What Is Transpiration
Transpiration is a process which helps in transportation of water within plant organs. This process is similar to that of evaporation, due to which loss of water takes place from the leaf surface, stem and flower of the plant. The opening on the surface of the leaves which helps in the process is called stomata which are again guided by guard cells which help in opening and closing of the pores. These openings are the pores through which water escape executing the transpiration.
The process creates a lower osmotic pressure due to which water is transported from the xylem of the root to the mesophyll tissue of the leaf cells. This pressure thus created is known as the transpiration pull. The transpiration pull establishes a suction pressure which enables water and minerals to reach different parts of the plant and provides adequate nourishment. This pressure thus created is also known as hydrostatic pressure. The amount of water escaping from the leaf surface affects the transpiration rate as obvious.
The process helps in cooling the plant in an excessive hot condition. This is why it is often suggested not to expose a plant to extreme sunshine as it wilts and dries out due to excessive transpiration rate. It is yet to be mentioned that the more the leaves in a plant, the greater is the transpiration rate. Transpiration is however a process which is affected by many external factors like light, humidity, temperature, and wind. Stomata pores open only whilst the presence of light, excepting those plants which execute night photosynthesis. Thus the presence of light facilitates transpiration as it opens the stomata pores guided by the guard cells. It is quite interesting to note how the transpiration rate is affected by wind.
When the evaporation of water occurs from the leaf surface the moisture or the water vapour remains settled above the surface of the leaf in the absence of wind thus making the potential drop a bit as their aren’t more space for the air above to hold on to much moisture. A windy climate can sway the water vapour away for more water vapour to be drawn out from the surface of the leaves. Again if the climate is more humid, the rate of transpiration is going to drop due to lesser water potential gradient. By water potential gradient we mean the pressure developed on the parts of the stem for a suction pressure to develop so as to pull the water molecules against gravity and supply it to the different parts of the plant.
Conclusion : More the temperature of the surrounding the more is the rate of evaporation, hence the transpiration rate. Thus a decreasing water potential gradient supports transpiration which is an important life process for plants.