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Agrometeorology: Temperature and Plant Growth

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Influence of Climate on Crops

Climate is the most important dominating factor influencing the suitability of a crop to a particularregion. The yield potential of the crop mainly depends on climate. More than 50 per cent ofvariation of crops is determined by climate. The most important climatic factors that influencegrowth, development and yield of crops are solar radiation, temperature and rainfall.

Effect of Temperature on Plant Growth

Temperature and crop production

Important for growth and development1.Optimum temperature is required for maximum dry matter accumulation.2.High night temperature – growth of shoot3.

Cardinal temperature points

All plants have maximum, optimum and minimum temperature limits. The limits are cardinaltemperature points. Optimum temperature range is very important.

Wheat3 – 4°C minimum

25° optimum

30° - 32°C maximum

Rice 10-12°C minimum

30-32°C optimum

36-38°C maximum

(1) Low temperature injury(2) High temperature injury

1) Low temperature:

Low temperature affects several aspects of crop growth viz., survival, cell division, photosynthesis,water transport, growth and finally yield.

(i) Chilling injury :

If the plants grown in hot temperature are exposed to lowtemperature, they will be killed (or) severely injured.

When the night temperature is below 15°C field crops may showyellowing symptoms (eg) Tropical annuals.

(ii) Freezing injury :

When the plants are exposed to how temperature, water freezes intoice crystals in the intercellular spaces.(eg) Cell dehydrationTemperate crops (potato, tea etc.,)

(iii) Suffocation : Formation of thick cover of ice/snow on the soil surface presents theentry of oxygen and crop suffers. This presents the respiration andlead to accumulation of harmful substances.

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Agrometeorology: Temperature and Plant Growth http://agritech.tnau.ac.in/agriculture/agri_agrometeorology_temp.html

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(iv) Heaving :Lifting of plants along with soil from its actual position by ice, crystals.This is a mechanical lifting.

Frost damage:

Low temperature near the canopy due to earth’s re-radiation. If the cell size is large the probabilityof frost damage is high.

(1) Advective frosts

Advective frosts are due to incursion of large masses of cold air over a region from the colderareas.

(2) Radiation frost:

Occur on clear calm nights when heat is freely radiated from all exposed objects.

(i) Hoar frost (or) white frost:

This is caused due to sublimation of ice crystals on objects like tree branches.

(ii) Black frost:

The vegetation is frozen because of reduction of air temperature.

Plant management against frost damage:

Frost free growing season1.Adjusting the sowing time2.Selection of resistant varieties3.Sprinkler irrigation4.

HIGH TEMPERATURE INJURIES

High temperature adversely affects mineral nutrition, shoot growth and pollen development resultingin low yield.

The critical temperature above which plants gets killed is called thermal ‘death point’.1.The temperature above 50°C may kill many annual crops. –2.The limit varies with plants; shade loving plants are killed at lower temperature.3.

Mineral Nutrition

High temperature stress causes reduction in absorption and subsequent assimilation ofnutrients.

1.

Absorption of calcium is reduced at temperature of 28º C in Maize.2.Nutrient uptake is affected by both soil and air temperature in rice.3.Nitrate reductase activity decrease under high temperature.4.

Shoot growth

High temperature, even for short period, affects crop growth especially in temperate cropslike wheat.

1.

High air temperature reduces the growth of shoots and in turn reduces root growth.2.High soil temperature is more crucial as damage to the roots is severe resulting insubstantial reduction in shoot growth.

3.

High temperature at 38º C in rice reduced plant height, root elongation and smaller roots.4.

Pollen development

High temperature during booting stage results in pollen abortion.1.In wheat, temperature higher than 27º C caused under-development of anthers and loss ofviability of pollen.

2.

A temperature of 30º C for two days at reduction division stage decreased grain yield bydrastic reduction in grain set.

3.

Scorching:

High temperature lead to dehydration and leaves are scorched.

Physiological activities:

Agrometeorology: Temperature and Plant Growth http://agritech.tnau.ac.in/agriculture/agri_agrometeorology_temp.html

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High temperature disturbs the photosynthesis and respiration.

Injury due to scorching sun:

High temperature causes injury on the exposed area of the plant (eg) Barcks it is know as ‘Sunsclad’

Burning off:

The symptoms are noticed on young seedlings due to high soil temperature. The seedlings arekilled.

Stem gridle:

High soil temperature causes stem scorches at the ground level (eg) cotton.

Stem girdle

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