A Developmental Study of Silicification in the Trichomes and Associated Epidermal Structures of the Inflorescence Bracts of the Grass, Phalaris canariensis L

Silicon accumulation is greatest in the abaxial epidermis ofthe inflorescence bracts of Phalaris canariensis L. It occursinitially in glumes 1 week before emergence, at low levels inthe trichomes and long cells, but at high levels in the papillae.Accumulation in long cells remains low throughout, althoughit increases with time. Papillae and prickle hair silicon countsconsiderably exceed values for other epidermal structures. Siliconis also deposited in glume macrohairs before emergence, andat maturity reaches intermediate levels. Little silicon is present in the macrohairs and long cells ofthe abaxial epidermis of the fertile lemma prior to emergence.After emergence, however, silicon is rapidly accumulated inthese structures, and at maturity they have the highest siliconlevels of all the mature bract tissues. Silicon accumulation in the lemma lags behind that of the glumeuntil emergence, when it increases more rapidly, and by maturityexceeds that of the glume in macrohairs and long cells. Thesignificance of the results is discussed in relation to wallthickening, bract anatomy and panicle emergence. Phalaris canariensis, L, canary grass, inflorescence bracts, silicification, trichome, glume, lemma