TOUCH-INDUCED AND METHYL JASMONATE-INDUCED LIGNIFICATION IN TENDRILS OF BRYONIA-DIOICA JACQ

The touch-induced free coiling response of Bryonia dioica tendrils is accompanied by the differentiation of supporting tissue at the ventral side of the organ, becoming the inner (concave) side of the coiled te ndril. As part of this process, the Bianconi plate, a continuous scler enchyma sheath stretching along the ventral face of the five bicollate ral vascular bundles, becomes strongly lignified. During this reaction , the extractable activity of phenylalanine ammonia-lyase in the tendr ils increases four- to five-fold, while the amount of PAL, as demonstr ated by immunoblotting, remains unchanged. This touch-induced process can also be elicited by airborne application of methyl jasmonate. The PAL inhibitor, 2-aminoindan-2-phosphonic acid (AIP) completely inhibit s both the touch- and methyl jasmonate-induced deposition of lignin-li ke material in the Bianconi plate, but has no effect on coiling. From these results, it can be concluded that the cessation of growth at the ventral side of a free-coiling tendril is not due to induced lignific ation but rather, lignification seems to serve the function of increas ing the mechanical strength of the coiled tendril.