Changes in phenolic acids and abscisic acid in sugar pine embryos and megagametophytes during stratification [Pinus lambertiana, dormancy, HPLC, high-pressure liquid chromatography]
1981
Murphy, J.B. | Noland, T.L. (Arkansas Univ., Fayetteville (USA). Dept. of Horticulture and Forestry)
The phenolic acids and abscisic acid (ABA) of sugar pine (Pinus lambertiana Dougl.) embryos and megagametophytes, separated by high-pressure liquid chromatography, were analyzed during 90 days stratification of the seeds. The phenolic acids occurred mainly as glycosides. Following hydrolysis, the majority of phenolics present could be identified as common benzoic and cinnamic acid derivatives. Levels of phenolic acids were relatively low in dormant seeds, but increased substantially in the embryos during stratification at 5 deg C, particularly cinnamic acid, p-coumaric acid, ferulic acid, and one unknown. This active synthesis during statification did not support an inhibitory function for phenolic acids. During stratification at 5 deg C, changes in ABA levels in both tissues followed a triphasic pattern, with no loss during the first 30 days, a significant decrease the second 30 days, and a lesser decrease the last 30 days. Loss of ABA from moist seeds at 25 deg C occurred three times as rapidly, so that by 30 days the ABA level of these seeds was equivalent to that of seeds stratified 90 days at 5 deg C; However, dormancy was not alleviated at 25 deg C. Application of exogenous ABA (10('-7) to 10('-4)M) to stratified seeds did not significantly reduce germination. Together, the above results did not support a primary role for ABA in the maintenance of dormancy in sugar pines. A correlated increase in phenylpropanoid metabolism and respiratory capacity with increased germinability during stratification suggests that loss of dormancy may be more closely dependent on increased levels of growth promoters or shift in metabolic pathways.
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