. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. 8 BULLETIN 169, U. S. DEPARTMENT OF AGRICULTURE. time. Although injury to root apices commonly took place before the seedlings appeared above the soil, most injured seedlings came up, and when the soil around the short root was kept moist the growth of the stem and leaves continued for some time at a normal rate. All of the development of the aerial parts of the seedlings shown in Plate I, figures 2, 3, and 4, was made after the extension of the root had been stopped by acid. Injured
. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. 8 BULLETIN 169, U. S. DEPARTMENT OF AGRICULTURE. time. Although injury to root apices commonly took place before the seedlings appeared above the soil, most injured seedlings came up, and when the soil around the short root was kept moist the growth of the stem and leaves continued for some time at a normal rate. All of the development of the aerial parts of the seedlings shown in Plate I, figures 2, 3, and 4, was made after the extension of the root had been stopped by acid. Injured seedlings ordinarily lived till the surface of the upper part of the root became brown and presumably impervious, as in the older parts of the root in healthy seedlings after two or three weeks. In the worst in- jured seedlings this root browning seemed to take place somewhat earlier than in healthy plants. The decrease in diameter which is no- ticed in the older parts of normal roots at the time of browning was seldom observed in acid- injured roots. Because the injured seedlings were not able to develop new root tissue, ab- sorption ultimately became impossible and death from drought ensued. The seedlings shown in Plate I, figures 2 and 3, have prac- tically reached this condition, though both still appeared to be growing normally when they were dug up. Plate I, figure 4, shows a seedling injured at the same time as that in Plate I, figure 3, which has recovered by recom- mencing root growth. Where the roots of injured seedlings were very short, the plants died very soon, either because the soil was allowed to dry out to be- low the level reached by the short root or be- cause the short root did not afford sufficient mechanical support for the top-heavy stem, and the seedling fell over or was washed out in watering. In the cases where injury was earliest, so that the radicle had scarcely emerged from the seed coat by the time its tip was killed, the seedlings failed to appea
Size: 962px × 2597px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherwashi, bookyear1913
