(c) Cobalt chloride is used to study water from a leaf and turns colour on absorbing water.
You have studied transpiration in an earlier class by enclosing a healthy plant in polythene bag and observing the droplets of water formed inside the bag. You could also study water loss from a leaf using cobalt chloride paper, which turns colour on absorbing water.
Macronutrients are generally present in plant tissues in large amounts (in excess of 10 mmole Kg^ –1 of dry matter). The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium. Of these, carbon, hydrogen and oxygen are mainly obtained from CO2 and H2O, while the others are absorbed from the soil as mineral nutrition.
Micronutrients or trace elements, are needed in very small amounts (less than 10 mmole Kg ^–1 of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.
In addition to the 17 essential elements named above, there are some beneficial elements such as sodium, silicon, cobalt and selenium. They are required by higher plants.
