Title: Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 13
Identifier: contributionsfro13univ (find matches)
Year: 1934 (1930s)
Authors: University of Pennsylvania. Botanical Laboratory; University of Pennsylvania. Morris Arboretum
Subjects: Botany; Botany
Publisher: Philadelphia : (s. n. )
Contributing Library: Penn State University
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
1004 Journal of Agricultural Research Vol. 51, no. 11 Dec. 1, 1935 Root Development of Pitch Pine 1005
Text Appearing After Image:
Figure 13.—Central roots of trees from saturated soil: A, Preliniiiuirx oxcnvntion of the largest tree, with water standing in the bottom of the hole. B. Under-wafer portion of the taproot of the same tree. It reached a depth of 6.5 feel. C, Roots of a smaller tree, fr site s* here the water table was only S inches below the soil surface; these roots reached a depth nf.' Uwi very few definite statements with respect to the occurrence of mycor- rhizae in nature on submerged roots. The negative findings of Bondois (^) constitute the only direct observations on tliis topic known to the writer. The fact that mycorrhizae had not been reported on sub- merged roots and that good drainage seems essential for the successful synthesis of mycorrhizae in culture (21) has led to the general opinion that they do not develop under saturated conditions. In some re- spects the presence of mycorrhizae far below a permanent water table is even more remarkable than the growth of the pine roots themselves. Interesting questions are raised as to the identity and physiology of the fungus involved—questions to which there are at present no answers. The other two trees taken from saturated soils grew on a lower site, in what probably was originally the ecotone between white cedar and pine stands. (Clearing had disturbed the natural vegetation.) The water table was about 8 inches below the surface in dry weather; for several weeks after a rainy period it remained only about 4 inches down. The site was not a true bog as known in glaciated regions. The surface soil to a depth of 6 to 10 inches was composed largely of fibrous plant debris, hummocks of cinnamon fern, and sphagnum moss. It was densely interwoven with living roots and rhizomes. This fibrous mat rested on sand, with a sharp line of demarcation. The specimen trees were 4 inches d. b. h. and about 20 feet tall, somewhat smaller than the one discussed above. Both were vigorous and healthy in appearance, the more recent internodes being 12 to 18 inches long. One of these trees was essentially taprooted, though the shaft forked into two almost equal and parallel parts and divided extensivelv into a fan-shaped mass of many-branched and contorted roots (fig/l3, (7). It ended at a depth of 4 feet, with a few mdividual roots going about 1 foot deeper. The finding of two such fans indi- cates that their formation is a normal response to the saturated condi- tion. Why this is the case must, at present, be left to conjecture. The branches did not originate wholly on opposite sides of the tap- root, which would seem to eliminate diarchy of the protostele as an explanation. In fact, many of the roots were triarch. This tree, also, showed numerous growing tips and mycorrhizal clusters. The second smaller tree had no taproot, but was anchored by four strong sinkers located a few inches out from the stump. They ended at depths of 2.5 to 3 feet. One of these obliqued downward at an angle of about 45°, which is notable as the only example found on any tree of a major root following such a course. (Major roots are almost always either definitely vertical or definitely horizontal.) This tree had developed no fanUke structure. These three trees demonstrate that pitch pine can thrive on satu- rated soils; that it will root soUdly and deeply on such soils, with no more than the usual danger of windthrow; and that mycorrhizae can develop under conditions of saturation. . .„ , . Before applying these conclusions generally, it will be necessary to examine trees in other regions and on other sod types. It is possible that conditions in the pine barrens permit a greater degree of aeration of ground water than usually occurs elsewhere. As is well known, many herbaceous plants that are intolerant of saturation will grow in water culture if properly aerated. Hole (M) has shown that some trees, at least, respond in the same manner. Hesselman (11) attrib- utes the growth of spruces in the saturated soils near springs to the

Note About Images