What Is Transpiration?
Transpiration is the loss of water from the plant through evaporation at the leaf surface. Transpiration happens when plant opens its stomata to let in carbon dioxide, water on the surface of the cells of spongy mesophyll and palisade mesophyll evaporates and diffuses out of the leaf. Transpiration is the main driver of a continuous column of water in xylem.
Transpiration occurs because plants take in more water than they actually need at a given time. It is a way of getting rid of excess water. When excess water is removed from the plant, the plant can easily access the necessary carbon dioxide that it needs for photosynthesis. In most plants, transpiration is a passive process largely controlled by the humidity of the atmosphere and moisture content of the soil.
Transpiration is greatly affected by the following factors:
- Temperature
- Energy availability
- The humidity gradient away from the surface.
- Wind speed
- Water availability
Morphological factors such as reduced leaf surfaces, heavy cuticle layer on the leaves, low numbers of stomata and stomata recessed below the other epidermal cells lowers the rate of transpiration. Desert plants such as conifers and cacti conserve water in these ways.
What Is Guttation?
Guttation can be described as the exudation or secretion of droplets of sap (xylem) through specialized tissue referred to as hydathodes. Guttation happens in certain plants that have vascular systems such as grass, barley, wheat, strawberries, tomatoes and other small plants. Guttation can also be defined as the process by which plants emit water at the tip of the leaf or in the injured leaf part.
Usually Guttation happens at night when the soil is very moist. If there is too much water in the soil, root pressure causes the water to squeeze out of the plant and onto the tips of the leaves or the blades of the plant. As water from the soil passes through the plant to enhance guttation process, it picks up minerals, enzymes and other chemicals and this is referred to as xylem sap.
Unlike transpiration process, guttation depends on certain
conditions like high relative humidity in the atmosphere and the amount of
water in the soil.
Also Read: Difference Between Respiration And Photorespiration
Transpiration Vs. Guttation In Tabular Form
| BASIS FOR COMPARISON | GUTTATION | TRANSPIRATION |
| Description | Guttation is the secretion of droplets of water from the pores of plants. | Transpiration is the loss of water by a plant in the form of vapor. |
| Occurrence | Guttation happens only through hydathodes. | Transpiration occurs through epidermal cells, lenticels or through stomata. |
| Regulation | Hydathode lacks a closing and opening mechanism and therefore guttation is unregulated. | The rate of transpiration is regulated through regulation of opening and closing of the stomata. |
| Factors Influencing The Process | Atmospheric humidity and availability of water have an influence on guttation process. | There are numerous factors that influence the rate of transpiration, some of the factors include: Nature of stomata Availability of water in the soil Wind flow Presence of transpiration inhibitors. |
| Plant Wilting | Excessive transpiration during dry seasons can result to plant wilting. | Guttation be it excessive or not, it will never cause plant wilting. |
| Transpired/ Guttated water | Guttated water is a dilute solution of both inorganic and organic substances. | The transpired water is pure water. |
| Occurrence | Guttation usually occurs at the margins and the tips of the leaves. | Transpiration occurs throughout the general surface of the leaves and the young stems. |
| Humid Condition | An increase in atmospheric humid condition has an effect of increasing the rate of guttation process | Increase in the atmospheric humid condition has an effect of reducing the rate of transpiration because this reduces diffusion rate. |
| Simple Diffusion | In the process of guttation, water loss is neither by diffusion nor any other process, but water just ooze out as small drops. | In the process of transpiration, water loss is through simple diffusion. Simple diffusion is whereby molecules move from a region of its highest concentration to a region of lower concentration. |
| Effect Of Dry Condition | Dry condition has an inhibiting effect on guttation. | The process of transpiration is favored on a great extend by dry conditions. |
| Period of Occurrence | Guttation usually occurs during night and early hours of the morning. | Most of the transpiration occurs during the hotter periods of the day. It is negligible during night time. |
| Xylem Pressure | Guttation occurs causes the development of a positive pressure in the xylem of the plant. | Transpiration causes the development of a negative pressure in the xylem of the plant. |
| Continuity of the Process | Guttation does not occur when the plant is under water stress (conditions of water deficiency). | Transpiration continues even when the plant is under water stress (condition of water deficiency). |
| Residue | A crust of salts is formed on the surface after the guttated liquid evaporates. | Transpiration does not leave anything on the surface of the plant. |
| Temperature | Guttation occurs when the temperature is low. | Transpiration occurs when the temperature is high. |
| Considered To Be | Guttation process is considered to be a type of secretion because hydathode is a secretory tissue. | Transpiration is never considered to be a secretion. |
Similarities Between Guttation and Transpiration
- Both processes occur through the leaf.
- In both transpiration and guttation water is lost through specialized pores.
- Both processes result in permanent water loss from the plant.
Also Read: Difference Between Diffusion And Facilitated Diffusion