1筛管sievetube伴胞companioncell筛管—被子植物的韧皮部,运输有机物.筛管由管状的无细胞核的活细胞连接成组成筛管的每个细胞叫做筛管分子sieveelements2筛管分子的细胞壁为初生壁性质。端壁称为筛板；分布有小孔--筛孔。3筛板和筛孔Maturesieve-tubemembersfromthephloeminthestemofcornandsquash.45P-proteinCallose筛管运送养分的速度10-100cm/h67受伤时，通过筛孔的原生质形成联络索阻断相邻的筛管分子筛孔纵切面（侧面观）8筛管分子的老化－－胼胝质沉积在筛板上，形成胼胝体－－阻断筛孔，失去输导功能。9胼胝体（绿色荧光）10P-protein(phloemprotein)•Aproteinfoundinlargeamountsinthesap-conductingsieveelementsofphloemtissueinplants.Ittakesvariousformsinthematuresieveelement,dependingonplantspecies,rangingfromanetworkoffilamentstodiscretecrystallinebodies.Onegeneralpropertyisitsabilitytoformagel,anditfunctionsasapuncturerepairsubstance,formingaplugatanysiteofdamageinthesieveelement,thuspreventinglossoffoodmaterialsbeingtranslocatedbythephloem.Inanintactfunctioningsieveelement,theP-proteinismainlyfoundliningtheinteriorwall.11•Longitudinalsectionofsievetubemembersinstemofcucumber(Cucumis).•ThismaterialwasfixedinsuchawayastoenhancetheformationofP-proteinplugs,twoofwhicharepresenthere,stainedred.12筛管分子侧壁上存在着初生纹孔场—筛管分子侧壁上存在着初生纹孔场—筛域筛域13伴胞-筛管旁边的一个或多个小细胞。Thephloeminthestemofsquash南瓜14sievetubememberscanhavemultiplecompanioncells15筛管分子与伴胞之间具有筛域和胞间连丝??16筛管和伴胞由一个细胞不等分裂产生17早期筛管分子伴胞181920Sievetubemembersandcompanioncellstypicallyfunctionforonlyafewweeksormonths,thenarereplacedbynewcells.21Transversesectionofphloeminacactus(Espostoopsisdybowskii).thephloemofthisspeciesistrappedbetweentheexpandingxylem22Transversesectionofoldstemofgrape(Vitis)fromastemthatwasmucholder;thesievetubemembersandcompanioncellshavecollapsedintothesolid,darkredmass23筛胞蕨类和裸子植物体内输导有机物的细胞。Transversesectionofafernrhizome(Pteridiumaquilinum).Thecenterofthismicrographisoccupiedbyxylem(thelargered-stainedcells),andsurrounding...
