Little is known about the physiological mechanisms underlying plant responses and their ability to recover
from water stress, especially responses that concern the root system. The effect of water stress on K+
and water flows in excised roots as well as the relationship ofthese flows with water stress tolerance was studied
in six sunflower (Helianthus annuus L.) cultivars. Plants growing in a growth chamber were subjected to
water stress by deficit irrigation for 15 days. After this period,the plants were re-irrigated and the exudates
from the excised roots were collected. Water stress reduced the shoot growth of all plants, although
differences were observed among the cultivars.While water stress stimulated the water flow in the excised
roots of all cultivars,K+(Rb+)uptake by the root and its discharge into the xylem was promoted only in those
cultivars that were more susceptible to water stress. The same effect was observed when plants were
subjected to water stress using polyethylene glycol(PEG)6000.The promotion of both K+ and water 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
Littleisknownaboutthephysiologicalmechanismsunderlyingplantresponsesandtheirabilitytorecover
from water stress, especially responses that concern the root system. The effect of water stress on K
+
and
water
fl
owsinexcisedrootsaswellastherelationshipofthese
fl
owswithwaterstresstolerancewasstudied
in six sun
fl
ower (
Helianthus annuus
L.) cultivars. Plants growing in a growth chamber were subjected to
waterstressbyde
fi
citirrigationfor15days.Afterthisperiod,theplantswerere-irrigatedandtheexudates
from the excised roots were collected. Water stress reduced the shoot growth of all plants, although
differenceswereobservedamongthecultivars.Whilewaterstressstimulatedthewater
fl
owintheexcised
rootsofallcultivars,K
+
(Rb
+
)uptakebytherootanditsdischargeintothexylemwaspromotedonlyinthose
cultivars that were more susceptible to water stress. The same effect was observed when plants were
subjectedtowaterstressusingpolyethyleneglycol(PEG)6000.ThepromotionofbothK
+
andwater
fl
ows
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
Little is known about the physiological mechanisms underlying plant responses and their ability to recoverfrom water stress, especially responses that concern the root system. The effect of water stress on K+and water flows in excised roots as well as the relationship ofthese flows with water stress tolerance was studiedin six sunflower (Helianthus annuus L.) cultivars. Plants growing in a growth chamber were subjected towater stress by deficit irrigation for 15 days. After this period,the plants were re-irrigated and the exudatesfrom the excised roots were collected. Water stress reduced the shoot growth of all plants, althoughdifferences were observed among the cultivars.While water stress stimulated the water flow in the excisedroots of all cultivars,K+(Rb+)uptake by the root and its discharge into the xylem was promoted only in thosecultivars that were more susceptible to water stress. The same effect was observed when plants weresubjected to water stress using polyethylene glycol(PEG)6000.The promotion of both K+ and water flowscould 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 periodLittleisknownaboutthephysiologicalmechanismsunderlyingplantresponsesandtheirabilitytorecoverfrom water stress, especially responses that concern the root system. The effect of water stress on K+andwaterflowsinexcisedrootsaswellastherelationshipoftheseflowswithwaterstresstolerancewasstudiedin six sunflower (Helianthus annuusL.) cultivars. Plants growing in a growth chamber were subjected towaterstressbydeficitirrigationfor15days.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+andwaterflowscould 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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