Editor’s note: This article has been reprinted. First published November 12, 2016.
Plants may seem like bystanders in the garden, but they are actually active communicators and have complex relationships with their surroundings. They don’t just absorb sunlight every day.
Plants have played an important role in human history beyond simply providing food. Before the advent of modern medicine, there were plants used for medicinal purposes. Ancient Egyptian scrolls detail 700 medicinal herbs and how they were used to treat patients.1
The World Health Organization (WHO) estimates that 80% of the world’s population uses mainly traditional remedies, many of which are derived from plants.2 Plants play a key role in the development of most new drugs, as manufacturers are using them to model synthetic drugs.3
Plants have a unique interconnectedness between each other, soil, microorganisms, pests and human health. Some of the latest research has discovered how plants know exactly when to increase their growth patterns to prepare for spring and summer.
Phytochrome has a dual function
In this short 1 minute and 30 second video, researchers at the University of Cambridge explain the process they discovered and how they expect it to be used in the future. An international team of scientists has discovered that phytochrome, a previously discovered plant molecule, performs two functions.4
Initially, scientists believed that plants only use phytochromes to sense light during daylight hours. Phytochromes are photoreceptor pigments primarily used to detect the red and far-infrared visible light spectrum.5 In plants, it was believed to be primarily responsible for germination, shade avoidance, and light sensing.
Exposure to red light triggers a chemical reaction that moves chromosomal proteins into a functionally active form, while exposure to darkness renders them inactive.6 Plants grow toward the sun as red light converts pigment proteins into active forms that increase the growth of plant cells.
Farmers and gardeners have known for centuries that when the weather warms, plants grow faster and begin to bloom, but now researchers are discovering the mechanisms behind this phenomenon.
Phytochromes, found in all plant cells when the sun sets, play another role in the health of some plants and measure the temperature of the night air.7 Scientists have discovered that the rate at which they change function is directly proportional to the ambient temperature.
In cold temperatures, the transition from active to inactive slows and plant growth also slows. As the weather warms, phytochromes become deactivated more quickly, triggering rapid growth in plants. This is the function responsible for early flowering of spring plants during warm winters.
Active phytochrome means slow growth
Phytochromes are activated during sunlight hours. In this state, it binds to plant DNA and intentionally slows growth. At night, phytochromes gradually become inactive and separate from the DNA, allowing the plant to grow again.
The inactivation of phytochromes in plants is called “dark return.” Lead study author Dr Philip Wigge, from the Sainsbury Laboratory at the University of Cambridge, explains the findings:8
“Just as mercury rises in a thermometer, the rate at which phytochromes return to their inactive state during the night is a direct measure of temperature. The lower the temperature, the slower the rate at which phytochromes return to their inactive state, so the molecules spend more time in their active state. , growth inhibition state.
This is why plants grow slower in winter. “Warm temperatures accelerate the return to darkness, allowing phytochromes to quickly reach an inactive state and dissociate from DNA, allowing genes to be expressed and plant growth to resume.”
This same process helps plants avoid shade from other plants and receive more sunlight. Once in the shade, phytochromes are quickly deactivated, which accelerates growth. These growths help the plant find sunlight.9 Interestingly, this light-induced change in plant pigment activity occurs within 1 second.10
Plants use day length or temperature to measure growth.
Not all plants use this method to determine when to increase growth. Some plants use day length instead. In warm winters, you may see daffodils blooming much earlier than expected due to their sensitivity to temperature.
The well-known garden rhyme relies on science discovered by chance. This rhyme was used to predict precipitation for the upcoming season. “Before the ashes are the oak, we will be drenched. Before the ashes are the oak, we will be watered.”
Oak trees rely on temperature to determine the start of their growing season, and ash trees depend on day length. Between 1751 and 1788, Robert Marsham recorded plant activity during spring on his estate in England.11 He pointed out that it is more common for ash trees to leaf out before oak trees.12
But that hasn’t been the case for the past few years. Just two years ago, in 2010 and 2013, ash trees had leaves before oak trees.13 Wigge explains:
“Oak trees are much more dependent on temperature, using phytochromes as thermometers to direct their development, while ash trees rely on measuring day length to determine seasonal timing.
Warmer springs increase the likelihood of hotter summers, which means oak leaves will emerge before ash. In a cold spring, you will see the opposite. “As Britons know only too well, cold summers are likely to bring rain.”
Farmers and gardeners use plant behavior to predict weather and harvests.
The effects of rising temperatures are being felt around the world. Although this study was conducted in the United Kingdom, other researchers are documenting similar changes in bud and leafing patterns in the United States.
A pilot project called Project Budburst, launched in 2007, allows people living anywhere in the United States to contribute to the data being collected.14
Measurements are taken as tree buds emerge and uploaded to a national database. Scientists around the world are studying these records to determine how a changing climate affects the timing of spring plant growth.
Scientists have noted that some plants are extending their growing seasons in response to climate change.
But while plants have ways to accommodate some of the changes, insects often reproduce and disperse based on sunlight rather than temperature. This can result in a mismatch between plant growth and insect pollination activity.15
Researchers also examined the relationship between heat and the time it takes to achieve harvest.
In one study using cucumbers, researchers found that plants grown early in the season needed more work to bloom and set fruit than plants planted later.16 Plants exposed to warmer temperatures appear to grow faster and produce fruit sooner, even if they were not planted earlier.
Montana State University Extension has developed a schedule of Growing Degree Days, or days when average temperatures are ideal for plant growth, to help farmers and gardeners better predict the best time to harvest.17 As warmer days begin to increase around the world, scientists at the University of Cambridge hope to use their research to breed wheat and rice plants that are more tolerant of warm temperatures.
Plants talk to each other and protect themselves from predators
Plants do more than just grow. They also communicate with each other and with predators. For example, when an insect begins to feed on a leaf, the plant “hears” or senses the insect’s vibrations and immediately mounts a defense.18
Researchers discovered that the plant deters bugs by producing phytochemicals that insects cannot eat. In these experiments, researchers recorded the plants’ responses to the vibrating sounds of caterpillars chewing. They later discovered that when plants were exposed to feeding sounds, they released greater amounts of phytochemicals to repel insects.
This study suggests that minor pest attacks on plants play an important role in promoting plant growth that contains higher levels of important nutrients for humans. One of the researchers noted the plant’s uncanny ability to distinguish between vibrations caused by a gentle breeze and those of a chewing insect.19
Another application of this discovery is to help strengthen plants’ natural chemical defenses by using vibration to increase chemical production. One of the researchers said:20
“This study also opens the window on plant behavior a little wider, showing that plants have many of the same responses to external influences as animals, although the responses appear different.”
Scientists have also discovered that plants use underground connections of mycorrhizal fungi, which form symbiotic relationships with plants. The fungus colonizes the roots and sends very fine filaments into the soil, which act as root extensions. Researchers discovered that these filaments transmit signals between plants, acting as an early warning system.21 This is one of the reasons soil tillage is so harmful because it disrupts and destroys important filaments.
