Metabolic Studies of N⁶-(²- Isopentenyl)Adenosine in Normal and Autonomous Tissues of Nicotiana tabacum L.

Abstract

<p>The nucleoside, N⁶-(Δ²-isopentenyl)adenosine (i⁶Ado) stimulates growth and differentiation of lines of tobacco callous tissue grown in culture. The nucleoside is extensively metabolized by the plant tissue. The hypothesisis been advanced that the expression of growth and differentiation is due to the interaction of some or all the metabolites of i⁶Ado rather than due to i⁶Ado alone or one of its metabolites.</p> <p>To study this hypothesis, the metabolism of i⁶Ado was followed in two lines of tobacco callous tissue. One line, KX, required the presence of i⁶Ado and auxin for growth, the second line, an autonomous line, 0-1, required neither hormone for growth. Both lines metabolized [8-¹⁴C]i⁶Ado, yielding a mixture of 12 metabolites, 9 of which were identified. Quantitatively the two patterns of metabolism differed. The principle product in the KX tissue was ribosylzeatin, whereas in the 0-1 tissue it was N⁶-(Δ²-isopentenyl) adenosine.</p> <p>The effect of other plant hormones, auxin and abscisic acid an the metabolism of i⁶Ado was studied. Auxin had no effect on i⁶Ado metabolism on 0-1 tissue, but in KX tissue it depressed the rate of uptake. Abscisic acid caused a change in ratios of i⁶Ado metabolites in KX tissue, but not in the autonomous tissue.</p> <p>These data do not prove or disprove the hypothesis mentioned above, they do indicate, however, that a varied pattern of metabolic products of i⁶Ado are formed in normal tobacco callous tissue.</p>