Respiration Rate,Catalase Activity,Peroxidase Activity and Growth of Roots of Citrus Rootstocks*

Observations of respiration rate, catalase activity, peroxidase activity ("physiological activity”) and some growth characteristics of roots of citrus rootstocks were made. These were carried out on seedlings of six rootstocks (five months old) grown in a standard nutrient solution and on seven- to ten-year-old budded trees growing in the orchard. The orchard trees, budded to only one scion, were propagated from the same rootstocks as were used in the study of seedlings. A comparison was also made of five additional scions budded on one rootstock.

A technique was developed to obtain roots from orchard trees for the study of their physiological and morphological characteristics.

Significant differences were found in the “physiological activity” of the roots of the various rootstock seedlings. A significant negative correlation existed between the final length of the main root and the physiological activity of the roots.

Significant differences were found in the physiological activity of the roots of the various mature rootstocks budded with Shamouti sweet orange.

A clear and marked influence of the various scions on the physiological activity of the roots of sour-orange was observed.

An obvious positive correlation existed between respiration rate, catalase activity and peroxidase activity of the roots. The use of two different H-donors resulted in differences in the peroxidase activity measured.

The significance of the variations in physiological response of the roots is discussed.