RELATION BETWEEN THE DEVELOPMENT OF ROOT SYSTEM AND SHOOT UNDER LONG- AND SHORT-DAY ILLUMINATION

Relatively fewinvestigations havebeenmadetodetermine thefactors whichaffect therelation ofthegrowthofrootstotops.A moreexact knowledge oftherelations between aerial andsubterranean plant parts and thedegree towhichthese maybemodified through cultural practices isof greatscientific andpractical importance. Extensive investigations have shownthatplants exhibit markedspecific andvarietal differences with respect torelative development ofrootswhengrownunderthesameen- vironmental conditions. Intensive studies on thegrowthofwheatby WEAVER, KRAMER,andRuin(20)andofcertain otherplants byCRIST andSTOUT(3)havealsomadeclear thatthereisa persistent tendency towards a positive correlation betweenrootsandshoots, increase insize oftopsbeingaccompanied byincrease insizeofroots.Although signifi- cantvariations intherelative distribution ofthegrowthrateoftopsand rootsoccurinnatureandmayreadily beinduced bychangeinenviron- ment,thefactremains thatthere isapersistent positive correlation insize oftopsandrootsregardless ofthewidevariations induced byspecial conditions. Themaintenance ofaproper balance between rootandshoot isofvery greatimportance. Ifeither istoolimited ortoogreatinextent, theother will notthrive. Therootsystem mustbesufficiently widespread toabsorb enoughwaterandnutrients forthestemandleaves, which, inturn, must