Plant responses to external and internal stimuli

Geotropism is a force that affects certain organisms.  Which of the following is an example of a plant responding to the external stimulus of gravity?

• A seedling growing towards a sunny window.
• Plant roots growing down into the soil.
• Flowers producing nectar to attract bees.
• A potted plant wilting when it dries out.

The flowers of the snow buttercup (Ranunculus adoneus) face one direction in the morning, move throughout the day, and face the other way be evening.  Most likely this is a response to which stimulus?

• Sun passing through the sky.
• Daily rainfall patterns.
• Daily rise and fall in temperature.
• Physical contact with passing animals.

Which of the following is an example of the effects of geotropism?

• Monarch butterflies migrate from Canada to Mexico each year.
• A hippopotamus submerges itself in water until the Sun goes down.
• A wilted flower returns to an upright position after being watered.
• A potted plant falls on its side, but it roots still grow downward.

A wilted plant will return to an upright position by using which of the following forces?

• Muscular contractions
• Gravitational attraction
• Turgor pressure
• Magnetic repulsion

When a seedling emerges upright from the soil, which force is it overcoming?

• Gravity
• Magnetism
• Repulsion
• Heat

Turgor pressure can help plants move.  Internal water pressure can cause-

• a wilted stem to return to an upright position.
• leaves to fall off a tree in the autumn.
• the roots of a plant to grow downward.
• a seedling to be carried by the wind.

Roots grow downward in the soil in response to-

• gravity
• sunlight
• water 
• wind

Which of the following best matches the stimulus with the correct response?

• F
• G
• H
• J

A student places a plant in a dark room next to a growth lamp, while providing sufficient water and nutrients to ensure the plant's growth and survival.  The plant is likely to respond by-

• bending towards the lamp.
• wilting and eventually dying.
• shedding all of its leaves.
• increasing its rate of photosynthesis

When a plant wilts due to a drought, it is responding to which of the following internal stimuli?

• Decreased water pressure within the plant cells.
• lack of nutrients carried by water in the plant.
• Decreased rate of photosynthesis in the stem.
• Increased storage of glucose in the leaves.