PHYSIOLOGIA PLANTARUM 92; 350-355. 1994 c,,,,yrighi © fhysioiogia nmtmm tv)4 Primed in Denmark - aU rigkfs reservetf Light-induced increase in the contents of ferulic and diferulic acids in cell walls of Avena coleoptiles: its relationship to growth inhibition by light Kensuke Miyamoto, Junichi Ueda, Satomi Takeda, Kazuko Ida, Takayuki Hoson, Yoshio Masuda and Seiichiro Kamisaka Miyamoto, K.. Ueda, J., Takeda, S.. Ida. K.. Hoson. T., Masuda, Y. and Kamisaka. S. !994. Light-induced increase in the contents of feru!ic and diferuiic acids in cel! walls of Avena coleoptites; its relationship to crowth inhibition by light. - Physioi. Plant. 92^ 350-355. White fluorescent light 15 W m^-) inhibited/(irna coleoptile growth. Light caused an increase in minimum stres.s relaxation time and a decrease in extensihility (strain/load) of coleoptile cell wall.s. Lighl increa.ved ihe content.s of ferulic acid (F,\) and diferulic acid (DFAl ester-linked to the hemicellulose I in cell walls. These changes in the phenolic contents correlated with those of the mechanical properties of cell walls, suggesting that light stimulates the formation of DFA in hemicellulose !. making cell walls rigid, and thus results in growth inhibiiion. The ratio of DFA to FA was almost constant in the dark, bul decreased in light, although it was almost constant in Oryza coleoptiles eiiher in the dark or in light {Tan et al 1992). Frotn this fact, it is speculated that in the light condition, the formation cf DFA in cell walls is limited in the siep ofthe peroxidase catalyzed coupling reaction to produce DFA, while in the dark it is limited in the step of the feruloylation of hemicellulose I. Key words - Avena sativa. cell wall, cell wall extensibility, coleoptile, diferulic acid, ferulic acid, growth inhibition. light, oat. A". Miyamoto and J. Ueda, College of Integrated Arts and Sciences, Univ. of Osaka Prefecture, I-I Gakuen-cho, Sakai 593, Osaka, Japan: S. Takeda and K. Ida. Dept of Natural Science, Osaka Women's Univ., Daiseii-cho, Sakai 591, O.saka, Japan: t. Hoson and S. Kamisaka (correspond'ing author}, Dept of Biology, Fac. of Science. O.saka City Univ., Sumiyoshi-ku, Osaka 558, Japan: Y. Masuda. Food Science Lab- oratory, Tezukayama College, Gakuenmitiami, Nara 631. Japan. , . . .. cel! wa!ls (McNeil et al. 1984). In addition to these Introduction , , ,,.,,-„ polymers, the primary cel! walls of Poaceae contain a The mechanism by which light inhibits shoot growth has significant amount of monophenols such as ferulic acid been studied in re!ation to the mechanical propenies of (FA) and coumaric acid (Harris and Hanley 1976, Smith ce!! walls, since cel! e!ongation is considered to be and O'Bden ! 979, Shibuya !984, Kamisaka el al. 1990), mainly determined by the extensibility of ce!! wa!ls (e.g. which are ester-linked to wall matdx polysaccharides see Masuda !978, !990). Much evidence indicates that (Han!ey !973, Whitemore !974, Ery 1983). light-induced inhibition of shoot growth is caused by a Cross-linkages among cell wal! polysaccharides can decrease in ce!l wal! extensibi!ity (Masuda et a!. !970, modify the mechanica! propenies of the ce!l walls (e.g. Euruya et al. 1972, Cosgrove 1988, Kige! and Cosgrove see Ery !986). EA bound to the ce!! wal!s undergoes a !991, Miyamoto et al. 1992a,b, Tan et a!. 1992). peroxidase catalyzed coupling reaction to produce dife- Matrix polymers such as pectins and hemicelluloses, rulic acid (DFA) (Markwalder and Neukom 1976), which and cel!u!oses are the major constituents of growing plant cross-!inks matrix polysaccharides. The formation of Received 3 February, !994; revised 3 June, !994 350 Physiot. Plam. 92, 1994