Online Plant Transpiration Lab

Here's the link for the online biology lab for plant transpiration.

Table

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Journal Questions

1) Describe the process of transpiration in vascular plants.
  The process of transpiration is the evaporation of water in plants through the stomata, which is located on the leaves for most plants.

2) Describe any experimental controls used in the Investigation.
  The experimental control is the transpiration rate of the plants in an hour under normal condition (room temperature and STP, without fan, heater or lamp)

3) What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?
  The factors I tested that increased the transpiration rate are wind, heat and light. The increase in wind and heat increased the transpiration rate for all plants, but the light only increased the transpiration rate for arrowhead, coleus, devil's ivy, English ivy and geranium.

4) Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?

  For most plants, the wind increases the transpiration rate more than other factors because the wind will increase the movement of water on the leaves, while reducing the layer of water vapor (boundary layer) on the leaf surface. 

5) Which species of plants that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?
  Rubber plant has the highest transpiration rates. Different species of plants transpire in different rates because they adapt to different environments through evolution.

6) Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?

  It would decrease the transpiration rate because the petroleum will prevent the stomata on the leaf from opening and evaporating water.

7) Of what value to a plant is the ability to lose water through transpiration?

  Because of its ability of cohesion, the water, while being transferred up through xylem, can also carry nutrients up from the roots. After the water is evaporated, the upper level of plant can absorb the nutrients and grow larger. Also, transpiration can moderate the surrounding temperature of the plant and increase air humidity.

- Andy Liu '15

Stuff about plant hormones

  Today I learned about three hormones that are important to plant growth. The first hormone is the auxin (IAA), and one of its major effects on plants is to stimulate the cell elongation and growth through phototropism. It's usually transported through parenchyma tissue from the shoot apex to the base at the rate of 10 mm/hr, and its direction is related to polarity instead of gravity. One of the major sites of auxin synthesis occurs in apical meristem of the plant. Binding to a receptor in plasma membrane of plant cell, the auxin is responsible for stimulating cell elongation. However, the cell elongation slows down when a high concentration of auxin occurs, since the production of ethylene, inhibitor of cell elongation, is induced to maintain homeostasis. Other effects of auxins include root and fruit development and secondary growth in the vascular cambium. 

Phototropism

  The second hormone I learned is the abscisic acid (ABA). The major function of abscisic acid is to slow down plant cell growth, in contrast to the function of auxins. Also, the acid controls plant cell dormancy. When a plant begins to wilt, the ABA in plant accumulates and allows stomata to close rapidly to reduce cell respiration and water loss. The acid is also the primary signal for plant to withstand droughts because ABA will be transported from root when a water shortage occurs. 

  The last hormone I learned is the ethylene. I already mentioned before that it is the inhibitor of cell elongation, and it is usually produced in response to harsh weather conditions, plant injuries, fruit ripening and high concentration of auxins. The change in balance of ethylene and auxin controls leaf abscission. For example, an aged leaf will produce less auxins and become more sensitive to ethylene. As the leaf accumulates more ethylene, the leaf will produce enzymes that digest cellulose and parts in the cell wall. Also, ethylene will also trigger the triple response when there is pressure on the stem, which slows down stem elongation and induces the plant to grow horizontally in order to circumvent the obstacle in front. Finally, the ethylene is also a part of positive feedback system, where it triggers fruit ripening, while fruit ripening induces more production of ethylene. 

- Andy Liu '15

FLOWERS, FLOWERS EVERYWHERE!!!! (lol)

1. I found this type of flowers near the Alamo dorm, and there are several trees like this one on campus. As you can see, the flowers mostly grow on the lower level of the branches, so the leaves on top can block the strong sunlight for them. The flower are also very open to pollen transport.

  Because of its high density on the tree, and its bright red color, this type of flowers is proven to be very attractive to bees. I found this bee collecting pollen 3 minutes after I began my observation.

2. I found these pink roses right next to Mr. Quick's house. As you can see, the pink roses are very open to pollen transport as well. The thorns on the stem of these flowers are used primarily for defense against predators, which they developed throughout evolution.

3. I also found this type of flowers near Mr. Quick's house. Even though these flowers are lower than the two types above, their position at the top of the bushes make them completely exposed to the strong sunlight. Also, the bright color of the flowers makes them attractive to bees as well.

- Andy Liu '15