Graduate Thesis Or Dissertation
 

The relationship of abscisic acid concentration in Douglas-fir needles to seedling vigor

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/p2676x92r

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  • A quantitative and predictive measure of seedling vigor during the regeneration chain would be of utmost help for forest regeneration work. This was the impetus to study the possibility of using abscisic acid (ABA) concentration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) needles as an indicative measure of seedling vigor prior to outplanting. The experiment included two lifting times (mid-November, mid-January), two pretreatments (normal dormancy, fall photoperiod), and three cold storage treatments (dark, light, and bareroot). Needle samples were taken four times during the experiment: 1) after 48 hours in the cold room, 2) prior to taking seedlings out of the cold room after 25 days of storage, 3) 48 hours in the growing environment, and 4) at the time of bud break. Seedling vigor in relation to treatments was assessed under two growing environments: 1) growth room and 2) cold frame. Seedlings were planted in mid-December and mid-February. The concentration of ABA in the needles was quantified by successive procedures of extracting ABA through poly-N-viriylpyrrolidone (PVP), diethylarninoethyl cellulose (DEAE), and octadecyl silica (C18) columns, preparative purification with high-performance liquid chromatography (HPLC), and final quantitation with gas-liquid chromatography (GLC) using an electron capture detector. Results indicate that time of lifting did not affect survival greatly, but markedly influenced the time of bud break. Storage treatments did not result in statistically significant differences in ABA concentrations, survival or shoot growth. Generally, pretreatment with supplementary light in the fall did not produce different results from the normal dormancy pretreatment. Considerable variability in ABA concentrations amongst treatments was found, an occurrence which probably precluded detection of its relationship to seedling vigor. However, there was a tendency, though not significant, of increasing ABA concentrations from mid-November to mid-January. The failure to detect a relationship between ABA and seedling vigor may have been due to a transitory role of ABA in stress conditions or inability to quantitate ABA in its site of action, stomata. Results of this study, along with those of previous studies, support continuance of research on ABA in physiology of plants and its potential use as an indicator of seedling vigor. However, a new synthesis of the role of ABA in seedling metabolism would be fruitful before undertaking new empirical studies as the whole concept of hormone action is undergoing a evolutionary realignment.
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