Author

Mingshu Zhang

Advisor

Harkess, Richard L.

Committee Member

Bi, Guihong

Committee Member

Gu, Mengmeng

Committee Member

Matta, Frank B.

Committee Member

Cox, Michael S.

Date of Degree

1-1-2014

Document Type

Dissertation - Open Access

Major

Horticulture

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Ivy geranium (Pelargonium peltatum) is a heat susceptible species with its heat tolerance varying among varieties. Reactive oxygen species (ROS) and in-vivo defense systems are related to plant heat damage and heat tolerance. Application of chelated-iron has also been reported to enhance ivy geranium heat tolerance; however, the correlation of ROS, relative enzyme stability, and iron content to differences in heat tolerance in ivy geraniums is unknown. Here we show that the H2O2 content and ROS scavenging enzyme stability in ivy geranium varies with varieties and active iron is not related to heat tolerance in ivy geranium. H2O2 content in mature leaves in both heat tolerant 'Beach' and sensitive 'Butterfly' increased under heat stress, but 'Butterfly' had a relatively greater increase of this toxic compound. Catalase (CAT) activities in young leaves in both varieties decreased. In young leaves of 'Butterfly', CAT activities decreased to a level significantly lower than that in old leaves while this did not occur in 'Beach'. Superoxide dismutase (SOD) activities in 'Butterfly' young leaves were also decreased. All these phenomenon coincided with the heat tolerance differences of the two varieties. Active iron content only changed with leaf age and did not vary between varieties or treatments. Our results demonstrated that ROS scavenging ability and relative enzyme stability may indicate heat tolerance in ivy geranium and that iron deficiency was not the cause of heat damage. Cell Membrane Themostability (CMT) and Triphenyl Tetrazolium Chloride (TTC) cell viability tests are alternative, laboratory-based screening methods for screening for heat-tolerance. Both CMT and TTC tests can represent the variance in heat tolerance observed in ivy geraniums. The results of both CMT and TTC tests correlated well with plant width and growth indexes although their correlations to plant chlorosis were low. Unlike TTC, CMT strongly correlated with plant width. CMT and TTC tests are complementary laboratory-based methods that can be applied to cultivar screening for heat tolerance in ivy geraniums.

URI

https://hdl.handle.net/11668/18991

Comments

cell viability||cell membrane themostability||reactive oxygen sprecies||heat tolerance||ivy geranium

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