Haveyoueverwonderedwhytherootsoftheplantsalwaysknowwhichwaytogrow—intothesoilbutnotaboveit?SomeBritishscientistshaverecentlysolvedthismystery.

ItturnsoutthatrootshavespecialhairsthattiethemintothesoilandhelpthemgrowtheirwaypastobstaclesateamattheJohnInnersCenterinNorwichreportsintheFebruary29issueofJournalScience.

“Thekeyisinthefuzzy(有绒毛的)coatofhairsontherootsofplants”saysprofessorLiamDolan.“Wehavefoundagrowthcontrolsystemthatenablesthesehairstofindtheirwayandtobecomelongerwhentheirpathisclear.”

Roothairsexplorethesoilinmuchthesamewayapersonwouldfeeltheirwayinthedark.Iftheycomeacrossanobstacletheymaketheirwayarounduntiltheycancontinuegrowinginanopening.Inthemeantimetheplantisheldinplaceasthehairsgrip(紧紧抓住)thesoil.

Thehairsareguidedbyacleverchemicaltrick.Aprotein(蛋白质)atthetipoftheroothairscalledRHD2helpsthemtotakecalcium(钙)fromthesoil.CalciummakesthehairsgrowandproducemoreRHD2andtakemorecalcium.

Butwhenanobstacleblocksthehair’spathorthehairreachesthesurfaceofthesoilthecycleisbrokenandgrowthstartsinanotherdirection.

ThissystemgivesplantstheflexibilitytoexploreacomplexenvironmentandtoliveineventhemostunpromisingsoilssaysDolan.

InpoorsoilssuchasinpartsofAustraliaandAfricanativeplantshaveadaptedbyproducingenormousnumbersofroothairs.Abetterunderstandingofthisadaptationwillallowscientiststodevelophairyrootedcropsthatcangrowinunfriendlyenvironments.

AccordingtoDolan“ResearchintheJohnInnersCenteristakingabreedingapproachtoincreasehairlengthinwheatbutitwillbesometimebeforenewcultivars(栽培变种)aredeveloped.”

【小题1】Thepassageismainlyabout_______.

A．whytherootsofplantsgrowintothesoilbutnotaboveitB．howtherootsofplantsgrowintothesoilbutnotaboveitC．theprocessofplantsgrowthD．agrowthcontrolsystemofplants【小题2】Howdoesthecirclework?A．RHD2takescalciumfromthesoilwhichmakeshairsgrowandproduce