Britishscientistsarebreedinganewgenerationofriceplantsthatwillbeabletogrow.insoilcon­tainingsaltwater.Theirworkmayenableabandonedfarmstobecomeproductivefarmsoncemore.TimFlowersandTonyYeo,fromSussexUnive

　　Britishscientistsarebreedinganewgenerationofriceplantsthatwillbeabletogrow.insoilcon­tainingsaltwater.Theirworkmayenableabandonedfarmstobecomeproductivefarmsoncemore.

　　TimFlowersandTonyYeo,fromSussexUniversity’sSchoolofBiologicalSciences,.havespentseveralyearsresearchinghowcrops,suchasrice,couldbemadetogrowinwaterthathasbecomesalty.Thepairshaverecentlybegunathree-yearprogramme,fundedbytheBiotechnologyandBio­logicalSciencesResearchCouncil,toestablishwhichgenesenablesomeplantstosurvivesaltycondi­tions.Theaimistobreedthiscapabilityintocrops,startingwithrice.

　　Itisestimatedthateachyearmorethan10millionhectares(公顷)ofagriculturallandarelostbecausesaltgetsintothesoilandstunts(防碍生长)plants.Theproblemiscausedbyseveralfactors.Inthetropics,mangrovesthatcreateswamps(沼泽)andtraditionallyformedbarrierstoseawaterhavebeencutdown.IntheMediterranean,aseriesofdroughtshavecausedthewatertabletodrop,allowingseawatertoseep(渗透)in.InLatinAmerica,irrigationoftencausesproblemswhenwaterisevaporatedbytheheat,leaving,saltdepositsbehind.

　　Excesssaltthenenterstheplantsandpreventsthemfunctioningnormally.Heavyconcentrationsofmineralsintheplantsstopthemdrawingupthewatertheyneedtosurvive.

　　Toovercometheseproblems.FlowersandYeodecidedtobreedriceplantsthattakeinverylittlesaltandstorewhattheydoabsorbincellsthatdonotaffecttheplants’growth.Theyhavestartedtobreedthesecharacteristicsintoanewricecrop,butitwilltakeabouteightharvestsbeforetheresul­tingseedsarereadytobeconsideredforcommercialuse.

　　Oncethecharacteristicsforsurvivingsaltysoilareknown,FlowersandYeowilltrytobreedtheappropriategenesintoallmannersofcropsandplants.Landthathasbeenabandonedtonaturewillthenbeabletobloomagain,providingmuchneededfoodforthepoorercountriesoftheworld.

　　4.WhichofthefollowingstatementsaboutFlowersandYeoistrue?

　　A.TheyarestudentsatSussexUniversity. B.Theyarericebreeders.

　　5.WhichofthefollowingisNOTmentionedasacauseoftheproblemdiscussedinthepassage?

　　A.Naturalbarri