Abstract

Transpiration is one of the most common processes of temperature regulation. The rate of transpiration depends on several weather factors, such as wind and humidity, as well as structural factors. Previous studies have shown that increase of air movement result in increase of transpiration by the plant. This study aims to prove if wind affects the transpiration of Centaurea cyanus plant by increasing the rate of transpiration. Using a potometer, the range of transpiration was measured every three minutes for a total of thirty minutes, resulting in an increased transpiration rate for the plant that had an air current applied to it. In conclusion, wind is indeed a contributing factor in the determination of transpiration rates, effectively increasing them in the sample plants.

Introduction:

Centaurea cyanus, more commonly known as “Bachelor’s button” or “Cornflower”, is annual flowering plant belonging to the Asteraceae family. Because C.cyanus can be easily cultivated in a wide variety of soils (preferably in well-drained soils) and can tolerate extremely exposure to sun light this herb can be easily grown in areas such as North America, Europe, Brazil, and Asia. Its leaves are long and they emerge alternately on the stem, which can grow up to a height of 16-35 inches and is usually very thin and ramified, with flowers (usually containing a wide range of colors such as blue, pink or white) growing at their tips. The flowers are hermaphrodites, meaning they have male and female organs, and are pollinated with the help of other organisms such as insects.

C. cyanus has a wide range of medical applications. In French herbal medicine it is used for the eye treatments in the form of poultices or eyewashes; the gentle antiseptic and astringent properties of cornflower make the herb especially

effective against inflammation in the region of the eyes and conjunctivitis. The seed have also been used as gentle laxatives for children and as a stimulant for enhancing digestion and to support some internal organs such as the liver.

Plant transpiration is the release of water vapor to the atmosphere through the stomata by the evaporation of water located in the intracellular spaces inside the plant. Approximately 10% of all moist found in the atmosphere is released by transpiration; however, many external factors contribute to the rate of transpiration in organisms. Several factors, such as temperature, humidity, soil moisture, and air movement contribute to how much water vapor is released from the organism. Humidity and air movement have a close relationship in terms of affecting the rate of transpiration in plants; as water inside the cell evaporates, it saturates the air surrounding the leaf with water vapor, increasing the humidity around the leaf, which in turn decreases the rate of transpiration. However, if wind is present, blowing away the humid air and replacing it with drier air, water evaporation inside the

plant will continue, and therefore, the rate of transpiration in the plant will rise. In this experiment the rate of transpiration of C.

cyanus, a common grassland plant, when a air current is applied.

Materials and Methods

The experiment was based upon seeing how the rate of transpiration of C. cyanus was affected when an air current is applied. A potometer, or transpirometer shown in fig. 1, was utilized, which is a device used for measuring the rate of water uptake of a leafy shoot. . The set-up consisted of a 1.0 mL pipette with water; a connector tube to transport the water; clamps to hold the pipette and the plant in place; two lamps to induce photosynthesis; a

syringe to refill the pipettes if necessary; and a fan to produce the air current. First the stem was cut with a razor blade in order to fit the plant in the connector tube. Then, with a syringe, the pipette was filled with water until the meniscus read 0.9mL approximately. The plant stems were then placed in the connector tubes and only one had a fan placed directly in front of it; the other served as a control group. Every three minutes, for a period of thirty minutes, the amount of water in the 1mL pipette was measured to see the rate of water uptake of each stem cutting, which is directly proportional to their rate of transpiration.

Fig.1: Potometer set-up

Results

At first large difference between the two plants were not shown, but after several minutes the plant with the fan placed in front of it exceled in showing more transpiration than the control. According to the observations made during the experiment Plant B, containing the variable (wind), as shown in figure 1, show a wide range of transpiration while the control shows not transpiration at all. From the minute 6, table 1, the plant with the fan placed in front of it excelled in showing more transpiration than the control. The amount of water absorbed, and therefore, the rate of absorption of Centaurea cyanus plant increased by a factor of approximately 68 when exposed to wind.

Table 1: Average values of absorbed water

Figure 1: Average values of absorbed water

0 3 6 9 12 15 18 21 24 27 300.700000000000001

0.750000000000001

0.800000000000001

0.850000000000001

0.900000000000001

0.950000000000001

Average values of absobed water

Control (without breeze) Experimental (with breeze)

Time (minutes)

Pipe

t mea

sum

ents

(mL)

*Pipet measurements are inversely proportional to the amount of water transpired.

Average amount of absorbed wate

Experimental: 0.1020mL

Control:0.0015mL

Average rate of absorption:

Experimental: 0.00340mL/min

Control: 0.00005mL/min

Increase Factor: 68

Discussion

The data in the Table 1 demonstrated that during the first few minutes a large difference between the two plants wasn’t evident, but after six minutes the experimental plant absorbed more quantities of water that the control plant. This is due to the fact that wind carries away the humid air over the plant’s surface, more specifically, the leaves. This, in turn increases the rate of water evaporation from the intercellular spaces inside the leaf, which increases the rate of transpiration. This is evident by the amount of water that the experimental plant absorbed; the plant was losing water through evaporation. These results are consistent with the information presented in the class textbook that states that this phenomenon is due to the fact that when there is wind present, the water vapor near the surface of the leaf is blown away, affecting the vapor pressure difference across the surface and accelerating the rate of evaporation of water from the intercellular spaces in the leaf, which in turn, increases the rate of transpiration (Raven et al., 2005). The results also coincide with recent investigations that state that increase air circulation

Time (minutes) Control (without breeze) Experimental (with breeze)0 0.8975 0.84603 0.8950 0.84456 0.8973 0.84409 0.8970 0.7985

12 0.8970 0.787515 0.8970 0.796818 0.8968 0.796021 0.8965 0.794824 0.8965 0.793527 0.8965 0.792530 0.8960 0.7440

increase the rate of transpiration (Thongba et al., 2010). In conclusion, the hypothesis of this investigation was proven to be true because the environmental factor, wind, did in fact increase the rate of transpiration of the Centaurea cyanus plant. Further investigations might be able to provide an insight into more adequate techniques for plant care.

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