Today we tell you about some new understanding of why cutting the main branch of a plant
or tree can lead to better development.
The findings are from researchers on two_continents.Professor Prezemyslaw Prusinkiewicz
of the University of Calgary in Canada led the research with scientists from Britain and Sweden.
Their study appears in the Proceedings of the National Academy of Sciences.
Researchers have known since the 1930s that the actively growing tip of a plant produces
a hormone(荷尔蒙)called auxin(生长素)．This hormone flows down the main stem.Scientists
say the auxin has an indirect effect on buds(芽)on the side of the stem to prevent branching.
T hese buds themselves also produce auxin.The research suggests that to grow,they have
to be able to export the hormone into the main stem.But the flow from the stem tip prevents
them from doing this.The researchers wanted to find out how this blocking happens.
Professor Prusinkiewicz is on leave in Australia,but he sent us an e－mail suggesting a
simple way to understand the process.Think of a major road crowded with traffic.So many
cars are on the main road that the cars on the side roads cannot enter.
The stem is like the crowded main road.The new research shows that the buds on the
side cannot export their auxin into the main stem because it is too full.But if that main shoot
is pruned(修剪),other buds below it can start exporting.They are no longer prevented from
growing.
Ottoline Leyser from the University of York says that after a plant is pruned,all the
inhibited(被抑制的)shoot tips compete with each other to grow.In doing this,the branches
influence each other"s growth.Nearby shoot tips are more likely to affect each other than those
that are far apart from each other.
Professor Leyser says the strongest branches grow best,wherever they may be on the
plant.The study found that the main shoot grows the best of all not because of its position at
the top of the plant,but mostly because it got there first.
B．Africa and Europe
C．North America and Europe
D．Australia and Europe
B．plant buds
C．the leaves of a plant
D．the roots of a plant
B．be protected
C．be watered as much as possible
D．be given much auxin
A．Researchers have recently found out that the growing tip of a plant produces hormones.
B．Auxin has a direct effect on buds to keep branches from growing.
C．Buds on the side of the stem can’t produce hormones.
D．In order to grow，the buds on the side of the stem export the hormones into the main stem.
B．When and how to prune plants?
C．Scientists help cut the mystery behind pruning
D．The great scientist-Prezemyslaw Prusinkiewicz
Hills,California,plan to pick up trash during their city"s annual cleanup.At the same time,Wissam Raed,12,
will be busy volunteering too.Thousands of miles away in Lebanon,Wissam plans to put on a play at an
orphanage and bring potted plants to elderly people at a senior citizen center.
Some other children like Nathan White,10,have personal reasons for volunteering.Nathan"s grandmother
died of a heart attack.To help raise money for medical research,Nathan participated in Jump Rope for
Heart.He and five other boys took turns jumping rope for two and half hours and collected more than US
$1,200 in donations for the American Heart Association.
Millions of children around the globe lend a hand to their communities every year.Schools and parents
also contribute to the rise in youth service.For example,many schools offer community service activities for
students to join.Teachers either combine volunteer work with classroom lessons or make service work a
requirement.Parents,on the other hand,encourage their kids to volunteer and do it with them.
Community service is particularly important in this depression time.As the need for monetary support
and other aid has increased,many charitable organizations have experienced a significant drop in donations.
Camille and other children who volunteer thousands of hours annually can fill in some of the gaps.
According to research, kids who start volunteering are twice as likely to continue doing good deeds
when they are adults.So,grab a paintbrush,a trash bag,or whatever you need to help your community.You"ll
love how you feel after helping others.Even dirty work can be lots of fun,if it"s for a good cause.
B．To ask charity organizations to serve the community.
C．To urge children to take part in volunteering activities.
D．To propose alternatives for doing community services.
B．Families and schools help to make community service popular.
C．Children now depend more on their teachers than on their parents.
D．Nathan White had a special reason to raise money for medical research.
B．It teaches children to take care of the sick.
C．It gives charity organizations some needed help.
D．It encourages parents and teachers to work together.
B．Children will probably leave school and work as volunteers.
C．Organizing sports events for the school is a kind of community service.
D．Children who do volunteer work are more likely to grow up to be caring adults.
professor David DeSteno, and his colleagues, who are conducting a research to determine how humans
decide to trust strangers.
The interdisciplinary(跨学科的) research project,funded by the National Science Foundation (NSF) ,
is being conducted together with Cynthia Breazeal,director of the MIT Media Lab"s Personal Robots
Group, Robert Frank,an economist,and David Pizarro,a psychologist,both from Cornell.
The researchers are examining whether gestures could affect our trustworthiness judgments."People
tend to mimic(模仿)each other"s body language,"said DeSteno,"which might help them develop intuitions
(直觉) about what other people are feeling."
This project tests their theories by having humans interact with the social robot,Nexi,in an attempt to
judge her trustworthiness.Without knowing the participants,Nexi has been programmed to make gestures
while speaking with selected participants-gestures that the team thinks could determine whether or not
she"s considered trustworthy.
During the first part of the experiment, Nexi makes small talk with them for 10 minutes, asking and
answering questions about topics such as traveling,where they"re from and what they like most about living
in Boston.
"The goal was to create a normal conversation with accompanying movements to see what the mind
would intuitively(直觉地) collect about the trustworthiness of another,"said DeSteno.
The participants then play an economic game called "Give Some",which asks them to determine how
much money Nexi might give them at the expense of her individual profit.Meanwhile,they decide how
much,if any,they"ll give to Nexi.The rules of the game allow for two distinct outcomes:higher individual
profit for one and loss for the other,or relatively smaller and equal profits for both partners.
"Trust mightn"t be determined by only one gesture,but rather a "dance" that happens between the
strangers,which leads them to trust or not trust the other," said DeSteno,who will continue testing their
theories by seeing if Nexi can be taught to predict the trustworthiness of human partners.
B．Three fields.
C．Four fields.
D．Five fields.
B．the voice communication
C．the gesturebased communication
D．the online communication
B．intuitively watch the trustworthiness
C．accompany the robot closely
D．play an economic game
B．a kind of entertainment
C．a simple gesture
D．one person"s gestures
reasons are various."School Refusal",formerly known as"School Phobia",is an actual
anxietybased disorder.Many children are vague about their complaints and unable to be sure
what is making them anxious,so it is sometimes regarded as typical childhood will fullness.
However,the effects of constant school refusal can be farreaching for your child"s education.
So,where"s the line between what"s normal and what"s not?"You need to look at whether
it is affecting the child or family"s normal life,"explains Christopher Kearney,Ph.D.In other
words,if a child"s grades are suffering from frequent absences or a parent"s job is disturbed,
it is time to look closely at the issue.Parents should listen carefully to children who say they
can"t go to school because of "untestable things"such as stomachaches or headaches.While
these complaints alone don"t necessarily indicate school refusal,there may be deeper problems
if combined with general complaints about school,talks of threats at school and so on.
There are different kinds of behavior in school refusal.Some children are influenced by their
friends who skip school to hang out with their friends,showing a sense of rebellion(叛逆)．
Some children cling to their mothers,screaming at the thought of having to enter the school
building.
However,that doesn"t mean that getting a child back into the classroom is impossible.
According to Maryann Roth,a school psychologist and guidance counselor(顾问),parents
should attempt to make the child get back to school,no matter how hard it is.Working closely
with school officials and possibly a specialist to create a plan is a necessary step.
B．unclear
C．curious
D．unusual
B．are afraid of endless tests
C．want to stay with their parents
D．feel bored and unsafe at school
A．take the problem seriously if their daily life is disturbed
B．discuss the seriousness of the problem with their children
C．take their children to see the doctor immediately
D．keep their children away from their rebellious friends
B．explain the phenomenon of “School Refusal” and how to treat it
C．remind parents to take good care of their children
D．explain that “School Refusal” is normal and not serious
A major source of teen stress is school exams,and test anxiety is not uncommon.When
you recognize your teen is under stress,how can parents help your teen stay calm before
an exam?
Be involved.Parents need to be involved in their teen"s work.__1__What they look for is
your presence-to talk,to cry,or simply to sit with them quietly.Communicate openly with your
teen.Encourage your teen to express his worries and fears,but don"t let them focus on those
fears.
Help them get organized.__2__Together,you and your teen can work out a timetable in
which she can study for what she knows will be on the test.
Provide a calm setting.Help your teen set up a quiet place to study and protect his privacy.
Give them a nutritious diet.It"s important for your teen to eat a healthy,balanced diet during
exam times to focus and do her best.__3__If this happens,encourage your teen to eat light
meals or sandwiches.A healthy diet,rather than junk food,is best for reducing stress.
__4__Persuade your teenager to get some sleep and/or do something active when she
needs a real break from studying.Making time for relaxation,fun,and exercise are all important
in reducing stress.Help your teen balance her time so that she will feel comfortable taking time
out from studying to spend time with friends or rest.
Show a positive attitude.__5__Your panic,anxiety and blame contribute to your teen"s
pressure.Make your teen feel accepted and valued for her efforts.Most importantly,reassure
your teen that things will be all right,no matter what the results are.
A．A parent"s attitude will dictate their teen"s emotions.
B．Exam stress can make some teens lose their appetite.
C．They will only make the situation worse.
D．Encourage your teen to relax.
E．The best thing is simply to listen.
F．Help your teen think about what she has to study and plan accordingly.
G．Your teen may also make negative comments about themselves.
reading and writing paper.No notebooks,no textbooks,no test paper.Nor are there any pencils
or pens,which always seem to run out of ink at the critical moment.A"paperless classroom"is
what more and more schools are trying to achieve.
Students don"t do any handwriting in this class.Instead,they use palm size,or
specially-designed computers.The teacher downloads texts from Internet libraries and sends
them to every student"s personal computer.
Having computers also means that students can use the Web.They can look up information
on any subject they"re studying from maths to social science.
High school teacher Judy Herrell in Florida,US,described how her class used the Web to
learn about the war in Afganistan(阿富汗) over one year ago.
"We could touch every side of the country through different sites from the forest to refugee
camps(难民营),"she said."Using a book that"s three or four years old is impossible."
And exams can go online too.At a high school in Tennessee,US,students take tests on
their own computers.The teacher records the grades on the network for everyone to see and
then copies them to his own electronic grade book.
A paperless classroom is a big step towards reducing the waste of paper.High school
teacher Stephanie Sorrell in Kentucky US said she used to give about 900 pieces of paper
each week to each student.
"Think about the money and trees we could save with the computers,"she said.But,with
all this technology,there"s always the risk that the machines will break_down.So, in case of
a power failure or technical problems, paper textbooks are still widely available(可用的) for
these hitech students.
the critical moment" mean?
B．Pens get lost easily,so you may not find them at the critical moment.
C．Pens may have little or no ink at the critical moment.
D．Pens use ink,while pencils don"t.
B．Computers.
C．Information.
D．Texts.
B．the Web taught them a lot
C．the Web is a good tool for information
D．the Web，better than the textbooks，can give the latest and comprehensive(全面的) information
B．teachers
C．trees
D．computers
B．Stop working.
C．Fall down.
D．Lose control.
- 1After a 68-hour flight in the Shenzhou VII spaceship, three
- 2到1991年12月21日，下列国家中，没有加入“独联体”的加盟共和国有①格鲁吉亚②立陶宛③爱沙尼亚④拉脱维亚[
- 3关于日本的明治维新和中国戊戌变法的共同点的叙述中，正确的是 ①都在文化教育方面采取了重要措施 ②都是自上而下的资产阶级改
- 4久置于空气中的澄清石灰水表面形成一层白膜，说明空气中含有少量______．饼干变松软，说明空气中含有少量______．
- 5计算：
- 6“最信仰基督的国王陛下将对下列各地的全部权利进行割让并保证交给不列颠国王陛下，即加拿大及其所在属地，以及布雷顿角岛和圣劳
- 7读世界某海区洋流分布示意图，回答：（每空2分，共10分）(1)按成因，A处属于在盛行风吹拂下形成的洋流，它是
- 8在的二项展开式中，的系数是 （结果用数字作答）.
- 9一定温度下，在恒容密闭容器中发生如下反应：2A(g )+B(g ) 3C(g )+D(g ),若反应开始时充入2 mol
- 10【题文】若函数，且则___________
- 1史学界把封建制度在世界范围内占统治地位的时期称为[ ]A．上古时期B．中古时期C．近代时期D．现代时期
- 2（1）某学生用螺旋测微器在测定某一金属丝时，测得的结果如图a所示，则该金属丝的直径d=______mm．另一位学生用游标
- 3（9分）“最美孝心少年”、“最美教师”、“最美司机”…… “最美”的他们用“最美的行动”诠释了对生命的珍爱。我们应该怎样
- 4已知直线m n和平面α，则m∥n的一个必要条件是（ ）A．m∥α，n∥αB．m⊥α，n⊥αC．m∥α，n⊂αD．m，n
- 5计算：x6y4÷x2y2=______．
- 6如图所示，A为电磁铁，C为胶木秤盘，A和C（包括支架）的总重量M，B为铁片，质量为m，整个装置用轻绳悬于O点，当电磁铁通
- 7如图是甲、乙两个物体做直线运动的速度一一时间图象．下列说法不正确的是（ ）A．甲在做匀速直线运动B．乙在做匀速直线运动
- 8—_____ is his hair?—It"s black.[ ]A. What classB. What g
- 9关于声现象，下列说法正确的是A．只要物体在振动，我们就能听到声音B．“不敢高声语，恐惊天上人”中的“高”指声音的音调高C
- 10在实施“中小学生蛋奶工程”中，某配送公司按上级要求，每周向学校配送鸡蛋10000 个，鸡蛋用甲、乙两种不同规格的包装箱进