The Annual Activity of Intermediary Roots of the Aleppo Pine

A study was made of the annual activity of intermediary roots of Pinus halepensis Mill. Roots were uncovered monthly around a few marked trees at three different groves, situated on different soils at varying heights above sea level. In the dormant root tip, metacutization was found to conform to type II of Plaut (1909). The suberized layer surrounds the initials and their immediate derivatives and unites by a bridge of suberized cells in the cortex with the secondary endodermis. When growth is resumed the cortical bridge persists and is seen as a brown band across the cortex, while the remnants of the layer which surrounds the apex are pushed to the outer boundary of the newly formed cortex. The main root activity takes place in the rainy winter and ceases in the dry summer. A pronounced resumption of root growth was observed in late summer, even though there was no rainfall. This growth ceased, and then was resumed at the onset of the winter rains. Neither a complete rest in root growth nor general activity was shown. Phenological observations show a lack of correlation between root and shoot growth. Inducing root growth by edaphic as well as other factors is discussed.