It’s so cold! You have long johns and down jackets, but what about the plants?

Winter is here, but fortunately the author (Yimu Foodie Team) has used a whole year of delicious food to store up a thick layer of fat to resist the cold. If we can sit around the stove, make a small fire, roast some sweet potatoes, and boil a cup of hot tea, that is the comfort that can only be found in winter.

In human history, facing the cold was not always so pleasant. During millions of years of evolution, humans had to shed their thick hair system to dissipate heat, but in order to obtain space and food, they had to put on various animal skins and conquer the colder places further north or higher. It was not until the past hundred years, with the blessing of various technologies, that well-fed and well-drinking humans truly set foot on the tops of the mountains in the South and North Poles and on all continents.

Gentiana depressa and snowy mountains (Photo: Shangguan Fazhi)

Fighting against the cold is difficult for humans, but how can it be easy for plants? In order to compete for sunlight and nutrients, many plants have embarked on a journey to cold regions, the Arctic and Antarctic Circles, or high mountains hundreds of millions of years ago.

In many high mountainous areas of the North and South Poles and continents, there are almost no trees due to temperature and water conditions. Instead, there are various low shrubs and a large number of lichens and mosses, which is why the tundra got its name. Nearly 25 million km² of the Earth's surface is covered by polar tundra, which is the truly coldest place on Earth.

Vegetation in the Arctic Circle (Image source: https://daac.ornl.gov)

The first difficulty that needs to be challenged in the process of advancing to the polar continent for survival is low temperature. On the one hand, low temperature will freeze the cell tissues of plants, and on the other hand, it will hinder the process of plant physiological metabolism.

For polar plants, what they fear is not the freezing cold of winter, but the unforgettable low temperatures of summer.

During the winter frost period, plants will reduce the water content in their bodies, increase antifreeze proteins, and enter a full dormant state. If they can hold on, the winter will pass.

Spring is their growing season and the beginning of their survival challenges. The average daily temperature in polar regions rarely exceeds 13-18°C, and often hovers between 5-8°C. For example, in the warmest areas of Greenland, the average temperature is still below 10°C in the warmest months, and the average temperature is above zero for only 2-6 months a year. They also have to face the frequent cold snaps in late spring, so every measure to keep warm and increase temperature is crucial for polar plants. Even a small increase in temperature can play a key role in the plants' growing season when every second counts, thereby gaining the opportunity to survive and develop. In order to resist low temperatures, polar plants have evolved a series of interesting and practical strategies.

Here, if you are tall, you may not survive

Most tundra plants are no more than 6-8cm tall, so the cold wind from overhead is not easy to blow in. In the relatively low surface microhabitats, there is a relatively high and stable temperature, which ensures that the growth process can proceed quickly.

Scientists have found that the air temperature of Saxifraga oppositifolia is only 0.5℃ at 2 meters above it, while the surface temperature can reach 3.5℃ at 1cm. The temperature between the buds of several flowers can reach 6℃. Other studies have found that some plants can make local temperature differences reach nearly 22℃ by taking advantage of environmental conditions, such as hiding deep in bushes or cracks in rocks.

Norwegian Saxifrage (Image source: Wikipedia)

On low surfaces, knowing how to cover yourself with a blanket is also an important skill.

Many plants hide themselves in old leaves that have died and fallen for many years when they germinate, which greatly reduces the adverse effects of cold on plant growth. Sometimes when faced with sudden cold snaps, the natural ice shell formed by ice and snow is also an important insulation layer, just like the igloos of the Arctic Eskimos, which can largely isolate the impact of extreme low temperatures.

Long johns are good, and plants in extremely cold regions know it

Like many animals, if many individuals are huddled together and covered with fur and long hair, it is undoubtedly a good strategy to keep warm. This is very common in polar plants. These fur not only protect the plants through the cold winter, but also play a key role during the flowering and fruiting period, ensuring that important reproductive organs such as flowers and fruits mature faster and are not damaged by frost.

Chionocharis hookeri (Photo: Shangguan Fazhi)

Saussurea quercifolia (Photo: Shangguan Fazhi)

Plants chase the sun. Does it look like you in the south wanting to get closer to the "little sun"?

The flowering temperature of polar plants is often higher than the growth and development requirements. Some species require a minimum temperature of 3-8℃ for flowering, while a large number of blooms require a temperature of 5-12℃. In order to track the warm sunlight, the petals of some plants form a reflector shape like a solar cooker, and the direction of the flowers rotates every day with the position of the sun in the sky. This is the famous "solar cooker" plant among polar plants. Studies have shown that this method can effectively increase the temperature by about 10℃. The more famous Arctic plants include the mountain fairy tree Dryas integrifolia and the Arctic poppy Papaver radicatum.

Mountain Fairy (nargs.org) and Arctic Poppy (www.dreamstime.com)

Using color is also a trick that polar plants will not miss. The temperature of some flowers will increase as the color becomes darker. Compared with light-colored flowers, some dark-colored flowers will increase the temperature by 4.2°C. The increase in temperature can accelerate the growth and development of flowers, and can also significantly improve the efficiency of pollination, encouraging insects that seek warmth to pollinate them. In alpine environments, various dark and even nearly black flowers are not uncommon.

Lamiophlomis rotata and Thermopsis barbata (Photo: Shangguan Fazhi)

If you are not destined to grow in a greenhouse, build one yourself.

In addition to using color to increase temperature, using petal structure to increase temperature is also an excellent way. Similar to the principle of Kongming lanterns or hot air balloons, the petals of many polar alpine plants form a bell-shaped structure, which effectively collects heat inside the flower, like a warm lantern to attract insects to visit.

Lilium lophophorum (Photo: Shangguan Fazhi)

Fritillaria delavayi (Photo: Shangguan Fazhi)

"Hot summer during the day and severe winter at night" is a description of the low-latitude and high-altitude polar environment. Here, sunlight radiation is not a luxury, so many greenhouse plants are born. If you can't grow in a greenhouse environment, then "build" one yourself.

The most famous Rheum nobile is a representative of greenhouse plants, with an average height of 1.5m. The light yellow translucent bracts of Rheum nobile wrap the racemes inside, which play a role in keeping the greenhouse warm. The temperature inside the inflorescence can be about 10℃ higher than that outside, which is an important place to attract some insects for dating, eating and even reproduction. Of course, the insects also give it pollination in return.

Pagoda yellow (Photography: Xiang Jianying)

Sacrifice a small part to preserve the overall situation. Surviving in low temperatures is more important.

In nature, rosette-shaped structures are not only geometrically beautiful, but also reflect the wisdom of plants in coping with the environment. This is particularly common in some xerophytic succulents and alpine polar plants.

The Dendrosenecio and Lobelia plants growing in the high mountains of Africa are well-known representatives of large rosettes, which have adapted to the cold climate of the high mountains of Africa through long-term evolution. Unlike the low tundra plants in the Arctic and Antarctic, they are not troubled by extreme low temperatures and permafrost, and the plants can reach several meters in height.

The rapid drop in temperature at night is the primary problem faced by these plants. The huge rosette leaves can fold together to form a shape similar to cabbage, protecting the flower buds inside the curled leaves from being harmed by the low temperature at night. Some species even curl their leaves inward at night to further isolate the cold air. In addition, the structure of the cabbage protects the internal stems and leaves from frostbite even if the external structure of the plant is destroyed and dies. The curled leaves of some of these alpine plants also secrete a viscous liquid, which uses the characteristics of the liquid's specific heat being greater than the air's slower heat dissipation to protect the flower buds that are very sensitive to low temperature damage. With these protective measures, even if the outside temperature is below zero, the temperature inside the plant can still be guaranteed to be above 2°C.

Dendrosenecio keniodendron and Lobelia keniensis

Source www.thenational.ae and it.wikipedia.org

It is good to be able to take advantage of the environment, but only if you can resist the cold can you live well.

For plants that can live in the beautiful polar wonderland, in addition to various sets of high-level "external skills", they also need "internal skills" that are plain, practical and effective.

Androsace spinulifera (Photo: Shangguan Fazhi)

Polar plants resist the damage caused by low temperatures by regulating high osmotic pressure in their bodies, allowing calcium ions to quickly flow into the cell fluid when the temperature drops rapidly. For example, Epilobium latifolium can suddenly encounter temperatures as low as -3 degrees Celsius during its flowering period, but it is safe and sound after thawing. Some shrub species that grow in the Arctic can also withstand temperatures as low as -8 degrees Celsius during their growing season.

Lichens can solve the problem of cold protection and physiological and biochemical activities under low temperatures by regulating antifreeze proteins and osmotic pressure control in the body. For example, some leaf lichens can be dehydrated to 50% and still respire efficiently, while others can photosynthesize under very low light conditions.

In the polar tundra, there are few annual plants, but more perennial herbs and low shrubs. The moonlight-like lifestyle of annual plants is not suitable for the harsh polar regions. There is no energy and resource storage and accumulation, and flowering and fruiting must be completed within a few months, which is too difficult for annual plants.

Perennial plants know how to continuously store and accumulate energy in their rhizomes to form huge energy storage tissues. The accumulation cycle of nutrients can last for several years, providing sufficient resources for flowering, fruiting and getting through the long winter.

Cassiope selaginoides - an evergreen dwarf shrub in alpine areas

(Photography: Shangguan Fazhi)

Lichens are also pioneers and leaders in low-latitude mountainous areas. In the cold, dry, and highly radiative environment of high altitudes, some lichens such as Squamarina, Lecanora, Gypsoplaca, Ophioparma, Thamnolia and Lethariella can still be found at altitudes of over 6,000 meters.

Rhizoplaca chrysoleuca (Photo: Shangguan Fazhi)

In order to adapt to the extremely cold and arid environment, the plants have to grow very slowly. The faster ones, such as Cladonia stellaris, grow 3.4mm per year, while the slower ones, such as Rhizocarpon geographicum growing in the Great Slave Lake in northern Canada, grow only 0.15mm per year on average. A palm-sized lichen you see in the wild in the polar regions may be thousands of years old.

Cladonia stellaris (Source: https://mapio.net)

Rhizocarpon geographicum & Chrysothrix (Photo: Shangguan Fazhi)

Red snow tea from 5,000 meters above sea level - Lethariella flexuosa (Photo: Shangguan Fazhi)

Plants growing in the Arctic Circle also have to face the challenge of insufficient sunlight radiation. In areas above 75 degrees north latitude, there are three months a year with almost no sunlight. This has forced these plants to evolve a variety of more efficient resource utilization techniques. For example, some Arctic plants have a higher chlorophyll ratio than alpine plants in the same group, which enables higher respiration and photosynthesis rates during the growth period, and quickly converts energy into sugars and oils for storage. Some sheep's beard grasses can store large amounts of carbon dioxide through their hollow stems, some of which can be reused to participate in photosynthesis, increasing energy utilization efficiency and allowing some grass plants to grow rapidly and dominate in the tundra. (PS: Antarctica is not mentioned because there are only two types of vascular plants in Antarctica)

Orange lichen landscape in Antarctica (Source: www.westarctica.wiki)

Why are flowers so gorgeous? Flowers bloom for those who please them.

No matter how adaptable polar plants are, or how well they live in the polar regions, they can only truly gain a foothold if they have the ability to reproduce and thrive.

The short summer lasts only 4-6 months, and they must complete the mission of growth, flowering and fruiting. The time left for them to bloom is short and busy, and they may also face the trouble of competing for limited pollinating insects when they bloom at the same time. In order to gain the attention and favor of these insects in just a few months, and to compete for the few pollinating insects such as bears, moths, butterflies, mosquitoes and flies, many plants cater to the preferences of these insects and use bright colors that insects like to form a beautiful and spectacular sea of ​​flowers. This phenomenon is particularly prominent in a humid environment with relatively abundant water and fertilizer conditions.

A sea of ​​primroses in the alpine wetland (Photo: Shangguan Fazhi)

In the battle for pollinating insects, flowers often need to grow taller and larger to attract their attention. Therefore, many polar plants are extremely extravagant in their flowering, and the flower shape often far exceeds the size of the plant itself. We don’t know whether each flowering can attract the favor of pollinating insects, but it is a miracle of nature and one of the most beautiful natural gifts left to mankind.

Primula bella and Meconopsis racemose

(Photography: Shangguan Fazhi)

Warm and humid tropical and subtropical regions seem to be a paradise for plants to survive and thrive, but they are also a battlefield of fierce competition. Some plants have to turn their attention to less friendly living spaces such as extreme cold places. At least there are not many competitors there, and they only need to find strategies to face the cold and harsh living conditions.

Life is never easy, but we have to create conditions even if they are not available. This is the courage of life.

(Special thanks to Professors Wang Lisong and Wang Xinyu from the Kunming Institute of Botany, Chinese Academy of Sciences for their identification and consultation on lichens)

References:

Yang Yang, Sun Hang. Research progress on functional ecology of alpine and polar plants[J]. Journal of Plant Taxonomy and Resources, 2006, 28(1):43-53.

LC Bliss. Adaptations of Arctic and Alpine Plants to Environmental Conditions[J]. Arctic, 1962, 15(2):117-144.

Bliss, CL. Arctic and Alpine Plant Life Cycles[J]. Annual Review of Ecology and Systematics, 1971, 2(1):405-438.

Johnson PL. Arctic Plants, Ecosystems and Strategies[J]. Arctic, 1969, 22(3):341-355.

Weiser CJ. Cold Resistance and Injury in Woody Plants[J]. Science, 1970, 169(3952):1269-78.

Kevan PG. Insect Pollination of High Arctic Flowers[J]. Journal of Ecology, 1972, 60(3):831-847.

Pearce RS. Molecular analysis of acclimation to cold[J]. Plant Growth Regulation, 1999, 29(1-2):47-76.

Archibold O W. Ecology of World Vegetation.[J]. 1995, 83(4):735.