Maxium temperatuer where plant growth stop

[Muhammad Bilal]

Assalam o alekum

Anyone could share me that what is the highest or maximum temperature where plant photosynthesis process and growth functions stop.
I see different temps by different source here on internet. some say at 30 Celsius plant stop growing and some says 35 and some 40.

[Farhan Ahmed]

Plant growth greatly reduces above 95 F, above 110 F growth is negligent.

[Muhammad Arif Khan]

A very interesting directly influencing gardening question, it got little response simply because of lack of (theoretical as well as practical) knowledge on our part.
Temperature chart of Lahore

http://dbffkv15yp72v.cloudfront.net/pro ... ture_c.png

The warm season lasts from April 19 to July 12 with an average daily high temperature above 35°C. The hottest day of the year is May 26, with an average high of 40°C and low of 26°C.

The cold season lasts from December 11 to February 14 with an average daily high temperature below 22°C. The coldest day of the year is January 4, with an average low of 6°C and high of 18°C.

If we were to consider the high temperature only, then there should be little growth from 19th April to July the 12th. But practically it is not so.
Even on the hottest day the low was 26C.
Is it that the rate of growth keeps changing minute to minute according to temperature?
How is it related to light, is the rate of growth effected by available light?
Do the plants adapt to temperatures different from there place of origin?

Here is where Agricultural sciences members can educate us.
Arif

[Muhammad Arif Khan]

Participation by our Agriculture Sciences Scholars is requested.
Arif

[newton]

I'm afraid i'm not an agricultural scientist nor a scholar merely an amateur with some limited knowledge, but I would like to contribute some of my humble knowledge.

There are certain plants that are adapted to tolerate higher temperatures. From my knowledge it is the mosses that are the colonisers of the highest temperature areas, typically 45-50 deg Celsius. after this follows the next group which are predominantly grasses then the cacti, scrubland bushes and trees. many of these plants don't actively grow but they are adapted to survive the temperatures.

Many plants when they encounter temperatures above their comfort zone will shut down their breathing or stomata, basically in order to conserve water, when this happens the water trapped in their leaves becomes overheated and the non-adapted plants wilt.

In response to the second part of your question, and ignoring the temperature at which plants start to die.

For plant growth to occur photosynthesis has to be greater than the rate of respiration. High temperatures basically cause faster respiration or breathing/usage of energy from glucose produced. When this is above the rate of photosynthesis or production of glucose then basically the plant doesn't have the capacity to grow. some plants ae adapted to tough this period out but very many simply cant and they either grow leggy or die off.

In practical terms on the ground individual gardens also have micro climates that can change the average temperature by a few degrees, the position of the sun, shade, soil composition, rocks and planting position all have a bearing. Indeed one can find crops or tender plants thriving in the most unlikely places where your neighbours plants may well be dying off because their overall maximum temperature tolerance has been exceeded.

Plants have evolved naturally to create a further micro climate around themselves where the ambient temperature is 2 degress les than the common norm. that's why the shade of a natural tree is more pleasant than the shade of a concrete structure which does not work to reducing the ambient temperature. The motto is if you plant a tree, no matter how small your garden is the shade will be a lot lot cooler than a concrete structure.

Another issue to consider is with high heat comes drought. Many seeds simply cant germinate at these temperatures.

There are some plants if they are conditioned from a very young age to tolerate high temperatures can survive. Scientific research has been done outlining the optimum temperature for seed germination and crop growing.

Tired now going to sleep and will reply in more details later.

[Muhammad Arif Khan]

I agree with you in totality.
I am not an agriculture sciences scholar, my knowledge is based on my experience.
It is never a single factor but always number of factors influencing the ultimate result.
Effect of temperature on growth;
Does it mean the ambient temperature that a plant is exposed to or the actual core temperature of the plant?
Effect of light on growth, again my experience, lower the light levels bigger the leaves of my Amaryllis, is it due to better growth?
I feel the leaves have a given amount of task of starch production, in optimum conditions they require certain surface area and in low light for the same output they have to have a bigger surface area.
I also feel the response of a plant is on minute to minute bases during day and night steered by moisture, soil temperature, ambient temperature, light, nutrients, concentration/balance of salts and humidity.
In May when it is very hot and dry the tip to upper 3rd of the Amaryllis leaves exposed to direct sun get burnt and those in semi shade keep growing and blooming. Similarly my day lilies are in full bloom during this period leaving aside the summer bloomers growing actively during these months.
Now it is up to the agriculture sciences scholar who started the thread to conclude and wined it up.

Arif

[Muhammad Arif Khan]

by Muhammad Arif Khan » August 19th, 2014, 12:38 pm

Participation by our Agriculture Sciences Scholars is requested.
Arif

by M Arif Khan 21/8/14
Now it is up to the agriculture sciences scholar who started the thread to conclude and wined it up.

Learner, your reply is still awaited.

Arif