Question 1

You are growing tomatoes and cucumbers in your garden which flower independently of day length because these plants are

Accepted Answer

Day-neutral plants are not dependent on day length for flowering.(Examples are tomato and cucumber. )

Question 2

When a ripe piece of fruit placed in a sealed glass container with several pieces of non-ripe fruit causes the non-ripe fruit to ripen,this is due to what group of plant hormones produced by the already ripe fruit?

Accepted Answer

Ethylene ripens fruit by increasing the activity of enzymes that soften fruits.

Question 3

Which of the following is chiefly responsible for the abscission of leaves,flowers,and fruit?

Accepted Answer

The presence of auxin,and perhaps gibberellin,probably initiates abscission.But once abscission has begun,ethylene stimulates certain enzymes,such as cellulase,which helps cause leaf,fruit,or flower drop.

Question 4

Which of the following statements about tropism is correct?

Accepted Answer

Growth toward or away from a stimulus,such as gravity or light,is a tropism.Growth toward a stimulus is called a positive tropism,and growth away from it is called a negative tropism.Phototropism is movement in response to a light stimulus.Gravitropism is movement in response to gravity.Thigmotropism is movement in response to touch.

Question 5

A plant physiologist is studying the cause of phototropism,which has what cause?

Accepted Answer

Positive phototropism of stems occurs because the cells on the shady side of the stem elongate due to the presence of auxin.

Question 6

The portion of the plant which is involved in controlling turgor movements is called

Accepted Answer

The portion of a plant involved in controlling turgor movement is a thickening called a pulvinus at the base of each leaflet.

Question 7

Which of the following have the largest effect on the biological clocks of plants?

Accepted Answer

Scientists suggest that biological clocks are synchronized by external stimuli to 24-hour rhythms.The length of daylight compared to the length of darkness,called the photoperiod,sets the clock.Temperature has little or no effect.

Question 8

A plant physiologist is studying plants which flower when the day length is shorter than a critical length,such as goldenrod and poinsettia,which implies that these are

Accepted Answer

Short-day plants flower when the day length is shorter than a critical length.(Examples are cocklebur,goldenrod,poinsettia,and chrysanthemum. )

Question 9

Which of the following enables plants to determine how much light a plant is getting?

Accepted Answer

Photoperiodism requires the participation of a biological clock,which can measure time,and it also requires the activity of a plant photoreceptor called phytochrome.

Question 10

Which of the following is an effect of a plant hormone other than ethylene?

Accepted Answer

Ethylene is involved in abscission and the ripening of fruits.Ethylene has other varied effects in plants,For example,ethylene,in addition to auxin is involved in axillary bud inhibition.Auxin,transported down from the apical meristem of the stem,stimulates the production of ethylene,and this hormone suppresses axillary bud development.Ethylene also suppresses stem and root elongation,even in the presence of other hormones.

Question 11

An unequal growth due to contact with a solid object is referred to as

Accepted Answer

Unequal growth due to contact with solid objects is called thigmotropism.

Question 12

If you were studying the internal mechanism by which a circadian rhythm is maintained in the absence of appropriate stimuli,you would be studying

Accepted Answer

The internal mechanism by which a circadian rhythm is maintained in the absence of appropriate environmental stimuli is termed a biological clock.

Question 13

If you were a biologist studying the coiling response in morning glory plants,what would you be studying?

Accepted Answer

Unequal growth due to contact with solid objects is called thigmotropism.An example of this response is the coiling of the tendrils or the stems of plants,such as morning glory.These growth changes occur when a plant part touches a solid object such as a trellis.The cells in contact with the object grow less,while those on the opposite side elongate.

Question 14

When a plant tracks the sun by means of turgor pressure changes in the petiole,this is called

Accepted Answer

Plant responses to environmental stimuli can involve movement,as when plants exhibit heliotropism,the tracking of the sun by means of turgor pressure changes in the petiole.

Question 15

Which of the following would cause a leaf cell to become turgid?

Accepted Answer

A leaf folds when the cells in the lower half of the pulvinus,called the motor cells,lose potassium ions (K+),and then water follows by osmosis.When the pulvinus cells lose turgor,the leaflets of the leaf collapse.Conversely,if water enters a limp leaf and cells exhibit turgor,the leaf moves as it regains its former position.This would be caused by an influx of K+,followed by an influx of water.

Question 16

In root cap cells,there are ________________ which are sensors that detect which direction is down.

Accepted Answer

Root cap cells contain sensors called statoliths,which are starch grains located within amyloplasts,a type of plastid.Perhaps gravity causes the amyloplasts to settle to a lower part of the cell.

Question 17

Which of the following would overturn what we know about phytochrome?

Accepted Answer

Phytochrome can be said to act like a light switch because it can be in the down (inactive)position or in the up (active)position.The presence of P_fr indicates that sunlight is available;P_r is present in the dark.

Question 18

Movements that occur over a regular 24-hour cycle are referred to as

Accepted Answer

Activities such as sleep movements that occur regularly in a 24-hour cycle are called circadian rhythms.

Question 19

Leaves that close at night are said to exhibit which movements?

Accepted Answer

Leaves that close at night are said to exhibit sleep movements.

Question 20

Which of the following statements is true about turgor movements?

Accepted Answer

Turgor movements are dependent on turgor pressure changes in plant cells.In contrast to tropisms,turgor movements do not involve growth and are not related to the source of the stimulus.

Quiz 24: Control of Growth Responses in Plants