PLANT ‘THERMOMETER’ TRIGGERS SPRINGTIME GROWTH BY MEASURING NIGHT-TIME HEAT
A photoreceptor molecule in plant cells has been found to have a second job as a thermometer after dark – allowing plants to read seasonal temperature changes. Scientists say the discovery could help breed crops that are more resilient to the temperatures expected to result from climate change
A
An international team of scientists led by the University of Cambridge has discovered that the ‘thermometer’ molecule in plants enables them to develop according to seasonal temperature changes. Researchers have revealed that molecules called phytochromes – used by plants to detect light during the day – actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.
The new findings, published in the journal Science, show that phytochromes control genetic switches in response to temperature as well as light to dictate plant development.
B
At night, these molecules change states, and the pace at which they change is ‘directly proportional to temperature’, say scientists, who compare phytochromes to mercury in a thermometer. The warmer it is, the faster the molecular change – stimulating plant growth.
C
Farmers and gardeners have known for hundreds of years how responsive plants are to temperature: warm winters cause many trees and flowers to bud early, something humans have long used to predict weather and harvest times for the coming year. The latest research pinpoints for the first time a molecular mechanism in plants that reacts to temperature – often triggering the buds of spring we long to see at the end of winter.
D
With weather and temperatures set to become ever more unpredictable due to climate change, researchers say the discovery that this light-sensing molecule also functions as the internal thermometer in plant cells could help us breed tougher crops. ‘It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to achieving this. Key crops such as wheat and rice are sensitive to high temperatures. Thermal stress reduces crop yields by around 10% for every one degree increase in temperature,’ says lead researcher Dr Philip Wigge from Cambridge’s Sainsbury Laboratory. ‘Discovering the molecules that allow plants to sense temperature has the potential to accelerate the breeding of crops resilient to thermal stress and climate change.
E
In their active state, phytochrome molecules bind themselves to DNA to restrict plant growth. During the day, sunlight activates the molecules, slowing down growth. If a plant finds itself in shade, phytochromes are quickly inactivated – enabling it to grow faster to find sunlight again. This is how plants compete to escape each other’s shade. ‘Light-driven changes to phytochrome activity occur very fast, in less than a second,’ says Wigge.
At night, however, it’s a different story. Instead of a rapid deactivation following sundown, the molecules gradually change from their active to inactive state. This is called ‘dark reversion’. ‘Just as mercury rises in a thermometer, the rate at which phytochromes revert to their inactive state during the night is a direct measure of temperature,’ says Wigge.
F
‘The lower the temperature, the slower the rate at which phytochromes revert to inactivity, so the molecules spend more time in their active, growth-suppressing state. This is why plants are slower to grow in winter. Warm temperatures accelerate dark reversion, so that phytochromes rapidly reach an inactive state and detach themselves from the plant’s DNA – allowing genes to be expressed and plant growth to resume.’ Wigge believes phytochrome thermo-sensing evolved at a later stage, and co-opted the biological network already used for light-based growth during the downtime of night.
G
Some plants mainly use day length as an indicator of the reason. Other species, such as daffodils, have considerable temperature sensitivity, and can flower months in advance during a warm winter. In fact, the discovery of the dual role of phytochromes provides the science behind a well-known rhyme long used to predict the coming season: oak before ash we’ll have a plash, ash before oak we’re in for a soak.
Wigge explains: ‘Oak trees rely much more on temperature, likely using phytochromes as thermometers to dictate development, whereas ash trees rely on measuring day length to determine their seasonal timing. A warmer spring, and consequently a higher likeliness of a hot summer, will result in oak leafing before ash. A cold spring will see the opposite. As the British know only too well, a colder summer is likely to be a rain-soaked one.’
H
The new findings are the culmination of twelve years of research involving scientists from Germany, Argentina and the US, as well as the Cambridge team. The work was done in a model system, using a mustard plant called Arabidopsis, but Wigge says the phytochrome genes necessary for temperature sensing are found in crop plants as well. ‘Recent advances in plant genetics now mean that scientists are able to rapidly identify the genes controlling these processes in crop plants, and even alter their activity using precise molecular “scalpels”,’ adds Wigge. ‘Cambridge is uniquely well-positioned to do this kind of research as we have outstanding collaborators nearby who work on more applied aspects of plant biology, and can help us transfer this new knowledge into the field.’
Questions 27-32
Do the following statements agree with the information given in Reading Passage 3?
In boxes 27-32 on your answer sheet, write
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
27. The Cambridge scientists’ discovery of the ‘thermometer molecule’ caused surprise among other scientists.
28. The target for agricultural production by 2050 could be missed.
29. Wheat and rice suffer from a rise in temperatures.
30. It may be possible to develop crops that require less water.
31. Plants grow faster in sunlight than in shade.
32. Phytochromes change their state at the same speed day and night.
Questions 33-37
Reading Passage 3 has eight sections, A-H.
Which section contains the following information?
Write the correct letter, A-H, in boxes 33-37 on your answer sheet.
33. mention of specialists who can make use of the research findings
34. a reference to a potential benefit of the research findings
35. scientific support for a traditional saying
36. a reference to people traditionally making plans based on plant behaviour
37. a reference to where the research has been reported
Questions 38-40
Complete the sentences below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 38-40 on your answer sheet.
38. Daffodils are likely to flower early in response to ………………….. weather.
39. If ash trees come into leaf before oak trees, the weather in ………………….. will probably be wet.
40. The research was carried out using a particular species of ………………….. .
LỜI GIẢI CHI TIẾT
27. The Cambridge scientists’ discovery of the ‘thermometer molecule’ caused surprise among other scientists.
Answer: NOT GIVEN
– There is no such information given in the passage. There is some information related to the discovery of the thermometer
molecule by Cambridge scientists in paragraph A, but there is no such information whether it caused surprise among other scientists or not.
28. The target for agricultural production by 2050 could be missed.
Answer: TRUE
– D paragraph, fourth line. “It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to
achieving this.” Here, it is given that the target for 2050 could not be achieved due to climate change. It means it could be missed.
29. Wheat and rice suer from a rise in temperatures.
Answer: TRUE
– D paragraph, fifth line. “Key crops such as wheat and rice are sensitive to high temperatures. Thermal stress reduces crop yields by around 10% of every one degree increase in temperature.” Sensitive means wheat and rice are affected by high temperatures.
30. It may be possible to develop crops that require less water.
Answer: NOT GIVEN
– There is no such information given in the passage.
31. Plants grow faster in sunlight than in shade.
Answer: FALSE
– In E paragraph, second line. “During the day, sunlight activates the molecules, slowing down growth. If a plant finds itself in shade,
phytochromes are quickly inactivated – enabling it to grow faster to nd sunlight again.” Here, it is given that sunlight slows the growth of a
plant, and in the shade, the plant grows faster to nd sunlight. The question statement contradicts the information given in the passage.
32. Phytochromes change their state at the same speed day and night.
Answer: FALSE
– In E paragraph’s 1st part’s second-last line. “’Light-driven changes to phytochrome activity occur very fast, in less than a second,’ says
Wigge. At night, however, it’s a different story. Instead of a rapid deactivation following sundown, the molecules gradually change from their
active to inactive state.” Here, the writer said that during the day, the state of phytochromes changes very fast. However, at night, it changes
gradually (slowly). The question statement contradicts the information given in the passage.
Questions 33-37. Which section contains the following information?
33. mention of specialists who can make use of the research findings
Answer: H
– In H paragraph, seventh line. “’Cambridge is uniquely well-positioned………. Into the eld” In these lines they talk about outstanding
collaborators (specialists) who work on more applied aspects of plant biology. Outstanding collaborators can help this new knowledge
(research findings) into the elds.
34. a reference to a potential benefit of the research findings
Answer: D
– In D paragraph, 8th line. “’Discovering the molecules that allow plants to sense temperature has the potential to accelerate the breeding of
crops resilient to thermal stress and climate change.” Here, the writer said that molecules have the potential to speed up the breeding of
crops. It is the potential (having the capacity to do something in the future) benet of the research.
35. scientific support for a traditional saying
Answer: G
– In G paragraph, third line. “In fact, the discovery of the dual role of phytochromes provides the science behind a well-known rhyme long used to predict the coming season: oak before ash we’ll have a splash, ash before oak we’re in for a soak.” Here, ‘well-known’ means ‘famous’, and it is said that this rhyme was used earlier (means it is traditional) to predict the season. The writer said that certain discovery gives the science behind this rhyme. Hence, it provides scientific support to this traditional rhyme.
36. a reference to people traditionally making plans based on plant behavior
Answer: C
– In C paragraph, first line. “Farmers and gardeners have known for hundreds of years how responsive plants are to temperature: warm
winters cause many trees and flowers to bud early, something humans have long used to predict weather and harvest times for the coming year.” Here, the writer said that farmers and gardeners know about plants’ behavior to temperature, and they used this knowledge to predict weather and harvest times (plan).
37. a reference to where the research has been reported
Answer: A
– In A paragraph’s 2nd part’s first line. “The new findings, published in the journal Science, show that phytochromes ….” Hence, the research
(new findings) has been reported in the journal Science.
Questions 38-40. Complete the sentences below.
38. Daffodils are likely to flower early in response to ………. weather
Answer: Warm (winter)
– In G paragraph, first line. “Other species, such as daffodils, have considerable temperature sensitivity, and can flower months in
advance during a warm winter.” Here, the writer said that daffodils flower early during a warm winter.
39. If ash trees come into leaf before oak trees, the weather in ………. will probably be wet.
Answer: Summer
– In G paragraph, eighth line. “A warmer spring, and consequently a higher likeliness of a hot summer will result in oak leafing before
ash. …….. a colder summer is likely to be a rain-soaked one.” The meaning of above lines is that warmer spring > hot summer > oak leafing before ash. The opposite of it: ash leafing before oak > colder spring > colder summer (rain-soaked). ‘Rain-Soaked’ means ‘wet’.
40. The research was carried out using a particular species of ………. .
Answer: Mustard plant(s) / mustard
– In H paragraph, second line. “The work was done in a model system, using a mustard plant called Arabidopsis, …” In the first line of this paragraph, the writer started discussing the research, and later in this line, it is said that the work was done using a mustard plant.
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