1 . Every August the clustered carline thistle (蓟) is one of the only plants that flower in most of Spain’s dry Mediterranean habitats, making it a dominant plant on the local bees and other pollinators. But how can the thistle survive, much less flower, when its neighbors are reduced to twigs and dust?
Spanish National Research Council evolutionary ecologist Carlo s Herrera had an amazing discovery when one day he peered into a thistle blossom to see how much nectar was inside and lightly touched the flower. He discovered that even after hours in direct sun, the flower heads were routinely five degrees cooler than their surroundings during the heat of the day, with the difference approaching 10 degrees for some flowers on the hottest days.
Sanna Sevanto, a physicist and plant physiologist at Los Alamos National Laboratory says that Herrera’s finding is exciting and could confirm a risky plant survival strategy that has, until now, only been theorized.
Sevanto and other scientists have documented that to perform photosynthesis (光合作用), leaves need access to carbon dioxide, which enters through tiny pores (毛孔) called stomata on the leaf’s surface. When stomata open to let carbon dioxide in, some water escapes; this causes evaporative cooling that lowers the leaf’s temperature slightly.
But for the Spanish thistles, evaporative cooling could be the goal rather than just a side effect of photosynthesis. Herrera suggests the plant could essentially be sweating: sacrificing precious water, so scarce in Spain’s dry summers, to prevent its delicate reproductive organs from overheating. She added that some flower species have stomata on their petals, which Sevanto says would be an easy route for releasing water. Opening stomata in a drought is a big gamble, though, and she notes that, so far, “we have not observed a plant that would do it to cool themselves.”
As heat waves become more frequent and intense with climate change, it’s increasingly important to study unusual adaptations that help plants survive heat stress. But ultimately, “whether these plants will have water enough to keep the system working,” Herrera says, “that’s another story.”
1. What was Herrera’s discovery about carline thistle in August?| A．It was the only plant that blossomed. | B．It was the only plant that survived. |
| C．It had little nectar in the flower. | D．It had lower temperature in the flower head. |
| A．To cool the key organs. | B．To take in carbon dioxide. |
| C．To accelerate photosynthesis. | D．To reduce water content in leaves. |
| A．Advantage. | B．Risk. | C．Shift. | D．Evolution. |
| A．Suspicious. | B．Positive. | C．Objective. | D．Unconcerned. |
2 . As the world’s oldest living organisms, trees have been our silent companions. Although they inspire a large quantity of fancy tales, the richness of what they say is beyond description.
The German forester Peter Wohlleben spent decades working and learning their secrets. Feelings are rarely applied to trees, but Wohlleben has done so without hesitation. According to Wohlleben, that humans do not speak the trees’ language does not mean they do not communicate. Trees are badly misunderstood even if they communicate with chemical and electrical signals.
Wohlleben claims that trees are creatures as human beings. In one of 50 cases, Wohlleben’s team sees the special friendships between trees, as they can distinguish between one individual and another. This means that trees do not treat all other trees the same. For instance, Wohlleben saw two old beeches standing next to each other. Compared to the usual case, each one growing its branches turned away from the other rather than toward each other. This kind of partnership is well-known to foresters. They know that such tree pairs are really like a human couple. If they chop one down, they need to chop down both because the other will die anyway.
Trees were also found to keep each other alive in different ways. They pass food to nearby sick trees and send signals to warn others of dangerous insects. In one of his investigations, Wohlleben also discovered a beech tree cut about 400 to 500 years ago. The trunk is still alive and was found with green chlorophyll (叶绿素) under the thick bark. Since it has no leaves to create sugar, the only explanation is that neighbouring trees have supported this tree for more than centuries.
The trees that suffered through drought were found to consume less water in the spring so that they will have more water available in the summer months. This implies that a tree can learn and remember a drought its whole life, acting on that memory by being more cautious about its water consumption.
1. What is the function of the first paragraph?| A．To arouse readers’ interest. | B．To introduce a topic. |
| C．To present a new discovery. | D．To demonstrate a heated debate. |
| A．Trees communicate in the same way as humans. |
| B．Trees can’t tell friends and enemies apart. |
| C．Trees are loyal to their partners. |
| D．Trees can keep each other alive within limited periods. |
| A．Because they have more water available in summer |
| B．Because they have suffered through drought before. |
| C．Because they don’t need so much water in the spring. |
| D．Because they can depend on the support from other trees. |
| A．Mysteries of trees are unfolded | B．Trees are our silent companions |
| C．Trees can adapt to the environment | D．Trees can form special relationships |
Science on Sundays is a programme of free monthly science talks which always brings the latest discoveries in plant science, as well as research linked to the plant collection at the Botanic Garden, to the visitors in a 30-minute short period of time. The programme in April is about tulips(郁金香).
Introduction
Time: 2:30 pm on Sundays
Title: In Search of Wild Tulips
Objects: adults and children aged 12+
Speaker: Brett Wilson at University of Cambridge
Background Information
The planted tulips are a common sight in spring gardens around the world, but have you ever considered where wild tulips grow? The wild ancestors of our much-loved gardening varieties can mostly be found in the mountains and valleys of Central Asia, far from the Netherlands, where most tulips are grown and bred. At the Botanic Garden, we have a National Tulip Collection where we grow many wild species including plenty of species from Central Asia. Over the last four years, Brett Wilson has been using something learned from books and combining with fieldwork to understand the diversity of tulips, with a view of identifying which species are most at risk of extinction.
Come and listen to Brett speak about the research and the adventures that have occurred in our search to find and protect wild tulips in this remote corner of the world. These will be live face-to-face talks taking place in the Botanic Garden Classroom for those visitors with interest.
1. What do we know about Science on Sundays?| A．It focuses on plants. |
| B．It is a paid programme. |
| C．It appeals only to children. |
| D．It is a live broadcast on weekdays. |
| A．By making assumptions. |
| B．By picking and collecting tulips. |
| C．By growing tulips in greenhouses. |
| D．By combining theory and practice. |
| A．To ask visitors to plant more tulips. |
| B．To call on visitors to listen to the talks. |
| C．To push visitors to take more botany classes. |
| D．To advise visitors to take adventure in remote areas. |
