It's not only palace fighting dramas that are filled with open and covert struggles and hidden scheming, but also the plant kingdom!

The National Day holiday is coming, and watching documentaries is a good way to pass the time. At the beginning of this year, the BBC launched a new plant documentary "Green Planet", which can be said to be one of the best plant documentaries in recent years.

Whether you know plants or not, you can follow David Attenborough's explanation and appreciate that the plant world is no less exciting than the animal world . For such a plant documentary with beautiful pictures and a broad perspective, it can withstand interpretations from various perspectives. However, due to the limited length, many special plants in the documentary can only flash by. We have summarized 10 extended knowledge points related to "Green Planet" . While recommending the documentary, we hope that everyone can understand more of the Easter eggs hidden in the documentary.

The fight of lianas

From the first episode, we see the struggles of the plant world, which are no less exciting than those of animals. Especially in the species-rich tropical rainforest, struggles are necessary to gain a foothold. The film selects the forest window formed in the tropical rainforest after the big tree falls as the venue for the struggle. With the help of time-lapse photography, we can get a glimpse of the action strategies of plants.

The struggle of plants is going on quietly | Episode 1 "Rainforest World"

The seemingly delicate vines in the rainforest are actually very sensitive. While they are growing vigorously, they constantly use their tendrils to explore the objects they climb.

Their tendrils are extremely sensitive and can sense physical touch . When they touch an object, auxin accumulates unequally on the contact surface and the non-contact surface, causing the tendrils to deform and begin to rapidly wrap around the target, thus closing the distance to the target and eventually hooking up with the host. The tendrils of some vines can even sense chemical signals , and their sensitivity is no less than that of our skin.

Of course, many plants have learned to avoid lianas , such as the balsa wood mentioned in the film, whose hairy leaves and rapid growth make it difficult for lianas to attack.

How to avoid being eaten? Make the predator so full that it can’t eat anymore

In mature tropical rainforests, plants also face the dilemma of renewal - the extremely rich species network brings countless predators and predators to plants. For example, the dense predator network makes it difficult for seeds that fall to the ground to survive . But plants have their own ways. For example, Dipterocarpaceae plants, as the founding species in the tropical rainforests of Southeast Asia, win by numbers. Through synchronous mast-fruiting, they gain a glimmer of survival in the midst of a large number of predators.

What the predators eat left over can sustain the population｜Episode 1: "Rainforest World"

This strategy is called "predator satiation", which means using far more food than the predator can eat to keep it busy . In addition, like many tropical plants, Dipterocarpaceae plants have recalcitrant seeds that can germinate directly without dormancy, which can further avoid seed predation.

This synchronized fruiting has been studied more in oak trees. Oak trees can even synchronize fruiting across species, so in good years, acorns can fill the paths under the oak forests. Local people in Europe have long known about this phenomenon, and they would use the good years of acorns to raise pigs, driving them up the mountains to fatten them up .

Pig fattening in the New Year | Très Riches Heures

The True Face of Victoria regia

In the second episode "Aquatic World", the most outstanding plant is undoubtedly Victoria amazonica , whose dominant temperament is as its name suggests. Botanical students may not have thought that the thorns on the back of Victoria amazonica leaves can crush the surrounding plants while growing and stretching.

A Close Look at the Thorns of Victoria amazonica｜Episode 2: The Aquatic World

Before watching Green Planet, I always thought that the thorns on the back of the Victoria amazonica leaves were to prevent underwater animals from eating them. But when the documentary showed its growth process through time-lapse, the purpose of the thorns was revealed. It turns out that when the leaves are not unfolded, the thorns on the back of the leaves extend from the leaves and curl up, playing the role of protecting the buds ; as the leaves grow and expand, the thorns are also able to sweep the lake surface , like an iron hoof that is invincible, and its domineering degree is no less than that of the lion king on the African grassland.

Cuscuta's "Overheard"

In the third episode, "The Changing Seasons", the parasitic plant dodder can use smell to track and contact different nettle plants, and use its sucking apparatus to steal nutrients from the host.

Dodder can find a host | Episode 3: Changing Seasons

Many people think that the impact of parasitic plants on their hosts is completely negative, but this is not the case. Dodder can use itself as a bridge to transmit pest signals between different host plants . Of course, dodder helps its hosts, essentially just for its own benefit. After all, when pests harm their hosts, they harm their own food.

Through the connection with the host, dodder can even eavesdrop on the host's flowering signal and bloom synchronously with the host plant. In this way, they can perceive the four seasons and complete their life history.

The popping sound of flowers

In South Africa's iconic fynbos, fire is part of the ecosystem and plants have evolved adaptations to regular fire .

Many fire-resistant Proteaceae plants are very common here, and the documentary compiles clips of them flowering in response to the climate - but when watching the video, you'll find that their flowering actually makes crackling sounds .

Flowering of Proteaceae plants | Episode 3: Changing Seasons

This may be the sound of plants flicking their stigmas - when pollen has already landed on the stigma, they will do this to achieve a second presentation of pollen . This is usually to ensure that the pistil is in the same position reproductively to facilitate cross-pollination.

After lying dormant for 15 years, it emerged only after the fire

Also in this part about fire, the documentary specifically tracks the "fire lilies" in South Africa.

This is Cyrtanthus ventricosus , a bulbous plant adapted to fire. It buries its buds in the ground in the form of bulbs to avoid natural fires, and does not easily emerge, hiding for 15 years. It was not until after the fire that they suddenly emerged from the ground in the ruins and bloomed bright yellow flowers. At this time, it became extremely bright and could quickly attract birds to visit and pollinate.

The "fire lily" that is very eye-catching in the ruins can be favored by birds｜Episode 3 "Changing Seasons"

But how does it know that a fire has burned when it is buried underground? In fact, a fire will change the temperature of the surface, and the ashes after burning will even change the physical properties of the soil, which is a rich and complex signal for plants. Studies have found that the flame drooping flower is triggered by the most direct signal of fire - the smoke itself.

Flame lily｜Green Planet

The 15-year hibernation of the flame vine is indeed impressive, but they are not the only ones, and 15 years is not even the longest. In South Africa, a bulb plant of the genus Lachenalia sargeantii was described in 1971 and had not been seen until 32 years later , when it was accidentally found after a fire. In addition to them, there may be more bulb plants in South Africa that are adapted to fire.

Tree Networking

Fungi grow fruiting bodies in autumn, but in fact, the hyphae buried underground are the main body of fungi. They are interconnected with the roots of plants to form invisible mycorrhizal networks .

There is a huge network hidden underground that cannot be seen | Episode 3 "Changing Seasons"

Large trees can also interconnect through a common mycorrhizal network to transmit substances and signals. This is like the real Avatar world, where old trees in the forest form network hotspots, connecting young trees and acting as their guardians. The documentary uses the term " wood-wide web " to describe this network system.

The term comes from a research article published by Suzanne Simard in Nature magazine in 1997, and the cover of that issue of the journal was named The wood-wide web.

Nature introduced this study with the title “The wood-wide web” | References [1]

This study opened the door to the world, proving that the underground mycorrhizal network is interconnected , just like the Internet we created, exchanging signals and nutrients between different individuals. The "Wood-Wide Web" also corresponds to the "World Wide Web".

Desert Cactus Mist Inhalation Techniques

The fourth season, "Desert World", focuses on how giant saguaros survive in arid environments - their leaves degenerate, and their stems form vertical grooves and ridges. The densely covered areoles on the ridges are used for defense, and the grooves become pipes for collecting water during rainfall.

A veritable giant column | "Green Planet"

But cacti in the desert will not easily let go of the rare water. Therefore, they not only use the areoles to collect water, but also collect fog water through the thorns .

Episode 4: Desert World

The thorns of the cactus family have microscopic longitudinal ridge structures. After the mist condenses, it flows downstream and is collected in the areoles. The areoles and thorns form a water-collecting continuum that does not miss any form of water.

The fog-collecting thorns on the cactus areola | References [2]

Nanny Plant

When explaining the giant column, the film also introduced the mutually beneficial relationship between the mesquite and the cactus. We generally believe that competition is dominant among plants living in the same area; but current research has found that when the environment is harsh, the mutual assistance relationship between plants may prevail , and they will benefit each other and fight against the harsh environment together.

Plants that provide shelter for other species are called " nurse plants ." For example, in the Sonoran Desert in North America, the mesquite tree provides shelter for young giant columnar plants beneath it. Its well-developed root system also absorbs groundwater to the surface, helping the giant columnar plants nearby to obtain water.

Similar nurse plants are found in alpine environments. In the mountains, cushion plants not only create a suitable microenvironment for themselves, but their cushions also serve as shelter for other plants. Therefore, the plant diversity within the cushion plant range is often higher than in the surrounding environment.

Plants transformed by cities

The fifth episode, "Sharing Weal and Woe," focuses on the relationship between humans and plants . Humans and plants are interdependent - on the one hand, the urban environment created by humans has fragmented the original habitats of plants; on the other hand, plants have repeatedly re-spread into cities, and although sometimes they can only find a place in the cracks of reinforced concrete, they have thus embarked on the path of adapting to the urban environment.

Plants that find a way to survive in the city | Episode 5: Sharing Weal and Woe

Crepis sancta can only live in such gaps in the city, remaining in the small spaces left for street trees. Fortunately, they have light seeds that can spread again from the natural habitats around the city.

Rabbits live in the gaps of the city | References [3]

Interestingly, after reoccupying the urban space, the seeds of the rabbit lettuce are heavier than those in the natural habitat . This is a strategy of giving up spreading. In other words, they "know" that they can't spread out, so they make a compromise - after all, except for this small area, the rest are reinforced concrete that they can't penetrate.

Rabbitweed seeds become heavier in urban habitats (right) | Reference 4

This is very similar to the island effect. When plants spread to an island, some will lose their ability to spread (such as the famous sea coconut). Since only seeds that fall around the mother plant can survive, the seeds roll inward from generation to generation, becoming larger and larger, competing with their compatriots for living space, germination and germination.

In a way, cities are indeed like artificial islands for plants.

Why not follow the old man to see plants during the short holiday｜"Green Planet"

Green Planet provides us with a window to understand the plant world, and I believe it will be an enlightenment to many people about plants . I hope this article can help everyone to further understand and explore the magical plant world on the basis of enlightenment.

References

[1] Simard, Suzanne W., et al. "Net transfer of carbon between ectomycorrhizal tree species in the field." Nature 388.6642 (1997): 579-582

[2] Ju, Jie, et al. "A multi-structural and multi-functional integrated fog collection system in cactus." Nature communications 3.1 (2012): 1-6.

[3] Otto, Sarah P. "Adaptation, speciation and extinction in the Anthropocene." Proceedings of the Royal Society B 285.1891 (2018): 20182047.

[4] Ju, Jie, et al. "A multi-structural and multi-functional integrated fog collection system in cactus." Nature communications 3.1 (2012): 1-6.

Author: Zhou Fang

Editor: Mai Mai

All the pictures in this article except those marked are from Green Planet

This article comes from the Species Calendar, welcome to forward

If you need to reprint, please contact [email protected]