Lesson 14:Landscape Resources: Water And Climate


  • Temperature affects the vital process of plant life like manufacture of carbohydrates (Photosynthesis) or protoplasm, which is the physical basis of life, transpiration, respiration, nutrient absorption, and translocation.
  • Sometimes the temperature may be so low that the plants are unable to manufacture carbohydrates or make protoplasm.
  • At other times, the temperature may be to high resulting in very high rates of respiration or transpiration.
  • At high temperature stomata may close down to check high rate of transpiration and in the process cause reduction in the manufacture of carbohydrates.
  • Higher rates of respiration use up the available carbohydrates which otherwise would have been used for growth and production.
  • Within each group, different crops need some specific temperature ranges for their proper growth and flowering, which is termed optimum temperature for the plant.
  • An optimum temperature is that with which a particular plant is able to have maximum photosynthesis to manufacture carbohydrates and have normal respiration rate so that the excess carbohydrates are available for obtaining the highest yields.
  • Temperature below or above the optimum levels may cause several abnormalities.

Night temperature

  • The optimum night temperature is very important for crop plants as new cells and the protoplasm for these cells are made only during night.
  • The night temperatures below or above the optimum range result in low yield. This happens because either the rate of respiration increases to a considerable extent at high temperature or the rate of photosynthesis decreases at a faster rate than the corresponding reduction in respiration rate.

Dormacy and rest period

  • Lower temperature is also responsible for dormant periods in plants in the temperate zones as the plant parts above ground level cease to grow because of unfavorable weather condition.
  • Some tropical plants also have periods of dormany because of high temperatures and dry seasons. Some plants have a specific rest period which is controlled by some internal conditions of the plant.
  • The principal plant structure which has a rest period is the vegetative bud, although some seeds also have rest periods.

Low temperature injuries

  • Plants are also physically injured because of low temperatures.
  • Some plants are winter hardy while others are not. Immaturity of tissues also causes winter injury.
  • It is better not to grow any crop commercially which is likely to be injured or killed by frost.
  • The low temperature injuries in Chrysanthemum are bronze coloured leaves, pink colorations in white flowers, delayed or no inflorescence induction.

High temperature injuries

  • High temperature also causes physical injuries to plants.
  • Leaf scorching and scalding are some of the effects of high temperature. Temperature also influences the occurrence of diseases and insect pests.
  • If the temperature is favourable for the survival of the pests, more damage will be caused by insects, pests and diseases.
Last modified: Tuesday, 13 December 2011, 8:08 AM