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Topic-
Temperature definition and meaning and role in agriculture.
Temperature-
Mean temperature is average of maximum and minimum temperatur.
In this chapter, higher or lower temperature indicates higher or lower
than optimum temperature.
temperature at which growth is nil or negligible and optimum temperature at which growth is maxumum.Most of the crop plants grow best at 15 to 30 C Many crop plants die at a temperature
of 45 to 55 C There are also optimal temperatures for different growth stages.
The minimum, maximum and optimum temperature of a crop are known as cardinal temperature.
telegram, cowpea. These crops are also called (roplcal cons. These crops are generally grown
in monsoon season and some also in summer season. The cardinal temperature range for warm
season crops are maximum temperature 45-50°C. minimum temperature 15-20 C and optimum
temperature 30.38"
Effect of temperature
Uptake of Corban Dioxide
The optimum temperature for net carbon dioxide uptake is about 24*c for wheat and barley.
Temperature increases above the optimum carbon dioxide decreased
due to increase in stomatal and mesophyll resinstance.
At optimum temperature, the activity of auxin, gibberellin and cytokinins (growth promoters)
e high and activity of abscisic acid (growth regulator) . At high or low temperature, the balance of growth substances change and affect
growth High growth rate of maize seedlings at 25 C is accompanied by a high activity of auxins,
gibberellins and cytokinins and low activity of acetic acid and the reverse occurs above 46°C.
Dry Matter Production
The response of dry matter production to temperature depends on the stage of the crop and
optimum temperature. Growth generally increases with increase in temperature up to optimum
temperature and later decreases.
Temperature infueunces growth and multiplication of insects and intern assest crops.
Damage by groundnut leaf miner is significantly and positively correlated with temperature Cold weather.
Lesion growth rate disease progress are significantaly higher at 20 to 25 degree Celsius.
The heat unit er growing degree-day concept was proposed to explain the relationship between growth duration and temperature. This concept assumes a direct and linear relationship growth and temperature.
A degree-day or a heat unit is the mean temperature above base temperature.
Temperature is a most important in agriculture and all living organism.
Thsnks
Topic-
Temperature definition and meaning and role in agriculture.
Temperature-
Mean temperature is average of maximum and minimum temperatur.
In this chapter, higher or lower temperature indicates higher or lower
than optimum temperature.
Cardinal Temperature -
For each species of plants, there are upper (maximum) and lower (minimum) limits oftemperature at which growth is nil or negligible and optimum temperature at which growth is maxumum.Most of the crop plants grow best at 15 to 30 C Many crop plants die at a temperature
of 45 to 55 C There are also optimal temperatures for different growth stages.
The minimum, maximum and optimum temperature of a crop are known as cardinal temperature.
Cool Season crops -
The crops which grow best in cool weather period are called cool season
Crop and are generally grown in winter season ( Nov to feb ) . Average
Temperature of 30-38*c . The importent cool season crops are wheat , barley, potato, oats etc .
These crops are called temperature
crops .
The virginal temperature ranges for cool season crops are maximum temperature 30-38*c minimum temperature 0-5*c and optimum temperature 25-30*c.
Warm Season Crops
The important warm season crops are rice, sorghum, maize, sugarcane, pearl millet, groundnut.telegram, cowpea. These crops are also called (roplcal cons. These crops are generally grown
in monsoon season and some also in summer season. The cardinal temperature range for warm
season crops are maximum temperature 45-50°C. minimum temperature 15-20 C and optimum
temperature 30.38"
Effect of temperature
Influence of temperature on growth -
Biochemical Reaction -
The rate of biochemical process are affected mainly by temperature.
Any chemical reaction increses with incresaes in temperature.
Temperature increases above the optimum carbon dioxide decreased
due to increase in stomatal and mesophyll resinstance.
Rate of photosynthesis -
Rate of photosynthesis is reduced due
to reduction in temperature.
Explanation
- At low temperature, the enzyme does not have enough energy to meet many substrate molecules, so the reaction is slowed.
- When the temperature rises, the particles in the reaction move quicker and collide more, so the rate of photosynthesis rises also
- At the optimum temperature, the enzyme is most efficient and the rate if maximum.
* At temperatures above 40°C the rate slows down. This is because the enzymes involved in the chemical reactions of photosynthesis are temperature sensitive and destroyed (denatured) at higher temperatures.
Influence on Growth Substances
At optimum temperature, the activity of auxin, gibberellin and cytokinins (growth promoters)
e high and activity of abscisic acid (growth regulator) . At high or low temperature, the balance of growth substances change and affect
growth High growth rate of maize seedlings at 25 C is accompanied by a high activity of auxins,
gibberellins and cytokinins and low activity of acetic acid and the reverse occurs above 46°C.
inhibitory effect of high temperature -
Dry Matter Production
The response of dry matter production to temperature depends on the stage of the crop and
optimum temperature. Growth generally increases with increase in temperature up to optimum
temperature and later decreases.
Pests -
Temperature infueunces growth and multiplication of insects and intern assest crops.
Damage by groundnut leaf miner is significantly and positively correlated with temperature Cold weather.
Disease -
The potato early blight disease intensity has a negetiv and significant correlation with average air temperature .Lesion growth rate disease progress are significantaly higher at 20 to 25 degree Celsius.
Growing Degree-Days GOD-
The heat unit er growing degree-day concept was proposed to explain the relationship between growth duration and temperature. This concept assumes a direct and linear relationship growth and temperature.
A degree-day or a heat unit is the mean temperature above base temperature.
Temperature is a most important in agriculture and all living organism.
Thsnks
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