Plants are living things. So can they feel pain? Plants don't feel pain the same way animals and people do, says Anke Steppuhn. She is a scientist at the Free University of Berlin in Germany. “What we define as pain usually has to do with a nervous system，” Steppuhn explains. When you put your hand too close to a hot stove, nerve cells send a signal to your brain. Your brain decodes(解码) that signal as pain. This causes you to pull your hand away before any serious damage is done.

Plants don't have nerves or brains, so they can't feel pain like we do. “But plants do recognize when something is hurting them，” Steppuhn says. Because they are rooted to the ground, they can't escape a dangerous situation. So they need other ways of fighting back.

The biggest threat to a plant's life is getting eaten. Some plants grow sharp little hairs. Other plants produce bad－tasting or even harmful chemicals. These force an attacker to abandon its meal. A plant called bittersweet nightshade does something even smarter, Steppuhn found. When a slug(蛞蝓) chews holes in a nightshade' s leaf, liquid begins dripping(滴) around the wound. It is almost as if the plant were bleeding. The liquid is sugary nectar(花蜜), and it happens to be a favorite food of ants. In their effort to collect the nectar, the ants swarm(蜂拥而至) all over the injured plant. They will attack anything that stands in their way. That includes the slug that damaged the plant in the first place. It's a very clever trick. Whenever a slug attacks a plant, the plant calls an army of ants to kill the slug.

Nectar isn't the only way plants attract bodyguards. They also release certain chemicals into the air when they are being eaten. People usually can't detect these smells. But wasps(黄蜂) can. When a wasp detects this cry for help, it races to the scene of the crime. If it finds the right kind of insect chewing down on the plant, the wasp will interrupt the attacker's meal. It will do this by laying eggs inside the insect’s body!

Swimming is well known to offer many health benefits, including building endurance and muscle strength. But what about swimming in icy cold water? This might not sound very appealing, but there’s evidence that it can actually be good for us.

Cold-water swimming is also called wild swimming, where people swim in natural bodies of water such as ponds, rivers, and the sea. Although jumping in might give a quick shock to the body, many enthusiasts claim they get used to it over time. In fact, research has found it to have many physical and mental benefits.

Apart from being a great way to exercise, spending time in the outdoors and near water can improve overall wellbeing. There’s plenty of anecdotal (传闻的) evidence suggesting that cold-water swimming has cured people’s illness, ranging from pain relief to an overall sense of feeling amazed.

One reason why getting into cold water might be beneficial is that it causes a stress response in the body. The more people do it, the better their reaction to stress becomes. Additionally, some experts believe that cold-water swimming helps the body prepare for other forms of stress by adapting to similar stressors. For example, it also helps reduce the stress of exercising at high altitudes.

People who want to try cold-water swimming should approach it with caution, swim with a friend if possible, and start during the summer when the temperatures are warmer. It might not be for everyone, but for those willing to take risks, the extra health benefits might be worth it.

An 11-minute quick walk every day could prevent one in ten premature deaths worldwide, according to the largest ever study of its kind. Globally, one in ten early deaths could be avoided if everyone met just half the NHS target for moderate (适度的)-intensity physical activity, the pooled data analysis suggests. The results were published in the British Journal of Sports Medicine.

Moderate-intensity physical activity is defined as activity that raises the heart rate and makes people breathe faster, but still leaves them able to speak. “If you are someone who finds the idea of 150 minutes of moderate-intensity physical activity a week a bit daunting, then our findings should be good news,” said Dr. Soren Brage, of Cambridge’s Medical Research Council epidemiology unit.

Researchers looked at 196 peer-reviewed articles, covering more than 30 million participants from 94 large study teams. They then examined the link between levels of physical activity and the risk of heart disease, cancer and early death.

At least 75 minutes a week of moderate-intensity activity lowered the risk of early death by 23%. It was also enough to reduce the risk of cardiovascular disease by 17% and cancer by 7%. “We know that physical activity, such as walking or cycling, is good for you, especially if you feel it raises your heart rate,” said Prof. James Woodcock, also of Cambridge University. “But what we’ve found is there are substantial benefits to heart health and reducing your risk of cancer even if you can only manage 10 minutes every day.”

The researchers calculated that if everyone in the studies had done the equal of at least 150 minutes a week of moderate activity, about one in six early deaths would have been prevented. But even if everyone had managed at least 75 minutes a week, about one in ten early deaths would have been prevented, the research found.