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1 July 1998 Effects of Shoot Apex Removal and Fruit Herbivory on Branching, Biomass and Reproduction in Verbascum thapsus (Scrophulariaceae)
Allanah C. Naber, Lonnie W. Aarssen
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Abstract

The purpose of this study was to interpret patterns of branching in natural populations of Verbascum thapsus L. (Scrophulariaceae) and to investigate whether the suppression of lateral meristems by apical dominance imposes a potential fitness cost in this species. Disruption of apical dominance by removal (clipping) of shoot apices resulted in shorter plants and greater branching but did not affect total biomass, number of fruits, number of seeds per plant or percent germination of seeds. Seeds from clipped plants, however, were approximately 30% heavier than those from unclipped plants, indicating that apical dominance imposes a potential fitness cost to V. thapsus. Plants with shoot apices intact were mostly unbranched but were more likely to be branched if they were taller. The fruits on the main stalks of these taller and more branched plants were significantly more heavily infested by a curculionid weevil (Gymnaetron tetrum Fab.). Lateral branches of these naturally branched plants, however, were less infested than the main stalks. These results indicate that the weevils are attracted to larger plants and that weevil damage may induce branching. An alternative hypothesis could not be discounted, i.e., that larger plants are more branched because they have greater resource availability, thus allowing release of lateral meristems from inhibition by apical dominance.

Allanah C. Naber and Lonnie W. Aarssen "Effects of Shoot Apex Removal and Fruit Herbivory on Branching, Biomass and Reproduction in Verbascum thapsus (Scrophulariaceae)," The American Midland Naturalist 140(1), 42-54, (1 July 1998). https://doi.org/10.1674/0003-0031(1998)140[0042:EOSARA]2.0.CO;2
Received: 13 June 1996; Accepted: 1 November 1997; Published: 1 July 1998
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