comes up. In animals and plants there is a whole genetic cascade of protein activation which comes from exposure to heat. It has been extensively studied in genetics as an event that turns on entire families of genes (hence the interest in trying to understand how this occurs). I assume this is a coping mechanism and this activation may take some time to produce a more resiliant plant. Summer may represent the time this activation occurs and produces a palm that is protected going into fall. A major heat event in May activates the heat shock genes but they are incapable of protecting the plant from that event as protection takes time and damage occurs from the ongoing "who opened the oven door" event.

Thanks. Some interesting stuff. Makes sense though as just with fungal and insect attacks, the only protection a plant has internally is the use of proteins to run cell functions that aid in defense while under attack.

Just as an arm chair botanist I would assume that the heat stress protein is made only under stress. So once the plant is back to its "normal" comfort zone, the protein production stops so it won't have any lasting effect going into a late season Santa Ana. Again, that's just my guess. Happy to be wrong.

[_Keith]

Any plant under stress for any reason is susceptible to disease, and an attractive to insects which is a further vector for disease. The cause of that stress, if you can't eliminate it, is irrelevant. Nature is predisposed to eliminating the weak through any method at its disposal. There you go, my prophetic statement of the night.