AbstractsBiology & Animal Science

It is a matter of common knowledge that most of our woody plants do not grow continuously throughout the year. The fact is brought to our attention especially in spring, when we may observe the awakening of the vegetation which has been dormant for some time. After the buds open, leaves and twigs continue to grow rather rapidly. Sooner or later, however, vegetative activity diminishes and finally ceases when the terminal buds are formed. The plants are gradually preparing to go into their rest period. What causes this annual suspension of growth? Is it due simply to the lack of suitable external growth conditions? Since the rest period of most of the woody plants happens to fall during winter when temperature and other factors are unfavorable for growth, we are liable to be led to believe that the annual rest is caused simply by external influences. If there is such a simple relation as this between winter and the occurrence of the rest period, then we should not expect plants to suspend vegetative activity if growth conditions remained favorable through the year.