Thanks for your opinions.
So temperature is much more important.It goes up to 100-110F in day time at summer here.So growth will stop at that temperatures.
Btw, you are all welcome to visit Turkey

That makes shade all the more important. You might also consider bedding your containers in the ground or in a container in the ground to make use of the fact that the ground will be cooler than the air. You certainly want to shield the containers from direct sun if you can, especially if they are dark (you can paint them white).

My thoughts were not about sunlight stress to citrus leaves, I was writing about the fact that none of my citrus trees have ever experienced any leaf burn or scorching from direct sunlight. Even growing at the high altitudes of Colorado. There is, of course, a direct relationship between the sun's rays and heat. But even in the shade when temperatures are above 96F, citrus growth will be little to none. I cannot talk from experience about growing citrus in Turkey. I have seen Meyer Lemons citrus and peach groves in Turkey via Google earth. It is a very nice looking place. - Millet

Millet, I agree with you on the problems from the roots getting too hot--I definitly saw symptoms last summer before I put up the shade cloth over my seedlngs (they are in black plastic pots). That is why I suggested That Meyer put his containers into the ground or into containers in the ground as it is unlikely that the ground will get to greater than 95 F more than an inch or 2 into the ground.

As for damage from excess light, while I have not read specifically about the photosynthetic process in citrus, but as part of my education I did study about the photosynthetic process in plants in general. I do not know of any reason to expect an exception for citrus. Clearly citrus have the ability to grow in full sun without visible scorching, but my earlier comments about damage from excess light are not always in the form of visible damage. At the risk of getting too technical, here is a paragraph from a webpage on biochemistry of photosynthesis (the website is posted below). Copied below is a paragraph about excess light.

Plant Protection

Plants have evolved a great ability to absorb light over the entire visible range of the spectra. Can they absorb to much energy. The answer is yes, so plants have developed many ways to protect themselves. IF too much light is absorbed, the pH gradient developed across the thylacoid membranes becomes greater. This is sensed by a protein, PsbS, and through subsequent conformational changes transmitted through the light-harvesting antennae, the excess light energy is dissipated as thermal energy. Mutants lacking PsbS showed decreased seed yield, a sign that it became less adaptable under conditions of stress (such as exposure to rapidly fluctuating light levels. Molecules called xanthophylls (synthesized from carotenes - vit A precursors) such as zeaxanthin are also important in excess energy dissipation. These molecules appear to cause excited state chlorophyll (a singlet like excited state dioxygen) to become deexcited. Without the xanthophylls, the excited state chlorophyll could deexcite by transfer of energy to ground state triplet dioxygen, promoting it to the singlet, reactive state, which through electron acquisition, could also be converted to superoxide. These reactive oxygen species (ROS) can lead to oxidative damage to proteins, lipids and nucleic acids, alteration in gene transcription, and even programmed cell death. Carotenoids can also acts as ROS scavengers. Hence both heat dissipation and inhibition of formation of ROS (by such molecules as vitamin E) are both mechanism of defense of excessive solar energy





http://employees.csbsju.edu/hjakubowski/classes/ch331/oxphos/olphotsynthesis.html

Skeet, your information is quite intriguing, and certainly worth additional study. As I read your posting, I immediately thought of the citrus groves growing in the high deserts of the world. I don't know about the Arizona and California deserts, they certainly get hot enough, but would have to look into their altitude to determine what the light intensity would be. Thanks for the link, I will have to study up on this. - Millet

Hello,
Photosynthesis... I had a long discussion about photosynthesis with a citrus fellow here in Germany, and we fought a strong blade battle, which his sword as sharp as mine!

Beside all the chemical things happaning in the photosynthesis process, mostly for energy resorbtion things and energy absorbtion control, the main things happen physically

So, Millet and Skeeter, Citrus is a common plant of the C3 typus, unlike like corn, Zea mays, which is C4 typus, has a saturisation level of solar radiation. About one thrid sunlight is the saturisation level in Citrus depending on Severtson (University of Florida). All above is not needed, and further resorbition of light is controlled by the mentioned chemical processesm, but mainly by control of evaporation and light resorbtion surface.
So shortly:
Citrus controls the photosynthesis by evaporation and in low day temperature more water is used in photosyntheses for gluccose production, than for evaporation. As more sunlight reaches the leaf surface, as higher the evaporation get's and lower the absorbtion of Carbondioxide will get, simply to maximize the evaporation of water. Evaporation has a cooling effect on the leaf lamina, preventing the leaf form getting to hot by solar radiation, because radiation not used by the photosyntheses process will by absorbed by the leaf cells, and transfered into heat (enrgy transfer from radiation energy to heat energy) This heat is the source of all sunburn!
And that's why plants with cold roots in direct sunlight, usually in spring outdoors suffer more from sunburn, as other plants. Because the cool spring nights and the cool morning temperatures inhibit high water uptake rates by the roots, and so sunliught hits the leaf unshaded with the full energy. Evaporation levels increase rapidly, but the roots won't be able to deliver the full evaporation level of water need to cool the leaf lamina, so local overheating of leaf areas will happen, causing sunburn.

But beside this process, Citrus has two other, additional ways of preventing to much solar radiation to the leaf surface.
First is the oil film on the lamina surface. The oil glances in the leaf will dispense oils to the leaf surface. We all know this, because the smell of these essential oils is in full sunlight much higher, than in morning hours. This oil will generate a film on the leaf lamina and may biologists consider this shiny film as an additional protection agains solar radiation, like a liquid sunscreen.
The shiny oil film will reflect light, and thus prevent sunlight from reaching the lamina surface or penetrate the cellular structure of the leaf, preventing the heat up process inside the plants leaf.
Next protection is a leaf curl. As one can observe: Citrus leaves have more silvery leaf downside. Simpl go to your plant and turn one leaf upside down and watch the downside, you will surely remark the silvery glance...
As solar radiation gets higher and higher, evaporation increases. If evaporation levels reach excess, and leaf damage may occur, because of more water is need for evaporation to prevent overheating as the whole system is able to evaporate, (Sorry, I do not know how to tell you correctly...) the plant curls the leaf. The leaf margins roll from side to the midvein, so shading the leaf lamina by itself and exposing the leaf downside to the sun, with it's shiny, bright color. So it seems, that the leaf downside has a much higher reflective ability than the shiny oil film, so the combination of shading, reduced exposed leaf surface and the bright leaf downside seems to reduce very effective the radiation stress to the leaf surface, and prevents overheating and excess evaporation in high temperature, high radiation circumstances.

Well, sorry for my bad english, but I hope you will understand...

Steve, good addition to the discussion, thanks. - Millet