Weather and Climate

Definition of weather, climate, microclimate, meteorology and agrometeorology ,Elements of climate and their effects on crop growth

1.Exterme high and low temperature are detrimental to crop growth and development.justify,(2075)

2.Define agrometrology. Discuss the effect of temperature and crop growth and development.(2075)

3.What do you mean by microclimate and discuss the effect of precipitation and relative humidity on crop growth and development.(2072)

4.Define weather and climate (2071)

5.Draw the light response curve to show the effect of solar radiation on field crops (2071)

ANSWERS

Extreme high and low temperature are detrimental to plant growth and development. Justify. ( 2075 )

The basic physiological and biochemical processes that occurs within a plant system like; photosynthesis, respiration, transpiration and activities of growth substances are all affected by temperature in one way or the other. Only at optimum temperature, these process can run smoothly leading to a healthy plant with high yield. Any deviation from optimum temperature whether high or low can have adverse effect on the plant growth .

• Effect on photosynthesis: Both high and low temperature has found to lower the rate of photosynthesis thus stunting the growth of the plant.
• Effect on respiration: At lower temperature the rate of respiration is slow and at high temperature,  due to enzymatic degradation, inadequate supply of oxygen etc causes low respiration rate.
• Effect on transpiration: Low temperature causes closure of stomata and high temperature causes excessive transpiration which leads to wilting and even closure of stomata.  
• Effect on activities of growth substances: The action of growth promoting substance such as auxin, gibberlin and cytokinin is highly temperature specific and their action are greatly impaired by high and low temperature.

The graph mentioned below also depicts how high and low temperature is detrimental to plant growth.

2.Define agrometrology. Discuss the effect of temperature on crop growth and development.(2075)

Agro-meteorology: A branch of applied meteorology which investigates the responses of crops to the physical conditions of the environment OR An applied science which deals with the relationship between weather/climatic conditions and agricultural production.

Effect of temperature on crop growth and development:

The basic physiological and biochemical processes that occurs within a plant system like; photosynthesis, respiration, transpiration and activities of growth substances are all affected by temperature in one way or the other.

• Effect on photosynthesis: When temperature is increased upto optimum temperature, rate of photosynthesis increases however upon further increasing beyond the optimum point the rate decreases. At lower temperature the photosynthesis rate drops also causing retardation in growth.
• Effect on respiration: At lower temperature the rate of respiration is slow, however after optimum temperature rate of respiration becomes high causing slow and inadequate plant growth at both high and low temperatures.
• Effect on transpiration: Lower temperature favors lower transpiration whereas higher the temperature, higher will be the rate of transpiration inorder to maintain temperature. Extreme high temperature leads to excessive transpiration causing wilting.
• Effect on activities of growth substances: Various plant growth regulators like auxin, gibberellins, cytokinins have increased activity at optimum temperature whereas the activity of growth inhibitors like Abscissic acid is low thus favoring plant growth.

The most notable effect of temperature is observed in growing durations of crops. Growth duration determines it’s dry matter production and yield thus crops growing at high temperature zone matures faster than in lower temperature zone.

Growing degree day is defined as the sum total of mean temperatures minus the base temperature( where the crop growth is zero).

Mathematically;

               GDD = [ (Tmax + Tmin) divided by 2 ] - Tbase

                                                                Where;   Tmax = Maximum temperature, Tmin = Minimum temperature, Tbase = base temperature

3. What do you mean by micro climate and discuss the effect of precipitation and relative humidity on crop growth and development. ( 2075 )

A micro climate is a local set of atmospheric conditions that differs from those in the surrounding areas, often with a slight difference but sometimes a substantial one.

Effect of precipitation:  

Precipitation is any product of the condensation of atmospheric water vapour that falls under gravity for instance; drizzle, rain, sleet, snow, graupel and hail.

Direct effects are:

• Selection of crops: High and well distributed rainfall areas are suitable for cereals and other popularly cultivated crops. At low and ill distributed areas are suitable for drought resistance crops.
• During high amount of precipitation in form of rainfall, crops are susceptible to rot diseases, water logging, damage of branches, etc.
• Snowfall and hailstorms may cause injury to the plant.
• Rainfall especially during the time of pollination can cause substantial reduction in the yield of the crops.

b. Effect of relative humidity: 

Relative humidity is the actual humidity present and the saturation humidity possible in that temperature.

• High relative density enhances the incidence of various diseases and pests and is very conducive for growth of several bacteria and fungi along with favorable environment for pest infestations.
•  On the other hand low RH leads to excessive evapotranspiration causing wilting of the plants and even closure of stomata rendering gaseous exchange , photosynthesis and respiration.

  4.Define weather and climate (2071)

Weather: A state or condition of the atmosphere at a given place or given instant of time. Weather is highly variable and varies even within an hour or from day to day.

Climate: The generalized weather or summation of weather conditions over a given region during comparatively longer period of time. OR Climate is the sum of statistical information of weather in a particular area during a specified interval of time usually a season or year or even a decade. Climate generally involves larger areas like zones, a country.

5. Draw light response curve to show the effect of solar radiation on the field crops. ( 2071 )