University of California

Vascular differentiation in the pear root


Katherine Esau

Author Affiliations

Katherine Esau was Assistant Professor of Botany and Assistant Botanist in the Experiment Station.

Publication Information

Hilgardia 15(3):299-324. DOI:10.3733/hilg.v15n03p299. April 1943.

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The present paper deals with the development of the root of Pyrus communis L., with special attention to the vascular tissues. Though considerable information is available on root structure of herbaceous plants (Hayward, 1938); (Esau, 1940),3 only one rather complete account of tissue differentiation in a root of a woody species appears to exist in modern botanical literature (Hayward and Long, 1942). The need for such accounts in the teaching of plant anatomy, especially in agricultural institutions, is obvious.

The present problem was selected also because of the writer’s interest in the differentiation of the phloem tissue in different organs of seed plants. Since many studies have been made on the phloem of roots of herbaceous plants (review by Esau, 1943), it seemed timely to add some data on the ontogeny of this tissue in a woody root.

Materials and Methods

The root material used in preparing the permanent slides and the photomicrographs was obtained from trees grown in a culture solution by the Plant Nutrition division at Berkeley. The material was killed in a formalin-acetic-alcohol fixing fluid and imbedded in paraffin after ordinary dehydration and clearing in mixtures of ethyl alcohol and xylene.

The roots grown in the culture solution were compared with soil grown roots from young trees 5 to 6 inches high grown from seeds of the Winter Nelis variety. The latter roots were examined in free-hand sections.

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Esau K. 1943. Vascular differentiation in the pear root. Hilgardia 15(3):299-324. DOI:10.3733/hilg.v15n03p299
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