Li Jiang

My family has two pets: a puppy and a bird. One day, when I was feeding them, I had a whim and mixed some pepper seeds into my food to feed them. A few days later, I found that the bird droppings that fell in the soil actually sprouted. I took a closer look, and it turned out that I had fed the pepper seeds. I looked at the dog poop next to me again, and nothing could germinate. I wonder why dogs eat Chili seeds and their feces don't germinate. So, I forced my poor dog to eat some pepper seeds, and poured its feces on the ground, covered with a layer of soil. But after careful observation for several days, I still didn't find the pepper buds growing.

Why do birds' droppings germinate when they eat Chili seeds, but dogs' droppings don't? With this question, I consulted many books. I found that this is caused by the different digestive systems of birds and dogs. The digestive organs of birds mainly include beak, crop, sand sac and front and back stomach. It has no teeth and does not secrete digestive juices such as saliva and bile. Its biggest digestive organ is the sand sac, which grinds food with the help of sand grains. But pepper seeds are hard and sand is not easy to grind. Pepper seeds that have not been ground are excreted with feces and germinate when they meet suitable soil and climate. Dogs are mammals with developed digestive organs. Its front teeth, canine teeth and molars can chew food very carefully and be fully digested and absorbed by other digestive organs in the body, thus destroying the structure of pepper seeds. In other words: Chili seeds are digested by dogs, and of course they can't germinate.

Pieris rapae experiment

Wu Yunlong

Paper lures butterflies.

Every spring and autumn, do you find that there are often many white butterflies (cabbage butterflies) flying in the garden? At noon on a clear and windless day, Pieris rapae is the most active and often flies in love. As long as you observe carefully, you will find that the male butterfly will fly to meet the female butterfly as soon as he sees it. At this time, the female butterfly will take off immediately, followed by the male butterfly, dancing in tandem, up or down, and then mating.

If you hang a piece of white paper the size of a pink butterfly with a thread and wave it constantly, there will often be a copulating male butterfly flying behind, mistaking it for a female butterfly and coming to woo. This experiment shows that the male Pieris rapae finds the female butterfly through vision.

Lay eggs on paper

After mating, the female Pieris rapae lays eggs about two days later, only one egg at a time, ranging from 20 to 500 eggs in a row. Pieris rapae lays eggs on the leaves of cruciferous plants such as Chinese cabbage, Chinese cabbage and radish. All you have to do is mash the leaves of cabbage, spread the juice on a piece of paper, and then spread this paper on the vegetable garden floor and observe it carefully. Soon, there will be cabbage butterflies flying over the paper and finally landing on the paper to lay eggs.

Pieris rapae chooses its spawning site according to the smell of cruciferous plants. This phenomenon is called chemotaxis in biology.

Leaf-feeding chemotaxis

The larvae hatched from Pieris rapae eggs eat leaves and grow up, and their bodies are turquoise, so people call them Pieris rapae. Pieris rapae is also selective in eating vegetables and leaves, and specializes in picking leaves of cruciferous plants. When you put the cabbage caterpillar on the toilet paper, you find that it won't bite the toilet paper. The toilet paper will bite when it gets wet with cabbage leaf juice.

Then, if you put the cabbage caterpillar on a non-cruciferous plant (such as rose leaves), you will find that it refuses to bite.

What are the hazards of kitchen fumes?

I believe that most people will answer without thinking: "Of course it is harmful!" But you don't necessarily know what kind of harm lampblack will do. We use experiments to reveal the answer to this question.

We bought two identical goldfish, like twins, and kept them in two fish tanks, one on the balcony and the other in the kitchen.

On the first day, the goldfish living in the two places had a good time, but there were some oil stains floating on the surface of the fish tank in the kitchen.

The next day, the goldfish on the balcony swam leisurely, breathing 42 times per minute. Goldfish in the kitchen swim less, breathing 35 times per minute, and oil stains on the water surface increase.

On the fourth day, the goldfish in the kitchen moved slowly, breathed more slowly, did not eat, and the wall of the fish tank was stained with oil. The goldfish on the balcony are still swimming happily.

On the sixth day, the goldfish in the kitchen died, and the one on the balcony continued to enjoy a good life.

Because goldfish live in the kitchen, their fate becomes very miserable. In order to verify the credibility of the experiment, we made a new experiment. This time we replaced the goldfish with two pots of daffodils, one on the windowsill of the bedroom and the other in the kitchen. As a result, the daffodil leaves in the kitchen were greasy on the third day, then the leaves turned yellow and the branches withered, and they were going to die on the eighth day. The longer the daffodils on the bedroom windowsill, the more magnificent they are, and the flowers bloom luxuriantly and fragrant.

Goldfish and daffodils in the kitchen can't get in touch with sunlight for a long time, so they can only breathe dirty lampblack, so they will die soon. Similarly, kitchen fumes do great harm to our health. Excessive inhalation of this air is prone to pneumonia, bronchitis and other diseases, and it is said that it may also cause cancer. Therefore, when cooking, everyone should let the air in the kitchen circulate and always turn on the range hood.

Can willow branches survive at both ends?

Chenpenling

From the general knowledge class, I learned that the stems of plants can reproduce after being inserted into the soil. Then, if the stem of a plant is inserted upside down or both ends are inserted in the soil, can it still survive? The following is a diary of my research on willow cutting.

On March 2, I cut nine willows that are about to sprout from the campus and divided them into three groups: three branches in each group, inserted directly, inserted back and inserted at both ends respectively. I often water them.

On March 9, the branches turned yellow and withered, but the teacher in the general knowledge class told me: "Although the willow branches look dead on the outside, there is still water in them, which has tenacious vitality." He encouraged me to keep observing and taking notes.

On March 14, I was surprised to find that tiny tender leaves grew at both ends of the straight-inserted, inverted-inserted: the leaves of willow branches were inserted straight up; Willow leaves with inverted branches, like a hook, turn up from below; Willow inserted at both ends, the lower part of the main stem at both ends grows luxuriantly, and the buds are exposed in the middle.

On March 30th, I thought: After so many days, have the willow branches taken root? So I dug out a willow branch of each cutting and found that the root buried in the soil was 2-3 cm long, thin and long. There are some small white round "tumors" at the base of the branches. According to the teacher, the small tumor will grow roots soon.

Today, the remaining six willow branches have become saplings. Through this experiment, I not only learned the cutting method, but also learned the whole process of cutting branches. I also proved that willows can survive by cutting backwards, forwards and at both ends. I intend to use this cutting technology to cut roses, pomegranates and other plants again.

Excerpt from Hands-on