Did the ginkgo tree, which has an unbalanced “male-female ratio”, also have a large population in the past?

Ginkgo seems to be a very common and ordinary plant. Especially in Chongqing, whether it is the famous mountain temples such as Tianxin Temple in Banan, Jinyun Temple in Beibei, and Huiguang Temple in Bayue Mountain, or in leisure squares such as Central Park, Xingfu Square, and Garden Expo Park, it is easy to find ginkgo.

In spring, the young leaves of ginkgo are green and lovely, showing the beauty of spring; in autumn, golden leaves cover the ground, which is the unique scenery of autumn; when the cold winter is approaching, the ginkgo nuts offered by the ginkgo tree are used to stew chicken soup or desserts, which is the best comfort against the cold.

Image source: Pixabay

Ginkgo trees: Serious imbalance in male-female ratio

I don't know if you have ever paid close attention, but it seems that some of the ginkgo trees on the roadside can produce ginkgo nuts, while others do not.

This is because most ginkgo trees are dioecious, meaning that the female and male cones grow on different plants. Male trees produce male cones, which are responsible for pollination; female trees produce female cones, which are responsible for producing seeds. Around March to April each year, pollen begins to be produced on male trees, which is spread to female flowers by the wind. In September to October, female trees will grow seeds with fleshy seed coats.

So how do we distinguish between male and female ginkgo trees? In addition to staring at the tree in autumn to see if it has "fruited", we can also observe it by its shape at other times. Generally speaking, the posture of female trees is more stretched, with a larger angle between the branches and the trunk; while male trees are more upright, with branches growing almost parallel to the trunk; if we observe more carefully, we can also find that female trees shed their leaves earlier, while male trees shed their leaves relatively later.

In nature, the male-female ratio of wild ginkgo trees is seriously unbalanced, with a ratio of about 9:1. However, when ginkgo trees are used as roadside trees in cities, the landscaping department generally only plants male trees instead of female trees. The main reason for not choosing female trees is that the "fruits" of ginkgo trees easily rot and stink when they fall to the ground, affecting the sanitation of the roads.

The "secret" of ginkgo

As a gymnosperm, Ginkgo does not actually have a true flower or fruit structure. The flesh-like structure outside the seed is actually the outer seed coat of Ginkgo. When the seeds of Ginkgo are not yet mature, they are green and do not produce a bad smell. When the seeds gradually mature and the outer surface begins to turn yellow, fatty acids such as butyric acid and caproic acid begin to be produced in the seed coat, which produce a smell similar to rotten fruit when they come into contact with oxygen.

Although this smell is unpleasant to humans, it is a signal to animals, which is equivalent to announcing that the seeds are ripe. When animals come to have a full meal, they also help ginkgo spread its seeds. However, our ancestors may have accidentally glimpsed the "secret" of ginkgo. Ancient Chinese people were very good at using ginkgo as food and traditional medicine, making ginkgo play a huge role.

However, it is worth noting that ginkgo nuts contain trace amounts of hydrocyanic acid and some substances that are prone to allergies, so it is not advisable to eat too much. In addition, do not pick ginkgo nuts from roadside ginkgo trees easily, because these ginkgo trees not only absorb harmful substances such as car exhaust for a long time, but also spray pesticides regularly, so eating these ginkgo nuts is very risky. If you want to eat ginkgo nuts, you must purchase them through formal channels and make sure they are cooked before eating.

Natural "recorder"

In fact, ginkgo not only brings us complex and magical food such as ginkgo nuts, but its own story is also bizarre and tortuous enough.

Ginkgo is a very ancient species. As early as the Permian period about 270 million years ago, before the appearance of dinosaurs, the oldest species of the Ginkgo order had already appeared on Earth. According to fossil evidence, the Ginkgo family was once "prosperous", with at least 5 families and hundreds of species, which were once widely distributed on various continents in the world at that time. The Ginkgo family not only witnessed the rise and fall of dinosaurs, but ginkgo nuts were also very likely to have been food for dinosaurs.

But with the rise of angiosperms in the Cretaceous period and the change of global climate, the plants of the Ginkgoales also declined rapidly like other gymnosperms. Today, Ginkgo is the only species in the genus Ginkgo in the family Ginkgoaceae. According to recent systematic studies, Ginkgo is very distantly related to other gymnosperms, and it can even be divided into a separate "Ginkgophylum" and is the only species in it.

The ancient bloodline of ginkgo makes it an important "recorder" for studying the evolution of life and climate change. For example, the shape of its fan-shaped leaves with notches is a faithful continuation of the appearance of its ancestors hundreds of millions of years ago. By comparing ginkgo fossils with existing ginkgo, scientists can also learn about the climate environment and carbon dioxide concentration of the ancient atmosphere, which also provides an important basis for predicting the future global greenhouse effect.

The lucky survival of ginkgo is entirely due to the protection of the mountains in southern my country. Since the middle Pleistocene (580,000 to 140,000 years ago), there have been only three wild populations of ginkgo in southern my country. Fortunately, although the ginkgo tree itself grows slowly, it can easily reproduce by tillering. The ancient Chinese people especially loved the ginkgo tree and often planted it in front of the house, especially in temples and Taoist temples, and gave it nicknames such as "Gongsun Tree", "Duck Palm Tree" and "Ginkgo Wood". It is precisely because of the careful care of the ancient Chinese for ginkgo that it has escaped the risk of extinction. Ginkgo has long gone abroad, and as a representative of oriental charm, it has taken root and sprouted in all parts of the world.

Here, we have to mention the origin of Chongqing and ginkgo. In the Jinfo Mountain area of ​​Nanchuan District, Chongqing, this is one of the last "refuges" for wild ginkgo. It is also the wild ginkgo community with the most complete annual ring structure, the longest span, the largest number of plants, and the oldest single tree age found in the world so far. In particular, an old ginkgo tree on the north slope of Jinfo Mountain is estimated to be about 2,500 years old, making it one of the oldest ginkgo trees in the world. If you have the opportunity to come to Jinfo Mountain, don't miss the encounter with this old ginkgo tree!

Source: Chongqing Science Writers Association

Author: Quasimodo in the Garden

Audit expert: Li Hanbin

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