STUDIES OF ROOT REGENERATION AND SHOOT GROWTH IN TULIP TREE (LIRIODENDRON TULIPIFERA L.)

ROBERT J KELLY, Purdue University

Abstract

Root regeneration of tulip tree (Liriodendron tulipifera L.) seedlings was greater when transplanted in the spring than in the fall. Indolebutyric acid (IBA) applied to the roots increased root regeneration with the greatest response at 1000 mg/liter in the spring and 3000 mg/liter in the fall. Root regeneration and shoot growth increased as chilling hours increased from 0 to 1680 hours; 1008 hours of storage at 2(DEGREES)C was sufficient to fulfill the chilling requirement. Photoperiod did not directly influence root regeneration in either the spring or the fall. There was an interaction of root regeneration and shoot growth of shoot pruned plants with season, IBA treatment, and level of pruning. Decreasing the light intensity of full sunlight reduced root regeneration and shoot growth. Applying IBA improved root initiation over untreated plants at all light intensities, but subsequent root growth decreased with decreased light. Root regeneration and shoot growth of tulip tree increased as the temperature of the growing environment increased from 10(DEGREES) to 21(DEGREES)C. IBA applied at the rate of 1000 mg/liter to the roots increased root regeneration and shoot growth at temperatures of 15.5(DEGREES) and 21(DEGREES). When air temperature was consistent 21(DEGREES) and soil temperature was varied from 10(DEGREES) to 21(DEGREES), root regeneration and shoot growth of untreated plants increased as soil temperature increased. IBA significantly increased root regeneration only after soil temperature was raised to 21(DEGREES). Endogenous levels of starch and sucrose measured in the taproot of dormant tulip tree decreased during the course of root initiation and elongation. Applications of IBA to the taproot stimulated root regeneration and resulted in larger decreases in starch and sucrose levels in the taproot. Reducing sugars tended to be higher in the taproot of those plants exhibiting increased rooting. Levels of starch, sucrose, and reducing sugars in the stem tissue declined during root regeneration, but there was no significant differences between IBA treatments. These results indicate that root regeneration in dormant tulip tree is dependent on the carbohydrates contained in the taproot with starch the major source.

Degree

Ph.D.

Subject Area

Botany

COinS