What? I've been picking pine cones for so many years, and you tell me it's not a fruit?

There is a "pine cone tower" hanging nearly 20 meters in the air in the Shanghai Natural History Museum, which is very eye-catching. Pine cones of all sizes are stacked up layer by layer, forming a huge pine cone.

Although pine cones are called "fruits", they are actually very different from the fruits we usually understand. In people's intuitive impression, pine cones seem to be the fruits of pine trees, but strictly speaking, pine cones are not fruits. Why is this?

How many floors does the “Pine Cone Tower” have?

The highest point is 20 meters from the ground, and the lowest point is 6 meters from the ground. This giant Internet celebrity "pagoda" hanging in the air is spectacular. If you count carefully, the "Pine Cone Tower" has 10 floors, with about 50 pine cones hanging on each floor , for a total of about 500 pine cones.

These pine cone specimens collected from around the world come from 10 species of pine plants, from top to bottom:

1. Sugar pine Pinus lambertiana

2. Cortese pine ( Pinus coulteri )

3. California Ponderosa Pine (Jeffreyi Pine) Pinus jeffreyi

4. Silverleaf Pine (Western White Pine) Pinus monticola

5. Longleaf Pine (Pinus palustris)

6. Pinus elliottii

7. Ponderosa Pine ( Pinus ponderosa )

8. Pinus resinosa

9. Tsuga heterophylla

10. Pinus contorta

If you look closely, you will see that the pine cones on each layer are of different sizes and shapes, each with its own characteristics and rhythm.

The sugar pine on the top layer is named because it can secrete sweet resin. As a giant tree that can reach a height of 70 meters, the pine cones of the sugar pine can reach a length of 50 centimeters , ranking first among pine trees.

The pine cones of the big-fruit pine on the second layer are also huge. Although the pine cones are only 30 to 40 centimeters long, they are very heavy. The heaviest pine cone can weigh up to 5 kilograms.

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Lumberjacks working under the tree may be hit by the tree and become dizzy and their lives may be in danger if they are not careful, so the big-fruit pine has another dark title, called "widow maker".

The wetland pine located in the middle layer has extremely strong resistance to adversity and has been widely introduced in the Yangtze River Basin and South China in recent years. Its pine cone length is about 13 cm.

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The smallest pine cone at the bottom is only 2 cm high, which is quite small among pine cones. The pine cones on the pine cone tower, from large to small, release the magic and mystery of biodiversity layer by layer.

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In fact, there are far more than 10 species of Pinaceae plants. There are 11 genera under Pinaceae alone, and the number of species exceeds 200. This species richness is rare among gymnosperms.

What is even more rare is that almost all genera of the Pinaceae family are distributed in China . In terms of the number of species, 32 species are native to China, including 7 endemic species. In this way, China is also a major resource consumer of the Pinaceae family.

Is a pine cone a fruit?

Pine cone is a general term for the spherical or oval cones of pine plants. However, although pine cones are called "fruits", they are not real fruits.

Pinaceae plants are gymnosperms, monoecious. The female reproductive organ is called megasporophylls , with ovules naked at the base of the megasporophylls (without carpels), and the male reproductive organ is called microsporophylls .

The microspore mother cells undergo meiosis to form pollen grains. When the pollen grains (male gametophyte) in the pollen sac complete the fertilization process with the archegonium (mature female gametophyte), the zygote develops into an embryo at the base of the megaspores. The embryo undergoes differentiation, and after maturity, the entire ovule develops into a seed, while the megaspores harden into woody seed scales, and the bracts develop into hard bract scales.

The "pine cone" we see is a layer of spirally interlocking and upwardly curved seed scales arranged in a tower shape, so the "pine cone" is also called a "pine cone". The seeds developed from the ovules hide at the base of the seed scales and escape when the cones crack and spread. Because the seeds are not covered by the pericarp and grow naked on the seed scales, gymnosperms get their name.

Because of the lack of pericarp, "pine cones" cannot be called true fruits, but rather a complex of seeds, seed scales, bract scales and cone axis (central axis) .

Cone development process | Adapted from Wikipedia Illustration: Gao Jie

Different pine species have different scales, sizes, shapes, colors, numbers, curvatures, and whether they are fused with bract scales, so we get a variety of "cones".

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Each kind of pine cone is exquisite and special , with delicate wood texture and clear wood fragrance. The pine cone is like a masterpiece of supernatural craftsmanship.

In addition to being decorative, pine cones also have a magical function, which is to act as a barometer of weather . This function is mainly achieved through the opening and closing of the woody seed scales.

When the seeds in the pine cones are ripe, in sunny weather, the seed scales will open flat, releasing the seeds hidden deep in the base, allowing the seeds to drift away with the wind to start a new round of life journey; in rainy weather, the scales will shrink and close to reduce the falling of seeds. This ensures the success rate of seed reproduction to a certain extent, which is the survival wisdom of pine trees, and also allows us to predict weather conditions by observing the state of the seed scales.

Pine nuts have wings?

The seeds of pine trees are pine nuts . Pine nuts are a type of "nut" (not a fruit), with one chamber, a hard seed coat as the outer shell, and the white part in the middle is the endosperm and the embryo it contains, which is also the most nutritious part.

In fact, in order to have a stronger ability to spread, the seed coat of most pine nuts will extend "wings" , so that under the action of wind, the seeds can take root and germinate farther away from the mother plant, avoiding competition with the mother plant for light and nutrients. For example, the sugar pine seeds mentioned above have huge seed wings.

Winged seeds | Source: Reference 3

However , the pine nuts we often eat have smooth seed coats and no wings. This is because most of the pine nuts sold as food on the market are "Northeastern pine nuts", which are mainly seeds of Pinus koraiensis , and the seeds of Pinus koraiensis happen to be wingless .

The main production areas of Korean pine in China are the three northeastern provinces, concentrated in the Changbai Mountain area in the northeast, the Jilin Mountain area and the mountain area south of Aihui in the Lesser Khingan Mountains. It takes 50 to 60 years for wild Korean pine to produce seeds, and pine nuts take 2 years to mature and be harvested. Although the maturity period is slow, this does not prevent "Northeast Pine Nuts" from occupying most of China's pine nut export industry with its excellent quality. In addition to Korean pine, the pine nuts on the market currently mainly come from Tibetan white pine Pinus gerardiana (Brazilian pine nuts from Pakistan) and Chinese pine Pinus armandi (Yunnan pine nuts).

The pine nut library of Korean pine is a copyrighted image. Reprinting and using it may cause copyright disputes.

Pine nuts are rich in vitamin E, unsaturated fats, minerals and carbohydrates, and are undoubtedly high-quality "nuts" (food).

However, because pine nuts have a high oil content, the more you eat, the better. Generally, 20 to 30 grams per day is appropriate . When choosing pine nuts, try to choose large, plump, smooth shells, and white kernels, and try to open them with physical methods. In addition to pine nuts, pine pollen also has the medicinal effects of astringing and stopping bleeding, drying dampness and healing sores. Pine pollen mainly refers to the dried pollen of Pinus massoniana, Pinus tabulaeformis, or several plants of the same genus.

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In addition to its edible and medicinal uses, pine trees are also important ecological and economic tree species, playing an important role in afforestation, greening, landscaping, construction materials and the papermaking industry.

In addition, pine trees are evergreen, handsome and tall, and they also represent longevity and integrity in traditional Chinese culture. China is rich in pine resources, but some species are endangered, so protection is urgent. If we work together to protect them, our pine cone pagodas will become more and more abundant!

References

[1] South China Botanical Garden. The life cycle of pine cones. https://www.sohu.com/a/285132673_288672

[2] https://www.weblio.jp/wkpja/content/

[3] Museum. https://mp.weixin.qq.com/s/MJpWWDnv3-uQ-5Kpkn2g5Q

[4] Plant Intelligence. https://www.iplant.cn/

Planning and production

Source: Shanghai Natural History Museum (ID: snhm01)

Author: Xu Shanshan Shanghai Natural History Museum Exhibition and Education Center

Editor: Wang Mengru

Proofread by Xu Lailinlin