1. Compare and contrast the functions of the plant hormones auxin, ethylene, cytokinin, and gibberellin.
2. Describe how water is pulled from the roots to the leaves of plants, including which parts of the plant are involved.
3. Describe the functions of guard cells.
4. Describe how sugar moves through a plant.
5. Compare and contrast phototropism, geotropism, and thigmotropism by giving an example of each.

1. Auxins is a plant hormone that plays role in the differentiation of vascular tissue, stimulates the release of ethylene, prevention of abscission, controls cellular elongation, and enhances fruit development. Cytokinin plays an important role in cell division, delay senescence, and activating dormant buds in plants. The function of ethylene hormone in plants is in fruit ripening, promoting abscission. Gibberellins stimulate pollen tube growth,  cause elongation of stems, initiate mobilization of storage materials in seeds during germination.

2. During transpiration, water is pulled from the roots to the leaves through a tissue called the xylem. As water evaporates out of the leaf, more water is 'pulled upwards' to replace lost water.

3. The stomata in the leaves are surrounded by guard cells. They can regulate the rate of transpiration by opening and closing the stomata.

4.During pressure flow, the sugar is transported from leaves to roots and phloem cells through the phloem via active transport.

5.

Phototropism refers to the growth of a plant in response to a light stimulus.

Example:  Sunflowers --  flowers turn to face with the sunlight.

Geotropism is a process in which plant grows in response to gravity.

Example: Roots -- grow downward in response to gravity

Thigmotropism is the directional response of a plant organ to  physical contact with a solid object.

Example: the growth of ivy on walls --  upon contact to walls

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