Significance of Air Temperature on Agriculture

• The growth of higher plants is restricted to between 0 to 60 ˚C
• But crop plants to a narrow range of 10 to 40 ˚C

Effect of low temperature on plant

a) Chilling Injury :Plants which are adopted to hot climate when exposed to low temperature are found to be severely injured

b) Freezing Injury : ice crystals are formed in the intercellular spaces and then within the cells which cause more injury on the structure of the protoplasm and plasma membrane, so that plant parts or entire plant may be killed or damaged beyond repair

c) Suffocation :Formation of thick covering of ice or snow on the soil surface; results in prevention of entry of oxygen; causes accumulation of harmful substances in the plants.

d) Heaving : injury caused by lifting up of the plant along with soil from its normal position

Effect of high temperature on plant

a) Sun scald : injury caused by high temperatures on the sides of barks

b) Stem girdle : surface burning of stem at the ground level; common in young seedlings of cotton in sandy soil

c) Denaturation of enzymes : At a given location, the period between planting and harvesting is not a specific number of calendar days but rather a summation of energy units, which may be represented as degree-days. A degree-day for a given crop is defined as a day on which the mean daily temp is one degree above the zero temperature (that is the minimum temperature for growth) of the plant.