Evolution of the secondary haustoria to a primary haustorium in the parasiticScrophulariaceae/Orobanchaceae |
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Authors: | Hans Christian Weber |
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Institution: | (1) Fachbereich Biologie-Spezielle Botanik, Philipps-Universität, Lahnberge, 3550 Marburg, Germany |
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Abstract: | In the parasiticScrophulariaceae andOrobanchaceae, two types of contact organs exist: secondary and primary haustoria. Secondary haustoria are lateral organs, developing in large numbers and only when the seedling is fully established. In contrast, a primary haustorium represents the first developmental stage of the seedling itself. In the root system of the parasiticLesquereuxia syriaca (=Siphonostegia syriaca) there are only secondary haustoria, but a few of them apparently develop in a terminal position. This is achieved by transferring the haustorial initiation region closer to the root apex. One can interpret this as a transformation of the apical meristem into a meristematic haustorial tissue. On the condition that an extreme shortening (abbrevation) of the primary root could happen, we discuss the transformation of the terminal secondary into a primary haustorium. |
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Keywords: | Angiosperms Scrophulariaceae Orobanchaceae Lesquereuxia = Siphonostegia syriaca Parasitism secondary haustoria primary haustorium apical meristem evolution |
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