| Seeds collected from each of five black walnut trees were removed from cold stratification at 60 day intervals and dissected into endocarp, cotyledon and embryonic axis. Methanol leachates from each tissue were partitioned against ethyl acetate at pH 2.5 and 8.0 GC (gas-liquid chromatography) and GC-MS (gas-liquid chromatography-mass spectrometry) were used to quantify compounds co-chromatographing with standard ABA, GA{dollar}sb3{dollar}, GA{dollar}sb{lcub}rm 4/7{rcub}{dollar}, t-zeatin and t-zeatin riboside. Measurements of respiration rates, adenine nucleotide ratios and ultrastructural studies were also conducted on black walnut embryonic axes during stratification.; Results indicate that compounds co-chromatographing with standard gibberellic acids and cytokinins were primarily responsible for controlling germination. The highest concentration of GA's during the first 60 days of stratification were found in the embryonic axis. Abscisic acid concentrations were highest in the embryonic axis, but only during later stages of stratification. Cytokinins appeared to play a permissive role in germination only during the later stages of stratification, and concentrations were highest in the cotyledon tissue. Some variation in plant growth regulators in seed from different trees was also observed.; Increasing respiration rates correlated well with changes in adenine nucleotide concentrations during stratification. The energy charge increased independent of length of cold stratification. In addition, ultrastructural studies showed that protein and lipids disappear early during the stratification period. |
