Littleisknownaboutthephysiologicalmechanismsunderlyingplantresponsesandtheirabilitytorecover
from water stress, especially responses that concern the root system. The effect of water stress on K+
and water flowsinexcisedrootsaswellastherelationshipofthese
flowswithwaterstresstolerancewasstudied in six sun
flower (Helianthus annuusL.) cultivars. Plants growing in a growth chamber were subjected to
waterstressbyde ficitirrigationfor15days.Afterthisperiod,theplantswerere-irrigatedandtheexudates
from the excised roots were collected. Water stress reduced the shoot growth of all plants, although
differenceswereobservedamongthecultivars.Whilewaterstressstimulatedthewater
flowintheexcisedrootsofallcultivars,K+(Rb+)uptakebytherootanditsdischargeintothexylemwaspromotedonlyinthose
cultivars that were more susceptible to water stress. The same effect was observed when plants were
subjectedtowaterstressusingpolyethyleneglycol(PEG)6000.ThepromotionofbothK+andwater
flows could be considered as a mechanism to tolerate water stress, through which the plant restores cell
turgidity, shoot water status and plant growth after a water stress period
Littleisknownaboutthephysiologicalmechanismsunderlyingplantresponsesandtheirabilitytorecoverfrom water stress, especially responses that concern the root system. The effect of water stress on K+and water flowsinexcisedrootsaswellastherelationshipoftheseflowswithwaterstresstolerancewasstudied in six sunflower (Helianthus annuusL.) cultivars. Plants growing in a growth chamber were subjected towaterstressbyde ficitirrigationfor15days.Afterthisperiod,theplantswerere-irrigatedandtheexudatesfrom the excised roots were collected. Water stress reduced the shoot growth of all plants, althoughdifferenceswereobservedamongthecultivars.Whilewaterstressstimulatedthewaterflowintheexcisedrootsofallcultivars,K+(Rb+)uptakebytherootanditsdischargeintothexylemwaspromotedonlyinthosecultivars that were more susceptible to water stress. The same effect was observed when plants weresubjectedtowaterstressusingpolyethyleneglycol(PEG)6000.ThepromotionofbothK+andwaterflows could be considered as a mechanism to tolerate water stress, through which the plant restores cellturgidity, shoot water status and plant growth after a water stress period
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