Which is a requirement associated with leaves as photosynthetic organs?
a)All leaf cells must have direct cell-to-cell contact with the vascular tissues.
b)Interior leaf temperatures must fluctuate between night and day.
c)Leaves must receive an extended period of darkness every day.
d)The mesophyll cells must be continually supplied with water vapor.
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| Answer: a |
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Why are dicot leaves broad and flattened?
a)to conserve energy required to produce thick leaves
b)to increase the transpiration rate through the cuticle
c)to maximize the exposure of the leaf surface to light
d)to reduce the mass that could cause limbs to break |
| Answer: c |
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Which epidermal feature of a leaf has the greatest impact on conserving water?
a)bulliform cells
b)cuticle
c)stomata
d)trichomes |
| Answer: b |
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If water loss from leaves is a concern, why do leaves have stomata?
a)to allow the diffusion of carbon dioxide and oxygen
b)to cause the leaf to curl inward in times of drought
c)to provide additional photosynthetic capabilities
d)to slow air movement close to the leaves |
| Answer: a |
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Which region of a leaf has the greatest concentration of chloroplasts and therefore the highest rate of photosynthesis?
a)lower epidermis
b)palisade layer
c)spongy mesophyll layer
d)upper epidermis |
| Answer: b |
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Which plant pigments belong to a class of molecules called flavonoids; appear red, purple, or blue; and protect plants from overexposure to ultraviolet light and extreme temperatures?
a)anthocyanins
b)carotenoids
c)chlorophyll b
d)xanthophylls |
| Answer: a |
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What functions to regulate the movement of substances between the vascular tissue and the mesophyll and protect the vascular tissue from exposure to air?
a)bundle sheath
b)guard cells
c)trichomes
d)xylem |
| Answer: a |
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Which is the best reason why it is advantageous for evergreen leaves of conifers to last for three to four years before being shed?
a)Coniferous evergreen plants in the tropics receive only about 12 hours of sunlight a day, so they must keep their leaves to compete with other plants.
b)Keeping their leaves provides the advantage of photosynthesis during the time of the year when potential photosynthetic rates are the highest.
c)Insect pests take a toll on coniferous evergreens, so they have to retain as many leaves as possible for as long as possible.
d)The metabolic cost of producing and retaining leaves is recovered via photosynthesis over several growing seasons as opposed to the single season.
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| Answer: d |
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Why have broadleaf plants evolved to be deciduous?
a)Abscission allows a plant to withdraw essential minerals.
b)Deciduous plants have a longer period for photosynthesis.
c)Leaf tissues would likely die of extreme desiccation in winter.
d)Secondary pigments are exposed to higher light intensity. |
| Answer: c |
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Which type of modified leaf encloses meristem tissue and protects it from injury and desiccation during winter months?
a)bract
b)bud scale
c)leaf scale
d)tendril |
| Answer: b |
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