of the Botanical Society of Edinburgh, 28: 117-118 (1923)
NOTE ON JUVENILE CHARACTERS IN ROOT AND STEM CUTTINGS OF ACANTHUS MONTANUS.
By L. B. STEWART
(Read 18th May 1922.)
Taking a root of Acanthus about a foot long, dividing it into portions of from 3 to 4 inches, and placing these in a propagating ease, it is found that the portion with the root apex attached continues to elongate, while the other portions generally develop side roots near the basal ends. In root cuttings of Acanthus there is always a tendency on the part of the cutting to produce more roots to begin with than there is for shoot production. On the meristematic tissue at the upper ends of each portion buds are formed of which one or two produce growth shoots, the remaining buds lying dormant. Seldom are more than two growth shoots sent up. Should three or four growths start away they have very short internodes and are weak in growth. The dormant buds remain fresh and green for two or three years and are ultimately overgrown by the growth shoots. Should, however, the growth shoots be knocked off or be cut off, one or more of the dormant buds will produce growth shoots.
The appearance of the growth developed from the three portions of root show marked contrasts, The shoot developed from the youngest piece of root which bears the root apex is juvenile in character whereas the growth formed on the oldest portion shows much more adult characters.
Bud formation on the normally lower end of the root portion is more difficult to induce, but this can be accomplished by inserting the portion of root first in the normal position until callus has formed, then by inverting the cutting and at the same time giving the callus a wound stimulus, buds are thereafter formed. Buds formed on the inverted cutting are not so numerous as are the buds formed on the normally placed cutting. Even after a growth shoot has developed from the normally basal end of an inverted cutting it will often be found that roots are produced from the base of this growth shoot. If these roots are allowed to develop the growth shoot soon disconnects itself from the parent cutting. The remaining buds on the inverted cutting are somewhat difficult to start into growth, but this can be done by hot water stimulation.
On the inverted cutting the growth shoots exhibit very juvenile characters and the leaves are miniature. Such leaves are rarely seen even on seedlings unless the seeds are small and weak. Further, the growth on the inverted cutting takes a longer time to pass through the transitional stages to the adult form.
In stem cuttings the same gradation in growth forms from juvenile to adult character is seen. A stem cutting, consisting of the terminal portion of the plant when rooted, goes on growing without showing any change in form. On an internodal cutting with one bud in the leaf axil the growth produced shows a juvenile form, while the growth from an internode with no preformed buds left adhering shows a very markedly juvenile growth form. All juvenile forms again show marked similarity to seedlings.