An ecological study of the leaves of Quercus coccinea Muench. and Betula lenta L. was undertaken by the writer during the summer of 1945 at the Mountain Lake Biological Station of the University of Virginia in Giles County, Virginia. The writer wishes to express his appreciation to Dr. I. F. Lewis, Director of the Mountain Lake Biological Station, and Mr. Ruskin S. Freer of the Department of Biology of Lynchburg College, Lynchburg, Virginia, for their invaluable aid in the pursuance of this problem

Miller, Robert C.

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A Comparison of Leaves of Quercus Coccinea Muench. and Betula Lenta L. from Heath Bald and Mesphytic Ravine Habitats

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 53 | Annual Issue Article 181946A Comparison of Leaves of Quercus CoccineaMuench. and Betula Lenta L. from Heath Bald andMesphytic Ravine HabitatsRobert C. MillerUniversity of VirginiaCopyright © Copyright 1946 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis Research is brought to you for free and open access by UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academyof Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu.Recommended CitationMiller, Robert C. (1946) "A Comparison of Leaves of Quercus Coccinea Muench. and Betula Lenta L. from Heath Bald andMesphytic Ravine Habitats," Proceedings of the Iowa Academy of Science: Vol. 53: No. 1 , Article 18.Available at: https://scholarworks.uni.edu/pias/vol53/iss1/18A COMPARISON OF I~EAVES OF QUERCUS COCCINEA MUENCH. AND BETULA LENTA L. FROM HEATH BALD AND MESOPHYTIC RA VINE HABITATS ROBERT C. MILLER Introduction An ecological study of the leaves of Quercus coccinea Muench. and Betula lenta L. was undertaken by the writer during the summer of 1945 at the Mountain Lake Biological Station of the University of Virginia in Giles County, Virginia. The writer wishes to express his appreciation to Dr. I. F. Lewis, Director of the Mountain Lake Bio-logical tSittion, and Mr. Ruskin S. Freer of the Department of Bio-logy of Lynchburg College, Lynchburg, Virginia, for their invalu-able aid in the pursuance of this problem. Procedure Leaves of Quercus coccinea Muench. and Betula lenta L. trees were collected on the heath bald on the summit of Bald Knob (elevation 4363 ft.), August 6, 1945. Leaves of Q. coccinea Muench. and B. lenta L. trees were collected in mesophytic ravines along Little Stony Creek (elevation 3553 ft.) and Hunters Branch Creek (elevation 3821 ft.) respectively, on August 10, 1945. These locations are in Giles County, Virginia, and are indicated on the Virginia-West Virginia Pearisburg Quadrangle map issued by the Virginia Geological Survey of the Con-servation and development Commission of the State of Virginia. Forty mature, well-formed leaves were selected from an individual tree of each species concerned in each habitat, for measurements. After gross measurements of length and width, a portion 10 mm. wide and 40 mm. long, along each side of the midvein in the middle of the leaf, was removed for sectioning. These pieces of leaf tissue were cut into strips about 3 mm. wide and placed in 70% thyl alcohol for two days to harden the tissues and remove the chlorophyll. After the allotted time in the 70% ethyl alcohol the strips of leaf tissue were sectioned on a hand microtome at about 17 microns by means of a sharp razor blade. The microscopic sections were dropped into 70'/r ethyl alcohol immediately after being cut. After a suffi-cient number of sections had been cut for each species from each habitat the sections were transferred to a saturated solution of Sudan III in 70'/r ethyl alcohol to stain the upper and lower cuticle. The sections were heated for one hour over a 60 watt lamp while in the straining solution. Then the sections were placed in 50% ethyl al-cohol to partly destain them and finally placed in glycerol. While in glycerol the sections were heated over a 60 watt lamp for 12 hours to remove any remaining ethyl alcohol and water. Lastly, 40 mea-171 1Miller: A Comparison of Leaves of Quercus Coccinea Muench. and Betula LenPublished by UNI ScholarWorks, 1946172 IOWA ACADEMY OF SCIENCE [VOL. 53 surements were made, by means of a microscope equipped with a calibrated ocular micrometer, of the thickness of the upper and lower cuticle, the upper and lower epidermis, and the total thickness of the leaf blade, of each species in each habitat. The results of the mea-surements are shown in the following tables. Results (In microns unless otherwise indicated) QUERCUS COCCINEA Muench. Heath Bald Max. Min. Ave. Upper Cuticle 8.5 5.1 5.69 Upper Epidermis 29.7 19.8 13.01 Lower Epidermis ......... 13.53 9.9 11.32 Lower Cuticle 5.1 3.06 3.91 Total Blade ..................... 256.62 197.4 225.99 Blade Length (in mm.) ........... . ..... 146.0 103.0 122.925 Blade Width (in mm.) .... . ........... 174.0 131.0 151.925 No of Layers of Palisade Tissue Hypodermis .. 3 Present (1 layer) BETULA LENTA L. Heath Bald Max. Min. Ave. Upper Cuticle 2.04 1.36 1.66 Upper Epidermis 26.4 13.2 17.72 Lower Epidermis ......... 20.79 9.9 14.88 Lower Cuticle ...... ........... 1.7 1.19 1.45 Total Blade ....... . .. 352.5 183.3 221.72 Blade Length (in mm.) .. ............ ...... 62.0 48.0 52.725 Blade Width (in mm.) .............. . No. of Layers of Palisade Tissue Hypodermis ... 40.0 27.0 32.8 3 Present ( 1 layer) Discussion Mesopthytic Ravine Max. Min. Ave. 5.1 2.72 3.33 22.1 13.6 18.66 13.6 8.5 11,31 2.04 1.36 1.58 189.0 140.0 161.0 162.0 103.0 119.075 160.0 98.0 126.425 2 Absent Mesophytic Ravine Max. Min. Ave. 1.7 1.19 1.64 20.4 10.2 13.98 20.4 10.2 14.83 1.7 .85 1.3 182.0 147.0 167.3 125.0 90.0 101.325 70.0 48.0 53.95 2 Present (1 layer) The results obtained by this series of measurements appear to show that Q. coccinea Muench. accommodates itself to the apparent xero-phytic conditions of the heath bald by a large increase in the amount of cuticle on the upper and lower surfaces, by an increase in the thickness of the upper epidermis, by the addition of a layer of hypo-dermis and an extra layer of palisade tissue. These features account for an increase of approximately 29% in the thickness of the leaves of Q. coccinea Muench. on the heath bald as compared with the leaves of the same species in the mesophytic ravine. B. lenta L. has accommodated itself to the apparently xerophytic 2Proceedings of the Iowa Academy of Science, Vol. 53 [1946], No. 1, Art. 18https://scholarworks.uni.edu/pias/vol53/iss1/181946] COMP ARIS ON OF LEAVES 173 conditions on the heath bald largely by a decrease in the size of the leaves. The leaves of B. lenta L. from the heath bald trees are ap-proximately 48% shorter and 39% narrower than the leaves of the same species from the mesophytic ravine. The leaf blades of B. lenta L. from the heath bald are approximately 25% thicker than the leaf blades of the same species from a mesophytic ravine because the leaves of the heath bald trees possess an extra layer of palisade tis-sue and an upper epidermis which is approximately 22% thicker than the upper epidermis of the leaves of the mesophytic ravine trees of the same species. Student members of plant ecology classes at the Mountain Lake Biological Station compiled records of the humidity of various habi-tats near the biological station during the summer sessions of 1939 and 1941 by means of Livingston porous cup atmometers. Their rec-ords show that the average daily loss of water from atmometers placed among the shrubs of Bald Knob for two week periods during both years was 11.32 c.c. In comparison, the average daily Joss of water from atmometers placed five feet from the ground on various species of trees in mesophytic forests was 10.01 c.c. for the identi-cal two week periods of the first portion of the experiment. Thus the amount of water evaporated from atmometers on Bald Knob is 1.31 c.c. or 11.5% in excess of the amount of water evaporated daily from atmometers in mesophytic forests. This may be considered a signifi-cant difference within the limitations imposed by the fact that hu-midity readings have been compiled for only two seasons. Student members of the plant ecology classes at Mountain Lake Biological Station have also rec'orded pH determinations in various habitats near the biological station. The pH reading on Bald Knob three inches below the surface of the soil in the heath bald is 4.5, while ten inches below surface the pH is 4.0. In a white oak forest a half-mile north of the biological station the pH one inch below the soil surface is 5.0 Six inches below the surface of the same soil the pH is 5.4. These determinations show the extreme acidity of the heath bald of Bald Knob. In conclusion it may be stated that Q. coccinea Muench is better adapted in general to dry situations than is B. lenta L. Gray's Manual mentions dry light soil as the habitat of Q. coccinea Muench. while indicating rich woods as the habitat of B. lenta L. The most obvious advantage of Q. coccinea Muench. is the thickness of the upper and lower cuticles of the heath bald trees. The upper cuticle of Q. coccinea Muench. of the heath bald is better than three times as thick as the upper cuticle of B. lenta L. from the same habitat. The lower cuticle of Q. coccinea Muench on Bald Knob is more than twice as thick as the lower cuticle of B. lenta L. of the heath bald. Another easily dis-cerned difference lies in the upper epidermis of the leaves. The upper epidermis of leaves from Q. coccinea Muench. on Bald Knob is ap-proximately 23% thicker than the upper epidermis of leaves of B. lenta L. from the health bald. 3Miller: A Comparison of Leaves of Quercus Coccinea Muench. and Betula LenPublished by UNI ScholarWorks, 1946174 IOWA ACADEMY OF SCIENCE MOUNTAIN LAKE BlOLOGICAL STATION, University of Virginia, Mountain Lake, Virginia. LITERATURE CITED [VOL. 53 Robinson, B. L. and Fernald, M. L. 1908. Gray's New Manual of Botany. Ed. 7. pp. 334, 342. American Book Company. New York. 4Proceedings of the Iowa Academy of Science, Vol. 53 [1946], No. 1, Art. 18https://scholarworks.uni.edu/pias/vol53/iss1/18

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A Comparison of Leaves of Quercus Coccinea Muench. and Betula Lenta L. from Heath Bald and Mesphytic Ravine Habitats

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