Hormones in Pear Seeds. II. Levels of Abscisic Acid, Dihydrophaseic Acid, and Their Metabolites in Relation to Seed Dormancy in Several Pyrus Species1

Abstract

Concentrations of abscisic acid (ABA), dihydrophaseic acid (DPA), and their metabolites were measured in mature pear seeds, using gas-liquid chromatography (GLC). ABA content of Pyrus communis L. cv. Bartlett seeds fell during imbibition, but was not affected by temperature (4 vs. 21°C) or time (0 to 4 weeks) of stratification in a moist medium. Levels of DPA and 3 of its metabolites were not correlated with dormancy. The amount of chilling required to break dormancy was not correlated with ABA or DPA content in imbibed, non-stratified seeds of 6 Pyrus species.

Effects of Storage Temperatures on Endogenous Growth Substances and Shoot Emergence in Freesia hybrida corms1

“…ABA occurs in a wide range of plants and plant organs and has been suggested to be involved in the regulation of dormancy (2,4,10,12,23,26,44,45,46) and scenescence (14,34). Recently, however, other authors have also commented on promotive roles for ABA ( 2 ,3 ,6 ,3 1 ,32)and some studies have found no correlation between dormancy and ABA (9,15,28,30,31,32,36); our data agree with these studies.…”

“…Commercially, freshly dug freesia corms are held at 28-31°C for 10-13 weeks to rapidly covercome dormancy, to insure rapid sprouting after replanting, and to prevent ' 'pupation,' ' the formation of a new and dormant corm on top of the old corm (3,9). Holding corms at 3-5° is reported to be effective in maintaining corm dormancy and preventing " pupation" (9,17). However 3-5°-treated corms still require a 28-31° treatment for rapid and uniform shoot emergence.…”