CHANGING ROOT-SYSTEM ARCHITECTURE THROUGH INHIBITION OF PUTRESCINE AND FERULOYL PUTRESCINE ACCUMULATION

Plant roots provide anchorage and absorb the water and minerals necess ary for photosynthesis in the aerial parts of the plant. Since plants are sessile organisms, their root systems must forage for resources in heterogeneous soils through differential branching and elongation (1 988) Funct. Ecol. 2, 345-351; (1991) Plant Roots: The Hidden Half, pp. 3-25, Marcel Dekker, NY. Adaptation to drought, for instance, can be facilitated by increased root growth and penetration. Root systems th us develop as a function of environmental variables acid the needs of the plant (1988) Funct. Ecol. 2, 345-351; (1986) Bet. Gaz. 147, 137-1 47; (1991) Plant Roots: The Hidden Half, pp. 309-330, Marcel Dekker, N Y. We show, in a model system consisting of excised tobacco roots, th at both a-DL-difluoromethylornithine (an inhibitor of putrescine biosy nthesis) and the rolA gene (from the root-inducing transferred DNA of Agrobacterium rhizogenes) stimulate overall root growth and cause a co nversion in the pattern of root system formation, producing a dominant or 'tap' root. These morphological changes are correlated with a depr ession in the accumulation of polyamines and their conjugates.