Persistent Link:
http://hdl.handle.net/10150/194362
Title:
Salinity Effects on Guayule Leaf Anatomy and Physiology
Author:
Poscher, Elisabeth
Issue Date:
2005
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Salinity usually reduces plant growth in terms of height and biomass, but can increase secondary metabolite production. This frequently reported observation in guayule (Parthenium argentatum Gray, Asteraceae) was investigated for possible mechanisms.Osmotic and specific ion effects of four chloride salts (CaCl2, MgCl2, KCl, and NaCl) on leaf anatomical and plant physiological parameters were studied. One-year-old plants of guayule line AZ 2 were grown under two salt concentrations (750 ppm and 1500 ppm) for each salt type (plus a control) in sand culture (semi-hydroponic) for eight weeks under controlled greenhouse conditions in Tucson, Arizona.Growth in height decreased with increasing salt concentration. Shoot dry weight, rubber, and resin contents, however, showed no significant differences between treatments, indicating no effect from either salt concentration or salt type. There was a trend for increasing rubber content with increasing salt concentration, although not statistically significant. At the same time, net CO2 gas exchange rates decreased significantly with increasing salinity.With increasing salt concentration, guayule showed osmotic effects in terms of height, indicating a lower hydraulic conductivity. Although plants of higher salt concentrations utilized significantly less water, they had the same shoot dry weights, rubber, and resin contents. Salt-stressed plants therefore achieved higher water use efficiencies. The diurnal net CO2 gas exchange rates were significantly reduced with increasing salinity; the nocturnal net CO2 gas exchange rates showed no significant difference between the treatments.Anatomically, it was found that the stomata were raised or elevated above the epidermis, and supported by upwardly curving cells. When guayule was grown under salt treatments, the trichomes were found to include deposits of material. Trichomes might act as a detoxification repository for excess ions. Although the physiological significance of raised stomata is unknown, it is hypothesized that the unique combination of raised stomata, indumentum, and multiple layers of palisade parenchyma allows for an overall high photosynthetic capacity and performance. During stress conditions such as salinity or drought, guayule might activate an internal CO2 concentrating mechanism, i.e., bicarbonate/CO2 pump, internal CO2 recycling, or PEP carboxylation activity.
Type:
text; Electronic Dissertation
Keywords:
Parthenium argentatum Gray; raised stomata; gas exchange; Rubisco activity; CO2 concentrating mechanism; salt stress
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Arid Lands Resource Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Ray, Dennis T.; Biel, Karl Y.
Committee Chair:
Ray, Dennis T.; Biel, Karl Y.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleSalinity Effects on Guayule Leaf Anatomy and Physiologyen_US
dc.creatorPoscher, Elisabethen_US
dc.contributor.authorPoscher, Elisabethen_US
dc.date.issued2005en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSalinity usually reduces plant growth in terms of height and biomass, but can increase secondary metabolite production. This frequently reported observation in guayule (Parthenium argentatum Gray, Asteraceae) was investigated for possible mechanisms.Osmotic and specific ion effects of four chloride salts (CaCl2, MgCl2, KCl, and NaCl) on leaf anatomical and plant physiological parameters were studied. One-year-old plants of guayule line AZ 2 were grown under two salt concentrations (750 ppm and 1500 ppm) for each salt type (plus a control) in sand culture (semi-hydroponic) for eight weeks under controlled greenhouse conditions in Tucson, Arizona.Growth in height decreased with increasing salt concentration. Shoot dry weight, rubber, and resin contents, however, showed no significant differences between treatments, indicating no effect from either salt concentration or salt type. There was a trend for increasing rubber content with increasing salt concentration, although not statistically significant. At the same time, net CO2 gas exchange rates decreased significantly with increasing salinity.With increasing salt concentration, guayule showed osmotic effects in terms of height, indicating a lower hydraulic conductivity. Although plants of higher salt concentrations utilized significantly less water, they had the same shoot dry weights, rubber, and resin contents. Salt-stressed plants therefore achieved higher water use efficiencies. The diurnal net CO2 gas exchange rates were significantly reduced with increasing salinity; the nocturnal net CO2 gas exchange rates showed no significant difference between the treatments.Anatomically, it was found that the stomata were raised or elevated above the epidermis, and supported by upwardly curving cells. When guayule was grown under salt treatments, the trichomes were found to include deposits of material. Trichomes might act as a detoxification repository for excess ions. Although the physiological significance of raised stomata is unknown, it is hypothesized that the unique combination of raised stomata, indumentum, and multiple layers of palisade parenchyma allows for an overall high photosynthetic capacity and performance. During stress conditions such as salinity or drought, guayule might activate an internal CO2 concentrating mechanism, i.e., bicarbonate/CO2 pump, internal CO2 recycling, or PEP carboxylation activity.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectParthenium argentatum Grayen_US
dc.subjectraised stomataen_US
dc.subjectgas exchangeen_US
dc.subjectRubisco activityen_US
dc.subjectCO2 concentrating mechanismen_US
dc.subjectsalt stressen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineArid Lands Resource Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRay, Dennis T.en_US
dc.contributor.advisorBiel, Karl Y.en_US
dc.contributor.chairRay, Dennis T.en_US
dc.contributor.chairBiel, Karl Y.en_US
dc.contributor.committeememberSilvertooth, Jeffrey C.en_US
dc.contributor.committeememberGunatilaka, Leslieen_US
dc.contributor.committeememberYensen, Nicholas P.en_US
dc.identifier.proquest1166en_US
dc.identifier.oclc137354226en_US
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