Primary productivity and climatic factors affecting rate of plant production.

Primary Productivity and climatic factors affecting rate of plant production.
M.sc Botany

1. NISHA KATARIA M.SC BOTANY P rimary Productivity

2. 2 In ecology, production (or productivity) refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per area per time (e.g. kg m –2  day –1 )

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4. 4 Primary Production Primary production describes the production of chemical energy in organic compounds by  producers The main source of energy for primary production is sunlight, but a fraction may be driven by chemosynthesis by lithotrophs Primary production may be categorised as one of two types: Gross primary production  (GPP) is the amount of chemical energy as biomass that a producer creates in a given length of time Net primary production  (NPP) is the amount of chemical energy that is not consumed by respiration (NPP = GPP – respiration)

5. 5 Secondary Production Secondary production describes the generation of biomass by heterotrophic organisms ( consumers ) This biomass generation is driven by the transfer of organic compounds between trophic levels via feeding Secondary production may also be categorised according to  gross  (total) and  net  (usable) amounts of biomass

6. 6 What is primary productivity? Primary productivity, the rate at which energy is converted to organic substances by photosynthetic producers, which obtain energy and nutrients by using sunlight, and chemosynthetic producers, which obtain chemical energy through oxidation. Nearly all of Earth’s primary productivity is generated by photosynthesis

7. 7 Primary productivity  is a term used to describe the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem. There are two aspects of primary productivity: Gross productivity  = the entire photosynthetic production of organic compounds in an ecosystem. Net productivity  = the organic materials that remain after photosynthetic organisms in the ecosystem have used some of these compounds for their cellular energy needs (cellular respiration).

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10. 10 Gross primary productivity , or GPP, is the rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time). Producers such as plants use some of this energy for metabolism/cellular respiration and some for growth (building tissues). Net primary productivity , or NPP, is gross primary productivity minus the rate of energy loss to metabolism and maintenance. In other words, it's the rate at which energy is stored as biomass by plants or other primary producers and made available to the consumers in the ecosystem.

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13. 13 Productivity  is the rate at which energy is added to the bodies of a group of organisms, such as primary producers, in the form of biomass.  Gross productivity  is the overall rate of energy capture.  Net productivity  is lower: it's gross productivity adjusted for the energy used by the organisms in respiration/metabolism, so it reflects the amount of energy stored as biomass. SUMMARY

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15. 15 The climatic factors are abiotic or non-living components of the environmental factors (outside of genetic factors) that affect plant growth and development. They are elements of climate.  There are other abiotic environmental factors, that is, topography and soil, which are treated in a separate page.  Under favorable conditions, gene expression is maximized. Ultimately, enhanced growth and development translates into high crop yields.  These climatic factors are enumerated below and either discussed briefly or a link is provided for specific elucidation.

16. 16 Light Light is a climatic factor that is essential in the production of chlorophyll and in  photosynthesis , the process by which plants manufacture food in the form of sugar (carbohydrate) and subsequently into other organic compounds. Through photosynthesis, the electromagnetic energy from the sun is converted to chemical energy which sustains almost all forms of life.

17. 17 Obviously this tree has a genetically dictated strong root system which enabled it to withstand the ravages of time, remaining defiant amid the terrifyint onslaught of the elements of climate particularly buffeting wind magnified by the pull of gravity

18. 18 Three properties of this climatic factor that affect plant growth and development are  light quality ,  light intensity , and  daylength or photoperiod .  Light quality  refers to the specific wavelengths of light;  light intensity  is the degree of brightness that a plant receives; and  daylength  is the duration of the day with respect to the night period.

19. 19 Water Water, as well as light, is an essential requisite to life. Some organisms can live without oxygen (called anaerobic), but these organisms and all others including all plants and animals inclusive of humans will perish without it. Rainfall is the most common form of precipitation and source of water to plants. It is the falling of water in droplets on the surface of the Earth from clouds. Other forms of precipitation are freezing rain, sleet or ice pellets, snowfall, and hail

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22. 22 Temperature The degree of hotness or coldness of a substance is called temperature (Eagleman 1985). It is commonly expressed in degree Celsius or centigrade ( o C ) and degree Fahrenheit ( o F ) . This climatic factor influences all plant growth processes such as photosynthesis, respiration, transpiration, breaking of seed dormancy, seed germination, protein synthesis, and translocation. At high temperatures the translocation of photosynthate is faster so that plants tend to mature earlier.

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25. 25 Relative Humidity The amount of water vapor that the air can hold depends on its temperature; warm air has the capacity to hold more water vapor than cold air. According to Eagleman (1985), there is almost one-half reduction in the amount of water vapor that the air can hold for every 10 C drop in temperature. Relative humidity (RH)  is the amount of water vapor in the air, expressed as the proportion (in percent) of the maximum amount of water vapor it can hold at certain temperature. For example, an air having a relative humidity of 60% at 27 C temperature means that every kilogram of the air contains 60% of the maximum amount of water that it can hold at that temperature . The relative humidity affects the opening and closing of the stomata which regulates loss of water from the plant through transpiration as well as photosynthesis. 

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28. 28 Wind as Climatic Factor Air movement or  wind  is due to the existence of pressure gradient on a global or local scale caused by differences in heating. On a global scale it consists of the jet stream flow and movement of large air masses. On the local scale only a smaller quantity of air moves. Surface winds are lower and less turbulent at night due to the absence of solar heating

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30. 30 Moderate winds favor gas exchanges, but strong winds can cause excessive water loss through transpiration as well as lodging or toppling of plants. When transpiration rate exceeds that of water absorption, partial or complete closure of the stomata may ensue which will restrict the diffusion of carbon dioxide into the leaves. As a result, there will be a decrease in the rate of photosynthesis, growth and yield 

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