Graduate Thesis Or Dissertation

 

Relationships between endogenous phenolic compounds of rhododendron tissues and organs and cold hardiness development Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5x21th998

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  • The leaching of water soluble phenolic compounds from cold stressed Rhododendron leaves was found to be a reliable indicator of tissue damage. In sublethally stressed leaf tissues, more and novel phenolic compounds appeared and were hypothesized to be precursors of cell wall components such as lignin and suberin. Subsequent radiolabeling of sublethally cold stressed tissues showed a preferential incorporation of the phenolic precursor phenylalanine into cell walls. The appearance of more and new phenolic compounds in intact leaves was found in four varieties of artificially cold acclimated Rhododendron. Phenolic polymers including suberin and lignin were also found in cold hardened Azalea (Rhododendron sp.) floral buds. Hardy Azalea floral buds appear to possess an ice nucleation barrier within bud tissues, which seems to prevent ice present in the stem and scales from nucleating water in the primordia. Non-hardy buds do not have such barriers. This physical barrier can be removed by a sublethal heat treatment of the buds; treated buds showed decreased hardiness as measured by differential thermal analysis (DTA), evidenced by a decrease in the number of low temperature exotherms (LTE's). Histochemical and photomicrographical studies suggest a lignified, suberized barrier occurs at the base of bud scales and pedicels, and beneath the bud axis.
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