Pollination is the transfer of a plant’s powdery reproductive material-pollen-from male plant parts to female ones, which allows the plant to reproduce. Most plants produce flowers that are pollinated by animals feeding on the plant’s pollen or nectar(sugar- rich liquid). Flowers often draw the initial attention of their pollinators by their bright colors, but most flowers also produce olfactory cues(smells) to attract attention. Olfactory cueing is more important for plants that rely on insects or mammals for pollination than it is for those that rely on birds. Birds, with very few exceptions, have virtually no sense of smell. Birds use vision for long-distance cues; insects have very poor distance vision but very keen abilities to detect fragrance(scent). Bat pollinators also have to rely more on their keen sense of smell as they move about in darkness.
Scent is typically a complex mixture of compounds emitted into the atmosphere, and the chemical structure of these compounds is closely tuned to attract the specific pollinators the plant most desires. Although the flowers of different species can be nearly identical in their color or shape, there are no two floral scents that are exactly the same because of the large diversity of volatile(gas- state)compounds and their relative abundances and interactions. Thus, scent is a signal that directs specific pollinators to a particular flower whose nectar and/or pollen is the reward. Species pollinated by bees and flies have sweet scents, whereas those pollinated by beetles have strong musty, spicy, or fruity odors. The fragrance of a flower is a finely tuned evolutionary response, not merely a horticultural curiosity, though our modern plant breeding programs have often disrupted these relationships by breeding for floral structure instead of fragrance. This is partially the result of plant-breeding programs designed to maximize the “life”of cut flowers. The production of fragrance has a metabolic (energy) cost to the flower. While fragrance increases the flower’s chance of being pollinated, it makes the flower wilt sooner. Everything being equal, a fragrant rose will wilt in a vase well before a nonfragrant one.
Plants can regulate the production of fragrance and tend to maximize it only when the flowers are ready for pollination and when their potential pollinators are active. The physical condition of the plant also affects the quality and production of fragrance. Plants that maximize their output during the day are primarily pollinated by bees or butterflies, whereas those that release their fragrance mostly at night are pollinated by moths and bats. During flower development, newly opened and immature flowers-those not yet ready to function as pollen donors-produce fewer odors and are less attractive to pollinators than are mature flowers. Once a flower has been sufficiently pollinated, quantitative and/or qualitative changes in flowers lead to their lower attractiveness and help to direct pollinators to unpollinated flowers instead, thereby maximizing the reproductive success of the plant.
The production of fragrance is complex and comes largely from the breakdown of certain structures in the flower. Fragrance can come from different parts of the flower. Some flowers have fragrant pollen, but it also can originate from parts of the petals and the pistil (the female reproductive part of a flower). Often it is produced in multiple locations, and the various fragrances mix with one another. Rose pollen, for example, contains a fragrance profile separate from the rest of the flower, but fragrances from the rest of the flower usually overpower pollen fragrances. The essential oils released evaporate and combine with one another to produce the distinctive fragrances recognized by the pollinators and ourselves. Different species of plants are more complex than others, depending on how complex their relationship is to specific pollinating insects. Orchids, for example, may produce one hundred different volatile compounds, whereas the garden snapdragon produces seven to ten.
Fragrance can be a lure that provides a tangible benefit to pollinators. Sometimes flowers produce compounds that are narcotics, and insects are lured and drugged until pollination is complete. Various orchids, among some others, produce sex pheromones that attract male insects looking for a mate or compounds they need to acquire a female. Other flowers produce products such as waxes and pheromones that insects store in their bodies to make them repellent to predators.
1
Pollination is the transfer of a plant’s powdery reproductive material-pollen-from male plant parts to female ones, which allows the plant to reproduce. Most plants produce flowers that are pollinated by animals feeding on the plant’s pollen or nectar(sugar- rich liquid). Flowers often draw the initial attention of their pollinators by their bright colors, but most flowers also produce olfactory cues(smells) to attract attention. Olfactory cueing is more important for plants that rely on insects or mammals for pollination than it is for those that rely on birds. Birds, with very few exceptions, have virtually no sense of smell. Birds use vision for long-distance cues; insects have very poor distance vision but very keen abilities to detect fragrance(scent). Bat pollinators also have to rely more on their keen sense of smell as they move about in darkness.
According to paragraph 1， which of the following pollinators is least likely to rely on olfactory cues to guide them to plants?
AInsects
BMammals
CBirds
DBats
2
Scent is typically a complex mixture of compounds emitted into the atmosphere, and the chemical structure of these compounds is closely tuned to attract the specific pollinators the plant most desires. Although the flowers of different species can be nearly identical in their color or shape, there are no two floral scents that are exactly the same because of the large diversity of volatile(gas- state)compounds and their relative abundances and interactions. Thus, scent is a signal that directs specific pollinators to a particular flower whose nectar and/or pollen is the reward. Species pollinated by bees and flies have sweet scents, whereas those pollinated by beetles have strong musty, spicy, or fruity odors. The fragrance of a flower is a finely tuned evolutionary response, not merely a horticultural curiosity, though our modern plant breeding programs have often disrupted these relationships by breeding for floral structure instead of fragrance. This is partially the result of plant-breeding programs designed to maximize the “life”of cut flowers. The production of fragrance has a metabolic (energy) cost to the flower. While fragrance increases the flower’s chance of being pollinated, it makes the flower wilt sooner. Everything being equal, a fragrant rose will wilt in a vase well before a nonfragrant one.
Why does the author point out that “While fragrance increases the flower’s chance of being pollinated, it makes the flower wilt sooner”?
ATo suggest that modern plant-breeding efforts to make certain flowers last longer involve limiting the capacity of these flowers to produce fragrance
BTo suggest that the methods used by modern plant breeders do not lead to the outcomes these breeders desire
CTo explain why modern plant-breeding programs have steadily improved a flower’s chances of being pollinated
DTo show why modern plant-breeding programs have resulted in flowers wilting more quickly than they naturally would
3
Scent is typically a complex mixture of compounds emitted into the atmosphere, and the chemical structure of these compounds is closely tuned to attract the specific pollinators the plant most desires. Although the flowers of different species can be nearly identical in their color or shape, there are no two floral scents that are exactly the same because of the large diversity of volatile(gas- state)compounds and their relative abundances and interactions. Thus, scent is a signal that directs specific pollinators to a particular flower whose nectar and/or pollen is the reward. Species pollinated by bees and flies have sweet scents, whereas those pollinated by beetles have strong musty, spicy, or fruity odors. The fragrance of a flower is a finely tuned evolutionary response, not merely a horticultural curiosity, though our modern plant breeding programs have often disrupted these relationships by breeding for floral structure instead of fragrance. This is partially the result of plant-breeding programs designed to maximize the “life”of cut flowers. The production of fragrance has a metabolic (energy) cost to the flower. While fragrance increases the flower’s chance of being pollinated, it makes the flower wilt sooner. Everything being equal, a fragrant rose will wilt in a vase well before a nonfragrant one.
According to paragraph 2， which of the following is true about floral scents?
ATo create their own floral scents, flowers combine compounds drawn from the atmosphere with compounds they produce.
BMany floral scents are surprisingly similar to one another because the number of pollinating species is limited.
CThe same types of floral scents attract both bees and beetles.
DFloral scents have evolved over time to function as signals for drawing a particular pollinator to a particular flower.
4
Plants can regulate the production of fragrance and tend to maximize it only when the flowers are ready for pollination and when their potential pollinators are active. The physical condition of the plant also affects the quality and production of fragrance. Plants that maximize their output during the day are primarily pollinated by bees or butterflies, whereas those that release their fragrance mostly at night are pollinated by moths and bats. During flower development, newly opened and immature flowers-those not yet ready to function as pollen donors-produce fewer odors and are less attractive to pollinators than are mature flowers. Once a flower has been sufficiently pollinated, quantitative and/or qualitative changes in flowers lead to their lower attractiveness and help to direct pollinators to unpollinated flowers instead, thereby maximizing the reproductive success of the plant.
According to paragraph 3， plants may maximize fragrance production based on all of the following factors EXCEPT
Athe plant’s physical condition
Bthe time of day when pollination is most likely to occur
Cthe quantity of potential pollinators
Dthe maturity of the flower
5
The production of fragrance is complex and comes largely from the breakdown of certain structures in the flower. Fragrance can come from different parts of the flower. Some flowers have fragrant pollen, but it also can originate from parts of the petals and the pistil (the female reproductive part of a flower). Often it is produced in multiple locations, and the various fragrances mix with one another. Rose pollen, for example, contains a fragrance profile separate from the rest of the flower, but fragrances from the rest of the flower usually overpower pollen fragrances. The essential oils released evaporate and combine with one another to produce the distinctive fragrances recognized by the pollinators and ourselves. Different species of plants are more complex than others, depending on how complex their relationship is to specific pollinating insects. Orchids, for example, may produce one hundred different volatile compounds, whereas the garden snapdragon produces seven to ten.
According to paragraph 4， which of the following statements is true about fragrance production in flowers?
AIn most flowers, the fragrance produced by pollen is not as strong as the fragrance produced by the rest of the flower.
BMost flowers produce fragrance at more than one location on the flower.
CMost flowers that have fragrant pollen do not have fragrant petals or pistils.
DIn some cases, fragrances from a group of flowers mix with one another to form a more complex scent.
6
Fragrance can be a lure that provides a tangible benefit to pollinators. Sometimes flowers produce compounds that are narcotics, and insects are lured and drugged until pollination is complete. Various orchids, among some others, produce sex pheromones that attract male insects looking for a mate or compounds they need to acquire a female. Other flowers produce products such as waxes and pheromones that insects store in their bodies to make them repellent to predators.
Which of the following can be inferred from paragraph 4 about orchids?
AThey produce fragrance in their pollen, petals, and pistils.
BThey have a less distinctive fragrance than other flowers do.
CThey have a very complex relationship with their pollinators.
DThey have a greater chance of being pollinated than snapdragons do.
7
Fragrance can be a lure that provides a tangible benefit to pollinators. Sometimes flowers produce compounds that are narcotics, and insects are lured and drugged until pollination is complete. Various orchids, among some others, produce sex pheromones that attract male insects looking for a mate or compounds they need to acquire a female. Other flowers produce products such as waxes and pheromones that insects store in their bodies to make them repellent to predators.
The word “tangible”in the passage is closest in meaning to
Asimilar
Bconcrete
Cadditional
Dsurprising
8
Fragrance can be a lure that provides a tangible benefit to pollinators. Sometimes flowers produce compounds that are narcotics, and insects are lured and drugged until pollination is complete. Various orchids, among some others, produce sex pheromones that attract male insects looking for a mate or compounds they need to acquire a female. Other flowers produce products such as waxes and pheromones that insects store in their bodies to make them repellent to predators.
In paragraph 5,all of the following are mentioned as strategies used by flowers to lure pollinators EXCEPT
Aproducing compounds that have a drug-like effect on pollinators
Bproducing compounds that smell like female insects
Cproducing compounds that attract females to the flower when males are present
Dproducing substances that help visiting insects to avoid predators
9
Pollination is the transfer of a plant’s powdery reproductive material-pollen-from male plant parts to female ones, which allows the plant to reproduce. [■] Most plants produce flowers that are pollinated by animals feeding on the plant’s pollen or nectar(sugar- rich liquid). [■] Flowers often draw the initial attention of their pollinators by their bright colors, but most flowers also produce olfactory cues(smells) to attract attention. [■] Olfactory cueing is more important for plants that rely on insects or mammals for pollination than it is for those that rely on birds. [■] Birds, with very few exceptions, have virtually no sense of smell. Birds use vision for long-distance cues; insects have very poor distance vision but very keen abilities to detect fragrance(scent). Bat pollinators also have to rely more on their keen sense of smell as they move about in darkness.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Natural forces such as wind and rain can carry pollen, but only a relatively small percentage of plants rely on these means.
Where would the sentence best fit？Click on a square sentence to the passage.
10
Pollination allows plants to reproduce.
ABecause pollinators typically depend more on olfactory than visual cues, flowering plants must rely more on scent than appearance to attract pollinators.
BModern plant-breeding practices have generally aided plant reproduction by genetically altering floral structures to accommodate a wider range of pollinators.
CFragrances vary in their chemical complexity and the locations on the plant where they are produced as well as the way in which they benefit pollinators.
DThe various compounds in floral fragrances help attract particular pollinators, who are rewarded for the activity of pollinating by gaining access to various substances.
EPlants can adjust their fragrance production over time to increase the chances that they are pollinated at the ideal point in their development, thereby ensuring the reproductive success of the plants.
FWhile some essential oils break down quickly, others persist and combine to produce complex scents of up to a hundred different compounds that attract pollinators.
