▁the ▁rh iz os phere ▁and ▁s per mos phere . ▁The ▁combining ▁form ▁la im - ▁from ▁ ▁( G reek : ▁ λ α ι μ ό ς ) ▁denotes ▁a ▁connecting ▁organ ▁( ne ck ) ▁while ▁- s phere ▁indicates ▁a ▁zone ▁of ▁influence . ▁Top ograph ically , ▁the ▁la imos phere ▁includes ▁the ▁soil ▁around ▁any ▁portion ▁of ▁sub ter rane an ▁plant ▁org ans ▁other ▁than ▁roots ▁where ▁ex ud ed ▁nut ri ents ▁( es pecially ▁sug ars ▁and ▁am ino ▁ac ids ) ▁stim ulate ▁micro b ial ▁activities . ▁Sub ter rane an ▁plant ▁org ans ▁with ▁a ▁la imos phere ▁include ▁hyp oc ot yl s , ▁ep ic ot yl s , ▁st ems , ▁st ol ons , ▁c orm s , ▁bul bs , ▁and ▁leaves . ▁Pro pag ules ▁of ▁soil - bor ne ▁plant ▁path og ens , ▁whose ▁germ ination ▁is ▁stim ulated ▁by ▁a ▁plant ▁ex ud ates ▁in ▁the ▁la imos phere , ▁can ▁initi ate ▁hyp oc ot yl ▁and ▁stem ▁ro ts ▁leading ▁to ▁" d amp ing - off ". ▁Path og ens ▁ ▁commonly ▁found ▁to ▁cause ▁such ▁dise ases ▁are ▁species ▁of ▁F us arium , ▁Ph oma , ▁Ph yt oph th ora , ▁P yth ium , ▁Rh izo ct onia ▁and ▁S cler ot in ia . ▁ ▁S ources ▁ ▁At kin son , ▁T . ▁G ., ▁et ▁al . ▁ 1 9 7