 In the last class we were seeing the weather element rainfall, for today's class we will discuss something on the temperature. Temperature means normally it indicates the hotness of your body, body may be inert material or biological material. So the air temperature has important role and plant growth and development. It triggers enzyme action, it triggers hormone, cell multiplication and why not all. Now say temperature is a general term, meteorologically in the case of agriculture meteorologically we define temperature at different ways. One is maximum temperature, this is a maximum possible temperature that occurs in a day may be 2.30 pm, this maximum temperature occurs. Then another one is minimum temperature the lowest level that occurs normally 5.30 am in the morning. So the temperature variation difference between the maximum temperature and minimum temperature we call it as diurnal variation or diurnal temperature. How much difference that occurs between the maximum temperature and minimum temperature. In the case of the temperature countries the minimum is very different between these two is very small. But in the case of the tropical situation the difference between maximum temperature and minimum temperature would be very large that also gets varied with the season. Then mean temperature, this is nothing but addition of these two maximum, minimum divided by the two of a particular day. Not only air temperature, we are also bothering about the soil temperature for crop production because soil temperature is very very important to motivate our roots, to grow roots, to put forth more small roots. So root temperature, microorganism growth and everything. Soil is a living body not a dead body because it also gets respite. So soil temperature is the triggering point that works very well in the soil. Then cardinal temperature you are very cardial to other people. So cardinal means the optimum temperature that triggers that motivates any bio system like plants and animal to grow very well. I like to provide some example for this cardinal temperature. So cardinal temperature is nothing but the optimum temperature for any growth. Growth means cell division, cell multiplication. So here you can see that for wheat germination a minimum of 3 to 4 point degree centigrade is required minimum. Below that there is no germination. Similarly if the temperature is more than 32 degree centigrade there is no germination of the wheat seeds. How the plant seeds are getting adapted to the temperature? Here I like to say the temperature means soil temperature. This is very very important. So when the soil temperature has greater link with your air temperature, when the air temperature is more the soil temperature also would be more. It is a dynamic system that is being operated under natural condition. Now coming to the barley, I have given different example. Barley is given, oats is given, maize, sorghum, rice and tobacco. But we could see some interesting variation between these two. So crops from temperate countries are also given like wheat barley oats. And crops from our tropical situations are also given. You kindly see the minimum temperature requirement for tropical crops like for example maize or sorghum or rice or tobacco. It is 8 to 10 degree, 10 degree centigrade minimum. But if you examine your temperate crops the minimum is 3 degree centigrade. So how crops are getting adapted to the temperature situation is very very important. So cardinal temperature in the absence of the cardinal temperature things will be something different. That is why in the change of the coming years there is climate change. As a result you get warmer world. When the temperature is warmer means your crop operation gets affected. This can be taken as an example for this statement. Now people say in the weather forecast we used to give heat wave is possible in the coming 3 to 4 days. Cold wave is possible in coming 2 to 3 days. In this case you must understand what is heat wave, what is cold wave. When the normal maximum temperature of the area is 40 degree centigrade or less, normal. Normal means over years, 30 years data. When the dead years data indicates that it is 40 degree centigrade. Then here normal heat wave, normal temperature means plus 1 to minus 1 degree centigrade. Above normal is plus 2 to 10 degree centigrade. Approximately above normal means plus 3 to 4 degree centigrade. We do not worry about all those things, we are worrying about severe heat wave. This is common in northern parts of India as an example where the temperature from the normal is more than 7 degree centigrade. Suppose the normal is 40 degree centigrade for a particular area, the temperature goes above 7 degree, 47 degree means there is heat wave. When heat wave comes means the crop gets affected, people gets affected, so cattle get affected. So we have to take adaptive strategy to maneuver these situations. Coming to the cold wave, this is also very very important. See here simply I can say when the normal temperature of the area is 10 degree or more, this scale given can be taken. So severe cold wave means if the temperature goes below the normal minus 7 degree centigrade. See here the temperature is 10 degree, see the rolling normal is 20 degree centigrade, example. If you deduct 7 minutes 30 degree centigrade, the temperature is 30 degree centigrade, severe cold wave prevails. This also has to be taken care carefully, consider for doing our agriculture. Now coming to the instruments, what are those instruments? You must be knowing very fully thoroughly, even then it is my duty to explain about some instrument. Maximum thermometer, it is to record your maximum temperature that prevails in a particular day. Here mercury is used and the minimum thermometer and the minimum lowest temperature that is being recorded by your fight at the AM in the morning, here alcohol is used. There is also chart is being used rotating charts by mechanical, so your battery or some system, thermograph. There is also one infrared thermometer, if you show like that, it takes the sensing mechanism, it has the sensing mechanism. So by noting the reading you can say that the plant is suffering from water stress or not or the temperature that the plant has. Then gross minimum thermometer, this is also very very important because it is being placed at the 15 centimeter above the ground level. So when the temperature, gross minimum temperature goes below means there is every possibility of getting frost. This is very very important for cold countries as well as for where the temperature goes below 10 degree centigrade. Then there are also soil thermometers, 5 centimeter, 10 centimeter, 15 centimeter, 20 centimeter, 30 centimeter, 60 centimeter soil thermometers. These are also some instruments being used to measure the hardness of a body. Next one is how the temperature units are expressed because in respect of the rainfall, we have used only single unit, millimeter. Here people use different, if you go to European country or some other, they use foreign heat India centigrade, somebody says absolute scale also they used. Degree Celsius is very common, degree foreign heat is also very common. But Kelvin or absolute zero, this is the point at which a gas would cease to exert any pressure. See in the case of the atmosphere layer, you have seen the left side of the column that is atmospheric pressure. When it is one above that, there is no gaseous pressure being exerted. So this is very important, I like to show something on this aspect above. If you want to convert the foreign heat degree to centigrade, the equation is given 5 by 9 into F minus 32, this is very very important. If you want to convert your centigrade to foreign heat, here also it is given between the bracket centigrade into 9 by 5 plus 32. The absolute scale is very very important. Absolute scale is zero degree becomes M, in the case of the absolute scale it is 273A. Suppose it means that today the temperature is 20 degree centigrade. You want to express in absolute scale means it is 293 absolute because for scientific reason we use the absolute scale also. So we must understand centigrade, foreign heat as well as absolute scale. But in common we use centigrade to express our hotness of your body as temperature. Thank you very much. In the next class we will see some more things.