Conditions and Resources

Conditions and Resources

Condition is Physicochemical features of the environment that may be altered by the activities of living organisms, but not consumed.  The example of conditions are temperature, relative humidity, pH, salinity, current velocity, soil structure and pollutant concentration. While resource is quantities of something that can reduced by the activities of a living organism during its growth and development. The example of resources  are solar radiation, inorganic materials - CO₂, water, oxygen, mineral nutrients (macro-, micronutrients), food, and space.

There are some effect of condition. They are:

1.      For each species, there is some level/concentration/intensity of a factor at which it does best - its optimum for that factor.

2.      Optimum conditions result in individuals with the highest fitness.

3.      Higher or lower levels of a factor result in reduced fitness or non-survival

For example there are some conditions and resources for the photosynthesys of Oryza sativa. The conditions are temperature, humidity, pH, salinity, soil structure. While the resources are water, mineral nutrients, air,  O₂, and the intensity of sunlight. 

Photosynthesis is influenced by two categories of factors - external or environmental and internal or plant factors. According to the law of limiting factors, put forward by F.F.Blackman in 1905, photosynthesis is limited by the most limiting factor. This means that, at any given time, only one factors is the most limiting factor among all and this factor determines the rate of photosynthesis.

1.      Carbondioxide

- In C₃ plants, the rate of photosynthesis increases with an increase. In CO₂ concentration upto 500 ml.l^-1.

- In C₄ plants, photosynthetic rate increases with an increase in CO₂ concentration. However these plants attain saturation at around 360 ml.l^-1 (as compared to C₃ plants - which is around 500 ml.l^-1)

The current level of CO₂ in the atmosphere is about 360 ml.l^-1.

2.      Intensity of Light

-Both quality and intensity of light influence the rate of photosynthesis.

-As the intensity of light increases, the rate of photosynthesis also increases. At a very high light intensity the rate of photosynthesis decreases as chlorophyll itself is destroyed due to high intensity. This phenomenon is called as photooxidation as it occurs in the presence of O_2.

-In moderate light intensities the rate of photosynthesis is directly proportional to irradiance.

3.      Temperature

Overall, the process of photosynthesis is sensitive to higher temperatures. This is because the enzymes involved in photosynthesis becomes inactive at higher temperatures. Low temperatures also inactivate the enzymes. Thus an optimum temperature is preferred. The optimum temperature lies between 15^o - 35^o C.

4.      Oxygen

Small quantity of oxygen is required for optimum photosynthetic electron transport.

5.      Soil Water

If water availability in the soil decreases, plants undergo water stress. Under the condition of water stress, the rate of photosynthesis declines, as istomata fail to open and leaf water potential decreases. It is observed that the rate of photosynthesis is reduced with the decrease hydration of the leaves.

6.      Nutrients

Among nutrients nitrogen influences the rate of photosynthesis. Reduction in nitrogen supply adversely affects photosynthesis, as nitrogen forms the basic constituent of chlorophyll. In general, all essential elements also affect the rate of photosynthesis.

7.      Leaf

Leaf age, leaf angle and leaf orientation also effect the rate of photosynthesis. Mg, Fe, Cu, Mn, Cl, S and K take part in photosynthesis.

8.      Air Pollutant

They decrease the rate of photosynthesis. Examples: Ozone, hydrogen fluoride, nitrogen oxide, sulphur dioxide, dust particles, smoke reduce light intensity and photosynthesis.