THE SIGNIFICANCE OF THE ANTHER TAPETUM IN THE BIOCHEMISTRY OF POLLEN PIGMENTATION - AN OVERVIEW

Flavonoids such as chalcones, flavonol di- and triglycosides as well a s anthocyanins are essentially involved in pollen pigmentation. Phenyl alanine ammonia-lyase (PAL) and chalcone synthase (CHS) represent two key enzymes in the biosynthetic pathway of flavonoids. In enzymatical studies the distribution of the two enzymes in anthers of Tulipa cv. ' Apeldoorn' was analysed. After separation of the loculus material in a pollen and a tapetum fraction the highest enzyme activities of both P AL and CHS were found in the tapetum fraction whereas the pollen fract ion showed only low enzyme activities. This was confirmed by immunohis tochemical studies using antibodies against CHS. The CHS was present i n the tapetum and epidermal cells of anthers at an early and middle po stmeiotic developmental stage. The results imply that the tapetum cell s play a crucial role in the flavonoid biosynthesis in the loculus of the anthers and consequently in the pollen pigmentation.