The tapetum and systematics in monocotyledons |
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Authors: | Carol A Furness Paula J Rudall |
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Institution: | (1) Royal Botanic Gardens, Kew, TW9 3AE Richmond, Surrey, UK |
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Abstract: | This paper critically reviews the homologies and distribution of tapetum types in monocotyledons, in relation to their systematics.
Two main types of tapetum are widely recognised: secretory and plasmodial, although intermediate types occur, such as the
“invasive” tapetum described inCanna. In secretory tapeta, a layer of cells remains intact around the anther locule, whereas in the plasmodial type a multinucleate
tapetal plasmodium is formed in the anther locule by fusion of tapetal protoplasts. In invasive tapeta, the cell walls break
down and tapetal protoplasts invade the locule without fusing to form a plasmodium. When examining tapetum type, it is often
necessary to dissect several developmental stages of the anthers. Secretory and plasmodial tapeta are both widely distributed
in monocotyledons and have probably evolved several times, although there may be some systematic significance within certain
groups. Among early branching taxa,Acorus andTofieldia have secretory tapeta, whereas Araceae and Alismatales are uniformly plasmodial. The tapetum is most diverse within Commelinanae,
with both secretory and plasmodial types, and some Zingiberales have an invasive tapetum. Lilianae (Dioscoreales, Liliales,
and Asparagales) are almost uniformly secretory. |
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