The hydrolysis of starch as related to the interruption of dormancy in the ash bud

Abstract In The Bud Of The Great Ash ( Fraxinus Excelsior L.) The Reserves Of Starch Stocked During Dormancy — The Presence Of Which Was Demonstrated By Use Of The Schiff-Periodic Acid Method — Were Used Differently In The Shoot Apex And In The Stem Tip Underneath The Meristem. In The Shoot Apex The Starch Was Mobilized Before The Resumption Of Growth Activity. During The Last Days Of Dormancy The Water Content In The Buds Remained Low, Inferior To The Threshold Which Characterized Them During Active Growth; But In The Shoot Apex The Water Potential, Measured In Terms Of The Degree Of Plasmolysis, Rose By Almost 15 - 105 Pa: some water which had been bound was liberated in the cells of the shoot apex, it could contribute to the hydrolysis of the starch into soluble sugars, which modified the requirement of water. This constituted, therefore, a decisive step in the passage from dormancy to active growth, and the interruption of dormancy was thus linked to an adequate increase of the water content in the bud. In contrast, in the stem tip underneath the meristem the progressive hydrolysis of the starch reserves constituted the response to the hydration of the bud which occurred after the resumption of growth, when the energy requirements resulting from the development of the annual branch were manifest.