Many woody plant species cannot be micropropagated commercially because they exhibit superinduction of secondary phenols (polyphenols) in response to excision and/or the high levels of plant growth regulators required to induce organogenesis. These phenolics may denature enzymes, inter1ere with electron transport systems in carbohydrate metabolisni, or alter the expression of endogenous growth substances. Basic research in plant biochemistry and physiology has provided many techniques by which the accumulation of secondary plant phenolics can be regulated. We propose to apply those techniques to the practical problem of micropropagating recalcitrant woody species. Phase I will involve large-scale screening experiments with susceptible species including pears, dogwoods, oaks, walnuts; and maples. The culture media will be modified with additives known to: (1) block the formation of o-quinones; (2) control the level of phenolic formation by partial inhibition of phenylalanine ammonia-lyase activity; (3) chelate phenolics in the culture medium or within the plant; and (4) selectively inhibit tannin biosynthesis.The potential commercial application as described by the awardee: Controlling the superinduction of secondary phenolic production in various stages of in vitro culture will permit the micropropagation of recalcitrant woody species for genetic manipulations as well as for commercial production.
